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Chapter 1.

Forest and primates, a general introduction to the conservation of endemic primates in the Sundaic region

Introduction The Sundaic region, also known as Sundaland, Malesia, or the Indo-Malayan region, and defined as Thai-Malay peninsula south of the isthmus of Kra, Sumatra, Borneo, Java and Bali, has been identified as one of the hottest biodiversity hotspots on earth (Meyers et al., 2000). The area ranks second in number of endemic plants, fifth in number of endemic vertebrates (excluding fishes), tenth for endemic plants / area ratio and endemic vertebrate / area ratio, and ranks seventh in having the least amount of primary vegetation remaining as percentage of the original extend. With the Philippines and Madagascar, the Sundaic region is the only area to appear in the top ten of all the above listed factors (Meyers et al., 2000). During interpluvial periods the region was originally covered by and large in rain forest of different types, depending on, among other things, altitude and soil type (Park, 1994). Interpluvial periods correspond with the 'glacial' periods in temperate regions and during such times so much of the northern and southern latitudes was covered in ice that sea levels were reduced by as much as 100 m. Along the south eastern edge of the Sunda Shelf, i.e. eastern Java and parts of Bali, drier forest types could be found including deciduous forest. Especially over the last decades, but much earlier in the lowlands of Java, due to rapid deforestation, large areas, are now converted into agricultural land, plantations, and, increasingly 'wastelands', i.e. virtually unoccupied land covered in e.g., alang-alang Imperata grassland and other depauperate vegetation types (e.g., Myers, 1989). The once large continuous areas of forest of the Sundaic region are home to a large variety of non-human primate species (hereafter 'primates'1). Depending on the taxonomy followed 26-28 species can be found in the region. This includes four of the eleven families commonly recognised (Corbet & Hill, 1992; Mittermeier & Konstant, 1996/1997): Loridae (one species), Tarsidae (one species), Cercopithecidae (17-18 species, including the bear macaque Macaca arctoides which occurs marginal in northern part of the Thai-Malay peninsula), Hylobatidae (six species), Hominidae (one or two species depending on whether the two orang-utan taxa from Sumatra and Borneo are given the species rank, see below). From a broad geographic perspective the region is important as it harbours a disproportionately large number of primate species and primate endemics (Mittermeier & Konstant, 1996/1997). With the exception of a few, most notably the long-tailed macaque M. fascicularis, most species are confined to natural forest. Some species are able to survive in certain man-made habitats, most notably certain forest plantations, but most of them will not survive for any length of time in these habitats.

1 Biologically and taxonomically humans are included in the order primates, for practical reasons however, in the present thesis, 'primates' unless specified otherwise normally denotes 'non-human primates'.

In this thesis I will present data on the ecology and conservation of the endemic primates of Java and Borneo. Combined, these two islands, and their smaller neighbouring islands, comprise more than half of the land surface of the Sundaic region. In this first chapter I will briefly introduce the islands of Java and Borneo (geology, climate, vegetation, human population etc.), the endemic primate species occurring on them and their conservation status. The main causes of the decline of the populations of the endemic primates on Java and Borneo are presented, after which a brief overview of primate conservation studies that have been conducted on the islands will be given. The chapter ends with a concise summary of the history of the present study, its aims, and an outline of the thesis. Background on the study islands Java is an island of about 130,000 km2 and politically includes the island of Madura (5,620 km2) which lies just north of the east Javan province. It is administratively divided in six areas, viz. West Java (at the end of 2000 this was split in two smaller provinces Banten and West Java), DKI Jakarta (the nation's capital), Central Java, DI Yogyakarta, and East Java (which includes Madura). As Indonesia’s political and industrial centre, it is one of the most densely populated areas in the World. The very fertile soils which lend themselves to terracing for irrigated rice, sustain about 115 million people, at an average population density of 862 people km-2 (Whitten et al., 1996). Geologically Java is dominated by its backbone of (active) volcanoes, running over the central axis of the island. Eleven volcanoes reach over 3000 m and with 3676 m Mt Semeru is Java's tallest mountain. Rivers are relatively short and run mostly from the central axis of the island straight to either the Java Sea or the Indian Ocean. Java is largely deforested and most of the remaining forest fragments cover (parts of) the numerous volcanoes; human pressure on the remaining forests is very high. Less than 10% of the original forest remains: 54% of the mountain forest, 19% of the hill forest, and only 2% of the lowland forest (Smiet 1992). The last mentioned forest type is now almost exclusively found scattered along the southern coast and in the easternmost part of the island. Once the island was probably completely covered by tropical forest (MacKinnon et al., 1982), but its destruction already commenced in the 15th century (Whitten et al., 1996). An estimated total area of 10 million ha of natural forest was present in the 17th century. Some hundred years ago four million were left, which was reduced to about one million in the first half of the 20th century. During the past 50 years no further significant change in forest cover has taken place (Smiet, 1990). At present deforestation has slowed down, but fragmentation and forest degradation continues (Smiet, 1992). Forest has been replaced by cities and villages, agricultural land, estate crop plantations (coffee Coffea sp., quinine Cinchona calisaya, sugar cane Saccharum sp.), forest plantations (teak Tectona grandis, pine Pinus sp., rubber Hevea brasiliensis), leaving the natural forest areas as habitat islands. Less than 25% of the remaining forest on Java is included in the protected area network (RePPProTT, 1990). The climate on Java differs greatly from the west to the east. The eastern part of Java and the north coast have a pronounced dry season, while in the western half it is weak and nowhere marked. In general, the wettest vegetation types (mixed lowland and hill rain forest and everwet montane forest) only occur in areas with at least 30 rainy days during the driest four consecutive months (van Steenis & Schippers-Lammertse, 1965), and hence is mostly found in the west and central part of Java.

Rain forest is also found throughout the otherwise seasonally dry east in the wet 'islands' which arise as a result of stowage on the southern and south-eastern slopes of the higher mountains (van Steenis, 1972). In the drier areas rain-forest is replaced by moist forest and deciduous forest. The island of Bali (5560 km2), situated east of Java, is politically a separate entity, but bio-geographically it is included in the Javan faunal province. Bali has a population of some three million people at an average population density of 520 per km2. Most humans live in the fertile southern part of the island (Whitten et al., 1996). Less than one fifth of the island remains under forest cover, most of which is situated in the central mountain range and in the northern part of the island (MacKinnon et al., 1982). Large-scale deforestation on Bali is more recent than on Java, and around the turn of the 20th century most of the northern half of the island was still covered with forest. The loss of forest during the 20th century has been largely due to the introduction of coffee, clove Syzygium aromaticum and coconut Cocos nucifera plantations, and use of fuel-wood (see maps in Whitten et al., 1996: 335). The climate of Bali is comparable to the eastern part of Java, with a long dry season along the north coast and a negligible dry season on some of the higher volcanoes (RePPProT, 1990). Borneo is much larger than Java, in fact with a size of 746,305 km2 it is the third largest island in the world (after Greenland and New Guinea). Administratively it is divided into the four Indonesian provinces of West, Central, East and South Kalimantan, the two autonomous Malaysian states Sabah and Sarawak and the Brunei Sultanate. The Indonesian part of Borneo covers some three quarters of the total land area of Borneo. Borneo mainly consists of relatively low lying areas and over half of the island lies below 150 m a.s.l. In the centre of the island lies a chain of higher hills and mountains, running from south-west to the north-east. Borneo's highest mountain is Mt. Kinabalu in Sabah, which is, with its 4101 m, the highest peak between the Himalayas and the mountains of New Guinea. Other than Java, Borneo is dissected by a large number of great rivers; the Kapuas river (1143 km in length) to the west, the Barito River (900 km) to the south, and the Mahakam River (775 km) to the east. High levels of weathering and leaching are characteristic of many Bornean soils (Burnham, 1984), and the soils on Borneo are generally much less fertile than the volcanic rich soils of Java. Borneo has a much smaller human population than Java (some 12.5 million in 1990: MacKinnon et al., 1996), and an average population density of less than 17 people km-2. All major cities are located near the coast, and population densities in large part of Borneo's interior are less than one person per km2. Within large parts of the island the infrastructure is poorly developed and boats are the main mode of transportation. Settlements are also concentrated along waterways. Borneo supports the largest expanse of lowland evergreen rain forest in the Sundaic region, with some 60% of the land surface still under natural forest (MacKinnon et al., 1996; Collins 1991: this figure may be as low as 45% due to deforestation over the last decades, E. Meijaard, in litt.). The forests are characterised by a high diversity of dipterocarps, the most important timber species in the region (Whitmore, 1984). Timber is a major source of revenue for the Malaysian states and for Kalimantan; oil-rich Brunei has less need to exploit its forest for timber. Large scale exploitation of forest for timber began at the end of the 1960s; in 1967 all Indonesian forests were declared property of the state. Some 90% of all forest

(excluding conservation areas) in Sarawak is under concession (MacKinnon et al., 1996) whereas the total are of forest under concession in Kalimantan is actually larger than the total area of remaining forest (Rijksen & Meijaard, 1999). Besides for timber production, every year vast areas are cleared for agriculture, plantations, human settlements and transmigration. Lowland forests in particular are directly threatened by these practises due to their accessibility and their higher soil fertility than higher altitude forests. The last few decades forest fires have taken an immense toll on the remaining forest areas. During the 1982-1983 fires an area of some 50,000 km2 was affected (Goldammer et al., 1999), and, although figures vary widely, the 1997 fires affected an area significantly larger than this. Less than 10% of the forest on Borneo are formally protected as conservation forest, and most of this is concentrated in the mountains (Sujatnika et al., 1995; MacKinnon et al., 1996). Most parts of Borneo have few months with rainfall less than 100 mm. Most of the hilly inland areas receive between 2000 and 4000 mm per year. West and Central Borneo are the wettest parts of the island, whereas certain parts of east Borneo have a longer dry season with several months receiving less than 100 mm of rain. However, nowhere is the dry season as pronounced as it is in eastern Java or Bali. The endemic primates of Java and Borneo On Java and Borneo a large proportion of the non-human diurnal primates are endemic, viz. three out of four and five out of 13 respectively. Six of these eight species are leaf monkeys (Cercopithecidae, subfamily Colobinae), whereas the other two are gibbons (Hylobatidae) (Oates et al., 1994; Geissmann, 1995) (see Table 1.1). In the other diurnal primate families present on Java and Borneo, viz. the macaques (Cercopithecidae, subfamily Cercopithecinae) and orang-utan (Pongonidae), endemism is absent (although consistent differences between the orang-utan from Borneo and Sumatra in mtDNA [e.g., Karesh et al., 1997], karyotype [Seuanez et al., 1979], habitus [e.g., Markham 1980] and morphology [e.g., MacKinnon 1973] suggest that the two are perhaps best treated as distinct species). Without exception, all of the endemic primates of Java and Borneo are found only in forested areas. For most species this originally consisted of everwet forest only (including riverine, swamp, and montane forest), apart from the ebony leaf monkey which is also found in deciduous forest. A number of species, in particular some of the leaf monkeys, can also be found in forest plantations; but mostly only if more natural forest is present nearby. Since large areas on Java and Borneo are deforested or are under severe threat of being deforested in the near future, and because of increasing human pressure on populations, most if not all endemic species are threatened with extinction. Half of them are included in the IUCN (1996) list of threatened species (see also Chapter 13 for a more detailed assessment of IUCN threat criteria). Two species of leaf monkey, i.e. red leaf monkey Presbytis rubicunda and Bornean leaf monkey P. hosei are listed as Lower Risk (least concern), whereas the Bornean gibbon is listed as Lower Risk (near threatened). White-fronted leaf monkey P. frontata is listed as Data Deficient, i.e. there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on distribution and / or population status (Table 1.1).

Table 1.1 Endemic primates on Borneo and Java and their IUCN threat status Sub(family) Species

IUCN status

Islands

Family Cercopithecidae, subfamily Colobinae grizzled leaf monkey Presbytis comata Endangered Java Bornean leaf monkey Presbytis hosei Lower Risk Borneo white-fronted leaf monkey Presbytis frontata Data Deficient Borneo red leaf monkey Presbytis rubicunda Lower Risk Borneo ebony leaf monkey Trachypithecus auratus Vulnerable Java, Bali, Lombok proboscis monkey Nasalis larvatus Vulnerable Borneo Family Hylobatidae Javan gibbon Hylobates moloch Critically Endangered Java Bornean gibbon Hylobates muelleri Lower Risk Borneo

Note that fuscous leaf monkey Presbytis fredericae is not included in this listing, as it is considered synonymous with P. comata (chapter 5). Based on Eudey, 1996/1997, Geissmann 1993, Oates & Davies, 1994. Main causes of decline Over the last few decades the interest in non-human primates in the Sundaic region has increased substantially, and researchers from many disciplines and from various countries have focused their attention on this diverse order. Ironically enough these years have also seen serious declines in primate populations. For an increasing number of species these declines threaten their survival. The major threats to wild populations of primates in the Sundaic region fall into three broad categories: habitat destruction (including total loss and fragmentation), hunting, and capture for local trade. It is important to understand the threats an endangered species is subjected to in order to make recommendations that could positively influence its survival. This is all the more important as the effects of different threats are cumulative. 1. Habitat destruction The main threat to the endemic primates of the Sundaic region is habitat destruction (e.g., MacKinnon, 1987; Eudey, 1996/1997). This includes not only the total loss of forest and its replacement by forest plantations, pasture, or other forms of cultivated land, but also the degradation of the forest. The continuous fragmentation of primary forests and the intensification of land use in the areas between the remaining forest patches result in isolation of the populations trapped in these forest remnants. Many species of primates are completely arboreal and will not cross open land of any width,

which makes them especially susceptible to the effects of forest fragmentation. In the long run, gaps between populations may soon become unbridgeable due to further habitat loss and fragmentation may result in loss of variability due to genetic drift and inbreeding depression. In practise, however, small population will often never reach this stage of the extinction vortex as they are wiped out by hunters, are captured for the pet-trade, or further habitat destruction will results in the death of the last remaining individuals. Thus, in all likelihood, the reduction and the fragmentation of the forests result in populations too small and too widely separated to persist in the long term. Another immediate threat to many of the endemic primates is encroachment by humans along the edges of the forested areas. As the infrastructure is being improved the accessibility is increasing and primate and man are getting more and more in conflict. This usually turns out to be unfavourable for the former species. 2. Hunting The greater accessibility may also increase hunting activities. More on Borneo than on Java and Bali, primates are hunted for food and sport, as crop pest and for medicine. Many rural people depend on wildlife meat for their protein and primates are frequently eaten. Hunting is deeply ingrained into almost all cultures on Borneo (Bennett et al., 1994). With little traditional controls and the almost universal availability of shotguns and cartridges (more so in the Malaysian States than in Kalimantan), the effect on primate populations is devastating. Although largely protected by law, in practise the only safeguard for most species is inaccessibility. With the spread of logging roads, and improved river transport no areas are anymore safe (Bennett et al., 1994).

With respect to the success of the conservation of primates, it is relevant to note that human attitudes towards primates differ greatly between religious groups, and that the distribution of religious groups differs between Borneo and Java (and Bali). For Hindus primates are often considered sacred and in certain areas and at certain times offerings are brought to primates (Wheatly, 1999). Primates are not considered sacred by Muslims, but religious restriction permits the consumption of primates. This is in contrast to Christianity where few dietary restrictions prevail. The human population on Java is predominately Muslim and only a small proportion is Christian or of another religion. Concentrations of Hindus on Java are only found in a few remote highland areas. Bali however, is predominately Hindu. The coastal regions of Borneo are mostly inhabited by people with a Malayan origin who have adopted Islam as their main religion. Most of Borneo's interior is inhabited by people of the Dayak and Punan tribes, many of which have been converted to Christianity, although animistic beliefs are still widespread (Cleary & Eaton, 1992). Over the last hundred years there has been a heavy migration from the interior towards the coastal areas, generally as a result of better health facilities, better education and better living conditions (Sirait et al., 1994) bringing people from different cultural and religious backgrounds in closer contact. At a different scale transmigration (in the present context mostly involving people from Java, Sumatra and Sulawesi migrating to (rural) Borneo) has done the same. In general, hunting of primates is rare or absent in most areas on Java and Bali (although in certain areas long-tailed macaques are hunted as crop pest, and sometimes for sport), whereas it is widespread on Borneo, especially in the interior. On Borneo all primates that constitute more than a mouthful of meat (involving all

species with the exception of the nocturnal slow loris and the tarsier) are frequently eaten (Caldecott, 1992). 3. Trade In the Sundaic region, the human attitude towards keeping primates as pets differ greatly from those in the western world and seems to differ little between religious groups. Capturing of primates for pets is widespread throughout western Indonesia, with trade routes mostly running from the 'outer islands' (Sumatra, Borneo, and Sulawesi) to Java, and within Java, from east to west (Nursaid & Astuti, 1996; Nursaid, 1998; R. Nursaid, pers. comm.). The trade in primates is a profitable business and although many species protected by law (both in Indonesia and Malaysia) they are frequently offered for sale at bird markets. Few quantified data are available, but it must be feared that trade in primates has increased, especially after the economic depression of the late 1990's (R. Sözer, pers. comm.; R. Nursaid, pers. comm.). Zoos and safari parks, just as some 'animal lovers', see primates, and preferably the rarer ones, as status symbols and important assets for their collections. It is beyond doubt that zoos and birdparks play an important role in education as well as in conservation of many animal species, but prudence is called for keeping some of the rarest species. Field studies on the endemic primates of Borneo and Java Most long-term primatological studies in Indonesia, and indeed in most of South-east Asia have been concentrated at a limited number of field stations. These stations are mostly situated in relatively pristine habitat, in areas with limited or no hunting pressure, and almost without exception in the lowlands (Table 1.2). At these field stations different aspects of the synecology of tropical rain forests and their inhabitants have been studied, including primates. Borneo seems to follow this pattern, but on Java few long-term studies have been conducted and many primatological studies have been conducted in isolation. From a conservation perspective the data collected at field stations (habitat preferences, densities, group sizes, and other population parameters) are often the only ones available. Examples of studies on the endemic primates of Borneo and Java are listed in Table 1.2. Table 1.2. Selected study sites on Borneo and Java where long-term studies (> one year or several shorter studies) on endemic primates have been conducted. Country State, Province

Study site

Altitudinal range

Study species

Principal researchers

Malaysia Sarawak Samunsam 0-50 N. larvatus E.L. Bennett, A. Sebastian

Sabah Danum valley Sepilok Kinabatang

200-300 50-100 0-100

P. hosei, H. muelleri P. rubicunda N. larvatus

A.D. (Grieser)-Johns A.G. Davies R. Boonratana

Brunei -- -- -- Indonesia West Kalimantan Gn Palung 0-100 P. rubicunda M. Leighton, N. Salafski Central Kalimantan Tanjung Puting

Barito Ulu 0-50 150-350

N. larvatus, H. muelleri x H. agilis

C.P. Yeager D. Chivers, R. Mather

South Kalimantan -- -- -- East Kalimantan Kutai

100-300 H. muelleri

D. Leighton, J.C. Mitani, P.S. Rodman, A Suzuki

West Java Ujung Kulon Telaga Patengan Pangandaran

0-100 1600-1800 0-50

H. moloch P. comata T. auratus

M. Kappeler, Rinjani Y. Ruhiyat, I.M. Wedana E. Brotisworo, K. Kool, E. Megantara, K. Watanabe

Central Java Dieng Cepu

300-800 0-100

P. comata, H. moloch, T. auratus T. auratus

V. Nijman Djuwantoko

East Java -- -- -- Bali Bali Barat 0-50 T. auratus T. Voght Lombok

-- -- --

Altitudinal ranges are approximate and refer to the main study areas; often higher parts are in the vicinity. Of the endemics on Borneo the gibbons are relatively well-studied, with long-term studies conducted in Kutai National Park (e.g., Mitani 1984, 1985ab; Leighton, 1987; Rodman, 1978, 1988), Danum valley (Johns, 1992; Grieser-Johns, 1997), and Barito Ulu (Chivers, 1992, including studies on the hybrid zone between H. muelleri and H. agilis: Mather, 1992). Of the colobines, only the proboscis monkey has been studied in detail at a number of localities throughout its range (e.g., Yeager, 1989, 1990, 1991, 1993; Bennett, 1988; Bennett & Sebastian, 1986; Boonrata, 2000). Red leaf monkey has been studied in detail in Sabah (Davies, 1987, 1991; Davies & Baillie, 1988) and to a lesser extent Central Kalimantan (Supriatna et al., 1986). Data on the other colobines is scant and often collected during short studies. Hardly any published studies are available on white-fronted leaf monkey (Blouch, 1997) or Bornean leaf monkey. Of the Javan endemics the Javan gibbon has been studied in detail in Ujung Kulon only (Kappeler, 1981, 1984 abc; Rinaldi, 1999), although some base-line surveys have been conducted in other parts of the island (Kappeler, 1981, 1984c; Asquith, 1995; Asquith et al., 1995; Nijman, 1995). The grizzled leaf monkey has been studied mostly in montane habitats (Ruhiyat, 1983, 1991; Sujatnika, 1992; Wedana, 1993), whereas this species is probably more common at lower elevations (Nijman, 1997b; chapter 6; Whitten et al., 1996). The ebony leaf monkey has a wider niche breadth than the other endemics and occurs in a large variety of forest types. This species has been studied mostly in the more open forest types, including teak plantations (Brotoisworo, 1983; Brotoisworo & Dirgayusa, 1991; Kool, 1993; Kool & Croft, 1992; Djuwantoko, 1991) and deciduous forest (e.g., Kartikasari, 1986; T. Voght, pers. comm.). No long-term studies on this species have been conducted in the rain forest, although it can be found in all wet forest types on Java. Most studies are selectively conducted in those areas where the study species are present at relatively high densities. This may introduce a bias for assessing the conservation status of primates. For example for estimation of total population sizes of primates often rely heavily on published density estimates and hence over-

estimation of true population sizes is likely to occur. Only recently have studies begun to evaluate the effects of habitat disturbance. However most factors of disturbance (selective logging, hunting, and fire) have been studied in isolation (e.g., Suzuki, 1984; Caldecott, 1992; Johns, 1985, 1992). In reality disturbances do not occur in isolation but seem to be tightly linked. As an example, it is not uncommon for a forest area to be selectively logged (during which the rules for proper forest management may or may not be followed), during and after which it is frequently visited by hunters. Parts of the concessions are subsequently invaded by opportunistic farmers and settlers, who take out some additional timber and 'non-timber products', including animals. During a extended dry season the forest is set alight, after which the remaining large trees are felled, and the last animals hunted out. Hence, for primates to persist in under the current management regime, it is necessary to assess the conservation status of these primates based on data collected over a variety of habitats in different stadia of re- and degeneration, facing different threats (human pressure, encroachment, logging, hunting etc.). Aims of the study There is a lack of base line knowledge concerning the ecology of most, if not all, endemic primates in Indonesia. The precise geographical distribution of many species has not been documented. The types of habitats preferred and the densities at which individual species occur in different land use types remains largely unknown. The likely impacts of current factors such as hunting, capturing, habitat alteration and habitat fragmentation are unknown for many of the primates concerned. The islands of Java and Borneo are excellent locations to study the effects of human interference on the survival and conservation of primates. On both islands similar endemic primates are found but the pressures facing these species are quite different. Java represents an area where little forest remains, where the pressure on the remaining populations of primates dates back several centuries, and where many people are no longer dependent on the forest, whereas Borneo represents an area in transition. Although still largely covered in forest, rapid changes in land-use and changing human attitudes will greatly alter the pressures that wildlife populations are facing. The history of deforestation on Java will most likely repeat itself on the other Sundaic islands, e.g., Sumatra and Borneo and possibly other parts of South-east Asia. These areas have a much higher number of primate species. The findings and conclusions of the present study will therefore aim at presenting a framework for the conservation of South-east Asian primates. In order to gain greater understanding in the conservation status of the endemic primates of Java and Borneo, this study set out to collect relevant ecological data and to document the pressures facing the different species. Specific aims of the research are: (i). To assess the geographical distribution of individual species on Java and Borneo (Chapters 6, 7, 9 and 11). (ii). To develop, test and evaluate census methods by which primate populations can be assessed and monitored (Chapters 2, 3 and 4). (iii) To determine the type and magnitude of the threats facing the individual species and habitats on the islands (Chapters 8, 9, 10 and 11).

(iv) Using data collected under (i), (ii) and (iii), to re-assess the conservation status of the endemic primates of Java and Borneo using the IUCN threat criteria (Chapter 12). and subsequently (v). To identify key areas for conservation based on densities of particular primate species, the co-existence of a disproportional large subset of primate species and management feasibility (Chapters 8 and 11). (vi). To discuss the results of the present study into greater perspective and formulate further research priorities (Chapter 13). Setting of the project The Zoological Museum of the University of Amsterdam has several decades of practical experience with conservation related studies in the tropics, including the Sundaic and Wallacean regions. During the decades prior to Indonesia gaining independence most studies were focused on descriptive taxonomy, although part the studies of among others Prof. Dr L.F. de Beaufort, director of the museum during 1922-1949, would nowadays be classified as biodiversity conservation research. Later Prof. Dr. K.H. Voous, curator of birds from 1940-1964, worked on the ornithology of the region and published some influential studies on the birds of Java and Sumatra (Voous, 1950; van Marle & Voous, 1988). In the years after Voous' superannuation the number of projects increased due to the activities of the former heads of the department of birds, Dr J. Wattel, and mammals, Dr P.J.H. van Bree. For vertebrates studies include: seabirds (de Korte, 1989, 1991; de Korte & Silvius, 1994; Argeloo, 1993; Argeloo & Dekker, 1996), megapodes (Dekker, 1990ab; Argeloo, 1992; Jones et al., 1995), pheasants (Sözer, 1997; Sözer et al., 2000, in press; Nijman & Sözer, 1997), birds of prey (van Balen et al., 2000; Sözer et al., 1998), woodpeckers (Lammertink, 1998, 2001), bats (Bergmans & Rozendaal, 1982, 1988; Bergmans & van Bree, 1986), and marine mammals (de Iongh et al., 1997; Kreb, 1999). The present project was initiated in 1996 and stems from an agreement between the Zoological Museum Amsterdam and the Zoological Museum Bogor with ongoing projects concerning woodpeckers, birds of prey, pheasants, primates, dolphins, and sunbears. Outline of this thesis: After the general introduction of primate conservation studies in the Sundaic region, in the following twelve chapters the results of field studies on Javan and Bornean primates which were carried out between 1994 and 2001 will be described, interpreted, and their implications discussed. Section I (Chapter 1-5) presents some background information on survey methodology, behaviour, and morphology. In Chapter 2 a comparison is made between three commonly used methods for estimating densities and biomass of rain forest vertebrates. Chapter 3 deals with the effects that behavioural changes in rain forest vertebrates due to habitat disturbance have on estimation of densities. Both chapters use data from the Bornean gibbon and Javan gibbon, but the results and conclusions are likely to be applicable to other animal groups as well. Chapter 4 deals with the calling behaviour of Javan gibbons. It presents data on the frequency of calling in both sexes, and explores the use of bio-acoustics in conservation studies.

Chapter 5 describes the geographical variation in pelage of grizzled leaf monkeys, one of the three endemic primates of Java. Contrary to previous studies it argues that a number of morphological and behavioural characteristics of individuals of the western populations of this species are not diagnosably different from those in the eastern part of the species' range. It is therefore argued that the grizzled leaf monkey on Java comprises only one species; for conservation purposes the populations on Java should be treated as one single unit. The following two sections deal with the geographical distribution, conservation status and conservation of the endemic primates of Java and Borneo; section II deals with the Javan species, whereas Section III deals with those from Borneo. Section II (Chapter 6-9) begins with addressing the geographical distribution of the two endemic colobines on Java. Chapter 6 deals with the grizzled leaf monkey and chapter 7 deals with the ebony leaf monkey. Chapter 8 presents data on the conservation status and distribution of the endemic primates in the Dieng mountains. Section III begins with presenting data on the distribution and conservation of proboscis monkeys on Borneo (chapter 9), and chapter 10 tells the story of the local extinction of this species from the Pulau Kaget Nature Reserve. Both chapters demonstrate the in-effectiveness of species conservation on Kalimantan. Chapter 11 attempts to assess the patterns of primate diversity on Borneo, and the implications of these patterns for the selection of priority sites for conservation. Section IV starts with a re-assessment of the conservation status of the endemic primates of Java and Borneo based on the present IUCN threat criteria (Chapter 12), incorporating data from the previous three sections. Finally an overall discussion and an integration of the different themes is presented (chapter 13). This chapter also provides some suggestions for further research on primates and their forest in Java and Borneo. Most chapters have been published in scientific journals, with a number of different co-authors. In order to increase readability as much as possible a single style is adopted. Nomenclature and english names for the different species follows Geissmann (1993) for the gibbons, and Oates & Davies (1994) for the colobines (see Table 1.1); these may differ from the ones used in the original publication.

Density and Biomass Estimates of Gibbons in Bornean Rainforest: a Comparison of Techniques

13

CHAPTER 2

DENSITY AND BIOMASS ESTIMATES OF GIBBONS (HYLOBATES MUELLERI) IN BORNEAN RAINFOREST: A

COMPARISON OF TECHNIQUES

with Steph B.J. Menken ABSTRACT Censuses were conducted of the Bornean gibbon in two forest areas (Kayan Mentarang National Park [TNKM] and Sungai Wain Protection Forest [HLSW], East Kalimantan, Borneo, in 1996 and 1999-2000, respectively) using three different techniques. Gibbons live in stable and cohesive groups in permanent territories and sing regularly, making it relatively easy to locate them. Firstly, range mapping 3.8 km2 (TNKM) and 5.0 km2 (HLSW) was executed to locate all groups and to map their ranges. Secondly, repeated line transects were run on permanent transects and along ridges. Encounter rates on ridges in both areas were higher than on the permanent transects, reflecting gibbons' preference for higher ground during morning hours. Thirdly, fixed point counts were executed, which make use of the frequent calling of gibbons; the locations from where gibbons were vocalizing were mapped during the early morning (06.00-09.00 hrs) from listening points at summits and ridges. Densities were calculated for two sets of data based on the distance (0.7 and 1.0 km) from where gibbons could be mapped. Overall, density estimates in both areas were relatively similar with between 2.1 and 2.9 groups km-2. The lowest density estimate for TNKM, obtained by the fixed point counts using a radius of 1.0 km (2.1±0.1 groups km-2 or 6.9±2.2 individuals km-2, corresponding with a biomass of 30.7±31.0 kg km-2) was some 30% lower than the highest estimate which was obtained by the line transect technique (2.9±0.2 groups km-2 or 9.9±3.3 individuals km-2, corresponding with 43.2±40.0 kg km-2). The lowest density estimate for HLSW however, obtained by the line transect technique (2.4±0.4 groups km-2 or 7.9±5.8 individuals km-2, corresponding with a biomass of 35.1±89.4 kg km-2), was up to 17% lower than the highest estimate obtained by the fixed point counts technique using a radius of 0.7 km (2.7±0.1 groups km-2 or 9.5±3.5 individuals km-2, corresponding with a biomass of 41.0±31.4 kg km-2). The interaction between site and census technique explained a large proportion of the variation in density, larger than census technique did alone. This data suggests that care must be taken when interpreting density estimates from different areas obtained by different techniques.

Forest (and) Primates

14

RINGKASAN

Perkiraan Kepadatan Populasi serta Biomasa Kelawat (Hylobates muelleri) di Hutan Hujan Borneo: Suatu Perbandingan Metoda (bersama Steph B.J. Menken): Sensus-sensus tentang Kelawat telah dilaksanakan di dua kawasan hutan (Taman Nasional Kayan Mentarang [TNKM] dan Hutan Lindung Sungai Wain [HLSW], Kalimantan Timur, Borneo, masing-masing pada 1996 dan 1999-2000) dengan menggunakan tiga metode yang berbeda. Owa hidup dalam rombongan yang tetap dan kohesif dalam teritori yang permanen dan secara teratur menyanyi, yang mempermudah untuk mencari mereka. Pertama, pemetaan rentang sejauh 3.8 km2 (TNKM) dan 5.0 km2 (HLSW) telah dilakukan untuk menemukan semua kelompok serta untuk memetakan masing-masing daerah jelajah. Kedua, metoda transek garis berulang-ulang telah dilaksanakan di transek-transek yang permanen dan di sepanjang punggungan bukit. Frekwensi pertemuan di punggungan bukit di kedua daerah tersebut lebih tinggi daripada di transek-transek yang permanen, mencerminkan preferensi Kelawat terhadap dataran yang lebih tinggi selama waktu pagi. Ketiga, metoda titik hitung yang tetap telah dilaksanakan, yang menggunakan frekuensi bersuara dari Kelawat; lokasi-lokasi yang dipakai Kelawat untuk bersuara telah dipetakan selama waktu pagi (jam 06.00-jam 09.00) dari tempat-tempat dengarnya di puncak-puncak dan punggungan-punggungan bukit. Kepadatan populasi telah dikalkulasikan untuk dua set data berdasarkan jarak maksimal (0.7 dan 1.0 km) yang dapat dipakai untuk memetakan Kelawat. Rata-rata, kepadatan populasi di kedua daerah tersebut adalah hampir sama dengan antara 2.1 dan 2.9 kelompok per km2. Perkiraan kepadatan populasi yang paling rendah untuk TNKM, yang didapatkan dari perhitungan titik-titik tetap dengan menggunakan radius 1.0 km (2.1± 0.1 kelompok km-2 atau 6.9± 2.2 individu km-2, setara dengan biomasa 30.7± 31.0 kg km-2) adalah 30% lebih rendah daripada perkiraan yang tertinggi yang didapatkan dengan metode transek garis (2.9± 0.2 kelompok km-2 atau 9.9±3.3 individu km-2, setara dengan 43.2± 40.0 kg km-2). Akan tetapi, perkiraan kepadatan populasi terendah untuk HLSW, yang diperoleh dengan metoda transek garis (2,4±0,4 kelompok km-2 atau 7,9±5,8 individu per km-2, berhubungan dengan biomasa dari 35,1±89,4 kg km-2), yaitu hingga 17% lebih rendah daripada perkiraan kepadatan populasi tertinggi dengan metoda hitung titik tetap dengan radius 0,7 km (2,7±0,1 kelompok km-2 atau 9,5±3,5 individu km-2, setara dengan biomasa 41,0±31,4 kg km-2). Hubungan antara lokasi dan metode sensus menerangkan bagian besar dari variasi kepadatan, daripada metoda sensus itu sendiri. Data ini memberi kesan bahwa kehati-hatian harus diambil pada saat kita menginterpretasikan perkiraan kepadatan dari berbagai daerah yang berbeda yang didapat dari metoda yang berbeda pula.


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INTRODUCTION Gibbons, or lesser apes (genus Hylobates), are widely distributed throughout the Indo-Chinese and Sundaic regions, from Assam and Bangladesh in the north-west, across southern China and Vietnam, through the Thai-Malay peninsula to Sumatra, Java, and Borneo. Apart from the siamang Symphalangus syndactylus, which occurs sympatrically with white-handed gibbon H. lar and agile gibbon H. agilis, in parts of their range, gibbons are largely parapatric with varying degrees of hybridization and reproductive isolation (Gittens & Raemaekers, 1980; Geissmann, 1995). On Borneo two species occur: the agile gibbon and the Bornean gibbon, H. muelleri (see Figure 2.1). The agile gibbon occurs in the southernmost part of Thailand, Peninsular Malaysia, central and south Sumatra, and in the south-western corner of Borneo, between the Kapuas and Barito rivers. The Bornean gibbon is endemic to Borneo and can be found in the remaining part of the island. In the contact zone at the headwaters of the Barito river, an apparently stable, hybrid population occurs (Mather, 1992).

Figure 2.1 Bornean gibbon Hylobates muelleri in Sungai Wain protection forest (photo G.M. Frederiksson).


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Bornean gibbons are completely arboreal and are confined to closed canopy forest in the lowlands and hills up to c. 1500 m a.s.l. (Payne et al., 1985; V. Nijman & E. Meijaard, unpubl. data). The species is largely frugivorous, eating mostly ripe, sugar-rich, juicy fruits (Rodman, 1978, 1988; Leighton, 1987). Bornean gibbons are territorial and live in monogamous family groups consisting typically of an adult pair and up to four offspring. Pairs perform elaborate duet songs that are thought to form and maintain the pair bond and to establish and maintain the territory (Raemaekers & Raemaekers, 1985; Mitani 1984; Leighton, 1987). The population may furthermore contain a number of floating (sub-adult) males and females, who call rarely. Bornean gibbon is classified as Lower Risk (near threatened) according to IUCN threat criteria (Eudey 1996/1997), and the species is protected throughout its range. Although the total area of forest on Borneo is still large compared to other parts of the distribution range of gibbon, every year vast areas are cleared for timber production, transmigration or agriculture and are increasingly lost due to arson (e.g., Rijksen & Meijaard, 1999). Especially lowland forests are directly threatened by these practices due to their accessibility and higher soil fertility than higher altitude forests. Throughout Borneo, accessibility has greatly increased over the last few decades: out-board motors and logging roads make all but the most remote areas accessible for exploitation. Only a small proportion of the lowland forest on Borneo is formally protected as conservation forest (MacKinnon et al., 1996), but especially in the Indonesian part of the island, many conservation areas are protected on paper only (Rijksen & Meijaard, 1999; Meijaard & Nijman, 2000). Numbers of Bornean gibbons are declining overall because of habitat disturbance or habitat alteration, and populations in some areas have been greatly reduced or even eliminated by hunting. Local gibbon populations are easily exterminated by hunting because of the species' loud songs, which attract attention, monogamy, which easily disrupts breeding, and strong sedentary behavior which renders both evasion of hunters and rapid re-colonization of depopulated areas more difficult (Bennett et al., 1987a). Range mapping of all known primate groups in a given area is generally considered to provide the most accurate approximation of true density for rain forest primates (see e.g., NRC, 1981; Skorupa, 1987). However, forest primates are difficult to census accurately. Because of the three-dimensional structure of the South-east Asian evergreen closed canopy forests, where trees can reach heights of 60 m and more, arboreal primates are difficult to locate. Range mapping is, furthermore, time consuming and labor intensive, and only applicable in relative small accessible areas. The technique is furthermore not suitable for rugged or mountainous terrain, where access can only be obtained via ridges. Although range mapping is considered more accurate, the most commonly used technique of estimating primate population density is the (repeated) line transect (NRC, 1981; Whitesides et al., 1988; Buckland et al., 1993). This technique depends on the detection of animals (or sometimes merely animal signs such as nests) on one or both sides of a survey path. Ideally, transects should be placed randomly or through a stratified random technique and should follow a straight line.


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In practice, however, transects often follow geographic features as crests, ridges and spurs (Blouch, 1997) or logging roads (Johns, 1985; Grieser-Johns, 1997). The technique has been employed for survey work (Davies & Payne, 1982; Bennett & Dahaban, 1995; Nijman & van Balen, 1998), comparative studies (Glanz, 1982; Johns & Skorupa, 1987; Yanuar et al., 1995; Johnson & Overdorff, 1999), and for estimation of population parameters in areas where other methods (mark-recapture, complete counts, home range or territory mapping) are not feasible (Green, 1978). Although line transects have been widely used for censusing gibbons (Marsh & Wilson, 1981; Davies & Payne, 1982; Johns, 1985; Haimoff et al., 1986; Bennett & Dahaban, 1995; Blouch 1997), Brockelman & Srikosamatara (1993) considered the technique not particularly suitable for this taxon. Gibbons live in small family groups which makes them difficult to detect and they can behave unpredictably (e.g., flee, hide, approach) when detecting humans. Brockelman & Ali (1987) and Brockelman & Srikosamatara (1993) discussed the possibilities of estimating gibbon densities by fixed point counts making use of gibbon’s great calls. Fixed point counts have the advantage of allowing density estimation over relative large areas in a short time span. A number of studies have been conducted with the specific aim of comparing different census techniques (Green, 1978; Whitesides et al., 1988; Defler & Pintor 1985; Mitani et al., 2000; Fashings & Cords, 2000; Brugiere & Fleury 2000), but few studies were conducted in South-east Asian forest and none involving gibbons have been published. Here we compare three different techniques, namely range mapping, repeat line transects, and fixed point counts, to estimate densities of Bornean gibbon at two lowland primary forest sites. METHODS Study Area Data were collected in the Kayan Mentarang National Park (Taman Nasional Kayan Mentarang [TNKM]) in Oct.-Dec. 1996 and Sungai Wain protection forest (Hutan Lindung Sungai Wain [HLSW]) in Dec. 1999-Feb. 2000. Both field studies lasted ten weeks. Figure 2.2 depicts the location of the study areas. Gazetted in 1980 as a strict nature reserve (cagar alam), Kayan Mentarang became a national park in 1997. With adjacent (proposed) reserves, TNKM totals some 20,000 km2. The study site proper was the Nggeng Bio river valley, in the surroundings of the Lalut Birai field station. The Nggeng Bio river is a tributary of the Bahau river which in this part of TNKM marks the eastern boundary of the reserve. The study area consists of rather steep hills intersected by many small streams, with the study conducted between c. 350 and 750 m a.s.l. The natural vegetation type in the area is lowland dipterocarp rain forest. Despite the existence of many rivers, true riverine terrace forest is rare or even absent. In many areas the riverbanks consist of steep, rocky gorges, with riverine forest only present in the more gently sloping areas. The Nggeng Bio river valley has been a restricted forest


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(tana ulen) of the nearby village of Long Alango for at least the last 75 years. Since hunting, fishing, cultivation, and collection of forest products have been mostly prohibited, the valley is still covered with mature, tall primary forest. Besides gibbons, other primates regularly recorded in the study area are Bornean leaf monkey Presbytis hosei, long-tailed macaque Macaca fascicularis, and pig-tailed macaque M. nemestrina (Nijman, 1997). Figure 2.2 Location of Kayan Mentarang National Park and Sungai Wain protection forest on the island

of Borneo. The squares show the locations of the study sites. Part of the Sungai Wain reserve was gazetted as a closed forest (hutan tutupan) in 1934 by the Sultan of Kutai. Since 1947, the forest received protection as a water catchment area for the oil industry in the Balikpapan region, and in 1983 it was gazetted as a protection forest (hutan lindung). As a research site for the Ministry of Forestry-Tropenbos program, HLSW became an orang-utan Pongo pygmeus, introduction forest in 1992. In HLSW, the study site proper was in the Bugis river valley, in the surroundings of the Camp Djamaludin field station. The area consists of undulating terrain with the study conducted between c. 50 and 127 m a.s.l. HLSW covers a variety of forest types, including fresh water swamp, riverine forest, moist lowland dipterocarp forest, and dry hill dipterocarp forest. In the east it is bordered by some unprotected mangrove forest. The study was conducted in the moist


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lowland dipterocarp forest and dry hill dipterocarp forest, with small parts in riverine forest. At present HLSW is the last remaining area covered with mature undisturbed primary rain forest in the south-eastern coastal region of East Kalimantan. In 1998, forest fires affected some half of the 100 km2 large reserve, but the central core remained untouched (Frederiksson & de Kam, 1999). Other primates regularly recorded in the study area are red leaf monkey Presbytis rubicunda, white-fronted leaf monkey Presbytis frontata, and pig-tailed macaque M. nemestrina. At the time of the study no zoological research had been conducted in TNKM other than a few short reconnaissance surveys (Yeager, 1991; Foead, 1995; van Balen, 1997) and no animals were habituated. In HLSW, some 20 introduced orang-utans were present (G.M. Frederiksson, pers. comm.), one of which was occasionally seen in the study area. No primatological studies have been conducted in the study area and no animals were habituated. In summary, both study sites are covered in tall mature forest, have been effectively protected since the beginning of the last century, no primatological studies have been conducted to date, and none of the primate species were habituated. This makes these areas one of the few in Borneo suitable for the study of primates in undisturbed forests. DATA ACQUISITION AND DATA ANALYSIS Range Mapping In TNKM a number of non-overlapping permanent transects were present; these transects were originally laid out to monitor the phenology of the forest. In HLSW a network of transects is present running north-south and east-west, and spaced some 500 m apart. In both areas, apart from the permanent transects a number of small trails allows access to much of the entire area. All records of primates were plotted on a map. In both study sites, apart from the first author, a number of researchers or field assistants were present, collecting additional data. In this way we collected data on the precise locations and group sizes of gibbons within an area of 3.8 km2 (TNKM; excluding the field station itself and its direct surroundings) and 5.0 km2 (HLSW), disregarding additional area due to slopes. Groups that were occasionally seen, but had more than an estimated three-fourths of their range outside the sample area, were omitted. Density estimates were obtained by dividing the total number of groups or the total number of individuals found by the census areas. Line Transects At both study sites, three transects were selected, which were between two and three kilometers in length. These transects were walked by V. Nijman; in TNKM occasionally a second observer was included. Data were collected in both directions, but always after a stop of at least 45 min, and always during periods of good weather. Since gibbons become less active in the afternoon (Leighton, 1987; V. Nijman, pers. observ.) only censuses that were completed prior to noon were included for analysis. An average walking speed of c. 1.5 km h-1 was maintained. A


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total of 142.5 km (TNKM) and 172.8 km (HLSW) were thus covered before noon. Densities of gibbons were estimated using the effective distance method of Whitesides et al., (1988). The density of groups km-2 is given by: D = n · A-1 = n · (L · 2 · (Ed + 1/2 S))-1 (equation 2.1) where D = density (groups km-2), n = number of groups seen, A = census area (in km2), L = length censused (km), Ed = Effective distance (km, estimated in m), and S = mean group spread (km, estimated in m). The effective distance is defined as the distance on each side of the transect at which the number of sightings at greater perpendicular distances equals the number ‘missed’ at nearer distances (Whitesides et al., 1988). It is determined by using a histogram of perpendicular distances and calculated as (Nt / Nf) · Fd, where Nt = total number of sightings, Nf = the number of sightings below the fall-off distance, and Fd = fall-off distance, defined as the maximum reliable distance beyond which the number of sightings is reduced by 50% or more (Brugiere & Fleury, 2000). The group spread is the diameter of the circle of equivalent area to that occupied, on average, by a group of primates. Group spread proved difficult to estimate and in order not to violate the underlying assumptions of the line transect method (such as deviating from the transect line, remaining at one position for a longer period of time and walking backwards to obtain a better view: Buckland et al., 1993; Krebs 1989), it was considered best to obtain group spread estimates from the range mapping technique. The variance among the means of the three transects was used as a measure of error in order to estimate confidence limits. When the density is known in groups km-2, the density of individuals is then calculated using the mean group size, as observed along the transect lines. For estimation of mean group size, only 'complete counts' (counts that were made when there was confidence that all members of the group had been actually observed) were included. Standard errors of the mean (s.e.) for individual densities were calculated following Raj (1968): s.e.(ID) = GD2 · (s.e.GS) + GS2 · (s.e.GD) + (s.e.GS) · (s.e.GD). (equation 2.2) Where ID = individual density (individuals km-2), GD = group density (groups km-2) and GS = mean group size. Brugiere & Fleury (2000) expressed the need to explore the influence of topography on bias in density estimation when using line transects. Therefore, in order to test for possible biases of censusing along ridges, spurs, and crests only, data from each transect line was converted into an encounter rate (average number of groups encountered within a band of 50 m per km surveyed between 06.00 and 12.00 hrs), and compared with encounter rate for one (HLSW) and two (TNKM) trails following main ridges.


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Fixed Point Counts The density of gibbons was calculated by mapping localities from where gibbons were vocalizing from four (TNKM) and three (HLSW) listening posts mostly positioned at summits or ridges. These listening posts had a hearing angle of at least 240°. The bearing and distance of gibbons singing between 06.00 and 09.00 hrs were plotted on a map (scale 1:25,000 [TNKM] and 1:17,000 [HLSW]). This time window coincided with the time of greatest singing activity in Bornean gibbon in Kutai National Park as reported by Mitani (1984). Mated female Bornean gibbons usually confine their singing behavior to duet song bouts only. The most prominent song contributions of female gibbons consist of a loud stereotyped phrase, the ‘great call’. This great call includes an acceleration type climax with fast bubbling notes. Great calls may be audible further than two kilometers (V. Nijman, pers. observ.). Adult males do not produce great calls, but often produce solo song bouts. During duetting the male and the female combine their song contributions to produce complex but relatively stereotyped vocal interactions (Geissmann, 1995). For surveying, only songs that included a great call were used and it is assumed that this indicates a family group (cf. Leighton, 1987). During calling, gibbons move only limited distances. Songs that map more than c. 500 m apart are considered to be given by separate groups (cf. Brockelman & Ali, 1987). Different groups calling simultaneously are distinguishable if one has knowledge of song organization; those singing at different times can be distinguished with a combination of directional, distance information and occasionally by individual characteristics. Since weather has been found to affect singing frequency in most if not all species of gibbon studied (e.g., Brockelman & Ali, 1987; Brockelman & Srikosamatara, 1993; this study), and since estimating distances is more difficult when it is raining or windy (V. Nijman, pers. observ.), censuses were only conducted during periods of suitable i.e., still and dry, weather. In a given population of gibbons on a given day there are also non-calling groups. The proportion of groups calling on an individual day (p) varies between gibbon species and between populations within gibbon species (Brockelman & Ali, 1987). For three (TNKM) and four (HLSW) groups, situated nearest to the field stations, the proportion of them calling between 06.00 and 09.00 hrs (p6-9) was estimated by remaining within hearing distance of a focal group for a period between five and 14 days. Only song bouts that included great calls produced by the female were included. The fixed point count technique requires knowledge of song organization and is probably suitable for experienced observers only (cf. Brockelman & Srikosamatara, 1993). Therefore, in TNKM, prior to the fixed point counts, a three week training period allowed improvement of distance estimation. In both study sites, during the line transect surveys and during non-census walks, vocal bouts were noted, and their distance and bearing were estimated at different times. Using triangulation from different locations along the transect and with the aid of


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topographic maps it was possible to check the distance estimates and subsequently to improve skills. The census area was obtained by plotting the locations of vocal bouts on a map. From this it was concluded that, taking into account the topography of the area, gibbon song bouts could accurately be recorded within a radius (r) of both 0.7 and 1.0 km. A radius of 1.0 km covers and area twice that of 0.7 km. The density of gibbons was calculated by D = n · p6-9

-1 · A-1 = n · p6-9-1 · (φ · π r2)-1 (equation 2.3)

where D = density (mated pairs km-2), n = the average number of groups heard calling from the listening posts on a given day, p6-9 = proportion of groups calling between 06.00 and 09.00 hrs, A = the census area, φ = the proportion of a circle from where gibbons could be heard (between 240° and 360°), and r = radius from where gibbons could be mapped (either 0.7 or 1.0 km). The variance among the means from the listening stations allowed an estimate of confidence limits. Fixed point counts sensu stricto do not provide information on group sizes, and hence no estimates on the density in number of individuals can be made using this technique. Data on group sizes were obtained by combining all accurate counts of gibbon groups at other times during the study in the wide surroundings of the listening points. Standard errors of the mean for individual densities were calculated following equation (2.2). Biomass Estimates Gibbon biomass was calculated based on group densities for each of the above census techniques. Geissmann (1993) tabulated weights of wild-shot animals of different gibbon taxa on Borneo. Weights of animals from the north-eastern part of Borneo (H. m. funereus) do not differ significantly from those in the south-eastern part (H.m. muelleri) (t-test, n.s.), and data are pooled in order to provide an average weight of Bornean gibbons in east Borneo. An adult female, on average, weighs 5.25 kg (s.e.=0.18, n=16) and an adult male 5.57 kg (s.e.=0.17, n=12); weights for two sub-adult females were 3.29 kg and 4.20 kg, respectively (Geissmann 1993: 347). Neonate weights of Bornean gibbons are some 0.40 kg (Geissmann & Orgeldinger, 1995). Few data are available on weights of the ‘average’ immature, but for calculation of biomass this was, arbitrarily, taken as halfway between birth weight and mature weight, viz., 2.91 kg (cf. T. Geissmann, in litt.). Groups always contained an adult male and an adult female (with a combined weight set at 10.82 kg), and a varying number of immatures (between none to four). Since each group contains an adult pair variation in group sizes reflects the variation in number of immatures in a group, and standard errors of group mass were calculated using the variation in number of immatures multiplied by the average weight of an immature. Standard errors of total biomass were then calculated using standard errors of both group mass and group density following equation (2.2).


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Statistical analysis were performed using Minitap 8.2, and throughout means are reported plus and minus one standard error of the mean (± s.e.). Significance was assumed when p<0.05 in a two-tailed test, although sometimes trends (0.05<p<0.10) are indicated. RESULTS A summary of the results, with estimates of densities and biomass, is presented in Table 2.1. First the results of the individual techniques are presented, after which a comparison is made between the three techniques. Table 2.1 Density and biomass estimates for Bornean gibbon Hylobates muelleri, obtained by three

different census for two areas (A: Taman Nasional Kayan Mentarang [Kayan Mentarang National Park], TNKM and B: Hutan Lindung Sungai Wain [Sungai Wain Protection Forest], HLSW) in East Kalimantan, Indonesia

Site↑

Census technique Census area↑(km2)

Density (groups km-2 ± s.e.)

Group size(ind. ± s.e.)

Density (ind. km-2 ± s.e.)

Group mass (kg ± s.e.)

Biomass (kg km-2 ± s.e.)

A Range mapping↑↑ 3.8 2.4 3.1 (±0.3) 7.4 - 7.6 14.0 (±0.8) 33.7 Line transects 0.46 (8.7) 2.9 (±0.2) 3.4 (±0.2) 9.9 (±3.3) 14.9 (±0.5) 43.2 (±40.0) Fixed point counts

r =0.7 km 5.3 2.4 (±0.1) 3.3 (±0.2) 7.9 (±2.5) 14.6 (±0.5) 35.1 (±32.6)

Fixed point counts r =1.0 km

9.7 2.1 (±0.1) 3.3 (±0.2) 6.9 (±2.2) 14.6 (±0.5) 30.7 (±31.0)

B Range mapping 5.0 2.6 3.5 (±0.3) 9.0 - 9.2 15.2 (±1.0) 39.5 Line transects 0.54 (11.6) 2.4 (±0.4) 3.3 (±0.2) 7.9 (±5.8) 14.6 (±0.7) 35.1 (±89.4) Fixed point counts

r=0.7 km 4.1 2.7 (±0.1) 3.5 (±0.3) 9.5 (±3.5) 15.2 (±0.8) 41.0 (±31.4)

Fixed point counts r=1.0 km

8.4 2.4 (±0.3) 3.5 (±0.3) 8.4 (±5.1) 15.2 (±0.8) 36.4 (±69.5)

↑ For line transects the smaller figure represents the actual census area (defined in equation 1), the

larger figure represents this area multiplied by the number of repeats. ↑↑ No standard error was calculated for a number of entries in the range mapping technique as the

group density estimate did not allow standard errors to be calculated, having its effect on calculation of standard errors for other entries.

Range Mapping TNKM: within the 3.8 km2 area, nine groups were present, totaling 28 individuals (mean group size 3.1±0.3, range 3-6). For three of the nine groups small parts of their ranges might have been outside the boundaries of the study area, whereas two not included groups might have had small parts of their range inside the study area. Once, a single gibbon, presumably a male, was encountered in the center of the study area. It was not observed again, and may have been only temporarily present in the area. The density was 2.4 groups km-2, corresponding with 7.4 individuals


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km-2, or 7.6 individuals km-2 when the single male is included. Biomass was estimated at some 35.8 kg km-2. HLSW: within the 5.0 km2 area, thirteen groups were present, totaling 45 or 46 individuals (one group consisted of three or four individuals) (mean group size 3.5±0.3, range 3-6). Of some seven groups small parts of their ranges might have been outside the boundaries of the study area. Of some four other groups, small parts of their ranges possibly fell inside the study area (subsequently these groups were not included). The density was 2.6 groups km-2 or 9.0-9.2 individuals km-2, corresponding with a biomass of 42.4 kg km-2. Line Transects TNKM: Encounter rates varied between 0.14 and 0.21 groups km-1, and did not differ between directions within transect routes (paired t-test, t=2.0, df=2, p=0.18), nor when one or two observers performed the survey (unpaired t-test, t=0.59, df=29, p=0.56), and thus data were subsequently pooled. Estimates of perpendicular distances did not differ significantly between transects (Kruskall-Wallis one way analysis of variance, p>0.10) and data from all transects were used in order to estimate the effective distance. This was estimated at 26.0 m, and using a mean group spread of 9.0 m (s.e.=0.9, n=14), following equation (2.1) a density of 2.9 groups km-2 (s.e.=0.16, n=3) was reached. The mean group size of gibbons detected along the transect lines from which accurate group counts could be made was 3.4 individuals (s.e.=0.18, n=9). Encounter rates along two ridges in TNKM (0.25 and 0.30 groups km-1) were higher than along any of the transects, approaching significance (mean encounter rate per 15 km: transects vs. ridges equals 27 vs. 41: binomial test, p=0.06). HLSW: Encounter rates varied between 0.08 and 0.20 groups km-1, and did not differ between directions within transect routes (paired t-test, t=3.46, df=2, p=0.07). Data from both directions were therefore pooled. Estimates of perpendicular distances did not differ significantly between transects (Kruskall-Wallis one way analysis of variance, p>0.10) and data from all transects were used in order to estimate the effective distance. Using an effective distance and a group spread of 28.0 m and 11.0 m (s.e.=1.0, n=20), respectively, this gives a density of 2.4 groups km-2 (s.e.=0.4, n=3). Mean group size detected along the transect line was 3.3 (s.e.=0.2, n=15). The encounter rate along one ridge in HLSW (0.30 groups km-1) was significantly higher than along any of the transects (mean encounter rate per 12 km: transects vs. ridges equals 19 vs. 36: binomial test, p<0.05). Fixed Point Counts TNKM: Gibbon songs peaked in the first few hours after dawn and were occasionally heard throughout the day. The proportion of days that female gibbons were calling between 06.00 and 09.00 hrs (p6-9) ranged from 0.75 (one group: nine out of 12 days) to 0.80 (two groups: four out of five days and 12 out of 14 days, respectively). For calculation of densities, each group was given the same weight and p6-9 was set at 0.78. A total of 17 days were spent on listening posts, at least


25

three days per listening post. The census area for r=1.0 equals 9.7 km2. Following equation (3) the density estimates obtained from the four listening posts ranged from 1.9 to 2.5 groups km-2, with an average of 2.1 groups km-2 (s.e.=0.1, n=4). For r=0.7 the census area equaled 5.3 km-2. The corresponding density equaled 2.4 groups km-

2 (s.e.=0.1, n=4). Combining all accurate counts of gibbons groups surrounding the study area, the average group size for Bornean gibbon was estimated to be 3.3 (s.e.=0.1, n=18). HLSW: More than in TNKM, gibbons in HLSW were frequently heard vocalizing prior to dawn, often commencing at c. 04.00 hrs. The average proportion of days that female gibbons were calling between 06.00 and 09.00 hrs was 0.70 (four groups were monitored over seven days). Eleven days were spent at listening posts, at least three days per listening post. The areas surveyed for r=0.7 km and r=1.0 km were 4.1 km2 and 8.4 km2, respectively. Following equation (3) the average density for r=0.7 equaled 2.7 groups km-2 (s.e.=0.1, n=3, range 2.5-2.9) and for r=1.0 it equaled 2.4 groups km-2 (s.e.=0.3, n=3, range 1.8-2.7). Average group size of gibbons in the the study site at large was 3.5 (s.e.=0.28, n=16). Comparisons of techniques For comparisons between techniques and for calculation of technique-site-interactions, densities expressed in groups km-2 were used, as all the other estimates were derived from these. For fixed point counts only the estimates with a radius of 0.7 km were included, as these are probably more accurate (see discussion), and estimates from fixed point counts with a radius of 0.7 km or 1.0 km are not independent. Table 2.2 Two-way Analysis of Variance on density estimates in Bornean gibbon Hylobates muelleri,

with fixed point counts (r=0.7 km) and line transects as techniques and Kayan Mantarang National Park and Hutan Lindung Sungai Wain as sites.

Source Degrees of

freedom Sum of Squares F p

Technique (A) 1 0.012 0.083 0.78 Site (B) 1 0.04 0.273 0.61 A x B 1 0.534 3.647 0.09 Error 9 1.317

In a two-way Analysis of Variance neither method nor site explain a significant proportion of variance in density, while their interaction is approaching significance (Table 2.2). At first sight the type of estimation procedure seems to make little difference to the outcome of the density estimation. However, given that the interaction is approaching significance and because in comparisons sites are often different, this suggests that prudence may be called for as the interaction is more important than methodology within sites. It is illustrative to compare densities obtained by the two techniques as a post-hoc test: for TNKM the difference between


26

techniques is larger than in HLSW (unpaired t-test, t=2.27, df=4 vs. t=0.87, df=2 for TNKM and HLSW respectively). Hence, density estimates vary more in TNKM than in HLSW. This may be related to the larger variation in micro-habitats in TNKM, including a greater altitudinal range than in HLSW. DISCUSSION Density and Biomass The estimates of population parameters obtained in this study are comparable with those reported from various other studies on Bornean gibbons that have been conducted in undisturbed lowland sites (MacKinnon, 1974; Rodman, 1978; Leighton, 1987; Mather, 1992; Bennett & Dahaban, 1995; Yanuar et al., 1995). Group sizes in Bornean gibbon seem to vary little with mean group sizes around 3.0-3.8 individuals (e.g., Leighton, 1987; Rodman, 1978), although habitat fragmentation fragmentation, in the absence of hunting, may lead to larger group sizes and locally larger densities, as offspring are unable to migrate out of their natal forest fragments (Oka et al., 2000). However, there seem to be a few anomalous reports of densities and/or group sizes in Bornean gibbon. First, Bennett (1994) reports a density of 5.3 groups km-2 at Belalong, Temburung district, east Brunei, and comments on the unussual group structure: "normally monogamous, associating in groups of four to five, comprising of an adult male, an adult female and their offspring, at Belalong a high proportion (42%) of the gibbon groups have more than one female". However, Bennett et al., (1987b), also working in Temburung calculated 'normal' densities of 3.3 groups km-2, and did not mention an atypical social structure. Second, Blouch (1997) estimated a density of no less than 10.20 groups km-2 or 31.42 individuals km-2 for south Lanjak Entimau, Sarawak, an estimate at least two times that of any other undisturbed forest area. Similar reports come from the adjacent Betung-Kerihun National Park (J.K. Gurmaya pers. comm. 1998). These estimates may be somewhat biased by the use of ridges and spurs for many of the transects (due to the difficult accessibility of the terrain), but densities in Lanjak-Entimau seem to be really much higher than in other sites where gibbons have been studied to date (R.A. Blouch, in litt. 2000). Like group density estimates, reported biomass estimates of Bornean gibbon seem to vary little among (undisturbed lowland) forest sites (Mather 1992; Suzuki, 1992; Bennett et al., 1987; Rodman, 1988; Davies & Payne 1982). However, comparing biomass estimates directly is complicated by the limited amount of data we have on group mass. In the present study, average group mass ranged from 14.0 to 15.2 kg, largely depending on the average number of immatures in the group. However, Rodman (1988) estimated group mass at 12 kg (mean group size 4.0 individuals; Rodman, 1978), Suzuki (1992) at 14.5 kg (mean group size 3.6 individuals), and Davies & Payne (1982) and Bennett et al., (1987) at 16 kg (mean group size 4.0 individuals).


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Range Mapping Range mapping is methodologically less demanding than either line transect walks or fixed point counts. There are few underlying assumptions, it is possible to deviate from the route to check anything uncertain and it can be done at all times of the day. Gibbons can be located by sight, hearing as well as smell. Range mapping is facilitated by a number of social characteristics of gibbons: groups are relatively stable and cohesive and live in permanent territories, groups are relatively easy to recognize individually by their age and sex composition, and mated pairs sing regularly. Brockelman & Ali (1987) stated that, under favorable weather conditions, an experienced observer can crudely map the ranges of all gibbon groups within an area of 1-2 km2 within a ten day period. Precision of range mapping increases with the number of observers and the length of the study period. However, intense censusing may create too much disturbance and as a result some animals may move out of the study area. We think that within the ten-week study periods all gibbon groups present within the study area were identified at an accuracy sufficient for the aims of the study, while disturbance levels were kept low. In small census areas, the ratio of edge to area increases, so that there is a greater chance of error per unit area in determining whether groups (or individuals) on the edges of the census area are inside or outside the boundary (Sen, 1982; Krebs, 1989). For gibbon studies, Brockelman & Ali (1987) recommended the census area to be at least five times larger than the average home-range size in order to reduce the edge effect. Home-range sizes of Bornean gibbon average 36 ha (range 33-43 ha) (Leighton, 1987). In the present study the census areas were some ten (TNKM) and 14 (HLSW) times larger than the average home range size and at least eight times larger than the largest home-range size reported. Although the study areas were large enough to contain a fair number of groups and in part had sharp boundaries (TNKM: the Bahau river; HLSW: boundary between burned and unburned forest), it is anticipated that the edge effect introduces the largest problem in establishing densities when range mapping. In both study areas groups that had small parts of their ranges outside the boundaries of the study area (and thus were included) were more numerous than those with small parts inside the boundaries (and hence were excluded). This difference may reflect a preference for including a group rather than excluding it. Floating individuals, i.e., mostly sub-adults that have left their natal area, may introduce another problem during range mapping, as a subjective judgement has to be made whether or not to include the animal(s). Floaters were rare in the present study, possibly reflecting difficulties in detecting single individuals that will behave inconspicuously as to avoid detection by resident pairs. However, floating animals may be genuinely rare as successful dispersal is hampered for reasons related to territoriality and monogamy. Floating sub-adults receive severe aggression from mated territorial adults (Tenaza, 1975; Mitani 1988) and undisturbed forests are generally saturated with territories. Few vacancies occur due to the mated status and relatively long life span of adults (Mitani, 1990). Although little is known about the fates of floaters, given the shortage of suitable habitat in a socially hostile


28

environment, it is reasonable to assume that many floating sub-adults soon die after leaving their natal groups (cf. Mitani, 1990). Line Transects While conducting line transect censuses, problems can arise when collecting data on group size and group spread. Gibbons live in groups that are tightly clustered, dispersed over rather small distances (a small group spread), and the chance of detecting all individuals in a group is large. Problems with grouping, as elucidated by Brockelman & Ali (1987), are less apparent in gibbons than in most other primates on Borneo. Their large size, their vocal behavior, and the accessibility of the permanent transects, allowed reasonably accurate counts and distance estimates. In species where groups either are dispersed over distances exceeding the limits of visibility, and where only parts of the group can be observed, or split in sub-groups for example when foraging, sub-groups may be counted as two (or more) independent groups. Gibbons do not split up in sub-groups, and hence the use of mean group size as obtained from ‘complete counts’, as opposed to party size (i.e., the number of animals ranging together in the forest at a certain moment: van Schaik et al., 1983), is unlikely to lead to over-estimation of true densities. For east African forest primates, Plumtre (2000) showed that group spread varies between different times of the day and between months, and recommended that survey techniques that used group spread not to be used. Yet, Fashing & Cords (2000) also working with east African forest primates, concluded that Whiteside et al.'s (1988) method, which incorporates species-specific group spread for estimating transect width (equation 2.1), provide the most accurate density estimates. We feel that variation in group spread in the present study introduced less of a problem compared to Plumtre's (2000) study. Gibbons live in tightly clustered groups, the line transect censuses were conducted in the mornings only, and seasonal variation in group spread in Bornean gibbons is expected to be generally small and unimportant given the short duration of the present study. It has been suggested that for gibbons, since at least some groups escape observation, line transects will tend to systematically under-estimate true densities (Marsh & Wilson, 1981). We are confident that relatively few groups were missed during transect walks as sighting angles >90° (reflecting groups that were initially ‘missed’) were uncommon (TNKM: 4% and HLSW: 6% of groups within the effective sighting distance). Density estimates from line transects in TNKM were just higher than from the other two methods, whereas in HLSW it was in line with estimates from the fixed point count. Hence, there is no indication that the line transect technique systematically under-estimates density. Estimation of sighting distances and/or perpendicular distances inevitably introduces error in calculation of the census area. Mitani et al., (2000) found that inter-observer variability in estimating sighting distances may be high. Since in the present study only one observer estimated perpendicular distances, inter-observer variability is absent, although distances may have been systematically over- or under-estimated. Steep slopes may introduce another problem in estimation of


29

perpendicular distances. Blouch (1997) estimated perpendicular distances assuming that the animals were on a plane with the observer's eye. In hilly terrain this will lead the area censused to be larger than the effective strip width indicates, and will create an over-estimation of true densities. Inaccurate measurement of transect length, which will be more apparent in rugged terrain, and failure to strictly follow the procedures at the beginning and end of the transect may introduce another source of error, albeit a minor one. In the present study a comparison was made between encounter rates at permanent line-transects and trails following ridges. In both areas, encounter rates from the ridges were 25-60% higher than from the transect lines. In hilly areas, gibbons use ridges disproportionately for singing and also spent incommensurate more time on ridges than in valleys (HLSW: V. Nijman, unpubl. data; Whitten, 1982) or along rivers (TNKM: Nijman, 1997). Preference for ridges is more pronounced in the morning than in the afternoon (Whitten, 1982), coinciding with the period most researchers conduct their transect walks. Positioning of transect routes along ridges is therefore not recommended as it introduces a bias and will lead to an over-estimation of true densities. Fixed Point Counts Density estimation by means of fixed point counts was the most time-efficient technique, and covered the largest survey area. The largest source of error is estimation of the distance between the observer and the location from where gibbons are calling. Accuracy decreases with increasing distance (Brockelman & Srikosamatara, 1993) and the error introduced in estimating density increases with increasing distance (Burnham et al., 1993). In the forest, calls can carry as far a two to three kilometers and estimation of distance for calls given at the farther end of the range are inevitably inaccurate (V. Nijman, unpubl. data). More distant groups, when calling simultaneously, can be recorded as one calling group. This may lead to under-estimation of true densities. Again the error arising increases with increasing distance. As air heats up in the morning it becomes harder to locate groups (D.J. Chivers in Duckworth et al., 1995), and thus accuracy of density estimation is greatest in the early morning. Calls carry poorly through vegetation and can best be heard from high vantage points, away from noisy rivers. By censusing in the early hours of the day and by taking the topography of the area into account bearings and distances can be estimated with more accuracy, whereas by limiting the analysis to the nearest calls only, inaccuracies in density estimation can be reduced. Although it is generally assumed that Bornean gibbons become active at dawn (Leighton 1987; Mitani 1984), especially in HLSW gibbons commenced calling often at 04.00 hrs when it was still dark. Estimation of distance at these times was obviously more difficult than during daytime, and like in TNKM, fixed point counts were only conducted between 06.00-09.00 hrs, coinciding with the time of greatest singing activity in gibbons. Censusing at times of low activity will lead to under-estimating densities (Burnham et al., 1993).


30

There are inherent difficulties in calculating the proportion of groups calling on a particular morning. This proportion varies with species, populations, and season (Brockelman & Ali, 1987). Both study sites are situated near the equator and compared to other parts of the gibbon’s range, seasonal variation is relatively small. The studies were furthermore short in duration making it unlikely that seasonal variation in the proportion of groups calling on an individual morning introduced a source of error. Calling frequency can be altered under the influence of various kinds of habitat disruption, such as sounds of chain saws, logging, or hunting (Johns, 1985, 1986; Nijman, 2001). Both HLSW and TNKM are relatively secure from logging and hunting and it is unlikely that during the study periods levels of disturbance increased or decreased. CONCLUSIONS There is considerable variation in density and biomass estimates among the three different census techniques. For group densities, the lowest estimate was 28% (TNKM) and 11% (HLSW) lower than the highest, for individual densities these figures were 30% and 17%, and for biomass 29% and 15%, respectively. In comparing temporal changes of gibbon populations or in comparing habitats with different degrees of disturbance, changes in the order of 10 to 30 % can be quite significant. Methodology did not explain a statistical significant proportion of the variance in density estimation, nor did site. The interaction between site and technique explained the greatest proportion of variation, albeit not significant. Like in many other studies the ‘true density’ in TNKM and HLSW is not known, as for this all individuals in the area should be individually recognizable (most likely only to be achieved by habituation), or some other, probably more intrusive, method should be employed (e.g., collecting, tagging). The different estimates may reflect differences in methodologies, but may also reflect non-homogeneous densities. Although the three techniques were employed in the same general area, the actual area sampled did differ in size and partially in location. For both study areas the smallest area was sampled by the line transects, and this area was completely included in the range mapping area. The largest area was sampled during the fixed point counts. For this method hill tops and ridges were chosen, and since gibbons tend to have a preference for ridges (V. Nijman unpubl. data; Whitten 1982) this may introduce a bias. If gibbons are not distributed evenly, than estimates at different spatial scales are expected to differ. This will be in part related to the differences that exist in crude density, i.e., the density in the study area as a whole, and ecological density, i.e., density in the habitat types actually occupied. The greater variation in micro-habitats present in TNKM and its greater altitudinal range than HLSW may account for the larger variation in density estimates in TNKM. The results of this study indicate that the interaction between site and technique explains the greatest proportion of the recorded variation and that different census techniques employed by the same observer can explain some 10 to 30 per cent of the


31

variation in density and biomass estimates. This result seriously questions the validity of directly comparing estimates obtained by different techniques from different areas often collected by different observers. Yet, this is precisely how comparisons (between densities and any other parameter) are done, viz., relying on data collected by others by a range of techniques over a range of areas. The large inter-observer variability in estimation of sighting distances, as reported by Mitani et al., (2000), clearly adds and subscribes to our viewpoint. ACKNOWLEDGEMENTS Thanks are due to the Indonesian Institute for Sciences (LIPI), the Directorate General for Nature Conservation (PKA formerly PHPA), the Ministry of Forestry and Crop Estates (MOFEC), and the provincial branch of the Forestry Department (SBKSDA) for permission to conduct field work in Indonesia. For information and help of various sort we are grateful to Ir A. Rachmat (SBKSDA, Samarinda), Dr T. Jessup, Dr C. Eghenter and Mr. A. Purmono (WWF-Indonesia), Messrs. D. Lenjau, I. Lawin, I. Njuk, and M. Sudana (WWF-Indonesia, Lalut Birai), Dr R.K. Puri (East-West Center, Hawaii), M. de Kam and S. van Helvoort (MOFEC Tropenbos, Samboja), G.M. Frederiksson (Sungai Wain), Dr D.M. Prawiradilaga (LIPI), Dr P.J.H. van Bree (ZMA, Amsterdam), Dr T. Geissmann (Tierärtzliche Hochschule Hannover), Dr R.A. Blouch (Kerinci Sebelat ICDP-project), Dr J.K. Gurmaya (Padjadjaran University Bandung), and Dr A.Ø. Mooers (Simon Fraser University, Burnaby). Additional financial support was received from the Society for the Advancement of Research in the Tropics, the Netherlands Foundation for International Nature Protection and Stichting Het Kronendak. Dr A.Ø. Mooers, Dr T. Geissmann, and Dr K. Nagelkerke (IBED, Amsterdam) commented on the manuscript


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Effects of Bavioural Changes on Density Estimation of Rain Forest Vertebrates

33

CHAPTER 3

EFFECT OF BEHAVIOURAL CHANGES DUE TO HABITAT DISTURBANCE ON DENSITY ESTIMATION OF RAIN FOREST VERTEBRATES, AS ILLUSTRATED BY GIBBONS (PRIMATES:

HYLOBATIDAE)

Pp 217-225 in: P.J.M. Hillegers and H.H. de Iongh (eds.). (2001).“The balance between biodiversity conservation and sustainable use of tropical rain

forests.” The Tropenbos Foundation, Wageningen, the Netherlands.

ABSTRACT Monitoring programmes often rely on changes in densities of single species to indicate an ecosystem's health. These densities are estimated by a range of census techniques, including line transects and fixed point counts. Using data from gibbons (Primates: Hylobatidae) the present study demonstrates that habitat disturbance (e.g., logging, encroachment) induces changes in the behaviour of species in such a way that it affects density estimation. As a result of disturbance, gibbons alter their response to humans, change their time budgets, and use different canopy levels. Calling rates are generally lowered in response to disturbance and relatively more calls are given at later times of the day. These behavioural changes alter the detectability of gibbons, both positively and negatively. The different factors influencing population estimation act in concert and may be difficult to separate to determine their effect. It is argued that in order to improve the effectiveness of monitoring and censussing, the link between behavioural biology and conservation biology should be strengthened. RINGKASAN Dampak perubahan perilaku yang disebabkan oleh gangguan habitat kepada perkiraan kepadatan populasi vertebrata hutan hujan, dicontohkan dengan owa (Primates: Hylobatidae) (pp 217-225 in: Hillegers P.J.M. & de Iongh H.H. (eds) The balance between biodiversity conservation and sustainable use of tropical rain forests. Tropenbos, Wageningen, 2001): Program-program monitoring seringkali bergantung pada perubahan kepadatan spesies tunggal dalam mengindikasikan suatu kesehatan ekosistem. Kepadatan-kepadatan ini diperkirakan dengan menggunakan metoda-metoda yang berbeda, termasuk metoda garis transek dan hitung titik tetap. Dengan menggunakan data owa (Primata: Hylobatidae) studi saat ini memperlihatkan bahwa gangguan habitat (seperti penebangan, perambahan) menyebabkan perubahan perilaku spesies sehingga mempengaruhi perkiraan kepadatan. Akibat gangguan, owa mengubah responnya terhadap manusia,


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mengubah penggunaan waktunya, dan menggunakan ketinggian kanopi yang berbeda. Rata-rata bersuara secara umum berkurang akibat gangguan dan relatif lebih banyak bersuara lebih siang. Perubahan perilaku ini mempengaruhi kemudahan pencarian owa, baik positif maupun negatif. Faktor-faktor yang berbeda mempengaruhi perkiraan populasi secara bersama-sama dan mungkin sulit untuk dipilah untuk menentukan pengaruhnya. Sedang didiskusikan bahwa untuk mengembangkan kefektifan monitoring dan penghitungan, hubungan antara biologi tingkah laku dan biologi konservasi harus diperkuat. INTRODUCTION Behavioural studies have been considered to be of limited value to conservation because of the discordance in the level of focus between behavioural and conservation biologists. Behavioural research focuses on the level of populations and individuals, whereas many conservation biologists claim that conservation is only effective on higher levels of biological organisation (Clemmons & Buchholz, 1997). Hence, in order to be meaningful, conservation research should focus itself on these higher levels. It may, however, be argued that single species can play an important role in monitoring the health of ecosystems when used as indicators. In order to be useful, indicator(s) should, amongst other things, be amenable, reveal meaningful trends, cost effective to monitor, be consistent, and yield data that are precise and unambiguous in its interpretation (GEC, 1998). Primates may meet some of these demands. They are present throughout the tropics over a large range of habitats, occur often in relatively high densities, and fulfil important roles in their respective ecosystems (Smuts et al., 1987). Hence, primates have been used frequently in monitoring programmes (Glanz, 1982; Brockelman & Ali, 1987; Johns & Skuropa, 1987; Whitesides et al., 1988). The two most commonly used census techniques to estimate primate densities employed in monitoring programmes or studies to quantify the effects of habitat disturbance are based on line transects (Sen, 1982; Whitesides et al., 1988) and to a lesser extent fixed point counts (Brockelman & Ali, 1987; Brockelman & Srikosamatara, 1993). The transect technique depends on the detection of animals (or sometimes merely signs such as nests) on one or both sides of a survey path. It has been employed for survey work, where rapid estimates of populations in inaccessible terrain or in widely different geographic areas are required (e.g., Payne & Davies, 1982; Nijman & van Balen, 1998). It is also used for detailed studies within a limited geographic area, including monitoring of temporal changes in density (Glanz, 1982), for comparisons of habitats within the same general area (Johns & Skuropa, 1987; Blouch, 1997; Johnson & Overdorff, 1999), and for estimation of populations in areas where other methods (mark-recapture, complete counts, home range or territory mapping etc.) are not feasible (Green, 1978; Blouch, 1997). When


35

using the transect method the number of groups detected, the effective sighting distance (an estimate of the distance at which the number of sightings at greater distances equals the number 'missed' at nearer distances) and the group spread (defined as the diameter of a circle of equivalent area to that occupied, on average, by a group of the species under consideration) are parameters needed for estimating densities (Whitesides et al., 1988). For the method to be meaningful, critical assumptions are (i) animals are not affected by the presence of the observer; (ii) groups are always detected on the transect line itself; (iii) groups behave independently. Censuses based on fixed point counts are widely used in ornithological studies (e.g., Reynolds et al., 1980; Bibby et al., 1992a) and are especially suitable in rugged terrain. A similar method has been developed to estimate the density of primates producing loud calls at predictable times of the day, e.g., Indri (Indridae), certain colobines (Colobinae), and gibbons (Hylobatidae) (e.g., Kappeler, 1984; Brockelman & Ali, 1987; Brockelman & Srikosamatara, 1993). This method is based on the number of groups that can be heard calling over a given number of days. The observer is situated at a vantage point and notes the number of groups calling within the census area. This method allows density estimation over relatively large areas in a short time span. In order to calculate densities using fixed point counts, parameters needed include the number of groups calling on a given day, the proportion of groups calling on a given day, and the radius of the area from within songs can be mapped (Brockelman & Srikosamatara, 1993). Critical assumptions include (i) only paired groups call; (ii) groups behave independently; (iii) groups call at least once during the study period. Johns (1985ac; 1986) followed a primate community in Western Malaysia while their habitat was selectively logged. In his study a number of behavioural changes following logging were observed in a number of species, including: (i) lar gibbon Hylobates lar showed a tendency to increase their freezing behaviour and fleeing noisily decreased; (ii) Activity patterns in H. lar and banded leaf monkey Presbytis melalophos changed with a significant increase in time spent resting and a significant decrease in time spent feeding and travelling; (iii) For the same two species there was a significant shift from the upper to the middle canopy level for all types of behaviour combined; (iv) During heavy disturbance, gibbons often ceased calling altogether, and calling rates may have remained depressed for several years after logging had ceased. Similar behavioural changes were found by J. Mitani (in Berenstain et al., 1982) when comparing the singing behaviour of Bornean gibbon H. muelleri in forest prior and after the drought and fire associated with the 1982-1983 El Niño Southern Oscillation Event. Population numbers remained unchanged, but audible ranges of songs decreased, frequency of singing declined, and gibbons sang from lower heights. Since these behavioural changes may be relevant to monitoring and censussing, the present study considers two questions: 1. How and to what extent do primates alter their behaviour in response to human induced changes in their environment (e.g., logging, hunting, encroachment), and 2. Do these behavioural changes affect


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population density estimates when using either the transect method or fixed point counts? The implications may be crucial when comparing the results of surveys in habitats differing in their degree of disturbance and in monitoring programmes where disturbance levels change over time. Whether behavioural changes do affect density estimation will be illustrated with examples from studies on different gibbon taxa from the Sundaic region, but the conclusions and recommendations are most likely to be valid for other regions and for other rain forest vertebrates as well, including other primates, mammals, and birds. In order to address the two questions, a comparison is made between the behaviour of gibbons in disturbed and undisturbed situations and the subsequent implications for monitoring are assessed. The behavioural changes can both affect the parameters needed for density estimation and violate the (critical) assumptions of the methods employed. MATERIAL AND METHODS Gibbons are territorial and live in monogamous family groups consisting of an adult pair with none to four offspring. Gibbons are completely arboreal, and are largely frugivorous. Paired groups give loud morning calls, which can be heard over several kilometres, whereas single individuals rarely call (Leighton, 1987; pers. observ). The present study concerns data collected on Bornean gibbon H. muelleri in East Kalimantan (Kayan Mentarang National Park and adjacent areas in 1996 [115°51E, 2°50’N]) and Javan gibbon H. moloch on Java (Gede-Pangrango National Park and adjacent areas in 1994-1999 [107°00’E, 6°45’S], and Dieng mountains proposed National Park and adjacent areas in 1995-1999 [109°35’E, 7°06’S]). Undisturbed and disturbed study sites were selected either in close proximity and were similar in climate, original vegetation type, altitude and topography (Gede-Pangrango and Kayan Mentarang), or a forest area was sampled before (1995-1998) and during logging (1999) during the same months of the year (Dieng). Given the close proximity and similarity of the forest areas, it is anticipated that the behaviour of the gibbons prior to the commencement of disturbance did not differ significantly. Sets of disturbed and undisturbed areas had mean densities differing less then 10%, which was established by a number of techniques (line-transects, range mapping, fixed point counts). For the present study, disturbance is taken in a rather broad term and may include hunting, encroachment, small scale logging, commercially (selective) logging, or a combination. Behavioural measurements were collected along line transects, on vantage points during fixed point counts, and ad libitum while surveying in the forest. Singing behaviour of at least eleven H. moloch groups was monitored in Dieng for 35 days in Sept-Oct 1998 (pre-logging) and for 25 days in Sept-Oct 1999 (during logging). Some additional data on singing behaviour of siamang Symphalangus syndactylus was collected in Way Kambas National Park, Sumatra (1994 and 1999 [105°36’E, 4°50’S]).


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For all analyses non-parametric statistics were used (Siegel, 1956) and Yates’s correction for continuity was applied in the χ2-tests where appropriate. RESULTS Behavioural changes affecting line transect censusing 1. Responses to observers The most common response of gibbons to the approach of a human is to flee. This can be accompanied by branch shaking and vocalising. Alternative responses include freezing, i.e., remaining immobile, and hiding, i.e., moving out of the field of vision of the approacher. Vocalisations are normally uttered only when the primates detected humans at close proximity. Table 3.1 Behavioural responses of two gibbons species to an observer in disturbed versus undisturbed

habitats. Cases where the gibbons did not detect the observer are excluded. Species Fleeing Fleeing Freezing Hiding Study site with vocalising without vocalising Hylobates muelleri Kayan Mentarang (1) undisturbed 20 10 4 1 disturbed 12 8 4 3 Hylobates moloch Gede-Pangrango (2) undisturbed 12 9 0 0 disturbed 5 5 1 0 Mts Dieng (3) undisturbed 60 32 2 1 disturbed 37 24 2 2 1. Undisturbed forest consisted of primary forest in the Nggeng Bio River valley, whereas disturbed

forest consisted of 45 year old secondary forest which was situated c. five km south-east in the Bua Alat river valley, East Kalimantan.

2. Undisturbed situation consisted of relatively undisturbed forest in Gede-Pangrango National Park, whereas the disturbed situation consisted of adjacent (smaller) forest patches outside the park boundaries.

3. Undisturbed situation consisted of old secondary forest near Linggo, Central Java, in 1998, whereas the disturbed situation consisted of the same forest area in 1999, when a small scale illegal logging operation was in force.

In response to the continued or the increased presence of humans, gibbons alter their behaviour (Table 3.1). Freezing and hiding and silently moving away becomes more common, though none of the differences are significant (χ2, all p>0.05). In all three study areas, and for both species, the response was in the same direction, i.e. gibbons tended to behave in such a way as to reduce the likelihood of being detected. Increase in freezing, hiding and silently moving away, makes it more difficult to locate or detect groups of primates and will lead to a decrease of groups


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detected. It is furthermore likely that group sizes will be under-estimated as it becomes more difficult to detect all individuals in a group. 2. Change in activity patterns Primates are most often detected when engaged in conspicuous activities such as vocalising, travelling or feeding, either due to visual or auditory cues of the animals themselves or their surroundings (moving of branches, falling fruit etc.). They are less easily detected when resting. Since time spent travelling and feeding is lowered in disturbed forests, this means that fewer groups will be detected in disturbed habitats. This will also include groups at the transect line, violating one of the critical assumptions of the method. Considered in isolation, the observed change in activity patterns will lead to an under-estimation of true densities in disturbed habitats. Figure 3.1 Percentage of canopy use by two gibbon species in disturbed and undisturbed habitats 1. undisturbed situation consists of hill forest in the Sungai Tekam, West Malaysia, whereas the

disturbed situation consists of the same area after >50% of the trees were lost due to selective logging (after Johns, 1986)

2. see footnote 3, Table 3.1. 3. Use of canopy levels Gibbons prefer tall trees for certain activities. Emergent trees and the upper canopy are disproportionately used (favored) for singing and travelling (cf. Kappeler, 1984; Johns, 1986). In disturbed forests, due to the loss of many large trees, generally activities have shifted from the upper to the middle canopy (Figure 3.1: H. lar: χ2= 89.4, df=3, p<0.01; H. moloch: χ2= 6.10, df=2, p<0.05, middle and lower canopy pooled). Since detection probability decreases with increasing distance between the


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observer and the animal, primates are more easily detected at lower canopy levels. In general, the shift to lower forest strata will lead to an increase of groups detected. Behavioural changes affecting fixed point counts censusing 1. Calling rates The frequency of calling in gibbons is dependent on, among other things, population density, weather (rain, wind), and seasonality of food production (e.g., Chivers & Raemaekers, 1980; Brockelman & Ali, 1987; V. Nijman, unpubl. data). Disturbance in the form of for instance logging will lead to an increase in ambient temperature in the forest, greater differences in temperature between day and night, and an increase in windiness (e.g., Grieser-Johns, 1997). These changes in the (micro)-climate of the forest can affect calling rates. Contrary to one of the critical assumptions of the fixed point count method, groups do not behave independently. In the present study it was found that songs were stimulated by neighbours (H. moloch and H. muelleri), and sometimes songs seemed to pass round the local population (H. moloch, H. muelleri, and S. syndactylus). Lowered calling activity makes detection less likely, whereas estimation of the proportion of groups calling on a given day becomes more prone to errors. 2. Timing of calls During a study into an undisturbed population of H. moloch, Geissmann & Nijman (2000) noted that some 85% of the female calls and all male calls were given within four hours after sunrise. In disturbed situations, timing of calling changes, with more groups calling later during the day (Table 3.2). As air heats up during the day locating groups becomes more difficult and the estimation of distance between the observer and gibbons becomes more error prone (cf. D.J. Chivers in Duckworth et al., 1995). Lowered precision in locating groups may result in two groups calling from the same general direction being recorded as one, whereas the estimation of the radius at which songs can be mapped becomes more difficult. This in effect can influence density estimation in either a positive or negative direction. Table 3.2 Number of days Hylobates moloch groups were heard calling at different times of the day

(Mts Dieng 1998-1999). Time after sunrise (hrs) Habitat <6 >6 Undisturbed 34 1 Disturbed 19 6 Fisher Exact probability test, p<0.01


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DISCUSSION The data indicate that gibbons (and probably other primates as well) do respond differently to the presence of humans, including surveyors, in disturbed habitats than in undisturbed habitats (cf. Johns, 1985a; 1986). In the present study, hunting levels were generally low, but high hunting pressure can alter the behaviour of primates to an even greater extend (Kavanagh, 1980; Watanabe, 1981). When conducting line transects, fewer groups will be detected in disturbed habitats as gibbons show an increase in freezing, hiding, and silently moving away. A decrease in conspicuous activities such as vocalising, travelling and eating, as reported by Johns (1985a; 1986), should lead to a decrease in number of groups observed, and may violate the assumption that all groups are detected on the transect line. Only if the decrease in number of groups is unequal for groups on the transect line and groups located farther away, in such a way that groups on the transect line are still always recorded, a decrease in groups detected will not necessary result in a reduction of estimated density (Skorupa, 1987). However, as there is no indication whatsoever that the number of groups detected on the transect line itself will not have decreased, one of the critical assumption of the line transect method is violated. This will lead to an under-estimation of true densities. Under-estimation of true densities will be even stronger when indeed actual group sizes are under-estimated owing to the increased difficulty in counting individuals. However, not all behavioural changes by gibbons will lead to an under-estimation of true densities, since the marked increase in the use of the lower to middle canopy over the upper canopy in disturbed habitats makes it easier for an observer to detect gibbons. Calling frequency in gibbons is dependent on a number of environmental variables, including population density, weather, temperature in the forest, and seasonality of food production (Chivers, 1974; Kappeler, 1984; Brockelman & Srikosamatara 1993; V. Nijman unpubl. data), which all might be affected by habitat disturbance. Logging will induce changes in the micro-climate of the forest including an increase in ambient temperature, greater differences in temperature between day and night, and an increase in windiness (e.g., Grieser-Johns, 1997). Habitat disturbance may also alter the acoustical environment on which organisms rely for communication (Clemmons & Buchholz, 1997). Increase in windiness will lead to a significant decrease in calling (H. pileatus: Brockelman & Srikosamatara, 1993), and changes in the ambient temperature may affect pre-dawn calling by males in two species (H. klossi and H. moloch), as pre-dawn calling in male Kloss' gibbons is positively related to temperature (Whitten, 1982c). Contrary to one of the critical assumptions of the fixed point count method, groups do not behave independently. Songs were stimulated by neighbours (cf. H. lar, Raemaekers & Raemaekers, 1985b), and songs seemed to pass round the local population as has been reported in other studies (Brockelman & Ali, 1987). Fixed point counts are furthermore affected by a depression of calling rates during the day, and possibly by an increase in pre-dawn calling. Lower calling rates make detection


41

less likely, and calls given later during the day makes distance estimation more difficult. Similar to the studies conducted by Johns (1985ac; 1986) and J. Mitani (in Berenstain et al., 1986), the present study compared the behaviour of primates in areas where the true density was either very similar or had remained virtually the same. Effects of a lowered (or increased) density were not taken into consideration. Habitat disturbance often has an effect on density, due to a lowered carrying capacity of the forest, lowered fecundity, higher mortality (aggravated by an increase in hunting), and sometimes due to groups migrating out or into an area. Lowered densities will introduce additional changes in the parameters needed for density estimation, including smaller group spread for smaller groups, smaller effective sighting distance due to reduced group sizes (e.g., van Schaik et al., 1983; V. Nijman unpubl. data), and a disproportionate reduction of calling rates (V. Nijman, unpubl. data). Alternatively, locally habitat disturbance may lead to larger group sizes and higher densities. In degraded forest with a discontinues canopy the obligate arboreal nature of many primates, and gibbons in particular, does not permit them to move from one remnant forest patch to another. This induces delayed dispersal of sub-adults, leading to larger group sizes and (temporarily) higher densities (e.g., Brockelmann et al., 1998; Oka et al., 2000). Comparing census data from habitats differing in degree of disturbance should be viewed with caution and conclusions should be drawn with care. The mere observation that certain animals are more/less often recorded in these different habitats in itself carries little information. Hence, comparisons of abundances of vertebrates in disturbed and undisturbed situations based on encounter rates only, as done extensively for example by Grieser-Johns (1997) when reviewing the responses of vertebrates in relation to timber production and biodiversity conservation in tropical rain forests, becomes in effect meaningless. CONCLUSION Habitat disturbance clearly alters the behaviour of gibbons, and probably many other vertebrates, in such a way that it affects density estimation. Behavioural alterations may be species specific, but may also be related to the types of disturbance, such as the presence or absence of hunting/capturing. Different factors influencing population size estimation act in concert, and may be very difficult to separate to determine their net effect. When comparing census data from habitats differing in their degree of disturbance, the effect of behavioural alterations should be recognised and conclusions drawn with care. It is concluded that there is an increased need for understanding the behavioural plasticity of indicator species, and behavioural studies should play a more prominent role in conservation. Strengthening the link between studies in behavioural biology and conservation biology is needed for improved monitoring and censusing (cf. Beissinger, 1997; Clemmons & Buchholz, 1997).


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ACKNOWLEDGEMENTS I wish to thank the Indonesian Institute of Sciences (LIPI), the Directorate General for Forest Protection and Conservation (PKA) and the Ministry of Forestry and Estate Crops (MOFEC) for allowing me to conduct this research. In this, the help of the Museum Zoologi Bogor, and especially Dr D.M. Prawiradilaga is kindly acknowledged. Financial support for the study came from the Netherlands Foundation for International Nature Protection (Van Tienhoven Stichting), Society for the Advancement of Research in the Tropics (Treub Maatschappij), and Stichting het Kronendak. Dr H. Albrecht (formerly Dept. of Animal Behaviour, University of Amsterdam) was instrumental in offering insight into the links between ethology and primate conservation. Dr P.J.H. van Bree (Zoological Museum Amsterdam) is thanked for his help throughout the project. Prof. Dr S.B.J. Menken and Dr A.Ø Mooers (ISP /ZMA, University of Amsterdam) gave valuable comments on a draft of this paper.

Calling Behaviour of Wild Javan Gibbons in Java, Indonesia

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CHAPTER 4

CALLING BEHAVIOUR OF WILD JAVAN GIBBONS HYLOBATES MOLOCH IN JAVA, INDONESIA

with Thomas Geissmann

ABSTRACT The Javan gibbon Hylobates moloch is endemic to the island of Java, Indonesia. As hardly any behavioural data are available for this endangered primate, we studied the singing behaviour of the easternmost population of this species in the Dieng mountains, Central Java, Indonesia in 1998-1999. The aim was to document the timing of singing, to quantify the amount of singing by the respective sexes and to explore the role of bio-acoustics for density estimation. We recorded location and sex of the singer, and starting and ending time of all song bouts we heard. We heard a total of 122 song bouts of at least 12 groups. Most groups could be identified by individual-specific song characteristics. No duet songs were heard. Most of the song bouts (91.5%) were female solo song bouts or female scream bouts. Pure female solo song bouts with one participant are significantly shorter in duration than female song bouts with two participants of the same group (median duration of 6 and 9 min, respectively). In contrast to earlier studies on the westernmost population of Javan gibbon, in which few if any male songs were heard, at least 8.5% of the song bouts in our study were male solo song bouts. Male songs are significantly longer in duration than female songs (median duration of 12 and 7 min, respectively). All male song bouts uttered before dawn (05:20 hrs) were produced in a chorus fashion, with at least three individuals participating. Choruses occur about once every 8.5 days and all lasted longer than the longest female solo song bout (range 42 min - 1h 47 min). Male choruses and female solo song bouts appear to be temporally segregated events: Most male songs (60%) started between 03:55-04:40 hrs, when it was still dark. All female songs, in contrast, started after 05:00 hrs and female singing activity peaked around 06:00. Neither regular male singing, nor male chorusing, nor regular pre-dawn singing, have previously been reported for Javan gibbons. Similarly separated periods of male and female solo songs and the absence of duetting are known from Kloss gibbons (H. klossii) on the Mentawai Islands and may represent a synapomorphy shared by H. moloch and H. klossii. The individual-specific song characteristics of Javan gibbons allow accurate mapping of groups. The density of gibbons at our study site was established as such at 1.9-3.7 groups per km2 corresponding with 6.7-13.1 individuals per km2. We reassess the suitability of gibbon songs as a means for estimating density and size of gibbon populations.


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RINGKASAN Perilaku bersuara Owa Jawa Hylobatus moloch liar di Jawa, Indonesia (bersama Thomas Geissmann): Owa Jawa Hylobatus moloch merupakan jenis endemik Pulau Jawa, Indonesia. Berhubung sangat sedikitnya data tingkah laku primata terancam ini, kami mempelajari perilaku bernyanyi populasi bagian paling timur spesies ini di Pegunungan Dieng, Jawa Tengah pada tahun 1998-1999. Kami bertujuan untuk mendokumentasikan waktu bernyanyi, untuk mengetahui jumlah nyanyian oleh masing-masing jenis kelamin dan untuk mengetahui peranan bio-akustik untuk perkiraan kepadatan. Kami mencatat lokasi dan jenis kelamin yang bersuara, dan awal dan akhir waktu bersuara yang kami dengar. Kami mendengar 122 suara panggilan dari sektidaknya 12 kelompok. Kebanyakan kelompok dapat diidentifikasi dari karakteristik suara individu yang spesifik. Tidak ada suara duet yang terdengar. Kebanyakan suara panggilan (91,5%) yaitu suara panggilan betina atau suara teriakan betina. Suara panggilan betina yang murni tunggal dengan satu anggota memilliki jangka waktu yang lebih pendek daripada suara panggilan betina dengan dua anggota di dalam kelompok yang sama (masing-masing rata-rata lama bersuara 6 dan 9 menit).Berlawanan dengan studi-studi lebih awal pada Owa Jawa populasi bagian paling barat, di mana sangat sedikit suara jantan terdengar jikapun ada, setidaknya 8,5% panggilan di daerah penelitian kami adalah suara panggilan jantan. Suara panggilan jantan secara signifikan lebih panjang durasinya dibanding suara panggilan betina (rata-rata masing-masing 12 dan 7 menit). Semua panggilan jantan yang bersuara sebelum fajar (jam 05:20) dihasilkan dalam bentuk bersahutan (chorus), dengan setidaknya tiga individu ikut terlibat. Sahutan terjadi kira-kira sekali setiap 8,5 hari dan semua bertahan lebih lama daripada suara panggilan tunggal betina terpanjang (rata-rata 42 menit- 1 jam 47 menit). Sahutan jantan dan suara panggilan betina tunggal secara temporal terjadi pada waktu terpisah: Suara jantan terbanyak (60%) dimulai antara jam 03:55-04:40, saat hari masih gelap. Sebaliknya, semua nyanyian betina dimulai setelah jam 05:00 dan puncak aktivitas bersuara betina sekitar pukul 06:00. Tidak ada nyanyian jantan tetap, atau sahutan jantan, atau nyanyian tetap sebelum fajar, yang telah dilaporkan sebelumnya untuk Owa Jawa. Periode bersuara tunggal antara jantan dan betina yang terpisah ini, serta tidak adanya duet juga dikenal dari Siamang Kerdil (H. klosii) di Kepulauan Mentawai dan mungkin mewakili synapomorfi antara H. moloch dan H. klosii. Karakteristik suara individu khusus Owa Jawa memungkinkan pemetaan kelompok-kelompok yang akurat. Kepadatan owa-owa di tempat penelitian kami begitu ditetapkan sebesar 1,9-3,7 kelompok per km2 setara dengan 6,7-13,1 individu per km2. Kami menetapkan kembali kesesuaian suara owa sebagai alat untuk memperkirakan kepadatan dan ukuran populasi owa.


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INTRODUCTION All gibbon species are known to produce loud, long and well patterned songs. Typically, songs are produced early in the morning. In mated pairs, male and female song contributions are sex-specific. In virtually all species, mated males spend at least as much time singing as mated females (e.g., Gittins, 1984ab; Haimoff, 1985; Raemaekers et al., 1984; Whitten, 1984). The following song patterns occur among gibbon species (Geissmann, 1993, 1995, and unpublished data; nomenclature and classification follow Geissmann, 1994, 1995, in press): (1.) Duet song bouts only (six species: all species of the genera Bunopithecus, Nomascus and Symphalangus); (2.) duets and male solo songs (four species: Hylobates agilis, H. lar, H. muelleri and H. pileatus); (3.) female solo songs and male solo songs (two species: H. klossii and H. moloch). Gibbon songs probably have several functions. These may include spacing among groups, defence of resources (such as territories, food sources or mates), mate attraction, strengthening of the pair bond and / or advertisement of the pair bond (Cowlishaw, 1992; Geissmann, 1999; Leighton, 1987; Mitani, 1984, 1985ab, 1987; Raemaekers & Raemaekers, 1985ab). The Javan gibbon is endemic to the western half of Java, Indonesia. Most populations can be found in the western province (Asquith et al., 1995; Kappeler, 1984b), but a few populations remain in the Central Javan province (Nijman, 1995). The most recent population estimates based on extrapolation of the available habitat, range from 2,000 animals (Supriatna et al., 1994) to 3,000 animals (Asquith et al., 1995); however, both studies did not take into account the Central Javan populations. The species has lost some 96-98% of its habitat (MacKinnon, 1984, 1987) and has merited the highest conservation priority rating for Asian primates (Eudey, 1987ab). The Javan gibbon is included in the Critically Endangered category according to the IUCN threat criteria (IUCN Species Survival Commission, 1996; Eudey, 1997), is protected by Indonesian law, and is listed on Appendix I of the CITES convention. So far the only comprehensive study on the behavioural ecology, including calling behaviour, of wild Javan gibbons has been conducted by Kappeler in 1975-1976 and 1978 (Kappeler 1981, 1984abc). Because males of the resident groups in his study area, Ujung Kulon, West Java [6°45'S, 105°20'E, see Fig. 4.1], did not sing, he concluded that territorial male gibbons do not sing. Two other short studies conducted in other parts of Ujung Kulon provide some data on calling behaviour but do not specify the sex of the calling animals (Gurmaya et al., 1995; Rinaldi, 1999). Considering the Javan gibbon's threatened status and the small amount of detailed information available on its behavioural ecology, all of which was collected on the westernmost population in Ujung Kulon, we set out to collect data on the species' calling behaviour in the opposite end of its distribution area, i.e. the Dieng mountains in Central Java (Fig. 8.1).


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The aim of the present study is threefold: (i) to provide an accurate description of male and female singing behaviour, (ii) to document the timing of Javan gibbon songs, (iii) to quantify the amount of singing of the respective sexes and of individual gibbons. In addition, (iv) we compare our results with those from previous studies from Ujung Kulon, (v) we discuss our findings in relation to current knowledge on gibbon phylogeny and (vi) we explore the role of bioacoustics in conservation monitoring studies of gibbons (in particular for density estimation). Figure 4.1 Map of Java showing the remaining forest areas inhabited by gibbons. Ujung Kulon is the

westernmost population and Dieng the easternmost. (gibbon distribution after Asquith et al., 1995; Kappeler, 1984a; Nijman, 1995; and Nijman, unpubl. data).

MATERIAL AND METHODS Study area and data acquisition The Dieng mountains harbour the largest population of Javan gibbons in Central Java, which is estimated at >500 individuals (Nijman & van Balen, 1998). Despite Central Java being largely deforested, the Dieng mountains are still extensively covered with forest ranging from about 300 m a.s.l. in the area north of Linggo to 2565 m a.s.l. at Mt. Prahu. The vegetation of the Dieng mountains is of the wettest type, and, roughly below 1,000 m, consists of mixed lowland and hill rain forest, and, up to about 2,400 m, consists of montane everwet rain forest (for a more complete description of the study area see Nijman & van Balen, 1998, chapter 8). The study area proper was at the Linggo Asri resort [7°06'S, 109°35'E], near the village of Linggo in the western part of the Dieng mountains, Central Java. The area is covered in a patchwork of old secondary forest mixed with more primary forest, and cultivated land. Its altitudinal range is between c. 450 and 650 m a.s.l. The climate is perhumid with daily maximum temperatures ranging between 27-


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31°C and an annual rainfall of about 6,000-7,000 mm. Only during the months July-Sept, less rainfall is recorded, but the monthly average remains above 100 mm (climatic data from the weather stations of Sumigih and Pagilaran, RePPProT, 1990). We monitored gibbon singing activity around Linggo Asri on a daily basis during 19 consecutive days from 23 Sept-11 Oct 1998. During the first 11 days, gibbon singing activity was monitored from predawn to dusk, the remaining 8 days covered the predawn-dawn period only (i.e. from about 1.5 h prior to dawn to 0.5 h after dawn). Subsequently, male pre-dawn singing was monitored again for an additional 15 days over the period 31 July - 25 Aug 1999. Dawn was defined as the time that colour was first discernible in the forest canopy (Gittins, 1984a), and occurred around 05:20 hrs local time. Sunrise was determined by the time the sun was first seen at the study site and occurred around 06:15 hrs. During each observation period, we recorded location and sex of the singer, as well as starting and ending time (to the next minute) of all song bouts heard. The density of gibbons was estimated by mapping of localities from where gibbons were vocalising, as detectable from one single listening post, as described by Brockelman & Ali (1987). From this fixed point count, density estimates were calculated using the following equation: D = n / (p · A) = n / (p · φ · πr2), (equation 4.1) where D is density (mated pairs per square kilometre); n is the average number of different groups heard calling per day, as determined over a ten day period; p is the estimated proportion of days on which gibbons sing, as established by monitoring the complete song output of two individually recognisable groups (AS-9 and AS-2); φ is the section of a circle from which gibbons could be heard; r is the radius from within which gibbons could be heard. We made a calculation for a smaller area, within which all groups could be identified by their song (r = 1.0-1.4 km; φ is 135°), and for a larger area, which also included unknown groups within hearing distance (r = 1.4-1.8 km; φ is 180°). Because more forest was intact in the larger area, the section of the circle from which gibbons could be heard is broader here. In addition to field work, songs of captive Javan gibbons were studied at the following zoos: Berlin Zoo and Munich Zoo (Germany); Jakarta Zoo and Taman Safari, Cisarua (Indonesia); Howletts Zoo and Paington Zoo (United Kingdom). The method of data collection was the same as that described above for wild Javan gibbons. Bioacoustic methods and definitions of bioacoustic terms All tape-recordings were made with a Sony TC-D5M tape-recorder equipped with a Sennheiser ME80 (+K3U) directional microphone or a Sony WM-D6C tape-recorder equipped with a JVC directional microphone.


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Sonagrams of song sequences were made with Canary 1.2.4 software (Charif et al., 1995) on an Apple personal computer (PowerMacintosh). Recording parameters: 11 kHz sampling rate, 16 bit sampling. Analysis parameters: FFT, Hamming analysis window; analysis resolution: 43.7 Hz filter bandwidth, 1024 points frame length; grid resolution: 23.1 ms time, 75% overlap, 5.4 Hz frequency resolution, 2048 points FFT size. Duration and frequency measurements of vocalisations were also carried out using Canary 1.2.4 software. The acoustic terminology largely follows that proposed by Haimoff (1984). A song is what fulfils the criteria set forth by Thorpe (1961, p. 15): "What is usually understood by the term song is a series of notes, generally of more than one type, uttered in succession and so related as to form a recognisable sequence or pattern in time", or, a song is a succession of phrases with non-random succession probability ("Strophenfolgen mit nicht-zufälliger Folgewahrscheinlichkeit", Tembrock, 1977, p. 33). Song bouts are separated from each other by an arbitrarily defined interval of >5 min. A duet occurs when one individual coordinates its vocalisations in time or type of vocalisation with those of another individual (Seibt & Wickler, 1982; Wickler, 1974), and a duet song is a song jointly uttered by two individuals and coordinated in time or phrases. Gibbon song bouts consist of phrases; phrases consist of notes. A phrase does identify a single vocal activity consisting of a succession of notes which are produced together in a characteristic manner, but which also may be produced independently. A note is any single continuous sound of any distinct frequency or frequency modulation, which may be produced during either inhalation or exhalation. Great calls are the most stereotyped and most easily identifiable phrases of gibbon song bouts and are produced by females of all gibbon species. Another characteristic phrase in many gibbon songs is the male's coda, a phrase which is produced at or near the end of the female's great call. A chorus is defined as the temporal overlap of song bouts of several individuals during a continuous time period which normally exceeds the duration of any single participant's song bout (Tenaza, 1976: p. 43). RESULTS Description of female song bouts Females typically produce two types of vocalisations during their song bouts: (1) simple wa notes or phrases of wa notes, and (2) great calls or aborted great calls. A female song bout is usually introduced by a variable but simple series of notes termed the introductory sequence. It consists of single wa notes uttered at irregular intervals and series of wa notes. Thereafter, great calls are produced with an interval of about 1-2 min. Between great calls, females usually produce so-called interlude sequences. Similar to the introductory sequence, the interlude sequences consist of single wa notes uttered at irregular intervals and variable series of wa notes. Series


49

which are separated from other notes by an interval of at least 5 seconds are termed "female short phrases". Figure 4.2 Sonagrams of representative phrases of female songs (a-c), female scream calls (d),

communal group calls (e), and male phrases (f-i), tape-recorded from captive and wild Javan gibbons. (a) female wa notes and great call from Ujung Kulon, West Java; (b) female wa notes and great call from Pelabuhanratu, West Java; (c) female wa notes and great call from Linggo Asri, Central Java; (d) screams and wa notes of two neighbouring females at the common territorial border in Linggo Asri, Central Java; (e) communal wa phrases of family group (ad. pair and juvenile) at Berlin Zoo, Germany; (f) male phrases from Gunung Lawet, Central Java; (g) male phrases "Omar" from Howletts Zoo (United Kingdom); (h) male phrases "Hilo" from Howletts Zoo (United Kingdom); (i) male phrases ("Paul") from Munich Zoo, Germany.


50

Female great calls (Fig. 4.2a-c) are announced by a particularly regularly paced series of wa's. The great call itself consists of 8-22 notes and often begins with a special inflected note, followed by one or several long notes of slowly increasing frequency. Through a steady shortening of both note duration and intervals, the great call develops into a series of accelerated wa notes building up to a trill-like climax, after which the speed of note delivery becomes slower again at the end of the great call (Geissmann, 1993, 1995). As already noted by Kappeler (1981, 1984c), great calls are not only highly stereotypic, but often exhibit distinct individual characteristics. Among the females of our study site, one individual (AS1) had a particularly short pretrill phase, another female (AS3) produced a particularly long trill, and another one (AS9) produced the transition between note 2 and 3 at lowered intensity. In some groups, two animals can be heard to produce synchronised great calls. Because adult males are not known to sing great calls, it has been assumed that synchronised great calls are produced by sub-adult daughters singing along with their mothers (Kappeler, 1981, 1984c). Observations on captive gibbons revealed, however, that immature gibbons of either sex may accompany their mother during great calls (Geissmann, unpublished data). Females of neighbouring groups appeared to avoid singing at the same time. Ongoing songs were often stopped as soon as a second group started to sing. Occasionally, two neighbouring groups were heard singing at the same time (e.g., AS1 and AS2), in which case the females produced their great calls in alternation. Females of Kappeler's study typically exhibited a locomotor display during the climax of their great calls ("each great call is accompanied by a burst of locomotion within the crown of the tree", Kappeler, 1984c: p. 381). This did not occur during the great calls we observed. Description of scream bouts Scream bouts mainly consist of screams and wa notes (Fig. 4.2d). Scream notes begin like wa notes with rapidly increasing frequency, but have a more complex drawn-out ending of less steeply increasing frequency ("wa-ee") or of several short frequency modulations. Scream bouts tend to last longer than female song bouts. We heard one female which, at variable intervals ranging from 1-12 min, produced scream bursts and wa notes during 41 min, but no great calls. Like female song bouts, scream bouts may occasionally be interrupted by great call phrases, but these appear to occur in longer and less regular intervals than in female song bouts. One scream bout had a duration of 18 min, but no great calls occurred during the first 12 min and only 3 great calls were produced during the whole bout. Another scream bout with a duration of 11 min included only one great call after 9 min. In some, but not all scream bouts, several group members were heard participating in the scream bursts. They became silent when a female sang her great call. Scream bouts appear to be common during group encounters and often included several groups vocalising near each other. A particularly spectacular one occurred during a meeting between groups AS1, AS2 and AS9, which resulted in a


51

continued exchange of scream bouts during 69 min. No individual was calling continuously during the entire exchange period, and each group resumed calling at least twice. Scream bouts, as described in the present study, appear to correspond to what has previously been described as "border conflicts between groups" (Kappeler, 1984c). According to Kappeler, all group members participate in producing the bursts of screams. Although males may have participated in some scream bouts several scream bouts that included only a single individual (the adult female) were recorded, suggesting that a participation of the male in scream bouts may not be the rule. A third category of loud calls was described by Kappeler (1984c) as "harassing call bouts" emitted as a response to potential ground predators. According to Kappeler's description, "harassing call bouts" consist of "loud screams emitted by all group members mixed with bursts of agitated movement." Although we did not observe anything fitting this description during our short study, we were not always close enough to the calling gibbons to tell whether agitated movement occurred during screaming or not. Therefore, our scream bouts may also include some "harassing call bouts". While the structure of scream bouts often differs from that of female song bouts, any attempt to exclude these from the following analysis would be subjective. A female song bout may become a scream bout if the females are upset during the course of the bout, and likewise a scream bout may normalise to a female song bout as the gibbons calm down. A similar observation has previously been made by Raemaekers et al. (1984: p. 179) on the distinction between normal duet song bouts and disturbed call bouts in white-handed gibbons (H. lar). There may be additional categories of call bouts produced by Javan gibbons. A bout consisting of communal bursts of wa notes produced by all group members (Fig. 4.2e) was heard once in captivity and once in Dieng. The reasons for the occurrence of this type of calling is unknown. These call bouts also included great calls at more or less regular intervals. The other group members immediately became silent each time the female sang a great call. After having tape-recorded such an unusual call bout from a family group of three individuals at the Berlin Zoo (Germany), it was played back to the same group on the following morning. The whole group immediately responded by inserting bursts of wa notes in synchrony with those on the tape. Each burst on the tape immediately triggered an identical one from the group, until the recorded song ended. Description of male song bouts Male phrases consist of simple hoots ("wa") and various more complex hoots. Among the latter, longer hoots with one or two frequency inflections ("wa-oo", "wa-oo-wa") are particularly prominent for this species (Fig. 4.2f-i). Some males regularly produce bi-phasic hoots (i.e. a wa note followed by an inhalation note, but softer than those of H. agilis). Only few males were heard to include short trills in their phrases.


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Male phrases are extremely variable. Even simple hoots in males phrases are rarely simple repetitions of identical notes, but often show a broad variability in frequency range and speed in frequency change. Whereas males in many gibbon species produce well patterned phrases (for instance H. klossii and all species of the genus Nomascus, pers. observation TG), male Javan gibbons were often heard singing with highly variable phrase patterns and sometimes would sing for minutes without distinct pauses which would have been helpful to recognise the beginning of a new phrases. Like males of other gibbon species (Geissmann, 1993, 1995), Javan gibbon males gradually build up their phrases, beginning with single, simple notes, uttered with long intervals. As less simple notes are introduced, these notes are combined to increasingly complex phrases, reaching the fully developed form only after several minutes of singing. Male solo song bouts of Javan gibbons usually start with short and soft hoots which resemble the "disturbance hoots" which are occasionally uttered upon detecting the observer. Although disturbance hoots need not develop into a male song, at least one male song during our study was produced after we met up with a group and after several minutes of disturbance hooting by the group's male. The excerpts of male solo songs shown in Figure 4.2f-i show distinct differences among each other. These appear to result from individual-specific song characteristics. Because each male was heard only few times, however, it is difficult to determine whether context-specific differences (i.e. different types of male song) also exist. It was our impression that male songs were less loud (and probably carried less far) than female songs. Timing of male and female songs During 11 consecutive days in Sept-Oct 1998, we heard a total of 122 song bouts and scream bouts of at least 12 groups. Most groups could be identified by individual-specific song characteristics. Most of the song bouts (n = 107) were female solo songs, but we also heard at least 10 male solo song bouts. Only 5 songs were to short or too far away too be reliably sexed. No duet songs were heard. Males phrases were heard neither as a response (coda) to female great call phrases, nor between female great calls nor during other female short phrases (see above). Individual females sang on most days and mostly once. Occasionally they sang twice a day and rarely three times or not at all. The average number of songs per day for the two closely monitored groups AS9 and AS2 was 1.2 (s.d. = 0.83; n = 9) and 1.2 (s.d. = 0.63; n = 10), respectively. All female songs in the Dieng mountains started after 05:00 hrs, and female singing activity peaked around 06:00 hrs (Fig. 4.3). Compared to Ujung Kulon, females in the Dieng mountains appear to sing slightly earlier (peak singing activity at c. 06:00 hrs vs. c. 06:30 hrs), and calling is spread out more equally over the morning. Starting times of all gibbon songs in Ujung Kulon differs between studies, with those of Gurmaya et al. (1995), having mean starting times peaking as late as c. 09:00 hrs.


53

0

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g bo

uts,

%

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a

Time of day, hours

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11 12 13 14 15 169 1084 65 7 17 18 193

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6011 12 13 14 15 169 1084 65 7 17 18 193

Figure 4.3 Frequency distribution of the starting time of gibbon song bouts on Java. (a) females in Ujung Kulon (n = 392 song bouts, Kappeler, 1984c); (b) gibbons of unspecified sex in Ujung Kulon (n = 114, Gurmaya et al., 1995); (c) gibbons of unspecified sex in Ujung Kulon (n = 49, Rinaldi, 1999); (d) females in Linggo Asri (n = 107, this study); (e) males in Linggo Asri (n = 20, this study). Dotted line: dawn (not available for Ujung Kulon), dashed line: sunrise. Sunrise in Linggo was determined by the time the sun was first seen at the study site, and hence time of sunrise may differ between mountainous areas and flat plains even if situated at the same longitude. Kappeler (1981, 1984c) provides the time of sunrise for his study site and determined it like we did (Kappeler, pers. comm. to TG). Gurmaya et al. (1995) and Rinaldi (1999) do not explicitly mention time of sunrise, but we infer it to be similar to that reported by Kappeler.


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Most male songs (60%) in the Dieng mountains started between 03:55-04:40 hrs, when it was still dark. We heard at least 10 male songs during 11 consecutive days of predawn-to-dusk observations. Considering that female songs of at least 12 individual gibbon groups could be heard from our listening post, the average number of male songs per day per group can be estimated as 0.08. It should be noted that this is a very conservative estimate: It includes one all male chorus for which only a minimum number of participants is available. In addition, male songs appeared to be less loud than female songs and could more easily go undetected than female songs. Apart from one solitary song bout which began at 05:12 hrs, all male songs bouts uttered before dawn were produced in a chorus fashion, with overlapping songs of at least 3 individuals. These pre-dawn male choruses were recorded four times during the whole study, i.e. twice during 19 consecutive days in Sep-Oct, and twice during 15 days in Jul-Aug. This corresponds to a chorus occurrence of about once every 8.5 days. Estimating the number of males involved during a chorus was difficult because of the distance between the chorusing gibbons and the observers; the median minimum number of males involved during a single chorus bout was ≥3.5 (n = 4 choruses, with a range of ≥3 to ≥5 males). In three instances, females started singing right after the male chorus had stopped, whereas once the last male (of an initial five males), stopped calling within one minute after the first female started her song. No male choruses and only four male solo song bouts in eleven days were heard after dawn. Male choruses and female solo song bouts appear to be temporally segregated events.

Figure 4.4 Frequency distribution of the song bout duration during 11 consecutive days in Linggo Asri

(females: median 7 min, range 3-18 min, n = 39 song bouts; males: median 11 min, range 8-42 min, n = 5 song bouts).

0 10 20 30 400

5

10

femalesmales

Cou

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Song duration, minutes


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Song duration Median durations of female song bouts and scream bouts are about 7 min (n = 39, range 3-18 min). Pure female solo song bouts with one participant have a median duration of 6 min (n = 17, range 3-18 min), female song bouts with two participants of the same group (presumably including an offspring of the main singer) have a longer duration (median 9 minutes, n = 13, range 6-15 min). The difference is significant (Mann-Whitney U test, p = 0.004). Male solo song bouts produced outside of male dawn choruses have a median duration of 11 min (n = 4, range 8-25 min). These male songs bouts are not significantly longer than female solo song bouts (Mann-Whitney U test, p = 0.056), but this may be due to the small sample size. Exact individual song bout durations during predawn choruses could not be determined because of the large distance between the observers and the singing males. At least one male was heard singing continuously for 42 min during one chorus, but this is a minimum estimate, because the chorus had started prior to detection. If this song is included in the comparison, median duration of male song bouts is 12 min, and male songs are significantly longer than female songs (Mann-Whitney U test, p = 0.016). Two completely monitored pre-dawn male choruses had durations of 1h 43 min and 1h 47 min, respectively, and two choruses which were already underway when detected by us had a minimum duration of 42 min and 45 min, respectively. All lasted much longer than the longest female solo song bout (18 min). Density estimation by use of song bouts The proportion of days that females were calling was 8 out of 9 days for group AS-9, and 9 out of 10 days for group AS-2. The fixed point count of identifiable groups in the smaller area, revealed that the average number of females calling on a given day was 3.5 (s.d. = 1.3; n = 10). A corresponding density of 1.9-3.7 groups per km2 was reached at. For the larger area, the average number of females calling on a given day was 6.7 (s.d. = 2.7; n = 10) and the density estimate is 1.5-2.4 groups per km2. The average group size near Linggo (i.e. at an altitude of 400-650 m) is 3.5 (s.d. = 1.2, n = 15 groups, range 2-6). This corresponds to a density of 6.7-13.1 and 5.3-8.5 individuals per km2 for the smaller and the larger area, respectively. DISCUSSION Frequency of male and female singing In virtually all gibbon species, mated males spend at least as much time singing as mated females. In Javan gibbon, however, Kappeler (1981, 1984c) heard only a single male song during 130 full days of listening in Ujung Kulon. This song was produced by an unmated "floating" male. Another single male song was heard outside of the study area (Kappeler, 1984c). Because no song was heard by any of


56

the resident males in his main study area Ujung Kulon, Kappeler (1981, 1984c) concluded that in Javan gibbons territorial males do not appear to sing. Kappeler does not indicate how many songs he heard during his whole study, but indicates that he heard 392 female song bouts in his study area during 89 days scattered over the whole year (Kappeler, 1984: p. 384). Because he heard only one male song bout within his study area, one can estimate that less than 0.3% of all song bouts he heard were male songs. In contrast, we heard at least 10 male song bouts during 11 consecutive days of predawn-to-dusk observations, and several more during 23 additional pre-dawn surveys. Hence, male song bouts in Dieng mountains constitute at least 8.5% of the total number of song bouts produced, and 50% of male songs heard during predawn-to-dusk observations were produced in all-male predawn choruses. Neither regular male singing, nor male chorusing, nor regular pre-dawn singing have previously been reported for Javan gibbons. Whether this is due to a lack of focused research at the appropriate time, or if pre-dawn calling is restricted to certain populations only is unclear. In our study area, male pre-dawn choruses occurred only about once per week (once every 8.5 days). It is possible that in previous studies, many male solo song bouts and all choruses were missed because of their pre-dawn occurrence. Because all previous data on singing behaviour of Javan gibbons was collected in the westernmost population of the species (Ujung Kulon), it is also possible that male calling and pre-dawn chorusing are more common in Central Java (or at least in the eastern part of the gibbons distribution range). Density estimation by use of song bouts Gibbon songs proved to be an appropriate mean to estimate gibbon density in the Dieng mountains. Data from the fixed point count suggest that densities in the surroundings of Linggo are in the order of 1.9-3.7 groups per km2 based on a small area (<1.2 km2) with individually recognisable groups, and 1.5-2.4 groups per km2 based on a larger area (<5.1 km2), including non-identified groups. The lower estimate for the larger area may reflect non-homogeneous densities or greater inaccuracy in estimating number of groups and distance for more remote groups. Densities reported from lowland sites on Java are in the order of 1.9-2.9 groups per km2, with average group sizes between 3-5 individuals (Kappeler, 1981, 1984c; Gurmaya et al., 1995; Rinaldi, 1999; Supriatna et al., 1994). Our density estimate is higher than previously reported by Nijman and van Balen (1998). Taking into account the higher densities of gibbons in the Dieng mountains, and since Nijman & van Balen (1998) followed Supriatna et al. (1994) in assuming that gibbons do not inhabit the forest edge, which they clearly do, the previous estimate of 519-577 gibbons for the Dieng mountains as a whole (Nijman & van Balen 1998) might be an under-estimate. Primates are frequently used as indicator species in monitoring programs. Although line transects may be the most commonly employed method to establish densities (Brockelman & Ali, 1987; Whitesides et al., 1988), for species that call at


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predictable times of the day, like gibbons, fixed point counts are a frequently used alternative (e.g., Haimoff et al., 1986; Brockelman & Ali, 1987; Brockelman & Srikosamatara, 1993). Fixed point counts have been used previously in the study of Javan gibbons (Kappeler, 1981, 1984a; Kool, 1992; Nijman & van Balen, 1998; Nijman, 2000). Because Kappeler's (1981, 1984c) study suggested that only mated female Javan gibbons sing, it has been assumed that every vocalising individual represents a family group (e.g., Nijman & van Balen, 1998). Densities are estimated by multiplying the average group size with the number of groups per area unit. Our findings indicate that at least 8.5% of gibbon calls heard in Central Java are male songs. We have little information concerning male calling in other parts of Java, but Gurmaya et al. (1995) and Rinaldi (1999) report that gibbon songs are occasionally heard well before dawn in Ujung Kulon (see Fig. 4.3). These calls may well have been produced by males. If in other areas, as in Linggo, some 8.5% of the songs heard are in fact male songs, it may imply that densities in the past may have been over-estimated considerably. In order to accurately estimate densities a (site-specific) correction factor has to be taken into account, or, better still, male and female calls have to be separated during data collection. With practice, Javan gibbons can be recognised individually by their song (Kappeler 1984c; Dallmann & Geissmann, 2001). Individual groups can thus be studied more easily without many of the difficulties involved in observing primates in tall tropical rain forest, without intruding into their habitat, without habituating groups, and without disturbing groups. As such, vocal recognition might be a more suitable tool for studying this critically endangered primate than some traditional methods. Vocal recognition furthermore facilitates for longitudinal studies (Baptista & Gaunt, 1997) which otherwise often require intrusive methods. Song comparisons in a phylogenetic context Whereas many gibbon species sing duet song bouts only (i.e. in all species of the genera Bunopithecus, Nomascus and Symphalangus), male solo song bouts occur together with duet song bouts in most species of the genus Hylobates. In the Javan gibbon, however duet song bouts do not occur. Instead, both males and females produce solo song bouts. The absence of duetting and the occurrence of female solo song bouts are characteristics which the Javan gibbon (Kappeler, 1981, 1984c; and this study) shares only with Kloss's gibbon from the Mentawai Islands (Tenaza, 1976; Whitten, 1980, 1982; see also Geissmann, 1993, for a discussion of the evidence for absence or presence of duetting in H. klossii). The absence of duetting and the occurrence of female solo song bouts appear to represent a synapomorphy shared by H. moloch and H. klossii, (Geissmann, 1993). In addition, male and female tend to sing at different times of the day: Most male song bouts occurred before dawn, most female song bouts after dawn. In some other species of the genus Hylobates (such as H. agilis and H. lar), males also tend to produce their solo songs before or at dawn, but they resume singing again later in the days when they participate in the duet songs with their mates (Geissmann, in prep.). In the Javan gibbon, however, no male choruses were heard after dawn.


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Similarly separated periods of male and female solo songs were also observed in Kloss's gibbons (Tenaza, 1976; Whitten, 1980, 1982). In this species, too, males preferentially sing solo song bouts before dawn, and females preferentially sing solo song bouts after dawn. This may represent another derived characteristic shared by H. moloch and H. klossii. Only the Javan gibbon, however, appears to have gone one step further. As pointed out by Geissmann (2000), gibbon songs probably evolved from male loud calls similar to those which are common in most recent Old World primates. In most Old World primates, females are not known to produce loud calls or utter only incomplete versions (e.g., Gautier, 1988; Herzog & Hohmann, 1984; Marler & Hobbett, 1975; Mitani, 1985c; Oates & Trocco, 1983; Steenbeek & Assink, 1998; Tenaza, 1989). Although male singing appears to occur considerably more frequently in our study than in Kappeler's study, the rate of male singing is still very low if compared with other gibbon species. In most gibbon species males participate in 0.18-1.90 song bouts per day (Gittins, 1984b: p. 422f), which in many species include both male solo and duet song bouts. Kloss's gibbon males (H. klossii) produce about 0.59 solo song bouts per day (calculated after data presented in Whitten, 1982, 1984). The lowest values were recorded in siamang populations. Although mated siamangs are not known to produce solo songs, 0.18-0.31 duet song bouts per day were recorded (Chivers, 1974: p. 263; Gittins, 1984: p. 422f), which is still more than 2-3 times higher than our estimated male singing rate for Javan gibbons of about 0.08 song bouts per day. In the Javan gibbons, the low rate of male singing, combined with a high rate of female singing (about 1.2 song bouts per day) appears to represent a complete reversal of the hypothetical ancestral situation. CONCLUSIONS Javan gibbons are unusual among gibbons in that duet songs do not occur and most song bouts are female solo songs or scream songs (91.5%). Individual females produced about 1.2 song bouts per day. In contrast to an earlier study in West Java, males in Central Java also produced songs, albeit less frequently than females (10 vs. 107 song bouts in 11 consecutive days). Individual males are estimated to produce about 0.08 song bouts per day (minimum estimate). Males prefer to begin their song bouts before dawn (before 05:20 hrs), whereas females sing later in the morning. Similarly separated periods of male and female solo songs were also observed in Kloss's gibbons (H. klossii) on the Mentawai Islands. This may represent a derived characteristic shared by H. moloch and H. klossii. The rarity of male singing in the Javan gibbon appears to be unique among gibbons. The extremely pronounced dominance of female singing over male singing appears to represent a complete reversal of the ancestral state.


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Javan gibbons can be accurately censussed by means of their vocalisation, but it is advised to separate male and female songs. The high degree of vocal recognition allows the species to be studied in detail in an non-intrusive manner. ACKNOWLEDGEMENTS The Indonesian Institute of Sciences (LIPI), the Directorate General for Forest Protection and Conservation (PKA) and the Ministry of Forestry and Estate Crops (MOFEC) is thanked for granting permission to conduct research on Java. Financial support for the study came from the Netherlands Foundation for International Nature Protection, Society for the Advancement of Research in the Tropics, and Stichting het Kronendak (to VN). We wish to thank the officials and staff members of the numerous zoos for permission to study the animals in their care and for useful information about the animals' previous history. Additional tape-recordings of Javan gibbons used in the present study were kindly made available by Dr. Markus Kappeler. We are particularly grateful to Robert Dallmann and Sylke Eyring for digitising parts of our tape-recordings. Robert Dallmann, Prof. dr. Steph B.J. Menken, and Prof. dr. Elke Zimmermann commented on an earlier version of this manuscript.


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Geographical Variation in Pelage Characteristics in Grizzled Leaf Monkey

63

5. GEOGRAPHICAL VARIATION IN PELAGE CHARACTERISTICS IN GRIZZLED LEAF MONKEY PRESBYTIS COMATA (DESMAREST, 1822) (MAMMALIA, PRIMATES, CERCOPITHECIDAE)

Modified and expanded version of Zeitschrift für Säugetierkunde 62: 257-264, 1997

ABSTRACT Two subspecies of grizzled leaf monkey Presbytis comata have been identified on the island of Java, Indonesia. The nominate form is found in West Java whereas P. c. fredericae occurs in Central Java. Geographical variation in P. comata has been studied both in museum specimens and in the field. Some alleged differences between the two described forms were found not to be diagnostic, while some intraspecific variation was of a clinal nature, with intermediate populations existing in the eastern part of West Java. It is concluded that a separation of P. comata into different subspecies let alone species is not warranted. None of the forest areas in Central Java are included in the protected area network. In order to preserve intra-specific variation it is timely that both the grizzled leaf monkeys and their the forest areas in Central Java are more actively protected. RINGKASAN Variasi geografis dalam karakteristik bulu pada Surili Presbytis comata (Desmarest, 1822) (Mamalia, Primata, Cercopithecidae). (Versi yang telah dimodifikasi dan dikembangkan dari paper yang dipublikasikan di Zeitschrift für Säugetierkunde 62: 257-264, 1997): Dua subspesies Surili Presbytis comata telah diidentifikasi di Pulau Jawa, Indonesia. Subspesies yang nominat ditemukan di Jawa Barat sedangkan P. c. fredericae terdapat di Jawa Tengah. Variasi geografis dalam P. comata telah diteliti baik di museum maupun di lapangan. Beberapa perbedaan dugaan antara kedua subspesies tersebut tidak terbukti, sementara beberapa variasi intraspesifik merupakan perubahan perlahan-lahan [sifat ‘klinal’], dengan populasi peralihan terdapat di bagian timur Jawa Barat. Disimpulkan bahwa pemisahan P. comata menjadi subspesies apalagi spesies berbeda tidak dapat dibenarkan. Tidak ada satupun kawasan hutan di Jawa Tengah yang masuk dalam jaringan kawasan konservasi. Untuk melestarikan variasi intra-spesifik maka saatnya sekarang untuk melindungi baik Surili maupun kawasan hutan di Jawa Tengah di mana mereka hidup, secara lebih aktif.

The MOFEC-Tropenbos-Kalimantan Project, Balikpapan, Indonesia

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INTRODUCTION On the island of Java, Indonesia, two single island endemic primate species can be found, both classified as endangered according to IUCN threat criteria (Eudey, 1987): the Javan gibbon Hylobates moloch and the Grizzled leaf monkey Presbytis comata (formerly P. aygula, see Weitzel & Groves, 1985). Grizzled leaf monkey is confined to the rainforests of the western half of the island while some remnant populations are found as far east as Mt Lawu, on the border of East Java (Nijman, 1997, chapter 6). Fossil finds, found in Middle Pleistocene deposits, indicate that the species' former distribution might have extended eastwards to Mts Wilis-Liman (Nijman, 1997; Theunissen, 1985). Two subspecies are traditionally recognised: P. comata comata (Desmarest, 1822), restricted by Sody (1930b) to West Java and P. comata fredericae (Sody, 1930), from Central Java. Eudey (1987) states that P. c. fredericae is known with certainty only from Mt Slamet, although Bartels (1937) reported the occurrence of the species on Mts Dieng and some specimens have been collected on Mts Dieng and Mt Lawu. During the last few years it has become apparent that P. comata still prevails in those areas in Central Java from which it was historically known (Seitre & Seitre, 1990; Nijman & Sözer, 1995; Nijman, 1997 chapter 6; M. Linsley, pers. comm., 1994). Recently, P. c. fredericae has been proposed as a separate species P. fredericae by IUCN (1994) and Brandon-Jones (1995, 1996a). The pelage colour of adults is the most striking difference between the two types: fredericae differs from the nominate race in having black upperparts instead of grey, and the underparts are black apart from the lower abdomen, innerside of the legs, which are white, and the upperpart of the chest, which is whitish or light grey. The vent in the nominate is entirely white. Hence the proposed English names of Javan grizzled leaf monkey for P. comata and Javan fuscous leaf monkey for P. fredericae (IUCN, 1994). If P. c. fredericae is considered to be a separate species it undoubtedly can be ranked among the rarest and most endangered primate species in the world, making it a top priority for primate conservation (cf. Brandon-Jones, 1995). It would be restricted to four isolated forest areas, viz., Mt Slamet, Mt Cupu-Simembut, Mts Dieng and Mt Lawu (Nijman, 1997, chapter 6), in a province with one of the highest human population densities of Indonesia. None of the forests are adequately protected and two of them, the first and the last of the localities mentioned above, are situated on an active volcano. The aim of this study is to describe the geographical variation in pelage characteristics among populations of grizzled leaf monkeys. Data collected over the entire range of the species and data obtained from the study of museum specimens form the basis of these descriptions.


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MATERIAL AND METHODS A total of 59 specimens in the National Museum of Natural History, Leiden (RMNH), the Zoological Museum, Bogor (MZB), the British Museum of Natural History (BMNH), London, and the Zoological Reference Collection (ZRC) of the National University of Singapore were examined, viz. 36 from the western province and ten from the central Javan province. For another 13 specimens studied no locality was given. During field surveys from 1994 to 2000 descriptions of external appearance and pattern of coloration of grizzled leaf monkey were made. Survey areas included the western half of Java, east to Mt Lawu on the border with the East Javan province. Mt Lawu is the easternmost locality where the species has been recorded (Nijman, 1997 and chapter 6). Special attention was paid to the populations in the central part of the species' range, i.e. the eastern part of West Java and the eastern part of Central Java, as it is here where the expected boundary between the two described subspecies is to be found. The number of animals and number of neonates of which a clear view was obtained per forest area was estimated by summation of the maximum number of individuals observed at different localities throughout the mountain complex. When a group was observed at a locality where it had been seen previously or when there was doubt whether a particular animal had previously been encountered or was in fact a different individual, a description was made, but it was not included in the total estimate of numbers. When grizzled leaf monkey were observed at the same locality in different years, only data from one year (the year with the highest number of observations) is included in the analysis. In the course of the study numerous bird markets were visited. If grizzled leaf monkeys were encountered at these markets, if possible, a description of its pelage was made. These descriptions provide additional information on the variation in pelage coloration, but since often there was no certainty about the origin of the animal, these descriptions were not included in the analysis. No specimens were collected and hence the descriptions are exclusively based on field observations and museum specimens. RESULTS Grizzled leaf monkey was observed in ten forest areas. These areas (with estimated number of individuals plus neonates of which a clear view was obtained given in parenthesis) are: Mt Aseupan (5+0), Mt Halimun (5+1), Mt Salak (15+2), Mt Pancar (5), Mt Gede-Pangrango (32+5), Situ Patengang (16+1), Mt Sawal (3+1), Mt Slamet (16+3), Mts Dieng (61+12), Mt Lawu (0). A typical grizzled leaf monkey ('comata') from the western part of West Java (e.g., Mt Pancar [106°54’E, 6°35’S], Mt Gede-Pangrango [107°00’E, 6°45’S]) has a


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rather dark grey dorsum with the hair on the back being longer than on the tail, legs and arms. The tail is dark grey to blackish, and arms and legs are dark grey, often darker than the back. The venter, innerside of arms and legs, and innerside of the tail are whitish. The species has a blackish prominent crest. In some individuals the hair on the back is rather short while in others it is longer. In individuals with longer hair the uppercoat is formed by longer dark grey or blackish hair while the undercoat consists of short dark grey hair. In individuals from the central part of West Java, i.e. the forest surrounding Situ Patengang, the sides of the venter near the flanks is intermingled with grey hairs; This same pattern is found in museum specimens e.g., RMNH 26820 from Mt Tilu [107°30’E, 7°09’S]1. Observations in the wild and study of museum specimens suggests that this is less so in animals from the western part of West Java (e.g., Mt Aseupan [105°50’E, 6°10’S], Mt Salak [106°45’E, 6°45’S]: RMNH 34335, -36, -38, 51891). Grizzled leaf monkeys from Mt. Sawal [108°16’E, 7°12’S] in the eastern part of West Java, are somewhat different in coloration from those in areas to the west and to the east. The dorsum is not different from animals to the west, although in the animals studied it is rather dark. The arms are very dark grey, almost black. The venter consists of a whitish or light grey throat, edged on the upper side of the breast by a broad grey band. This band originates from the flanks and is narrower in the centre, with a thin whitish cross band. The lower abdomen, innerside of arm, legs and tail are whitish. The same pattern of coloration, but less pronounced, was found in a skin labelled P. aygula aygula and collected at Ceringin-Cisaga [108°30’E, 7°27’S] near Banjar, West Java, near the border with Central Java (RMNH 34296) (Fig. 5.1). This individual has rather dark arms, though at Mt Sawal the animals had even darker arms. Insert Figure 5.1 approximately here In typical grizzled leaf monkey ('fredericae') from Mt Slamet [109°13’E, 7°19’S] or Mt Prahu [109°55’E, 7°20’S] (e.g., MZB 2993, -94, -95, RMNH 14612) the dorsum is black, the throat and upper chest are white or light grey, the lower abdomen, innerside of the legs, arms and tail are white, while the remainder is black with a thin nearly white cross band. In other parts of the Dieng mountains some of the animals are less dark in colour. The pattern of coloration is as in the typical form, but the dorsum is (very) dark grey, not black, and resembles those of the Mt Sawal animals. For an overview of pelage characteristics based on field observations, see Table 5.1.

1 In April 2000, Roland Wirth showed me a photograph of a single grizzled leaf monkey currently held

in Howlett's Zoo, England, UK, which was obtained from Bandung Zoo. This individual is dark grey and shows a ventral pattern intermediate to those from western Java and the area between west and central Java. Although the exact origins of this individual are not known, it is likely that it originates from the area near Bandung.


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Figure 5.1 Geographical variation in pelage characteristics of the venter in grizzled leaf monkey

Presbytis comata. From left to right: RMNH 26824, Tapos, Mt Salak, West Java; RMNH 34296, Ceringin, West Java near border with Central Java; RMNH 34346, Tegal Sari, Mt Slamet, Central Java.


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Table 5.1 Pelage characteristics of grizzled leaf monkey Presbytis comata based on field observations on nine mountain complexes on Java, listed from west to east. The number of individuals of which a clear view was obtained is given in parenthesis.

Locality

Venter Dorsum Arms Dorsum neonate

Mt Aseupan White (3) grey (5) grey (5) - Mt Halimun White (5) grey (5) grey (5) light grey (1) Mt Salak White (12) (dark) grey (15) (dark) grey (15) grey (2) Mt. Pancar White (4) (dark) grey (5) dark grey (5) - Mt. Gede- Pangrango

white (32) (dark) grey (28) (dark) grey (28) grey (5)

Situ Patengan

white, greyish on the flanks (6)

dark grey (16) dark grey (16) grey (1)

Mt. Sawal white with dark grey band on breast, narrow in centre (3)

dark grey (3) blackish (3) dark grey (1)

Mt. Slamet white with black band on breast (16)

black (16) black (16) black (3)

Mts Dieng white with dark grey band on breast (24); white with black band on breast (30)

dark grey (24); black (37)



Grizzled leaf monkey has been observed in both primary and secondary forest, in ecotones and in the forest interior. The species is present in lowland forests, in forests on steep slopes and hills, and in montane and upper montane forests. There is no differentiation in habitat or altitudinal preferences between populations in the east or west. In behavioural terms all forms are indistinguishable from one another. Most notably the vocalisations, in particular the alarm call, of animals on Mt Halimun, Mt Salak, Mt Gede-Pangrango, Mt Sawal, Mt Slamet, Mts Dieng and Mt Lawu are qualitatively similar (cf. Bartels, 1937). In other Presbytis species, e.g., those on Sumatra and Borneo, the different species are readily distinguished by their specific vocalisations (e.g., Wilson & Wilson, 1977; Aimi & Bakar, 1992; 1996; pers. observ.). Sody (1930b) noted that inhabitants of the Mt Slamet region, where he obtained the specimens described as fredericae, were not familiar with the Javan native name surili, nor did they made a linguistic distinction between grizzled leaf monkey and the sympatric ebony leaf monkey Trachypithecus auratus; both species were named lutung (Sody, 1930a). Lutung is the local name used for the more common and more widespread ebony leaf monkey in West and Central Java, and Bali, while this species is named budeng in East Java. Bartels (1937) reported that grizzled leaf monkey was known as rekrekan in the Mts Dieng region. In the present study, it was found that grizzled leaf monkey is locally known as surili throughout west Java, east to Mt Sawal (inclusive). From Mt Slamet to Mts Dieng it is known as (lutung) rekrakan or (lutung) rekrekan. In certain areas, e.g., on Mts Dieng and Mt Lawu, some informants were aware of the presence of two types of leaf monkeys, but both of them were called lutung or budeng (confirm the findings in Mt Cupu-Simembut


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by Linsley & Nawimar, 1994; also Brandon-Jones, 1995). The linguistic separation between fredericae and comata in rekrakan and surili, respectively, is accounted for by the two different languages, Javanese and Sundanese, spoken in different parts of the island (the boundary between the two languages runs almost parallel to the provincial boundary) and is most likely not of biological significance. DISCUSSION Intraspecific variation, in particular the coloration and pattern on the venter, in Presbytis comata is not geographically disjunct but seems to be of a clinal nature with intermediate populations existing in areas between those from where the two subspecies have been described. Whether or not more populations of the species remain in these intermediate areas remains unclear. As nowadays large areas of Java have been deforested, populations of grizzled leaf monkeys are found scattered throughout West and Central Java. However, there seems to be no major gap in the species distribution between West Java and Central Java, nor does there seem to be a geographical or ecological barrier in the intermediate area that can explain a possible separation between populations east or west of the provincial boundary. One of the morphological characters on which the separation between comata and fredericae has been based, namely the dorsal coloration, shows, at least in the populations on the Dieng mountains, considerable variation and cannot be used as a diagnostic character. Vocalisations of populations in the western part of its range do not seem to differ from those in the eastern part. On the basis of the data presented above, it can be concluded that the separation of western and eastern populations of grizzled leaf monkey into two different species is not warranted. Neither form can be recognised as a diagnosably distinct taxon and therefore the appropriate name for the species (sensu lato) remains Presbytis comata (Desmarest, 1822). For those who do not wish to abandon the use of trinomials, it should be understood that these can only be used to identify populations within a continuum of geographical variation. The geographical limits of these populations will, however, remain arbitrary. If the central Javan population were to recognised as a different species, it would rank among the most endangered primates in the world. In the most recent IUCN listing (IUCN, 1996) it is classed as Data Deficient, i.e., more information is required on the exact nature of its population status and future prospects, but it is likely that it belongs in one of the threat categories (critically endangered, endangered, vulnerable). Recent field surveys (Nijman, 1997; Nijman & van Balen, 1997; chapter 6) found the species to be present in all forest areas from where it was known historically. The species is to be rather common in certain forest areas (Mts Dieng and Mt Slamet), but rare in others (Mt Lawu). Like many of the western


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populations, those in the east are isolated from each other by large areas of unsuitable habitat and seem to be in need of active conservation efforts. None of the forest areas in the eastern part of West Java or Central Java are included in the protected area network, although most of them have been proposed as such for a long time (MacKinnon et al., 1982). The present study indicates that the eastern populations of grizzled leaf monkey are not diagnosably distinct from those in the west and as such should not be treated as separate species. Yet, it is timely that both the grizzled leaf monkeys and their the forest areas in Central Java are more actively protected in order to preserve intra-specific variation. The tripartite distribution of the grey leaf monkeys of the genus Presbytis in the Sundaic region, currently known as comata (western Java), thomasi (northern Sumatra), and hosei (north-eastern Borneo), has been a protrackted issue of debate. Pocock (1934) considered these taxa as constituting four different species, including two on Borneo (sabana and hosei on Borneo some populations show adult sexual dimorphism in crest shape and extent of white on the brow while others are monomorphic, resulting in the description of a number of (sub)species: see Brandon-Jones, 1997). Chasen (1940) subsequently considered them to be races of a single species, P. comata, as did some authors afterwards, e.g., Hooijer (1962). This made P. comata a polytypic species, with a distribution following the periphery of Sundaland. The three zones were regarded as areas of convergent evolution by Medway (1970) and in his more cautious interpretation the three forms (comata, thomasi, and hosei) were considered to be separate species, a view supported by Groves (1970) and most subsequent workers (Napier, 1985; Weitzel et al., 1988; Corbet & Hill, 1992; IUCN, 1994). In contrast, Brandon-Jones (1978, 1984, 1993, 1996a), while ignoring the diagnostic differences in vocalisation that exists between the three taxa ('...for reasons of consistency, geographic variation in vocalisation must remain subordinate in taxonomic status to geographic variation in pelage colour...' Brandon-Jones, 1996b: p 72) regarded them as relicts of a single population, differentiated at the subspecific level. The grey-backed taxon is perceived as a relict in its present disjunctive distribution, representing an earlier coloniser of the Sundaic region. Brandon-Jones (1993) postulated that the phylogeny of the genus involves unidirectional integumental colour degradation, comparable with Hershkovitz' (1968) theory of metachromism. In this view the pelage colour of the pre-glacial relict species in the genus Presbytis is predominantly black (Brandon-Jones, 1978, 1993), after which bleaching occurs via the eumelanin pathway from (brown to) grey to white (Hershkovitz, 1968). Thus, those mammal species that are characterised by a very dark/black coloration can, generally, be regarded as progenitors of all living members of their group. If we follow the Brandon-Jones (1987, 1993) model and accept the predominant glossy black P. potenziani from the Mentawai islands of the west coast of Sumatra, as the sole representative of the genus during a Pleistocene period of climatic deterioration, after which it evolved (or 'degenerated' as preferred by Brandon-


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Jones, 1993) into the grey P. comata (sensu lato), then the present occurrence of melanistic individuals in that taxon warrants further explanation. The present finding of populations intermediate in coat coloration and pattern and the presence of greyish individuals in the easternmost populations of P. comata, show that the species is more variable in its pelage coloration than previously assumed. If P. comata from Java is considered conspecific with P. thomasi and P. hosei, intraspecific variation in pattern and coloration below the head (which is generally more conservative then the pelage colour itself: Wilson, 1978; Wilson & Wilson, 1977) in the Javan populations would be larger then variation between comata, and extralimital thomasi and hosei. In conclusion, grizzled leaf monkey P. comata on Java can not be separated into two different subspecies or even species as neither form can be recognised as a diagnosably distinct taxon. Moreover the large variation in pelage characteristics within the Javan populations makes it increasingly more difficult to consider them conspecific with the other grey-backed leaf monkeys --P. thomasi and P. hosei-- from north Sumatra and north-eastern Borneo, respectively. ACKNOWLEDGEMENTS I wish to thank Mr Boeadi (Zoological Museum Bogor), Dr C. Smeenk (National Museum of Natural History, Leiden), Dr P. Jenkins (British Museum for Natural History, London) and Dr C.M. Yang (Zoological Reference Collection, Singapore) for allowing me to examine specimens in the collections under their care, S.J. Booth, Dr P.J.H. van Bree, Dr C.J. Hazevoet and an anonymous reviewer for constructive comments on the manuscript. Research on Java was made possible due to the co-operation of the Indonesian Institute for Science (LIPI) and the Directorate General of Forest Protection and Nature Conservation (PHPA). Dr P.J.H. van Bree is thanked for his help and support throughout the study.


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Occurrence and Distribution of Grizzled Leaf Monkey

CHAPTER 6

OCCURRENCE AND DISTRIBUTION OF GRIZZLED LEAF MONKEY PRESBYTIS COMATA (DESMAREST, 1822)

(MAMMALIA: PRIMATES: CERCOPITHECIDAE) IN JAVA, INDONESIA

Contributions to Zoology 66: 247-256, 1997

ABSTRACT The grizzled leaf monkey Presbytis comata is confined to the rain forests of West and Central Java, Indonesia. In order to determine its distribution, a review of the literature, evidence from the study of museum specimens, and the results of recent surveys are presented. Recent surveys in the central parts of the island indicate that P. comata is still present on four volcanic mountain complexes, viz. Mt. Sawal, Mt. Slamet, Mts. Dieng, and Mt. Lawu. The present paper gives the results of the surveys combined with a review of its distribution. Altitudinal and habitat preferences, and the conservation status of the species are discussed. RINGKASAN Keberadaan dan distribusi Surili (Presbytis comata Desmarest, 1822) (Mammalia: Primata: Cercopithecidae) di Jawa, Indonesia (Contributions to Zoology 66: 247-256, 1997): Keberadaan Surili Presbytis comata tergantung kepada hutan hujan Jawa Barat dan Tengah, Indonesia. Untuk menentukan distribusinya, suatu review literatur, bukti dari studi spesimen museum, dan hasil-hasil survey terbaru dipaparkan. Survey terbaru di bagian tengah Pulau Jawa memperlihatkan bahwa P. comata masih terdapat di empat komplek gunung berapi, yaitu Gn Sawal, Gn. Slamet, Pegunungan Dieng dan Gn. Lawu. Paper ini memaparkan hasil-hasil survey dengan review distribusinya. Preferensi ketinggian dan habitat, serta status konservasi dari spesies ini juga didiskusikan. INTRODUCTION Indonesia supports a relatively high number of colobine monkeys belonging to the genus Presbytis sensu stricto and, due to the partial isolation of Asia and the intermittent connection between islands, the country includes numerous endemic taxa. One of these is the grizzled leaf monkey Presbytis comata (Desmarest, 1822) [formerly P. aygula, see Weitzel & Groves, 1985], endemic to the island of Java,

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Forest (and) Primates viz. the West and Central Javan provinces. Animals of this species live in single male groups containing three to over thirteen individuals. During the day the troops frequently visit the middle and lower layer of the forest, whilst resting at night in the upper layer (Ruhiyat, 1983). The species is stricktly arboreal and is restricted to rain forest areas with a continuous forest canopy. Grizzled leaf monkeys plays an important ecological role as one of the principal arboreal shoot- and leaf-eating mammals of the Javan rain forest (Medway, 1970), although fruit may also be eaten when available (Sujatnika, 1992). Little is known about the ecology of the species, and particularly knowledge about its distribution at the individual and population level is limited (Supriatna et al., 1994). Java is Indonesia’s most cultivated large island and has a long history of forest conversion and degradation. Nowadays less then 10% of the original forest remains in Java and especially West and Central Java have suffered from deforestation. In these two provinces 48% of the montane forest, 14% of the hill forest and less then 2% of the lowland forest remains (MacKinnon et al., 1982). For the latest update on land use and ecological issues concerning the island of Java (and Bali), see Whitten et al. (1996). Because of its small, fragmented populations and its severely reduced habitat the grizzled leaf monkey is considered to be among the most endangered primate species in the world (Eudey, 1987). P. comata -- together with another Javan endemic, the Javan gibbon Hylobates moloch (Audebert, 1799) -- have suffered more than any other Malaysian primate from deforestation (MacKinnon, 1987). Population size estimates have been theoretically calculated and range from 8040 (MacKinnon, 1987) to 2285 (Supriatna et al., 1994). Sody (1930a) described the subspecies P. c. fredericae based on specimens collected on the southern slopes of Mt. Slamet, Central Java. This subspecies differs from the grizzled nominate from West Java in having a dark collar on the upper side of the chest and a dark belly region, and by the occurrence of melanistic individuals. A more elaborate discussion on geographical variation in pelage characteristics in the grizzled leaf monkey is discussed elsewhere (Nijman, 1997b, chapter 5). Otherwise very little has been written about the occurrence of grizzled leaf monkeys in Central Java. If mentioned at all, the species was most frequently reported to occur on or to the east of Mt. Slamet (Chasen, 1940; Hooijer, 1962; Medway, 1970; MacKinnon, 1987; Weitzel et al., 1988; Ruhiyat, 1991; Corbet & Hill, 1992). Apart from Kappeler (1984a), who conducted a gibbon survey in 1978 and visited some sites in Central Java and M. Linsley (pers. comm, 1994) few people have extended or concentrated their (biological) surveys into Central Java (see e.g., Appendices II and III in Whitten et al., 1996). Eudey (1987) states that P. c. fredericae is known with certainty only from Mt. Slamet. However, Bartels (1937) reported the occurrence of the species on the northwestern slopes of the Dieng mountains, and moreover some specimens have been collected on the Dieng mountains and Mt. Lawu, on the border between Central and East Java (National Museum of Natural History (hereafter RMNH), Leiden, coll. Bartels, no. 14612, 14613, and 14614).

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The only other record from the eastern half of the island comes from Eugène Dubois who collected a fragment of the right palate with P3-M2 in situ of a Presbytis sensu stricto from a Middle Pleistocene deposit in Sumber Kepuh [112°5' E, 7°30' S], East Java (RMNH, coll. Dubois, no. 3780). The sediments in which the fossils were found are of volcanic origin and Dubois inferred that the animals in the deposits died due to a volcanic eruption. Based on the structure of the sediments he concluded that most likely this had been an eruption of Mt. Wilis (cf. Theunissen, 1985). The aim of the present paper is to synthesize the main results from studies published in various journals and unpublished reports, not all of which are easily accessible, and to integrate this with new data on the distribution and conservation status of central Javan populations of the grizzled leaf monkey collected during two field surveys in 1994 and 1995. An overview of the historic and present distribution of grizzled leaf monkey is given, after which new data on the species gathered in the central parts of Java are presented. Finally, altitudinal and habitat preferences are discussed, and some recommendations for conservation are given. METHODS Study sites In order to assess the current distribution of grizzled leaf monkey in the central parts of Java, data were gathered over an eight months (March-Sept.) period during 1994, with an additional two months (June-July) survey in 1995. Surveys were conducted in almost all forest areas larger than 5000 ha, between from the east of Mt. Papandayan and Mts. Wilis-Liman. The forest areas visited included Mt. Sawal, Mt. Segara, Mt. Slamet, Mts. Dieng, Mt. Sundoro, Mt. Sumbing, Mt. Merapi, Mt. Muria, Mt. Lawu and Mts. Wilis-Liman (see Table 6.1). Together the forests on these mountains comprise more than 90% of the remaining natural forest in the central part of the island. In the same period additional data on the distribution of the species were collected on Mt. Pancar and Mt. Gede-Pangrango, both in West Java. Survey methods The area was surveyed by scanning the forest area from vantage points over the canopy and by surveys inside the forest along available trails. Data were collected on habitat type and order of disturbance, and when the species was detected, notes on group size, age-class composition, habitat utilization, altitude, and behaviour were taken. Additional data on the presence or absence of grizzled leaf monkeys was gathered by semi-structured interviews with local people living in the vicinity of the forests and with officers of nature conservation and forestry departments. Comprehensive information on the distribution of the species was obtained from the study of specimens in the Museum Zoologi (Bogor, MZB), the British Museum of Natural History (London, BMNH) and the National Museum of Natural History (Leiden, RMNH), from the literature, and from unpublished data obtained by correspondents.

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Forest (and) Primates Table 6.1 Study sites on the island of Java, Indonesia

Locality Status1 Coordinates E-S Forest type2 Alt. Range3

Mt. Pancar unp. 106°54’ 6°35’ wet hill 700-1000 Mt. Gede-Pangrango NP 107°00’ 6°45’ wet hill-montane 800-3019 Mt. Sawal Wr 108°16' 7°12' wet hill-montane 700-1764 Mt. Segara [nr]/unp. 108°48' 7°07' wet lowland-submontane 300-1812 Mt. Slamet [nr] 109°15' 7°15' wet hill-montane 700-3000 Mts. Dieng [wr]/unp. 109°37' 7°05' wet lowland-montane 250-2565 Mt. Sundoro Pf 110°00’ 7°17’ wet montane 2000-3135 Mt. Sumbing [nr] 110°04’ 7°22’ wet lowland-montane 500-3371 Mt. Merapi [rf] 110°26’ 7°32’ wet montane 900a-2911 Mt. Muria [nr] 110°52’ 6°37’ moist hill-submontane 600-1620 Mt. Lawu [nr] 111°11’ 7°40’ wet submontane-montane 1000-3000 Mt. Wilis-Liman [wr] 111°46' 7°48' moist-wet hill-montane 600-2563

1 NP = national park (Taman Nasional), nr = nature reserve (cagar alam), pf = protection forest (hutan

lindung), rf = recreation forest (hutan wisata), unp. = unprotected, wr = wildlife reserve (suaka margasatwa), [ ]=proposed.

2 After MacKinnon et al., 1982. 3 Numbers in italic represent approximate lower and upper limits of forest; a Before the eruption on 22-11-1994: present state of forest unknown but lower limit has gone up

considerably and only the eastern slopes are left covered with natural forest (Rudiyanto, pers. comm., 1996).

RESULTS Geographic distribution Figure 6.1 and Table 6.2 show the localities where grizzled leaf monkeys have been recorded, both in historic and recent times. The species’ distribution encompasses the area from the westernmost tip of the island at Ujung Kulon to Mt. Lawu on the border between Central and East Java. It has been recorded in 33 forest patches, most of which are located in the West Javan province and a few records originate from the Central Javan province. The only records from East Java are those from Mt. Lawu and the Middle Pleistocene fossil excavated at Sumber Kepuh. Distribution in the central parts of Java In this section, information gathered in the central parts of the island are discussed in a west to east sequence. Mt. Sawal. The characteristic vocalizations of the grizzled leaf monkey were recorded in a secondary forest patch, on the southern slopes at 1025 m a.s.l. The dense cover prevented sightings of the animals although the group was very close at hand. Three other individuals and a juvenile were seen later resting in an emergent tree in the primary forest at an altitude of 935 m a.s.l.

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Table 6.2 Localities with records, and altitude when available, of grizzled leaf monkey Presbytis comata, forest type with its approximate present altitudinal range, and climate type.

No.* Locality Coordinates

E-S Forest type**

Alt. range forest

Climate type↑↑

Alt. record. (reference)↑↑↑

1. Ujung Kulon 105°20’-6°45’ L 0-623 2-3 0-200 (1-2) 2. Cerita 105°50’-6°10’ L 100 2 (3) 3. Ranca Danau 106°00’-6°10’ L 90-744 3 (3-4) 4. Haurbentes-Jasinga 106°27’-6°31’ P 200-470 3 200-470 (5) 5. Cikepuh/Cibanteng 106°25’-7°12’ L 0-235 2 (6) 6. Halimun 106°30’-6°40’ H/SM/M 500-1929 3 (4) 700-1075 (7), 900-1200 (6) 7. Pelabuhan Ratu 106°32’-6°59’ L 100 2 30 (8) 8. Mt. Salak 106°45’-6°45’ SM/M 1700-2211 3 600 (a) 9. Jampang 106°47’-7°15’ -- -- 2-3 (b) 10. Mt. Pancar 106°54’-6°35’ H 700-1000 3 785-850 (9) 11. Mt. Gede-Pangrango 107°00’-6°45’ H/SM/M 800-3019 3 900-1400 (9), 1000-2600 (5) 12. Ciwangi 107°02’-7°04’ - - 3 1200 (8) 13. Sanggabuana 107°15’-6°35’ L/H 150-1219 2 (6) 14. Mt. Magesit 107°20’-7°05’ SM/M 1000-2078 3 (10) 15. Kamojang 107°22’-7°10’ M 1400-2250 3 1390-1625 (11) 16. Mt. Simpang 107°25’-7°15’ H/SM 600-1600 3 (10) 17. Mt. Tilu 107°30’-7°09’ SM/M 1200-2177 3 (4-10-11) 18. Burangrang 107°33’-6°46’ SM/M 1000-2000 2-3 (6) 19. Cibeureum 107°33’-7°10’ -- -- 3 (c) 20. Mt. Kencana 107°35’’7°18’ H/SM/M 600-2182 3 (10) 21. Mt. Papandayan 107°45’-7°20’ SM/M 1000-2622 3 (11) 22. Patenggang 107°46’-7°08’ M 1600-1775 3 1600-1775 (11) 23. Cikajang 107°47’-7°22’ -- -- 3 900 (d) 24. Mt. Limbung 107°50’-7°25’ L/H/SM 300-1815 3 (10) 25. Magesit Kareumbi 107°54’-6°54’ H/SM - 2-3 (6) 26. Mt. Sawal 108°16’-7°12’ H/SM 700-1764 3 915-1025(9) 27. Mt. Ciremay 108°25’-7°00’ SM/M 1000-3078 3 (12) 28. Ciringin 108°30’-7°27’ -- -- 3 (e) 29. Mt. Slamet 109°15’-7°15’ H/SM/M 700-3000 3 1000 (f) 1400 (g) 1500(13) 700-2350 (9) 30. Mt. Cupu/Simembut 109°26’-7°14’ L/H 350-1000 3 350-100 (14) 31. Mt. Lumping 109°38’-7°07’ L/H/SM 250-1327 3 300-1300 (9) 32. Mt. Prahu 109°55’-7°10’ M 1600-2565 3 1300-1400 (15), 2500-2565 (9) 33. Mt. Lawu 111°11’-7°40’ SM/M 1000-3000 2 1500-1600 (h) 1880 (9) 1900 (3) 34.

Sumber Kepuh 112°05’-7°30’ -- -- 1 (M.Wilis 2-3)

(i)

* Cf. Figure 6.1 ** L = lowland forest (0-500 m); H = hill forest (500-1000 m); SM = submontane forest (1000-1500

m); M = montane forest (1500 m and above) P = forest plantation. ↑ Italic numbers represent approximate altitudes (after MacKinnon et al., 1982; Kappeler, 1984; own

obs.). ↑↑ Climate types based on the number of rainy days during the four driest consecutive months of the

year (abbreviated as RDFDCM). 1 = areas with 0-10 RDFDCM; 2 = areas with 10-30 RDFDCM; 3 = areas with more than 30 RDFDCM (aftervan Steenis, 1965).

↑↑↑ Key: (1) Hoogerwerf, 1970; (2) Gurmaya et al., 1992; (3) S. van Balen, pers. comm., 1995; (4) van der Zon, 1979; (5)Sujatnika, 1992; (6) Supriatna et al., 1994; (7) Kool, 1992; (8) Napier, 1985; (9) present study; (10) MacKinnon et al., 1982; (11) Ruhiyat, 1991; (12) Weitzel et al., 1988; (13) Seitre & Seitre, 1990; (14) Linsley & Nawimar (1994) in Brandon-Jones, 1995; (15) Bartels, 1937. (a) RMNH 34302/34336/34337/34338; (b) MZB 3817; (c) RMNH 26822; (d) MZB 6646; (e)

RMNH 34296; (f) RMNH 34318; (g) MZB 167; (h) RMNH 14614; (i) Middle Pleistocene fossil, coll. Dubois no. 3780, RMN

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Forest (and) Primates Figure 6.1 Geographical distribution of grizzled leaf monkey Presbytis comata on Java, Indonesia. The

map shows areas covered with natural forests, excluding mangrove and swamp forest (after RePPProT, 1990), and the localities where grizzled leaf monkeys havebeen recorded. Numbers correspond with those listed in Table 6.2.

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According to local villagers and staff from the forestry department, grizzled leaf monkeys are also present in the higher parts on the northern slopes, although the species was not recorded there. Mt. Slamet. Both in 1994 and 1995, groups of grizzled leaf monkeys were recorded on several occasions on the southern slopes near the hotwater springs near ‘Pancuran tujuh’, north of the village of Baturaden. Group sizes ranged from 4-5 to 10 individuals and records were established at altitudes between 700 and 910 m a.s.l. On 30 June 1995, the vocalizations of the grizzled leaf monkey were heard coming from the edge of the forest at 1985 m, on the eastern slopes of Mt. Slamet. The same day two other groups were observed. The first group consisted of more than three individuals and was seen descending to a lower part of the mountain from an altitude of 2150 m a.s.l. A few moments later a group of ebony leaf monkeys Trachypithecus auratus (E. Geoffroy, 1812), were seen heading in the same direction. It is not clear whether the two species formed one group or were divided into two separate groups. A mixed group of both species was observed later that day: a group of nine leaf monkeys -- three to four of which were grizzled leaf monkeys -- were seen moving in the upper layer of the canopy, in oak-laurel forest at an altitude of 2350 m a.s.l. Mts. Dieng. Grizzled leaf monkeys were found in different parts of this c. 255 km2 large forest block, ranging from lowland to upper-montane. The species was first seen on 5 June 1994, near the summit (2565 m) of Mt. Prahu in the easternmost part. Two individuals were moving through the upper strata of the forest, and one could be observed for up to half an hour (Nijman & Sözer, 1995). Near this observation point, in June 1995, a group of leaf monkeys was observed but it was not clear whether or not grizzled leaf monkeys were involved. In the lower parts near the village of Linggo, seven times a group was seen ranging from three to 13 individuals and two groups were detected by means of their vocalizations only. Records were established at altitudes of 1300 m a.s.l. on Mt. Lumping to 650 m near Linggo, but the species was also reported to occur at the lower parts to c. 300 m a.s.l. Mt. Lawu. The species was recorded once during five days of surveying, in the montane forests (1880 m) between Cemoro Sewu and the waterfall of Mojosemi near Sarangan, East Java. On 12 July 1995, the characteristic diagnostic vocalization of the grizzled leaf monkey was heard and a few minutes later a group of at least seven leaf monkeys was observed. Although the light conditions were far from optimal due to the incoming darkness, the shape of the monkeys and the clear presence of a pale belly and underside of tail left no doubt that grizzled leaf monkey was involved. Groups of ebony leaf monkeys were also observed in the area. According to local informants, two types of budeng (East Javan name for ebony leaf monkey) were present. I have not spoken with anybody who was familiar with the name (lutung) rekrakan (Javanese name for grizzled leaf monkey), nor have

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Forest (and) Primates I heard of anyone who had a local word to describe the species other than budeng or lutung (the latter name is used in West and Central Java and Bali to indicate ebony leaf monkeys). On 8 October 1988, S. van Balen (pers. comm., 1995) recorded a group of grizzled leaf monkeys consisting of 10-15 individuals, at c. 1900 m a.s.l. in the forests above Cemoro Sewu. Mt. Wilis. Nowadays only the southeastern slopes of Mt. Wilis are left covered with rain forests and might provide a suitable habitat for the grizzled leaf monkey. The remainder of this mountain complex consists of disturbed secondary forest, bushland and some patches of primary forest. The species was not recorded to be present. In May 1994, Linsley and Nawimar (in Brandon-Jones, 1995b) observed grizzled leaf monkeys on Mt. Cupu-Mt. Simembut in a fragment of natural forest apparently totally surrounded by pine plantations or open ground. In none of the other forest areas of Central Java have grizzled leaf monkeys been recorded, nor did we receive information that could indicate its presence. DISCUSSION Distribution The present study shows that the distribution of the grizzled leaf monkey shows a very scattered pattern with records originating from 33 forest areas. In some of these areas the species is only known with certainty from historic observations and whether or not the species is still present in these localities remains to be solved. Grizzled leaf monkey is a stricktly arboreal species and even relative small areas without forest will not be crossed. The populations in most of the forest areas are thus isolated from one another. Furthermore within the forested areas the forest itself is often not continuous resulting in the fragmentation into sub-populations of grizzled leaf monkeys with a limited or unknown possibility of migration. Surveys in the central parts of Java revealed that the grizzled leaf monkey is still present in all three localities where it has been reported formerly. The independent observations of the species on Mt. Lawu by two observers might be significant, as Brandon-Jones (1995b) questions the validity of Mt. Lawu as the site of collection for the skin collected by Bartels (RMNH 14614). The Bartels did collect on Mt. Lawu, and whether or not this skin was indeed collected on Mt. Lawu or on the Mts. Dieng, as suggested by Brandon-Jones (1995b), might be of historic interest only. At present it is unlikely that, apart from the Mts. Pembarisan-Mt. Segara and perhaps some small isolated forest patches, the species will be present at any other locality. Mts. Pembarisan is an area of lowland and hill forest probably over 200 km2 of which c. 130 km2 are proposed as conservation forest (MacKinnon, 1987) where both Javan gibbon and ebony leaf monkey were observed (Nijman & Sözer,

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1995). Most of the forests in Central Java are severely diminished, and almost all remaining forest areas were visited for several days. In some areas, for instance Mt. Sundoro and Mt. Sumbing, the absence of P. comata may simply be explained by the total lack of suitable habitat, i.e., the total absence of closed canopy forest. In other areas the absence is more difficult to explain. Some areas seemed, at least from the human observer’s eye, to contain suitable habitat. Most of the forests on the central Javan mountains are rather disturbed, either as a result of human influences and/or of natural causes. Those areas that seem suitable at present may consist of regrowth, while isolation did not allow them to be colonized. It was not until 1990, when Seitre & Seitre (1990) observed grizzled leaf monkeys on Mt. Slamet, that there was any certainty about the continued existence of the species in Central Java. Grizzled leaf monkeys were also reported to occur on Mt. Slamet by M. Linsley (pers. comm., 1994). The present study shows that the scanty information we have on the eastern half of the species’ distribution is equally likely due to the limited amount of focussed research done in the area as well as to the rarety of the species. However, it must be stressed that the species is present at few localities only and the nature of the species evades easy observation. Furthermore, for unexperienced observers melanistic individuals are easily confused with the more common Ebony leaf monkey. With the observations of grizzled leaf monkeys at Mt. Sawal, the (historic) presence on Mt. Ciremay and at Cisaga, and the present observations at Mt. Slamet, Mts. Dieng and Mt. Lawu, it becomes clear that the species shows a more or less continuous, though very scattered, distribution from Ujung Kulon in the west to Mt. Lawu in the east. Altitudinal distribution Some confusion exists in literature about the altitudinal distribution of the grizzled leaf monkey. Older researchers (e.g., Hoogerwerf, 1970; Medway, 1970) consider the species to be restricted to the lowlands and not to high mountainous regions, and also MacKinnon (1987) restricts the species to the lowland and hill forest up to 1500 m altitude. According to Whitten et al. (1996) the species’ altitudinal limit is probably about 1250 m a.s.l., although it is sometimes found higher than this, particularly where lowland forests have diminished in area. The given altitudes at which museum specimens were collected range from sea level to 1600 m a.s.l. Recent workers (e.g., Ruhiyat, 1983, 1991; Supriatna et al., 1994) however, consider the species to be confined to higher elevations between 1200 and 1800 m a.s.l., and according to Supriatna et al. (1994), individuals have rarely been noted below 1200 m a.s.l. In Table 6.2 the approximate present-day altitudinal range of the forest on the different localities is given, as well as altitudes at which individuals have been reported, in present or historic times. From these data it becomes clear that the species covers the whole range between lowland and mountains from sea level up to above 2500 m a.s.l. As in West and Central Java more than twice as much forest

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Forest (and) Primates remains above the 1000 m line than below (MacKinnon et al., 1982), it is possible that the species nowadays is more easily observed in montane areas than in lowland and hill forests. In some forest areas densities may be very low and the lack of sightings prevents any density estimates from being made (e.g., Ujung Kulon: Hoogerwerf, 1970; Gurmaya et al., 1992; Halimun: Kool, 1992). Calculated densities range from 28 individuals per km2 at altitudes between 650-850 m on Mts. Dieng (Nijman & van Balen, 1997, chapter 7), 4-5 per km2 between 900-1200 m in Halimun (Maitar in Supriatna et al., 1994), 25 per km2 at 1300-1500 m on Mt. Gede (Sujatnika, 1992; Sujatnika, pers. comm., 1995) and 11 per km2 at 1400-1600 m at Kamojang to 35 per km2 at elevations between 1600-1800 m in Patenggang (Ruhiyat, 1983). As the primary production of the forest decreases with increasing altitude, and the forest composition changes as well, densities at higher altitudes may be lower when compared with lower altitudes. All dietary studies on the species (Ruhiyat, 1983; Sujatnika, 1992, Harjanti, 1996, Nurdiana, pers. comm.) have been conducted in montane forests above between 900 and 2100 m a.s.l. Sujatnika (1992) and Ruhiyat (1983, 1991), respectively, found that only 8% and 14% of the species' diet consisted of fruit and seeds. Harjanti (1996), in contrast, found that some 58% of its diet comprised of fruit and seeds, whereas also Nurdiana (pers. comm.) reported that some 30% of the species diet consisted of fruits. A review of the diet of different Presbytis species found that a proportion of 45-65% of fruit and seeds is typical (Bennett & Davies, 1994). However, these other species were invariably studied in lowland forests. Whether the findings by Sujatnika (1992) and Ruhiyat (1983, 1991) are indicative for living in a sub-optimal habitat and whether or not the species is ‘forced’ to live in mountain forests, due to the ongoing deforestation and disturbance in the lowlands, remains to be solved. Habitat preferences Recently grizzled leaf monkeys have been recorded in both primary and secondary forest, as well as in some plantations (Seitre & Seitre, 1990; Sujatnika, 1992). According to Supriatna et al. (1994) the species might prefer younger rather than mature forest stands, though the present study indicates that the species is present in both primary and secondary forest habitats. Most likely the optimal habitat for the species will be rather undisturbed primary forest; the incidental observations of grizzled leaf monkeys in degradated forests or even plantations may not lead to the conclusion that the species can survive in these habitats for a long period of time. The plantation where Seitre & Seitre (1990) observed the species was situated adjacent to relatively undisturbed natural forest (pers. obs.), while the population in Haurbentes-Jasinga studied by Sujatnika (1992) most likely has been ‘trapped’ inside the plantation forest, unable to move out as there is no adjacent forest left (Sujatnika, pers. comm. 1995). The original forest cover in Java consisted of two types; rain forest in the West and monsoon forest in the East (Van Steenis, 1965), Central Java forming the transition zone between the two. The wettest forest types, viz. the mixed lowland

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and hill rain forest and the montane everwet forest occur only in those areas with at least 30 rainy days during the four driest consecutive months of the year (Van Steenis, 1972). On the southern and southwestern slopes of some of the higher mountains in the otherwise seasonally dry East Java, some patches of everwet rain forest exist. Condensation at higher altitudes causes rain to be given off by the otherwise dry South-East trade winds, resulting in ‘wet islands’ (Van Steenis, 1972). The distribution pattern of mixed lowland and hill rain forest and the montane everwet forest corresponds roughly with the distribution of the grizzled leaf monkey, with the vast majority of records originating from the wettest areas (see Table 6.2). The forests on Mt. Lawu lie far inside the drought area and the population of grizzled leaf monkeys on this mountain is postulated to be a relic of a formerly larger distribution. Conservation status Although the range of the grizzled leaf monkey appears to be more extensive than formerly suggested, the species should still be considered as among the world’s most endangered primate species. As discussed above, the species distribution is severely fragmented and it is likely that many populations in the smaller areas contain too few animals to be viable. In the western part of its range at least some of the larger populations occur in relatively safe nature reserves or national parks, most notably Ujung Kulon, Halimun, and Gede-Pangrango. Although populations in these areas are not totally safeguarded from loss of habitat, or occasional poaching or killing, at least there is a chance that these populations may survive in the long term. This is in contrast with the larger populations in the eastern part of the species’ range, all of which are found in unprotected forest, protected forest in water catchment areas, or production forest. None of the forest areas on Mt. Slamet, Mts. Dieng, and Mt. Lawu are protected as conservation forests, although all three areas have been recommended as such (MacKinnon et al., 1982; RePPProT, 1990). Although more data on the status of the grizzled leaf monkey is needed, especially for those populations in the central part of the island, some recommendations for its preservation can be given. In order to get a better insight in the population status of the grizzled leaf monkey it is suggested to perform a comprehensive survey on the distribution of the species. As little is known about the ecology of the species (cf. Supriatna et al., 1994), more detailed studies could be focussed on the species' habitat preferences and its ability to adapt to various degrees of disturbance over the widest possible range of habitats, in different stadia of re- and degeneration. A dietary study in a lowland forest area, e.g., Mts. Dieng, can explain whether the difference between the reported diets of grizzled leaf monkeys and other members of the genus are intraspecific or due to the fact that grizzled leaf monkeys have been studied in mountain areas and the others in lowland forests. As conversion of natural forest, forest fragmentation and encroachment are an ongoing process, raising the status of one or preferably more of the above-mentioned Central Javan forest areas to a higher conservation status, e.g., wildlife reserve,

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nature reserve, or even national park, seems of prime importance for the survival of the eastern populations of the grizzled leaf monkey. On the basis of the extent of forest and the number of endemic (bird) species present, the two most important forest areas for conservation are considered to be those on Mt. Slamet and Mts. Dieng (Nijman & Sözer, 1996; see also chapter 8). As Java is one of the world’s most active volcanic areas and Mt. Slamet is an active volcano, for the long-term preservation of the grizzled leaf monkey, protection of the population on Mts. Dieng seems most feasible. By following the recommendations of MacKinnon et al. (1982), with the extension into the lowland zone as proposed by Nijman & Sözer (1996), not only the grizzled leaf monkey would benefit from such an action but also several equally unique and endangered wildlife species, most notably the Javan gibbon and the Javan hawk-eagle Spizaetus bartelsi Stresemann 1924. ACKNOWLEDGEMENTS I would like to thank the Indonesian Institute for Science (LIPI) for their sponsorship and the Directorate General of Forest Protection (PHPA) for allowing me to conduct the fieldwork. Mr. Boeadi (Museum Zoologi, Bogor), Miss P. Jenkins (British Museum of Natural History, London) and Dr. C. Smeenk (National Museum of Natural History, Leiden) are acknowledged for access to specimens under their care, and Dr. J. de Vos (National Museum of Natural History, Leiden) for providing information on the Middle Pleistocene fossil. Resit Sözer and Bas van Balen are thanked for their work during surveys. Constructive comments were made by Dr. P.J.H. van Bree, Dr. J. Chapman, Dr. C.J. Hazevoet, S. Cooper, and Dr. H. Albrecht when reviewing earlier versions of the manuscript and also two reviewers made helpful comments.

Geographical Distribution of Ebony Leaf Monkey

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CHAPTER 7

GEOGRAPHIC DISTRIBUTION OF EBONY LEAF MONKEY TRACHYPITHECUS AURATUS (E. GEOFFROY SAINT-

HILAIRE, 1812) (MAMMALIA: PRIMATES: CERCOPITHECIDAE)

Contributions to Zoology 69: 157-177 (2000), with additional data.

ABSTRACT As one of the fundamental units of ecology and biogeography, the geographic distribution of the endemic and threatened ebony leaf monkey Trachypithecus auratus (E. Geoffroy Saint-Hilaire, 1812) on the islands of Java, Bali, and Lombok (Indonesia) has been assessed. All localities where the species has been collected are listed, and forty-two areas (each in itself consisting of numerous smaller sites) where the species has been recorded are discussed. The species occurs in a large variety of forest types, including mangrove, beach, and freshwater swamp forest; everwet lowland and hill forest; dry decidious forest; montane forest up to 3,000 - 3,500 m a.s.l.; and in some forest plantations (teak Tectona grandis, rasamala Altingia excelsa, acacia Acacia spp). In East Java, certain populations are dimorphic, containing, besides the more common melanic individuals, also erythristic individuals. This erythristic pelage morph only occurs in the easternmost part of Java of which the line between Mt. Penanggunang and the surroundings of Mojokerto running south-wards, via Wonosalam and Blitar, to Mts Kidul roughly forms the western boundary. Localities where individuals of the erythristic pelage morph have been collected or observed are given. RINGKASAN Distribusi geografis Lutung Trachypithecus auratus (E. Geoffroy Saint-Hilaire, 1812) (Mammalia: Primata: Cercopithecidae) (Contributions to Zoology 69: 157-177, 2000, dengan tambahan data): Sebagai salah satu bagian ekologi dan biogeografi yang mendasar, distribusi geografis Lutung Trachypithecus auratus (E. Geoffroy Saint-Hilaire, 1812) yang endemik dan terancam punah di Jawa, Bali dan Lombok (Indonesia) telah ditentukan. Seluruh lokasi dimana spesies pernah dikoleksi didaftarkan, dan empat puluh dua daerah (pada setiap daerah tersebut di dalamnya termasuk beberapa tempat-tempat yang lebih kecil) dimana spesies pernah tercatat, didiskusikan di sini. Spesies ini terdapat di banyak tipe hutan, yaitu di hutan mangrove, hutan pesisir, hutan rawa air tawar; hutan dataran rendah dan pebukitan yang selalu basah; hutan kerangas; hutan pegunungan sampai ketinggian 3000-3500


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m dpl; dan di beberapa hutan tanaman (Jati Tectona grandis, Rasamala Altingia excelsa, Akasia Acacia spp). Di Jawa Timur, populasi-populasi tertentu bersifat dimorfis, di samping individu-individu hitam [melanic] yang lebih umum, juga terdapat individu-individu kuning [erythristic]. Tipe bulu ‘erythristic’ ini hanya terdapat di bagian paling timur Jawa, dengan batas barat kira-kira garisnya antara Gn. Penanggungan dan sekitar Mojokerto ke arah selatan, melalui Wonosalam dan Blitar, menuju Pegunungan Kidul. Lokasi-lokasi dimana individu-individu dengan tipe bulu ‘erythristic’ telah dikoleksi atau diamati dipaparkan di sini. INTRODUCTION Being located in the extreme east of the Sundaic subregion, Java and Bali are the most isolated of the remaining land masses and also furthest from the Asian mainland. Java harbours a slightly impoverished non-human primate fauna compared to the other Sundaic islands. There are 5 species, including one nocturnal prosimian, the slow loris Nycticebus coucang (Boddaert 1785) compared to 13 species on Borneo and 12-13 species on mainland Sumatra; the exact species number depends on the taxonomy followed. However, a relative high proportion of them are endemic, viz. 60% (compared to 38-43% on Borneo, and 8-17% on mainland Sumatra). The endemics comprise one species of Hylobatidae, the Javan or silvery gibbon Hylobates moloch (Audebert, 1799) and two species of Colobinae, the grizzled leaf monkey Presbytis comata (Desmarest, 1822) and the ebony leaf monkey1 Trachypithecus auratus (E. Geoffroy Saint-Hilaire, 1812). The Javan gibbon and the grizzled leaf monkey are confined to the wettest forest types, which are more common to the western part of the island, and can be found as far east as Mts Dieng and Mt. Lawu, respectively (Nijman and Sözer, 1995; Nijman, 1995, 1997b). The ebony leaf monkey’s range encompasses a larger area, and the species can be found in other forest types as well, on Java, Bali and Lombok.2 Despite its distribution encompassing a larger area than the other Javan endemics, its range is still restricted, and its habitat has largely dissappeared. Ebony leaf monkey are listed as Vulnerable according to the IUCN threat criteria (Eudey, 1987; IUCN, 1996). The species is protected by Indonesian law and is listed on Appendix II of the CITES convention.

1 Ebony leaf monkey is also known as ebony or moor langur, Javan leaf monkey / langur, silver(ed)

leaf monkey / langur, amongst others. Some of these names, however, are also used for the grizzled leaf monkey Presbytis comata and silvered leaf monkey Trachypithecus cristatus. Locally ebony leaf monkeys are known as either lutung (both melanic and erythristic individuals) and in parts of East Java budeng (usually only the melanic individuals)

2 Based on a single skin, probably originating from the northwestern part of Vietnam, Brandon-Jones

(1984, 1995) described subspecies Semnopithecus (Trachypitecus) auratus ebenus. As it is of little relevance to the present paper, and pending more information on this taxon and its distribution, it is not discussed further.


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The ebony leaf monkey has for a long-time been regarded as conspecific with the silvered leaf monkey, T. cristatus (Raffles 1821) (e.g., Pocock, 1935; Napier, 1985; Wolfheim, 1983), but it was given its specific status by Weitzel and Groves (1987). The species specific status of T. auratus is now generally accepted (e.g., Weitzel et al., 1988; IUCN, 1994; Brandon-Jones, 1984, 1995a; Corbet and Hill, 1992; Oates et al., 1994; Maryanto et al., 1997) although Rosenblum et al. (1997) found a high diversity in mtDNA between and among populations of T. auratus and T. cristatus, without however, a clear distinction between populations of Pensinsular Malaysia, Sumatra or Java. T. cristatus and T. auratus occur allopatrically with the former having a disjunct distribution with populations from southern Burma, southern Thailand, Cambodia and southern Laos and Vietnam, and from the western coast of West Malaysia, Sumatra and Borneo (Corbet and Hill, 1992), while the latter, as stated before, ranges from Java eastwards to Lombok. Both species can be distinguished by skull and dental characters (Weitzel and Groves, 1987; Maryanto et al., 1997). Furthermore, T. cristatus is brown, brownish-grey or blackish brown, while the Javan species is more blackish tingled with brown and grey. In both species some populations are polymorphic in pelage coloration, with melanic and usually a small proportion of erythristic individuals occurring together. This proportion may vary between areas. In the ebony leaf monkey, these populations are restricted to the easternmost part of Java (see Discussion), while in the silvered leaf monkey these populations hitherto only have been recorded from Abai at the mouth of the Kinabatangan River in eastern Sabah, Borneo (Davis, 1962; Payne et al., 1985). Weitzel and Groves (1987) concluded that the type specimen of T. auratus, an erythristic female, must have originated from the easternmost part of Java (see also Brandon-Jones, 1995a). Little is known about the ecology of the species in natural forest areas, since only a limited number of studies have been conducted so far. Most of the comprehensive studies, i.e., those of Brotoisworo and Dirgayusa (Brotoisworo, 1983; Brotoisworo and Dirgayusa, 1991), Kool (1993; Kool and Croft, 1992), and to a lesser extend Megantara (1994) have been conducted in the Pangandaran nature reserve. Pangandaran is a small c. 500 ha. uplifted limestone peninsula at the southeastern corner of West Java. Parts of the area are covered with teak, Tectona grandis and mahogany, Swietenia spp., stands, while the remainder consists of rather dry evergreen forest (Whitten et al., 1996). Data presented by Brotoisworo (1983) suggest densities of c. 185 to 195 individuals km-2. Typical densities in areas where the species has been studied, which are often selected because the species is relatively common, range in the order of 20 to 75 individuals km-2 (Kartikasari, 1986; Supriatna et al., 1988; Bismark and Wiryosoeparto, 1980 in Supriatna et al., 1988; Nijman and van Balen, 1998), with probably the more typical density leaning towards the lower figure (unpubl. data). Pangandaran receives more visitors than any other conservation area in Indonesia, possibly 500,000 annually (Whitten et al., 1996). Densities of the other primate in the reserve, the long-tailed macaque Macaca fascicularis (Raffles 1821) are very high (pers. observ.), quite likely resulting from the visitors feeding them. The large numbers of visitors and the high density of


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macaques most likely has its effect on the socio-ecology and structure of the ebony leaf monkey population. Hence, findings and conclusions arising from studies conducted on the species in Pangandaran are probably not representative and cannot unhesitatingly be extrapolated to other areas. As many other species within the genus Trachypithecus, the ebony leaf monkey lives in groups with one adult male and a number of immature males, females, and young (see reviews by Bennett and Davies, 1994; Newton and Dunbar, 1994). These group sizes range from three to over 30 individuals (pers. observ.; Supriatna et al., 1988; Brotoisworo, 1983). Group sizes on Java seem to differ between areas with different climatic conditions; median group sizes in areas with a more pronounced dry season, which are mainly found in the eastern half of Java as well as along the island’s northern coast, tend to be larger than those found in areas with a perhumid climate (unpubl. data). Extra-group males either live as solitaries or can team up with other bachelor males in bands or small groups (pers. observ.; Bennett and Davies, 1994; Brotoisworo, 1983). A number of studies have been performed on the species’ feeding behaviour (Kartikasari, 1986; Supriatna et al., 1988; Brotoisworo and Dirgayusa, 1991; Kool, 1993; Djuwantoko et al., 1994) often partially in teak plantations. Like all colobines, ebony leaf monkeys possesses a fore-stomach digestive system, which allows them to break down cellulose (Bauchop and Martucci, 1968; Kay and Davies, 1994). This makes the species able to cope with a substantial amount of foliage, a relative unnutricious food source, in their diet (for an overview of food selection in colobines see e.g., Waterman and Kool, 1992). Indeed, although depending on habitat type and seasonality, a large part of their diet consists of leaves and flowers (55% and 67% Kool, 1993; 56% Kartikasari, 1986; 59% Supriatna et al., 1988; 90% Brotoisworo and Dirgayusa, 1991; 94% Djuwantoko et al., 1994). As in most colobines, ripe fruits is not a favoured food source, and often only the seeds are consumed. When fruit is eaten, e.g., figs Ficus spp, mahogany Swietenia macrophylla, and acacia Acacia leucophloea, it is mostly not ripe (Kool, 1993; Kartikasari, 1986). The geographic distribution of a species is perhaps the fundamental unit of ecology and biogeography. It affects probability of extinction (Jablonski, 1987) and different range sizes of species ultimately determine the number of species in a given area. The distribution of a species is determined by its geographical range and by the evenness or patchiness of occurrence within its range. Ecological analysis of species distribution patterns depends on the accuracy of the distributional data on which it is based: if a distributional pattern has been incorrectly described any interpretation of that pattern will be erroneous (cf. Wiens, 1992). Brockelman & Ali (1987) stress the importance of publishing reliable and detailed data on the distribution of primates. The need for accurate mapping of species’ ranges, their relevance to biogeographic processes and the structure of local species assemblages, and the potential sources of error in estimating species-range-size distributions have recently been discussed by Jones (1998) and Gaston (1996). Furthermore, for the proper assessement of a species’ conservation status and in order to monitor changes


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in abundance, range, and status an accurate description of its range of occurrence is essential. Therefore, as part of an ongoing study on the ecology and conservation status of ebony leaf monkey, the present paper attempts to thoroughly assess the geographical distribution of ebony leaf monkeys on Java, Bali and Lombok. METHODS The data originate from surveys conducted by the author over a period of 16 months in March-September 1994, June-July 1995, August-September 1997, September 1998-January 1999, June 1999-February 2000, June-September 2000 on Java, Bali, Lombok, Madura, and Kangean. The presence or absence of ebony leaf monkeys was assessed by surveying inside the forest and by scanning over the forest from vantage points (hill tops or forest edge). While in the forest areas additional information on the presence of ebony leaf monkeys was gathered by interviewing local inhabitants in Bahasa Indonesia. These findings were supplemented with data derived from the literature, information from collected specimens stored in various museums, and from personal correspondence with other observers. All records listed are those of the author, unless stated otherwise. Areas in which ebony leaf monkeys were observed are listed by province and in a west to east sequence. For each area the county names in which it is situated is given, a short description of the type of habitat is presented, the status and records of ebony leaf monkeys in that area are listed, as are the specimens, if any, which have been collected. Specimens collected were either collected in the described area itself or the described area nearest to the site of collection. Abbreviations employed for the institutions at which the specimens are stored are: ZMA: Zoological Museum Amsterdam, the Netherlands; RMNH: Natural Museum of Natural History, Leiden, the Netherlands (many skins have only a collector’s number and no access number); MZB: Museum Zoologicum Bogoriense, Bogor, Indonesia; BMNH: Natural History Museum, London, UK; ZRC: Zoological Reference Collection, Singapore. Note that some areas discussed in fact constitute of numerous isolated patches of forest, and that ebony leaf monkeys are not by definition present throughout the entire area. Furthermore, within forest areas ebony leaf monkeys may prefer certain parts above others. Localities from where information was received about the presence of individuals of the erythristic pelage morph, either from direct observations, from hearsay evidence or from other biologists working in the area, as well as localities from where erythristic specimens have been collected, are indicated. RESULTS For the geographic location of of the areas discussed in this section, see Figure 7.1. All localities are discussed in a west to east sequence, and are classed by province.


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Figure 7.1 Geographical distribution of ebony leaf monkey Trachypithecus auratus (E. Geoffroy Saint

Hilaire, 1812) on Java, Bali, and Lombok, Indonesia. The map shows areas covered with natural forest (after RePPProT 1990), and the areas where Trachypithecus auratus has been recorded. Note that on this scale many small areas of forest do not show. The stippled line includes the area from where individuals of the erythristic pelage morph have been recorded. Numbers correspond with those thearea account.


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Province of West Java (including DKI Jakarta) 1. Ujung Kulon County: Pandeglang. Habitat: Ujung Kulon is a more than 750 km2 area of old secondary lowland forest, with primary forest in the higher parts. The peninsula is relatively secure from logging and encroachment, but the mainland part is threatened by surrounding cultivation. Status: The species is present mainly in the coastal zone and along the rivers, but also in the interior (July 2000; Hoogerwerf, 1970). Hoogerwerf observed ebony leaf monkey mainly in the peninsular part of the reserve, but the species is also present on the mainland on Mt. Honje (Gurmaya et al., 1992; Ruhiyat, 1991). The species is not present on Peucang or Panaitan island (Hoogerwerf, 1970). Specimens collected: Niur: MZB 6694. 2. Ranca Danau, Mt. Karang and Mt. Aseupan Counties: Pandeglang, Serang. Habitat: Fragmented patches of forest with the last remaining substantial area of fresh water swamp forest in Ranca Danau totalling c. 250 km2, while another 170 km2 is present in two patches in the adjacent Gunung Tukung Gede Nature Reserve. Several thousands of hectares of disturbed lowland forest remain on Mt. Aseupan, while c. 100 ha of lowland forest is protected as recreation forest near the Curug Gendang waterfalls, Carita. On Mt. Karang c. 30 km2 of montane forest remains ranging from c. 1000-1778 m. Status: A small number of groups were observed near the waterfalls, as well as near the guard post at the entrance of the recreation forest at Carita (Sept. 1997; July 2000); one group was observed to foray into the adjacent Rasamala Altingia excelsa plantation. S. van Balen (in litt., 1998) recorded the species on the 1346 m tall Mt. Pulosari, c. 6 km south-east of Mt. Aseupan (Oct. 1995). The species is present in the swamp forests of Ranca Danau and hill forest of Mt. Tekung Gede (Melish and Dirgayusa, 1996), as well as in the montane forests of Mt. Karang (April 1995: S. van Balen in litt. 1998). Specimens collected: Ujungtebu: ZRC 4382. 3. Dungus Iwul and Yanlapa County: Bogor. Habitat: Dungus Iwul is a small relict patch of primary forest (9 ha) surrounded by rubber Hevea brasiliensis plantation (MacKinnon et al., 1982). Despite its size the


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reserve is significant as one of the few remnants of low altitude lowland tropical rain forest left on Java (Whitten et al., 1996). Yanlapa is a slightly larger (32 ha) nature reserve, consisting of lowland rainforest on red clay soil, relatively well protected and used for scientific study (MacKinnon et al., 1982). Status: Dungus Iwul is inhabited by a single group of ebony leaf monkeys, which occasionally foray into the surrounding rubber plantation (S. van Balen in litt. 1998; Whitten et al., 1996). In Yanlapa, not only ebony leaf monkeys are present, but also grizzled leaf monkeys (S. van Balen, in litt., 1998). 4. Mt. Halimun and Mt. Salak Counties: Sukabumi, Bogor, Banten. Habitat: The Halimun National Park covers lowland and hill forest from 500 to 1929 m (MacKinnon et al., 1982). The park proper totals 400 km2, with some additional lowland forest being situated outside the park boundaries. The Mt. Salak is a 2211 m tall volcano, well vegetated above the 1000-1200 m line. Encroachment from surrounding agriculture and large tea estate enclaves, hunting and illegal gold mining form major threats to the area. Status: The ebony leaf monkey is a well known inhabitant of the Halimun National Park (e.g., Ruhiyat, 1991), and by virtue of its size the area probably harbours a significant population of the species. Observed frequently near the Cikaniki research station (Aug. 2000). Kool (1992) reported of the sighting of four, most likely different groups in the western part of the Halimun reserve; one group in Aug. 1989 (S. van Balen in litt. 1998). Mt. Salak: regularly observed by S. van Balen (in litt., 1998); a group of seven individuals was observed lower montane rain forest feeding in river valley on the southeastern slopes (Aug. 1997) and one group was heard near Kawa Ratu (Sept. 1998). Specimens collected: Jasinga: MZB 6694, 3188; Leuwilang: MZB 2344,-5; Mt. Salak: ZMA 5327, RMNH; Cisalak: MZB 558; Bolang: MZB 1876, 560. 5. Jampang Kulon County: Sukabumi. Habitat: The forests in this rugged and sparsely populated area have partially the status of protection forest, and is scattered into several smaller, and one larger forest block. The altitudinal range lies between sea level and c. 700 m a.s.l. The Cibanteng Nature Reserve in the northern part of this area and the Cikepuh Game Reserve (together more than 8500 ha) were established in 1925 and 1973 respectively (MacKinnon et al., 1982). Cibanteng is a coastal lowland forest, and is adjacent to larger Cikepuh Game Reserve. The habitat is mostly secondary forest with patches of primary forest and grassland.


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Status: Ladjar and Simanjuntak (1994) studied populations of the species in the Cikepuh Game Reserve and found them present from Citirem to Cibuaya. S. van Balen (in litt., 1998) recorded ebony leaf monkeys in Feb. 1987 in the forests of Ciogong near the village of Sindabarang on the southern coast. Ebony leaf monkeys are probably present in a large number of forest areas within this rugged and sparsely populated area. Furthermore, ebony leaf monkeys may survive in a number of forest areas along the West Javan southern coast possibly from Cikepuh intermittedly to Leuwang Sancang [11]. Specimens collected: Teluk Pelabuan Ratu: ZRC 4380; Ciwangi: BMNH 1909.1.5.14,-15,-16,-17. 6. Mt. Gede-Pangrango, Puncak, Megamendung, Mt. Pancar Counties: Bogor, Sukabumi, Cianjur. Habitat: The Mt. Gede-Pangrango are two well-known volcanoes, south of Bogor. A pass runs through the Puncak area, with the Gede-Pangrango to the south and Telaga Warna Nature Reserve and Megamendung to the northeast. Although virtually the entire area is enclosed in the 15,000 ha Gede/Pangrango National Park, ranging from 500-3019 m a.s.l., encroachment from surrounding agriculture, hunting, and other activities impose continuous threats. The Telaga Warna area forms a 350 ha nature reserve, but the remaining part of the area is much threatened by holiday resorts and encroachment of tea estates. Mt. Pancar is a somewhat isolated hill of 800 m with moderately disturbed forest on its summit. Status: Ebony leaf monkeys have been observed in a number of localities, i.e., Pasir Pogor (June 1994), above Selabintana (Sept. 1997), Cibodas (June 1995; Sept. 1999; June 2000), the forests near Taman Safari Cisarua (Aug. 1994), Telaga Warna (Sept. 1997), near Cibulau (Aug. 1997), and an isolated population survives on Mt. Pancar (July 1995). The species is most likely to be present throughout the entire forest area. Specimens collected: Mt. Pancar: BMNH 1907.6.18.1; Cikaso: MZB 8008; Mt. Pangrango: RMNH; Cikujang: MZB 6693; Cibodas: BMNH 1949.423, 1954.62, MZB; Sindanglaja: collected by Robinson and Kloss (1919). 7. Muara Gembong, Muara Angke-Kapuk, Tanjung Sedari Counties: Bekasi, DKI Jakarta. Habitat: Muara Gembong is a mangrove area at the mouth of the Citarum River, c. 60 km east of Jakarta. In 1981 at least 1000 ha of mangrove forest was left, by 1984 some areas had been converted into rice fields, settlements and fish ponds, and by 1987 the forest were almost completely destroyed (Supriatna et al., 1989). The Muara Angke-Kapuk is a small nature reserve totalling 15.4 ha, west of Jakarta. The


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area is covered with mangrove forest in a river delta (MacKinnon et al., 1984). Tanjung Sedari is a 8200 ha large proposed nature reserve, wich is presently largely devoid of its mangrove forest (Rombang & Rudyanto, 1999). Status: In the Muara Gembong, the ebony leaf monkey lived in groups of up to 30 individuals, at a density of 20 individuals km-2, but currently there is hardly forest left (Supriatna et al., 1989). The Muara Angke supports small populations of ebony leaf monkeys and long-tailed macaques Macaca fascicularis (MacKinnon et al., 1984). Silvius et al. (1987) report of the presence of ebony leaf monkey in Tanjung Sedari. The conversion of mangroves into fish and shrimp ponds and the intensification of shrimp ponds especially along the north coast of Java, increased dramatically during the last decades. Most tall trees dissapeared and it is very hard to find any piece of forest that might be suitable for ebony leaf monkeys. Mauk, another (proposed) nature reserve, that was known for its mangrove and swamp forest (MacKinnon et al., 1982) appeared to be completely devoid of closed forest and/or tall trees (van Balen et al., 1993). If the north coast of West Java still holds additional populations of ebony leaf monkey, regretably these will be small and isolated from one another, making them especially vulnerable to extinction. 8. Sanggabuana Counties: Purwakarta Habitat: The forests of Sanggabuana or Jati Lahur comprise of c. 5000 ha, approximately 2500 ha of which have been proposed as a recreation forest (MacKinnon et al., 1982). The area is covered with mostly disturbed lowland forest ranging from c. 150 to 1291, and is centered around the artificial lake of Jati Lahur. Despite being somewhat disturbed, the area is important for the conservation of primates as all three Javan endemics do occur in the area. Status: The species is reported to be present by B.O. Manullang (pers. comm. 1997); small number of individuals observed in Oct. 1986 (S. van Balen in litt. 1998). 9. North Parahyangan Counties: Bandung, Sumedang, Purwakarta. Habitat: The highlands around Bandung are collectively known as the Parahyangan (from para: many, and hyang: Gods). The northern part includes a number of tall volcanoes of which the Tangkuban Perahu is the most well known. The area furthermore includes some interesting (proposed) reserves, including the Mt. Tapomas Hunting Reserve (1250 ha), and Burangrang Nature Reserve (2700 ha). Status: The species is has been reported to be present in Burangrang and Mt. Tapomas (MacKinnon et al., 1982). Wiltjes-Hissink (1953) observed ebony leaf monkeys on the southern slopes of Tangkuban Perahu above Lembang at 1700 m


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a.s.l., whereas Rombang & Rudyanto (1999) report the presence of the species on Mt. Manglayang. Specimens collected: Subang: ZRC 4374,-5. 10. South Parahyangan Counties: Bandung, Garut, and Cianjur. Habitat: The extensive mountain forests south of Bandung form a more or less continuous block, locally intersected plantations and roads. Generally forest in the area is forest is extant above c. 1200 m a.s.l. A number of nature reserves are established in the area, of which the most important ones are Mt. Tilu (8,000 ha), Mt. Simpang (15,000 ha) and Kawah Kamojang (8,000 ha), six others being less important because of small sizes; more importantly, four new reserves have been proposed across the area, totalling a coverage of almost 70,000 ha, ranging from 300 to 2182 m a.s.l. (MacKinnon et al., 1982). Status: Observed near Situ Patengan, Mt. Patuha (July 2000). Ruhiyat (1991) reported ebony leaf monkeys to be present at an additional number of sites throughout the South Parahyangan, i.e. Mt. Halu, Mt. Tilu, Mt. Papandayan, and Kawah Kamojang. Most if not all observations were made in areas at 1200 m a.s.l. and above. MacKinnon et al. (1982) reported the species to be present also on Mt. Simpang. Probably, ebony leaf monkey is present throughout the entire area in numerous isolated populations. Specimens collected: Pengalengan: RMNH; Tirtasari: RMNH; Cibeureum: RMNH. 11. Leuweung Sancang County: Garut. Habitat: The Leuweung Sancang area contains a 2157 ha nature reserve ranging from sea level to 180 m a.s.l. The area is covered with sand dunes, mangroves, beach forest and primary rain forest on limestone. The outer parts of the reserve are heavily damaged by illegal tree cutting (MacKinnon et al., 1982). Status: Ruhiyat (1991) and A.R. Purnawa (pers. comm. 2000) reported the species to be present in the area. Further information is not yet available. 12. Mt. Ceremai Counties: Majalengka. Habitat: Mt. Ciremai is a 3078 m tall volcano south of Ceremai; c. 12,000 ha of forest have been proposed as recreation forest (MacKinnon et al., 1982)


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Status: There have been no reports on the presence of ebony leaf monkeys, but Napier (1985) reports the presence of twelve skulls from Cirebon, which may have originated from this mountain. Specimens collected: Cirebon: RCS(OM) S70.43(A)(G) (Napier 1985). 13. Mt. Sawal Counties: Ciamis. Habitat: The forests on Mt. Sawal comprise of an isolated patch of forest of c. 5400 ha, which have been designated as a wildlife reserve. Ranging from 600-1704 m a.s.l. the area contains tree species as Altingia excelsa and Podocarpus imbriacata and may be a valuable area for both flora and fauna (MacKinnon et al., 1982). Ceringrin is situated in the lowlands below 200 m a.s.l, whether or not forest remains is not known. Status: The species was recorded in a secondary forest patch, on the southern slopes of Mt. Sawal at c. 1100 m a.s.l and in a patch of Acacia trees (July 1995). The species was not recorded on the northern slopes, but according to local officers of the forestry departement the species is present troughout the reserve. Specimens collected: Ceringrin: RMNH. 14. Pangandarang-Karangnini Counties: Tasikmalaya, Ciamis. Habitat: Pangandaran is a small c. 500 ha uplifted limestone peninsula at the southeastern corner of West Java. The area consists of a 38 ha tourist park, adjacent to a 457 ha large nature reserve (MacKinnon et al., 1982). Parts of the area are covered with Teak and Magogany stands, while the remainder consists of rather dry evergreen forest (Whitten et al., 1996). Karangnini consist largely of beach forest and teak forest. The latter is intersected by the Cikabuyatan river, the valley of which is covered with mixed forest. Status: Pangandaran has been the location where a number of researchers have colllected data on ebony leaf monkey (e.g., Brotoisworo, 1983; Brotoisworo and Dirgayusa, 1991; Kool, 1993; Kool and Croft, 1992; Megantara, 1994). The species is very common and in the tourist park and adjacent nature reserve at least 5 different groups observed were fully habituated to the presence of humans (Sept. 1997). Group sizes are relative large in comparison to other West Javan localities. In Karangnini three groups were observed at the mouth of the Cikabuyatan River (Sept. 1997).


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Specimens collected: Pangandaran: BMNH 1909.1.5.4,-5,-6(a),-7; Kalipucang: BMNH 1909.1.5.18. Province of Central Java (including DI Yogyakarta) 15. Segara Anakan-Nusa Kambangan Counties: Cilacap. Habitat: Sagara Anakan is the shallow bay on the southern coast of Java into which the Citanduy, Cibereum, and other rivers flow. The area consists of a complex of mangrove and tidal swamp forests. South of the area lies the 300 km2 island of Nusa Kambangan. The island largely is under control of the Prison Service of the Minsitry of Justice, as three highly secured prisons are situated on the island. On the island c. 8000 ha of largely undisturbed lowland forest remains. Status: Erftemeijer et al. (1988) reported ebony leaf monkeys to be present in groups of up to 10 individuals in the ‘better’ forest areas, i.e., further inland in Segara Anakan. Near Kabujatan, three groups were observed retreating on a small hill after having spent the day in the mangrove forests (Sept. 1997). On Nusa Kambangan (Sept. 1997) no ebony leaf monkeys observed, but the species was known to most of, if not all, of the villagers of Klacis. Apparently the species occurs all over the island. Specimens collected: Jumblang: MZB 2094; Cilacap: BMNH 1909.1.5.8,-9,-11,-12,-13; Karangbolong: ZRC 4.377. 16. Mts Pembarisan Counties: Brebes. Habitat: In this severly under-explored lowland and hill rainforest area on non-volcanic soils, c. 13.000 ha is proposed as a nature reserve (MacKinnon et al., 1982); to the south the area is bordered by extensive Pine plantations, to the east by Teak forest. The area was regarded as one of the most valuable remaing forest in Central Java (MacKinnon et al., 1982). Status: One group of c. 8 individuals was observed on Mt. Segara, in the eastern part of the Pembarisan mountains (July 1994). No further information is available. 17. Mt. Slamet Counties: Banyumas, Brebes, Tegal, Pemalang, Purbolinggo. Habitat: The 3418 m Mt. Slamet is Java's second tallest mountain. On the wetter southern slopes extensive forest remains down to 700 m a.s.l. On the eastern slope forest disappeared below 1900 m a.s.l. Currently the forest above 1000 m a.s.l. on Mt. Slamet are a proposed nature reserve of 15,000 ha (MacKinnon et al., 1982),


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while proposals to include the forests at lower elevations have been made (Nijman and Sözer, 1996). Status: Ebony leaf monkeys have been observed on the southern slopes above Baturaden at c. 700-800 m a.s.l. (April-Aug. 1994; June 1995). The species was also present in oak-laurel forests on the upper eastern slopes above Blambangan, where three groups were observed between altitudes of 2,200-2,800 m a.s.l. (June 1995). Specimens collected: Kaligua: MZB 6690,-91,-92; Kalikidang: RMNH; Curugilang: RMNH. 18. Mt. Cupu-Simembut County: Banjarnegara. Habitat: On these mountains small fragments of natural forest, surrounded by either open ground or pine plantations, remain. The altitudinal range of the forests in this area lies from c. 350-1000 m a.s.l. Status: Linsley and Nawimar (1994 in Brandon-Jones, 1995) reported the species to be present in a forest block on a slope of the Tambra river, south of the Argus confluence. 19. Mts Dieng Counties: Pekalongan, Batang, Tenaggung, Wonosobo, Banjarnegara. Habitat: The mountains north and northwest of the Dieng plateau are still covered with an extensive block of natural forest covering the total range from lowland to upper montane. On the northern foothills of Mt. Lumping above Linggo, the forest (partly a former coffee Coffea spp. plantation abandoned in the 1930s) are forested above c. 300 m, while on the eastern slopes of Mt. Prahu, in the east, only above 1500 m. The forest totals 25,500 ha, of which the area above 1000 m is a proposed game reserve (MacKinnon et al., 1982). Currently the area below 1000 m a.s.l. is unprotected forest managed by the Ministry of Forestry (Perum Perhutani), but proposals to protect the lowland forests in the western part of the area have been put forward (Nijman and Sözer, 1996). Main threats to the area are planned logging of the lowland forest near Linggo and the conversion into rubber, pine Pinus merkusii, or damar Auracaria spp. plantations. Status: A number of groups were observed throughout the lowland and lower montane forest in the westernpart of the Dieng mountains, and in the montane forest in the central, western and eastern parts (Sept. 1994; June-July 1995; Sept. 1998-Jan. 1999; July 1999-Feb. 2000; July-Aug. 2000). The species was reported to be present in the upper montane forests of Mt. Prahu as well. Bartels (1937) reported on the occurrence of mixed groups of P. comata and T. auratus in the Pagilaran plantation


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at c. 1300-1500 m a.s.l. Densities at the lowland forests near Linggo are in the order of 20 individuals km-2 (Nijman and van Balen, 1998). Specimens collected: Pagilaran: RMNH. 20. Ceruk Sewu County: Temanggung. Habitat: A small patch of isolated secondary forest on a cliff near a waterfall. The area is used as a tourist resort. Status: One group of ebony leaf monkeys was observed, most likely only a few other groups might present. The group was observed feeding near the waterfall and seemed partially habituated to the presence of humans (May 1994). Specimens collected: Candi Roto: RMNH. 21. Mt. Ungaran Counties: Salatiga. Habitat: This small isolated volcano near Semarang is covered with forest above 1500 m, and a c. 5,500 ha area is proposed as nature reserve (MacKinnon et al., 1982). Status: What was most likely this species has been recorded in Oct. 1998 on Mt. Ungaran’s western slopes (F. Arga Narata and Sugihartono, pers. comm. 1998), and ebony leaf monkey have been collected nearby, in Gendangan. Specimens collected: Gendangan: MZB 6695. 22. Mt. Merapi and Mt. Merbabu Counties: Slemen (DI Yogyakarta), Magelang, Blora, Sukoharjo. Habitat: The twin volcanoes Merapi and Merbabu c. 15,000 ha are proposed as a recreation forest (MacKinnon et al., 1982). The southern slopes of Mt. Merbabu seem to have little remaining natural forest, a situation similar to the northern side of Mt. Merapi. In November 1994 an eruption devastated part of the forest on the southern slopes, but spared most of the forest to the east. The northern slopes have been deforested since long whereas the western slopes are devastated by a permanent outflow of lava. Mt. Merapi is situated north of one of Java’s larger cities, Yogyakarta, and is very attractive for recreational purposes. Status: Ebony leaf monkeys have been observed on the southern slopes above Kaliurang in 1994, a few months prior to the eruption (June 1994). In the following


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year (July 1995) ebony leaf monkeys were said to be present in small patches of forest on the northwestern slopes of Merapi at c. 1500 m a.s.l. The species is probably present throughout the area (F. Arga Narata and Sugihartono, pers. comm. 1998). 23. Mt. Murio Counties: Jepara, Kudus, Pati. Habitat: The peaks of this dormant volcano on Java's northern coast are covered with mostly secondary forest from c. 600-1602 m a.s.l. The lower, central parts of the complex are cultivated. The forests on Mt. Murio are a proposed nature reserve (MacKinnon et al., 1982). Status: H.V.J. Sody collected two females at Pangonan at an altitude of 550 m a.s.l. During two surveys (Aug. 1994; July 1995) in the forest above Colo, no ebony leaf monkeys were observed, although the forest were seemingly still suitable. According to local inhabitants ebony leaf monkeys used to occur here, but nowadays only long-tailed macaques were present. On 3 July 1995 while in the forests near the Jalong coffee plantation on the eastern slopes of Mt. Murio we received information that the ebony leaf monkey is still present in these forests, but the species was not observed by me. Specimens collected: Pangonan: RMNH. 24. Cepu County: Blora. Habitat: The region is known for its vast extend of teak forests, which often alternate with small patches of alang-alang Imperata cylindrica grass and secondary vegetation. Status: Djuwantoko and collegues (1992; Djuwantoko et al., 1994) studied the feeding and ranging behaviour of ebony leaf monkeys in the forests plantations near Cepu. Rappard (1941), residing in the village of Cepu, reported on ebony leaf monkeys in the teak forests nearby. The status remains to be solved, but the species is likely to be present in a number of (isolated) forest areas. 25. Mt. Lawu Counties: Karanganyar. Habitat: Mt. Lawu is situated on the border between Central and East Java. The upper slopes of the mountain remain forested. The volcano is a popular tourist attraction. A c. 21,000 ha large nature reserve has been proposed (MacKinnon et al., 1982).


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Status: Ebony leaf monkey were observed on the southern and southeasten slopes at altitudes between 1800-2400 m a.s.l. (Aug. 1994; June-July 1995) Specimens collected: Mt. Lawu: RMNH. Province of East Java 26. Mt. Liman-Wilis Counties: Madiun, Nganjuk, Kediri, Tuban, Trenggalek, Ponorogo. Habitat: The mountain complex comprises four summits of which the Liman is the tallest (2563 m a.s.l.). Forest fires occur regularly and large parts of the area are covered with shrubs and small trees and sparse Casuarina forest on the upper slopes. The lower southeastern slopes of Mt. Wilis are still well forested, while in the other parts scattered patches of forest remain amidst secondary forest, regrowth, bushes, and plantations. The forests on Mt. Wilis are a proposed 45,000 ha large game reserve, while two small areas, Mt. Sigogor (190 ha) and Picis (28 ha), are long-time registered nature reserves (MacKinnon et al., 1982). Status: A number of groups of ebony leaf monkeys were observed mainly in the eastern and northern part of the area between altitudes of 1,300-1,600 m a.s.l (July 1995). The species was observed in the primary forests of both nature reserves, as well as in planted pine and acacia stands. Specimens collected: Madiun: BMNH 1938.11.30.9. 27. Mt. Penanggunang-Mt. Arjuno Counties: Modjokerjo, Malang, Pasuruan. Habitat: The Mt. Kawi and Mt. Arjuno area is presently a mozaic of partly regenerating former coffee plantations, partly degrading lowland, hill and montane forest in varying degrees of disturbance (Smiet, 1992). Only small parts of the area have protection in three existing nature reserves, of which the almost 5,000 ha of Arjuno Lalijiwo is by far the largest. Mt. Pananggunang is situated north of Arjuno, and remains largely covered in forest from c. 600 to the summit at 1653 m a.s.l. Status: On Mt. Pananggunang a fair number of groups were observed near the PPLH Centre for Environmental Education, and near the Hindu temples of Candi Colotundo (Aug. 1997). This is probably the locality with the highest percentage of groups containing one or more red individuals. On Mt. Arjuno groups were observed in the lowland forests near the village of Tretes, between 1250 m a.s.l. and the saddle at 2250 m a.s.l. at the northern slopes (Aug. 1997), between 1300-1700 m a.s.l. near the hot water springs of Cangar, and at 1500 m a.s.l. near the Batu Ondo(k) waterfalls, on the southern and southeastern slopes (Sept. 1997, Nov.


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1998). Individuals of the erythristic pelage colour morph have been recorded in the area. Specimens collected: Kawarasan: RMNH; Rembang: BMNH 1938.3.14.2, 1954.57; Arjuno: MZB 1731, -2, ZRC 4378, -9; Mojokerto: BMNH 1938.11.30.12; Pugeran: MZB 3620. 28. Mt. Kawi-Kelud Counties: Malang, Blitar, Kediri. Habitat: Some 50,000 ha of continuous forest between the volcanoes of Mt. Kawi and Mt. Kelud ranging from 300 to 2806 m a.s.l. is a proposed nature reserve (MacKinnon et al., 1982). For a description of the area see Smiet (1992). The area suffers heavily from forest fires. Status: Three groups observed at altitudes between 1200 and 1700 m a.s.l. near the waterfalls of Cuban Rondo, Mt. Kawi (Sept. 1997). Kohlbrugge (1896) reported on specimens from Lawang. The species has been collected throughout the area. Individuals of the erythristic pelage colour morph have been reported from in the area. Specimens collected: Blitar: MZB 3372; Batu: RMNH. 29. Mts Kidul and P. Sempu Counties: Malang. Habitat: The Kidul mountains on the southern coast of Malang are covered with some large stands of largely undisturbed lowland rain forest. The Lebakharjo and Bantur forests, respectively covering 13,000 and 5,000 ha, constitute two of the most important areas of lowland forest on Java, and have been proposed as reserves (Whitten et al., 1996; Bekkering and Kucera, 1990). Only a few hundred hectares near Balekambang, receive protection as a recreation forest. Wood cutting and hunting form major threats (MacKinnon et al., 1982). The area is connected through plantations, secondary forest area and separated by a road from the 57,000 ha Mt. Bromo Tengger Semeru National Park. The island of Sempu is situated a few hundred meters of the coast of the Lebakharjo and Bantur forests, and has been designated as a nature reserve. Status: Observed in Oct. 1989 near the village of Pujiharjo in Lebakhardjo (S. van Balen in litt., 1998). Three groups of ebony leaf monkey observed near Balekambang, both in the beach forest as in the rain forest adjacent to it (Aug. 1997), and the species seems to be present throughout the entire area. Individuals of the erythristic pelage colour morph have been reported to be present by local


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wardens in Balekambang and Nursahid et al. (1996) reported on the occurrence of erythristic individuals on P. Sempu. Specimens collected: Wonokoio: RMNH. 30. Mt. Bromo-Tengger-Mt. Semeru Counties: Probolinggo, Malang, Pasuruan, Lumajang. Habitat: The Bromo-Tengger National Park is best known for its spectacular 10 km wide Tengger Caldera, its sand sea with squats the active volcano Mt. Bromo. The Mt. Semeru is Java’s tallest mountain rising 3,676 m a.s.l. Its slopes are covered with some undisturbed lower and upper montane forests as well as Casuarina forests. Status: Van Bemmel-Lenneman and van Bemmel (1940) reported on the occurrence of ebony leaf monkeys in the Tengger mountains, and noted that the species occurs relatively high up, in the surroundings of the Smeroehoeve at 2100 m a.s.l., and even higher up near the summit of the Semeru. Also van der Veen (1940) recorded a number of ebony leaf monkeys that had died at Semeru’s summit. Individuals of the erytristic pelage morphs apparantly were more abundant than the melanic morph (van Bemmel-Lenneman and van Bemmel, 1940). Kohlbrugge (1896) reported on specimens from Puspo. Beudels & Hardi (1980) list the species for the national park and R. Nursahid (pers. comm. 1998) reported the species to be common on Semeru’s western slopes. Specimens collected: Tosari: RMNH. 31. Nusa Barung County: Jember. Habitat: Nusa Barung is an island c. 6,000 ha in size, 10 km of the southern coast of the eastern part of Java. It is covered in deciduous forest and has been a reserve since 1920 (MacKinnon et al., 1982). Timber theft posses a significant threat to the island and most marketable timber has been removed (Whitten et al., 1996) Status: Whitten et al. (1996) and MacKinnon et al. (1982) reports the presence of ebony leaf monkeys on the island. 32. Daerah Tinggi Yang Counties: Probolinggo, Bondowoso, Jember. Habitat: The Yang highlands comprise of an undulating plateau between 1,700 and 2,400 m a.s.l. The vegetation of the plateau mainly consist of Casuarina forests and grassy meadows. The forests are partially enclosed in a 14,500 ha wildlife reserve.


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Threats to the area include poaching, burning of the grasslands, and use of the area for military exercises (MacKinnon et al., 1982). Status: MacKinnon et al. (1982) report ebony leaf monkey to be present on the Yang Plateau. The species was reported to be present on Mt. Lamongan, west of the plateau (Aug. 1997). Individuals of the erythristic pelage colour morph have been recorded in the area. Specimens collected: Jember-Puger RMNH; Jember: MZB 6698; Pegunungan Yang: MZB 1927; Besuki: RMNH. 33. Pasir Putih, Mt. Ringgit and Mt. Beser Counties: Bondowoso, Panarukan. Habitat: Pasir Putih is a popular tourist beach on the northern coast of East Java. Just outside the village some fringes of mangrove forest still can be found. These forest are connected with the deciduous forests on Mt. Ringgit and Mt. Beser by a c. one km wide strech of teak forest. The forest on Mt. Ringgit and Mt. Beser are among the few remaining areas of deciduous forest left on Java. On Mt. Ringgit c. 2000 ha has been proposed as nature reserve, while on Mt. Beser c. 4000 ha has been proposed as wildlife reserve, both areas should be managed together (MacKinnon et al., 1982). Status: Ebony leaf monkeys have been observed in the mangrove forests near Pasir Putih, and in the teak forests between Pasir Putih and Mt. Ringgit (Aug. 1997, I. Setiawan, pers. comm. 1997). The species is very common on Mt. Ringgit (Aug. 1997); over 6 groups, observed in teak forest, in dense shrubs, and in dry deciduous forest. The erythristic pelage colour morph is present (I. Setiawan and A. Prima Setiadi, pers. comm. 1996), which was confirmed by local inhabitants. 34. Meru Beteri Counties: Jember, Banyuwangi. Habitat: This 50,000 ha lowland forest ranging from sea level to 1223 m a.s.l. has the status of national park; it is the last area where the presence of Javan tigers has been confirmed (MacKinnon et al., 1982). The former coffee plantation enclave is presently being abandoned, but encroachment from the outer sides keep threatening the integrity of this important area. The national park is separated by a relatively narrow area of plantations, secondary forest and a road from the Ijen Mountains. Status: Ebony leaf monkeys are most likely to be present throughout the greater part of the National Park. Hoogerwerf (1972) reported ebony leaf monkeys to be common, especially in the surroundings of Bandi Alat and Sukamade. Bismark and Wiryosoeparto (1980 in Supriatna et al., 1988) studied the species in Meru Beteri,


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and reported densities of 20 individuals km-2. Seidensticker and Suryono (1980 in Whitten et al., 1996) illustrated the unevenness of ebony leaf monkey in the Meru Betiri National Park, indicating a preference for beach and hill forest. 35. Mts Ijen Counties: Banyuwangi, Bondowoso, Ampera, Jember. Habitat: The area is only partly protected by the 2,560 ha nature reserve of Kawah Ijen Merapi Ungup-ungup, and three tiny reserves. More important reserves are proposed for Mt. Raung (60,000 ha) in the southwest to Meru Betiri and Maelang (70,000 ha) in the northeast to Baluran National Park (MacKinnon et al., 1982). Status: Frequently observed along the road from Lijen to Kawah ungup-ungup (Aug. 2000). A number of specimens have been collected both at (Kawah) ungup-ungup, as some adjacent sites. Individuals of the erythristic pelage colour morph have been recorded in the area. Specimens collected: Kendeng III: MZB 705,-6; Ungup-ungup: BMNH 1954.56, MZB 704, ZRC 4372; Sodong Jerok: BMNH 1954.57,-8,-9; Tamansari: BMNH 1954.60, ZRC 4376. 36. Baluran Counties: Besuki. Habitat: The Baluran National Park totalling 25,000 ha with savannah and monsoon forest centered on the dormant volcano of Mt. Baluran (1250 m). There is a small moist forest inside the volcano crater, and the extensive coastline is covered with beach forest and mangroves. Status: A fair number of groups observed in the beach forests near Bama, along the road from Wonorejo to Bekol, and in the savannah near Bekol. Groups up to 25 individuals were not uncommon (Aug. 1997). The species occurs throughout the park, including Mt. Baluran, but is perhaps most easily observed in the beach forest near Bama. The erythristic pelage colour morph occurs in the Park (S. Hedges and M. Tyson, pers. comm., 1998). Specimens collected: Bajulmati: BMNH 1954.61; Kosambikamp: MZB 6696,-7,-9, 6700. 37. Alas Purwo Counties: Besuki. Habitat: Alas Purwo (or Blambangan, or Banyuwangi Selatan) is a 62,000 ha lowland forest reserve ranging from sea level to 360 m a.s.l. in the driest part of


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Java. Presently the area is a nature reserve (MacKinnon et al., 1982). Wood cutting forms the major threat to the habitat. Status: Appelman (1939) recorded ebony leaf monkeys in small numbers. Likewise, Hoogerwerf (1972) reported the presence of the species near Pantjur on the western coast, but noted that the species was rather rare. Observed in Nov. 1989 and May 1990 at Gucur near Pasar Anyar, both in natural and teak forest, and near Trianggulasi (May 1990) (S. van Balen, in litt., 1998). The erythristic pelage colour morph occurs in the Park (S. Hedges and M. Tyson, pers. comm., 1998).

Island of Bali 38. Bali Barat Counties: Jembrana, Buleleng. Habitat: The Bali Barat National Park consists of a large variety of forest types, including (disturbed) savannah, mangroves, and mixed monsoon forest, as well as some sub-montane forests. The national park proper covers an area of just 19,000 ha, but inclusion of the proposed extension to the east would increase it to an area of 77,000 ha. Status: Observed near the summit of Gn Klatakan and along S. Teluk Teluk (Aug. 2000). The species was recorded throughout the year, especially on the Prapat Agung Peninsula (S. van Balen, in litt. 1989). According to Wheatley et al. (1993) the Bali Barat National Park may have the last viable population of ebony leaf monkeys on the island. It is not clear whether their statement refered to the national park proper or that it included the park’s eastern extension. Specimens collected: Sendang: RMNH E 9, 27,35,38,39,77. 39. Mt. Batukau Counties: Buleleng, Tabanan. Habitat: Relative undisturbed moist hill, sub-montane and montane forest on recent volcanic soils. The existing three nature reserve are centered around volcanic lakes and totals 1762 ha. An extension as to include the three reserves to one large area covering the whole Batukau complex (c. 20,000 ha) have been proposed (MacKinnon et al., 1982). Status: Pocock (1935) described subspecies stresemanni based on specimens collected by E. Stresemann, from this locality. No further details available. Wheatley et al. (1993) furthermore reported on the possible presence of ebony leaf monkeys near the dry forest on the mountains near Amlapura, on the eastern part of Bali. Hence, the species might be present in other parts of the mountanous interior of Bali. Specimens collected: Danau Bratan: BMNH 13.3.6.1.


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Island of Lombok 40. Mts Mangsit Counties: Lombok Barat Habitat: Small patch of lowland forest on the western coast of Lombok. Status: No information available, but the species had been collected in June 1896 (Napier, 1985). Specimens collected: Mangsit: BMNH 1939.1143. 41. Mt. Rinjani Counties: Lombok Tengah and Timor Habitat: The Gunung Rinjani National Park covers an area of 40,000 ha, of largely montane forest. Despite its excistence since 1941, the park has failed to preserve the once very dense primary forest cover, at least on the northern and northeastern part. Nevertheless, the national park is the only extensive forest complex covering the mountainous northern part of Lombok (MacKinnon and Artha, 1982). Status: Eight different groups observed near the waterfalls of Senaru and on the northern slopes of Gn Rinjani between 650 and 1500 m a.s.l. (Aug. 2000). Horst (1935) recorded ebony leaf monkeys in the forests on the southern slopes of Mt. Rinjani, between Sewala and Pusuk up to 1400 m a.s.l. In May 1990, the species was found at 600 m a.s.l. south of Bayan (S. van Balen in litt. 1998). Kitchener et al. (1990) reported ebony leaf monkeys to be common on Lombok, and observed groups of one or two individuals on Mt. Rinjani. Specimens collected: Sembalun: MZB 6688; Sapit: MZB 6689. 42. Suranadi and Pucuk Counties: Lombok Barat Habitat: Suranadi is a small (52 ha) recreation park c. 25 km east of the capital city Mataram. The area comprises of mixed moist forest in a small patch around a water source and is important for local water protection (MacKinnon and Artha, 1982). The forest west of the Pucuk Pass, north of Mataram, are isolated from those on Gn Rinjani; the status of these forests is unknown. Status: A single group (three individuals) observed from the Pucuk Pass (Aug. 2000). In Surandi, seen in groups of one or two, with the largest group consisting of five individuals (Kitchener et al., 1990). Ebony leaf monkeys on Lombok seem to occur in smaller groups than in similar habitats on Bali or Java.


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DISCUSSION Habitat and Range Figure 7.1. shows the natural forest cover on the islands of Java, Bali and Lombok (after RePPProT 1990). Note that many smaller forest areas, including coastal fringes of mangrove forest, do not show at the scale used. The map also indicates the forty-two areas from where the species has been recorded. Undoubtedly, the species might be present in other areas not yet surveyed, but the present listing probably gives a fairly accurate account of the species’ distribution. Furthermore, it clearly illustrates the severe degree of fragmentation of populations of ebony leaf monkey, possibly having its effect on the survival of the species. Oates et al. (1994) erroneously restrict the range of the genus Trachypithecus as far east as the Greater Sundas, excluding Lombok, but include this island, as well as Bali, in the range of the genus Presbytis. P. comata ranges on Java as far east as Mt. Lawu, on the border of Central and East Java (Nijman, 1997; chapter 6), but does not occur on Bali or Lombok. The islands of Java and Bali are situated on the Sunda Shelf, while Lombok forms part of Wallacea, the transition zone between the Oriental and Australian faunal regions. Although not providing a total barrier, the deep water of the Lombok Strait has restricted contact with the Lesser Sunda Islands. In Malesia, primates are largely restricted to the Sundaic region, with only tarsiers Tarsier spp. having reached Sulawesi, and macaques Macaca spp. reaching into Sulawesi and the Lesser Sundas. Ebony leaf monkey is the only colobine that ranges into Wallacea. It has been suggested, firstly by A. Everrett (Hartert, 1896), that the species was almost certainly introduced by Balinese Rajahs on Lombok. Alternatively, the possibility that the species might have been a recent colonizer has been considered (e.g., Eudey, 1987). De Iongh et al. (1982) observed black monkeys on the Kangean Islands, and reported the possible presence of ebony leaf monkeys on the islands. The Kangean Islands are a group of rather isolated islands situated on the eastern edge of the Sunda Shelf, c. 125 km east of Madura and c. 125 km north of Bali. Bergmans and van Bree (1988), referring to the above mentioned observations, reported the possible presence of the species on Kangean and speculated about the introduction of a number of mammals on the islands by humans. In an attempt to clearify the distribution of ebony leaf monkeys on the Kangean island, I visited Kangean for five consecutive days in August 1997. Throughout the island long-tailed macaques were numerous (cf. de Iong et al., 1982), but no ebony leaf monkey was seen or heard. The pelage of long-tailed macaques on Kangean Island is darker than those from mainland Java, and was described as dark grey (rather than brown with a reddish or greyish gloss), often looking blackish under field conditions. For long-tailed macaques to be darker pigmented is a known phenomenon on small islands on the Sunda Shelf (e.g., Simuelue: van Schaik and van Noordwijk, 1985; Nias: Miller, 1903; Karimunjawa and Bawean: Sody, 1949). Local inhabitants and officers of the forestry departement on the island, some of


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which were familiar with ebony leaf monkeys from mainland Java or Bali, claimed that the species was not present on the island. Both S. van Helvoort (pers. comm. 1997) and Dr H.H. de Iongh (in litt. 1999) do not recall having seen ebony leaf monkeys on the Kangean Islands. In conclusion, ebony leaf monkeys are most likely not present on the Kangean Islands nor are there any indications that they were present in the distant past. The reports of ‘black monkeys possibly or likely ebony leaf monkeys’ (de Iongh et al., 1982; Bergmans and van Bree, 1988), most likely refer to long-tailed macaques, which can have a rather dark pelage coloration on the island. Ebony leaf monkeys are most likely absent from the island of Madura as well. The island is very arid and virtually all forest has long disappeared (Whitten et al., 1996). During three days of surveying on the island in August 1997 no suitable area of forest was found on the island, and no information indicating the presence of ebony leaf monkeys was received. Few remnants of mangrove forest found on the southern coast between Nipah and Jrengik were to small and the trees too stunted to offer suitable habitat. Ebony leaf monkey, however, do occur on the islands of Sempu, several hundreds of meters off the coast near the Lebakhardjo and Bantur forests [29 in the area account and in Figure 7.1], and Nusa Barung [31], which is situated 10 km of the southern coast of the eastern part of Java. At least three scenarios can account for the presence of the species on these islands, none of which is mutually exclusive. Firstly, the ebony leaf monkeys on Sempu and Nusa Barung can be considered relict populations from a time when the sea level was lower as to provide a ‘land bridge’ to the islands. As Nusa Barung is separated from mainland Java by a relative deep strait, this relict population must have become isolated somewhere at the end of the last glacial period, at least 8-10,000 YBP, while for Sempu the separation may be dated somewhat later. Secondly, the species might have been introduced by man. Ships might have transported the animals to the islands, where it was, accidentally or deliberately, set free. Thirdly, the species has been able to (re)colonize suitable islands without the help of man, anytime from the time the islands became separated up to the present day. For long-tailed macaques Wallace (1869) already noted that “this species is very frequent on the banks of rivers, and may have been conveyed from island to island on trees carried down by floods.” Similarly, ebony leaf monkeys might have spread naturally east to Lombok. Since the last ice-age there has been more than sufficient time to colonize an island with a similar climate and vegetation, and on which no other (competiting) colobine could exclude it. Given the species ability to occupy mangrove and beach forests, and the relative narrowness of the straits (although the Lombok Strait is broader that the Bali Strait), this possibility cannot be ruled out a priori. Van der Zon (1978) reported the species to be present in mangrove, swamp, and lowland rainforest up to 1500 m a.s.l., often near human settlements. Medway (1970) considered its habitat to be inland forest from the lowlands up to almost 2,000 m a.s.l. Bennett and Davies (1994), in contrast, claim that the species is restricted to coastal and riverine habitats. In fact, the species occurs over a wide


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range of habitats, from beach forests and swamp forests to dry deciduous forests, and from mangrove, riverine, and lowland rain forest to upper montane forests up to 3,500 m a.s.l. Probably the species' ability to cope with considerable amounts of leaves in its diet allows them to live in a large variety of forest types. Ebony leaf monkey occur(red) in the small remnants of mangrove forests on the northern coast of West Java and East Java [7, 33], as well as in the larger mangrove and swamp area of Segara Anakan [15], on the south coast of Central Java. It occurs in forests along rivers and waterways and in the fresh water swamp forests [2]. In the western half of the island, it is widely distributed in the pockets of rain forest ranging from sealevel [1, 2, 5, 10] to the upper montane forests at 2,500 m a.s.l. and above [6, 17, 19]. In the eastern part of its range, it occurs both in the pockets of rain forest both at sea level [34] and on the eastern and southeastern slopes of the higher volcanoes [27, 28, 30, 41], in the fire resistant Cemara Casuarina junghuhni forests [26, 27, 32], as well as in the dry deciduous forests [33, 36, 38]. In the rain forest environment ebony leaf monkeys seem to be (almost) strictly arboreal, while in the more open forest types, e.g., dry decidious forest and upper montane forest, it seems to be more terrestrial. The species is able to cope with a certain degree of habitat disturbance. It seems to survive in secondary forest types as well as some man-made forests such as damar Auracaria spp, pine Pinus merkusii, acacia Acacia spp, rasamala Altingia excelsa, rubber Hevea brasiliensis and teak plantations [2, 3, 13, 14, 17, 24, 26, 33]. Often, however, these plantations are situated adjacent to other more natural forest areas [e.g., 2, 13, 24, 33], while others are intersected e.g., by (river) valleys with a more diverse forest type [14, 17]. Typically, ebony leaf monkeys are found in or near these natural forest remnants. Alternatively some populations can be found ‘trapped’ in small fragments of (natural) forest, unable to move out as there is no adjacent forest left [e.g., 3, 20]. Although the species has been observed in a wide range of forest areas, generally it can be assumed that ebony leaf monkeys are dependent on natural forest in one form or another, and that large stands of monocultures offer little if any suitable habitat for the species. Distribution of the erythristic pelage morph The erythristic pelage colour morph, besides the more common melanic pelage colour morph, hitherto has only been recorded in East Java. Pfeffer (1965) erroneously reported erythristic individuals to be common in West Java and absent from East Java. Whitten et al. (1996) states that the erythristic occurs in Central and East Java, albeit more common in East Java. Hoogerwerf’s (1972) statement that “In Central and East Java another subspecies occurs [ ], among which adult reddish-colored individuals were regularly noted...”, may also have given the impression that the erythristic pelage morph also occurs in the central parts of Java.


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Figure 7.2 Melanic pelage morph of ebony leaf monkey Trachypithecus auratus (E. Geoffroy Saint-Hilaire, 1812), Taman Safari Zoo, Cisarua, West Java 1999. Figure 7.3 Three individuals of the erythristic pelage morph of ebony leaf monkey Trachypithecus auratus (E. Geoffroy Saint-Hilaire, 1812), Taman Safari Zoo, Cisarua, West Java 1999. Figure 7.4 Melanic (foreground in cage) and erythristic pelage morph of ebony leaf monkey Trachypithecus auratus (E. Geoffroy Saint-Hilaire, 1812), Taman Topi, Bogor, West Java 1999. In Indonesia, many species of primates, including formaly protected species such as the ebony leaf monkey, are openly offered for sale, in this particular case in front of the police station. Note that the illegal primate trade includes transports over considerable distances as the nearest site where the erythristic pelage morph occurs [Mt. Penanggunang-Mt Arjuno] is more than 1000 km by road from Bogor.


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In fact, they have been reported only from the easternmost part of East Java, i.e., the area bordered roughly in the northwest by Mt. Penanggunang [27] and the surroundings of Modjokerto south, via Wonosalam and Blitar [28] to Mts Kidul near Balekambang [29], east to the southeastern tip of the island at Alas Purwo [37], and north to Baluran [36], and back along the northern coast via Pasir Putih and Mt. Ringgit [33] to Rembang [27] and Mt. Penanggunang (See Figure 1). Although the erythristic pelage morph may be rare in certain areas, it was generally known to inhabitants living in the area. The morph is present in fairly large numbers in the collections of the various museums visited, indicating a collector’s bias towards the rarer type. Various surveys to Mt. Wilis-Liman [26] and Mt. Lawu [25] failed to find erythristic individuals, nor were they known to inhabitants or officers of the forestry departments. Hence, the western boundary of the distribution range of the erythristic pelage morph in all likelihood runs east of Mt. Wilis-Liman. Currently, no erythristic individuals have been recorded in the large teak stands east of Cepu [24], but the area is under-explored. If present, the northern boundary would be extended considerably. Erytristic individuals have not been recorded from either Bali or Lombok, and it is not known whether they occur on the island of Nusa Barung [31]. They have been recorded on the island of Sempu, south of Mts Kidul [29]. In certain populations, e.g., those in Balekambang, probably only a small proportion of the individuals is of the erythristic pelage colour morph, while in others, e.g., those found in the surroundings of the temples of Candi Colotundo, near Trawas on Mt. Penanggunang, up to 15-20% of the individuals are. Van Bemmel-Lenneman and van Bemmel (1940) reported the erythristic pelage colour morph to be more common than the melanic pelage morph on Mt. Semeru [30]. ACKNOWLEDGEMENTS

The surveys could not have taken place without the cooperation of the Indonesian Institute for Sciences (LIPI), the Directorate General for Nature Conservation and Forest Protection (PKA), the Ministry of Forestry and Estates Crops (MOFEC) and the regional forestry departements, to all of whom I would like to express my gratitude. Drs Boeadi (Museum Zoologi, Bogor), Dr P.J.H. van Bree (Zoological Museum, Amsterdam), Dr P. Jenkins (Natural History Museum, London), and Dr C. Smeenk (National Museum of Natural History, Leiden) are acknowledged for access to specimens under their care. For sharing records of Trachypithecus auratus, for providing other information, or help of various sort I am grateful to: F. Arga Narata and Sugihartono (Kutilang IBC, Yogyakarta), Dr S. van Balen (Agricultural University Wageningen), D. Cornelissen, Dr. T. Geissmann (Institute für Zoologie, Tierärtzliche Hochschule Hannover), S. Hedges (University of Southhampton), Dr B.A. Manullang (formerly WWF-IP), R. Nursahid (KSBK, Malang), A.V. Reijngoud, A.P. Setiadi (YPAL, Bandung), R. Sözer (ISP/ZMA), I. Setiawan and Sujatnika (BirdLife International Indonesia Programme) and M. Tyson (Manchester


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Metropolitan University). Dr. H.H. de Iongh and S. van Helvoort are thanked for providing information on the black monkeys of the Kangean Islands. Dr. H. Albrecht (Dept. Animal Behaviour, University of Amsterdam), Dr C.J. Hazevoet (Museu de História Natural, Lisboa), R. Sözer and an anonymous reviewer made constructive comments on previous versions of the manuscript. Additional financial support was received from the Society for the Advancement of Research in the Tropics (Treub-maatschappij), the Netherlands Foundation for International Nature Protection (Van Tienhoven Stichting), and Stichting Het Kronendak. Dr P.J.H. van Bree is thanked for his help throughout the project.


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A Faunal Survey of the Dieng Mountains, Central Java

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CHAPTER 8

A FAUNAL SURVEY OF THE DIENG MOUNTAINS, CENTRAL JAVA, INDONESIA: DISTRIBUTION AND

CONSERVATION OF ENDEMIC PRIMATE TAXA

with S. (Bas) van Balen, Oryx 32: 145-156, 1998

ABSTRACT A faunal survey was conducted in May-September 1994 and June-July 1995 in the Dieng mountains, one of the last remaining larger patches of forest in the Central Java province, Indonesia. All three primate species endemic to the Javan faunal region -Javan gibbon Hylobates moloch, grizzled leaf monkey Presbytis comata and ebony leaf monkey Trachypithecus auratus- were found to be present. Javan gibbon only occurs in the lowland and hill forests in the western part of the study area, while the latter two species were found to be present throughout the area from lowland to montane forests. Although more research needs to be done on habitat preferences and densities at which the primates occur, the available data suggest that the Dieng mountains may harbour the second largest population of both Javan gibbon and grizzled leaf monkey in the same location. In order to safeguard these two endangered primates it is suggested that the reserve system in Java be expanded to include the Dieng mountains. RINGKASAN Suatu survey fauna Pegunungan Dieng, Jawa Tengah, Indonesia: penyebaran dan konservasi taxa primata endemik (bersama S. (Bas) van Balen, Oryx 32: 145-156, 1998): Suatu survey fauna telah dilakukan pada bulan Mei-September 1994 dan Juni-Juli 1995 di Peg. Dieng, salah satu blok hutan cukup besar terakhir yang tersisa di Propinsi Jawa Tengah, Indonesia. Semua tiga spesies primata yang endemik Regio Fauna Jawa –Owa Jawa Hylobates moloch, Surili Presbytis comata dan Lutung Trachypithecus auratus- telah ditemukan kehadirannya di sini. Owa hanya terdapat di hutan dataran rendah dan hutan pebukitan di bagian barat dari lokasi penelitian, sementara kedua jenis lainnya ditemukan berada di seluruh lokasi penelitian dari mulai hutan dataran rendah sampai dengan hutan pegunungan. Meskipun dibutuhkan penelitian lebih mendalam mengenai preferensi habitat dan kepadatan spesies-spesies tersebut, data yang ada menunjukkan bahwa Peg. Dieng barangkali mengandung populasi terbesar yang kedua, baik untuk owa maupun lutung, di tempat yang sama. Untuk melindungi kedua jenis primata terancam punah ini disarankan bahwa sistem kawasan lindung di Jawa diperluaskan sehingga mencakup Peg. Dieng.


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INTRODUCTION Despite Central Java being one of the most densely populated and most deforested areas in Indonesia, several patches of natural forest remain throughout the province. This natural vegetation is restricted almost exclusively to hydrological forest reserves capping summits and ridges. A few of these forests descend into the hill or even lowland zone, but more often they only cover the upper part of the mountain above 1500-2000 m. Few of these patches are adequately protected and fewer still have received recent attention of the conservation community. It has long been known that several ‘West Javan’ species with high conservation priorities reach the easternmost limit of their distribution in Central Java but most conservation efforts or even general survey work seem to be restricted to West Java (see e.g., Appendix II and III in Whitten et al., 1996). Given the lack of knowledge on the current distribution and status of several animal species in Central Java, we present results of a faunal survey in the largest remaining area of natural forest in Central Java, the Dieng mountains (also known as Mt. Prahu or Mt. Perahu, named after its highest peak: Figure 8.1). Between May 1994 and July 1995 six visits were paid to the forests of the Dieng mountains. The aim of the visits was to obtain data on the bird and mammal fauna of the region in order to make recommendations for the conservation of the area. The subject of the present paper is to discuss three primate taxa found in the area: Javan or silvery gibbon Hylobates moloch, grizzled leaf monkey Presbytis comata and ebony leaf monkey Trachypithecus auratus. The Javan gibbon is endemic to the western half of Java. Most populations can be found in the western province (Kappeler, 1984), but a few remain in Central Java (Nijman, 1995; Nijman & Sözer, 1995). The most recent population estimates, based on extrapolation of the available habitat, range from 2000 animals (Supriatna et al., 1994) to 3000 animals (Asquith et al., 1995). The species is accorded the highest conservation priority rating for Asian primates (Eudey, 1987), and has recently been listed as Critically Endangered by IUCN (1996). The grizzled leaf monkey is also endemic to the western half of the island of Java, as far as Mt. Lawu on the border with East Java (Nijman, 1997b). The central Javan populations have been proposed a seperate species Presbytis fredericae (e.g., Brandon-Jones, 1995), but Nijman (1997a) showed some of the alleged differences not to be diagnostic, while some intraspecific variation was of a clinal nature. Like the Javan gibbon the species is severely threatened mainly due to habitat destruction (Eudey, 1987; MacKinnon, 1987; Supriatna et al., 1994). Population sizes have been calculated and range from 8040 animals (MacKinnon, 1987) to 2285 animals (Supriatna et al., 1994). Grizzled leaf monkeys have been classified as Endangered according to IUCN (1996).


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Figure 8.1 The Dieng mountains, Central Java, Indonesia, with localities mentioned in the text (G.

stands for Gunung meaning Mountain, and S. stands for Sungai meaning River). The bold line indicates the reserve boundaries as proposed in the present paper. The smaller map shows the island of Java with areas covered with natural forest, excluding mangrove and swamp forest (afterRePPProT, 1990); with the Dieng mountains in black. Note the degree of isolation of forests on Java.


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The ebony leaf monkey is more widespread than the former species and is restricted to Java and the smaller islands of Bali and Lombok to the east (Weitzel & Groves, 1985). The species is listed as Vulnerable (IUCN, 1996) METHODS Study site The Dieng mountains are situated in the middle part of Central Java between c. 109°32’-109°56’E and 7°04’-7°13’S. Administratively they lie largely in the counties (kabupaten) of Pekalongan and Batang, with small areas in Banjarnegara, Wonosobo, Temanggung and Kendal. The area is made up of a number of largely dormant volcanoes that are more or less contiguous, surrounded by their foothills and adjoining plains. In the western part most peaks are less then 2000 m high (e.g., Mt. Langit, 1628 m; Mt. Besar, 1579 m), while to the east the mountains become higher. Mt. Prahu, in the easternmost part, at 2565 m the highest. On the north-western and north-eastern part of these mountains a block of forest extends from lowland to upper montane: in the west the forest descends to c. 300 m and on the eastern slopes of Mt. Prahu to c. 1500 m. The forests total roughly 255 km2 (RePPProT, 1990), disregarding the additional area due to slopes. The archaeological well known Dieng plateau situated at an altitude of c. 2000 m, borders the area in the south-east and contains some interesting lakes, which are gazetted as nature reserves: Telogo Warna (40 ha), Telogo Dringo (26 ha) and Telogo Sumurup (20 ha) (MacKinnon et al., 1982). Rainfall is plentiful throughout the year with average of 4000-7000 mm; only between June and September there is little less rainfall. In most of the study area more than 40 rainy days are recorded during the four driest consecutive months of the year (van Steenis, 1965). In the lowlands the average daily temperature is 22-34°C with an average of 26°C. Temperature decreases with altitude; at 2000 m it has become 14°C (van Steenis, 1972). At the Dieng plateau, and other areas above 2000 m, frost can occur at night, especially in the dry season. The vegetation of the Dieng mountains are of the wettest type: mixed lowland and hill rainforest, below c. 1000 m, and montane ever-wet rainforest to c. 2400 m (van Steenis, 1972). As a result of human disturbance and/or natural conditions meadows with few trees cover the upper parts of Mt. Prahu. Throughout the area some large patches of undisturbed primary forest remain, but most of the area is somewhat disturbed. The forests near the village of Linggo partly consist of a former coffee plantation which, according to local inhabitants, has been abandoned in the 1930’s. Halfway between Linggo and Mt. Lumping small patches of bamboo indicate a former settlement. Regrowth has resulted in a secondary forest, with emergent older trees distributed throughout. In the central part of the area, along the road from Kroyakan to the Dieng plateau, and in the north-west, wet rice fields are present (see Figure 8.2).


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The forests on the Dieng mountains are not yet protected as conservation forest. The parts above 1000 m are formally protected as hutan lindung (protection forest). Forests protected in this category are state-owned and serve as water catchment, to maintain soil fertility and to prevent erosion and land slides (Anonymous, 1996). Also a small part of the lowland forests near Kroyakan receive some form of protection as hutan negara (an unclassified state owned forest category); here collection of fire wood and forest products is prohibited. The lowland forest near Linggo are managed as hutan produksi (production forest) and in 1995 were still planned converted it into rubber and/or pine plantations. The forests on Mt. Prahu above the 1000 m line, i.e. roughly the eastern half of the Dieng mountains, have been proposed a suaka margasatwa (wildlife sanctuary) (MacKinnon et al., 1982). The study area is largely surrounded by tea plantations in the north and south, by pine plantations in the east and west, by rubber plantations in the north-west, and by agricultural land in the south-east. It is crossed by at least three roads running from north to south: from Kayen via Linggo to Peninggaran, from Kroyakan to Batur and the Dieng plateau and from Bawang to Dieng. The latter two are used only for local traffic. Figure 8.2 A view of the lowland forests near Linggo, Dieng mountains, Central Java, with on the

foreground areas cleared for wet rice fields.


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Data acquisition and survey methods We surveyed the Dieng mountains on six occasions totalling 16 days of observation: (i) on 5 May 1994 VN and Resit Sözer (RS), visited the northern part of Mt. Prahu from the village of Bawang; (ii) on 4-6 July 1994 VN and RS visited the Dieng plateau and the southern slopes of Mt. Prahu; (iii) VN, RS, Iwan Setiawan and Andi Prima Setiadi, surveyed the eastern slopes of Mt Prahu from Tretep and the forests near Linggo on 27 August 1994; (iv) on 25 September 1994 VN surveyed the forests near Linggo; (v) on 9-11 June 1995 VN and SvB visited the Dieng plateau and the southern slopes of Mt. Prahu; and on 11-16 June 1995 the surroundings of Linggo, including a two days visit to Mt. Lumping; and (vi) on 29 July 1995 VN travelled along the road from near Batur to Kroyakan, with short surveys inside the forest on the north side of Mt. Rogojembangan and near Kroyakan. The survey covered almost the total altitudinal range from 300-2565 m, with only a small gap at 1800-2000 m. We spent almost equivalent amounts of time in the lowland and hill forest below 1000 m as in the montane and upper montane forests above 1000 m. The primate surveys were as much as possible concentrated in the interior of the forest areas and was targeted to the three endemic primate taxa: Hylobates moloch, Presbytis comata and Trachypithecus auratus. According to local informants the long-tailed macaque Macaca fascicularis was also present as might be the slow loris Nycticebus coucang, but these two species were not recorded during the survey. The area was surveyed from vantage points over the canopy and by walking inside the forest along available trails. The presence of gibbons was established mainly by their calls. Gibbon density in the forests between Linggo and Mt. Lumping, covering an area of c. 11 km2 between altitudes of c. 300-1300 m, was estimated by plotting the locations of gibbon song bouts heard from fixed points and while surveying on a map. In the same area a transect of 3.8 km in length, partially along an existing trail, was walked using a fixed strip width of 100 m, and was repeated four times. This allowed density estimates to be made for the two leaf monkeys. Whenever a primate or a group of primates was encountered observations were made ad libitum (Altmann, 1974), and data on the habitat were collected. Ad libitum sampling is not to be recommended for long-term comprehensive studies but can be useful during preliminary observations (Martin & Bateson, 1993). Ad libitum sampling was used by default because there were no established trail systems in the area, the study covered a relative short time span, the study animals were not habituated, and the observation conditions were relatively difficult. Additional information on the presence or absence of primate species was gathered by interviewing local inhabitants, collectors of forest products (e.g., coffee and rattan) and officers of the forestry department.


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BRIEF HISTORICAL ACCOUNT OF FORMER FAUNAL EXPLORATION Relatively little faunal exploration has been done in the study area other than on the Dieng Plateau itself. Some botanists like S.H. Koorders (October, 1891), C.A. Backer (January, 1917; see Bünnemeyer, 1918) and C.G.G.J. van Steenis (August, 1930) have collected on the Dieng Plateau and Mt. Prahu (van Steenis-Kruzeman, 1950). The naturalist Junghuhn (1854) visited the Dieng Plateau and Mt. Prahu (March-April 1840, October-November 1845). The interior and the western parts of the study area have always been somewhat neglected. The only zoologist who contributed considerably to our knowledge of the area is Thomas Horsfield who collected in October 1816. He made some collections of birds and mammals in the area, some of which are type specimens (Horsfield, 1824; Mees, 1989). Bartels (1937) reported on a series of Presbytis comata skins collected at an altitude of c. 1300-1500 m, which he received from Mr Landberg, owner of a plantation on the north-western slopes of the Dieng mountains. Apart from Kappeler (1984), who visited Mt. Prahu in 1978 during a gibbon survey, other primatologists, such as Asquith et al. (1995), Martarinza (pers. comm. 1994) and M. Linsley (pers. comm. 1994), did not survey the Dieng mountains. Kappeler did not find forest below 2100 m on Mt. Prahu, and did not find any gibbons. As a result of the insufficient coverage by naturalists the forest on the Dieng mountains was for a long time considered to be of only minor significance for the preservation of Javan biological diversity. The area was accorded the lowest overall priority ranking in MacKinnon et al. (1982), although the area was stated to be 'an important water catchment and of some botanical and faunal interest'. RESULTS Primate distribution and habitat preferences Javan gibbon were found to be present between altitudes of c. 300 and 1300 m. from Linggo and Mt. Lumping in the west to Mt. Rogojembangan in the south-east (Table 8.1). Gibbon habitat consisted of secondary forest with a rather dense and close canopy, and undisturbed primary forest. The detected gibbons all appeared to prefer the taller trees for resting, foraging and locomotion. Gibbons were seen on three occasions: a single adult, two adults and a group of seven. On the basis of simultaneous or alternating vocalisations and sightings, a total of 10-12 groups could be recognised in an area of c. 11 km2 between Linggo and Mt. Lumping. Assuming an average group size of 3.3 individuals (cf. Kappeler, 1984) the density of gibbons was estimated to be 3.0-3.6 individuals km-2. Two additional groups were found at the northern slopes of Mt. Rogojembangan and near Kroyakan, respectively. Grizzled leaf monkey were found to be present in the western part of the study area and on the higher parts of Mt. Prahu (Table 8.1). In July 1994 two individuals were observed near the summit of Mt. Prahu (Nijman & Sözer, 1995) and on 11 June 1995 a troop of monkeys were detected near this former observation point.


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However because of the dense cover and the angle of observation it was not clear whether these individuals were grizzled leaf monkeys or ebony leaf monkeys. Table 8.1 Groups or individuals of Javan gibbon Hylobates moloch, grizzled leaf monkey Presbytis

comata and ebony leaf monkey Trachypithecus auratus observed in the Dieng mountains, with altitude at which the observations were made.

Species Date No. groups

heard No. individuals

seen Altitude Locality

H. moloch 27/08/’94 2 c. 400-600 Linggo 1 600 Linggo 25/09/’94 2 c. 400-600 Linggo 1 c. 750 Linggo (centr.) 1

11-14, 16/06/’95 3-4 c. 300-700 Linggo 12/06/’95 2 765 Linggo 13/06/’95 1 880 Linggo (centr.) 1 7 885 Linggo (centr.) 14/06/’95 2 c. 850-900 Linggo (centr.) 14-15/06/’95 5-6 c. 1000-1300 Mt. Lumping 29/06/’95 1 c. 1200 Mt. Rogojembangan 1 c. 700 Kroyakan P. comata 05/07/’94 2 2565 Mt. Prahu 11/06/’95 1 2500 Mt. Prahu2

13/06/’95 11 (+2 neonates) 780 Linggo 9 (+ 1 neonate) 820 Linggo 2 820 Linggo >1 650 Linggo 14/06/’95 >4 925 Linggo (centr.) 1 1085 Mt. Lumping 1 1150 Mt. Lumping 15/06/’95 >2 820 Linggo 7 775 Linggo T. auratus 25/09/’94 >3 750-800 Linggo >4 750-800 Linggo 7 (+1 neonate) 850 Linggo (centr.) 12/06/’95 3 765 Linggo 15 (+4 neonates) 780 Linggo 10-12 (+1 neonate) 815 Linggo 14/06/’95 1 1300 Mt. Lumping 15/06/’95 1 865 Linggo (centr.) 8-10 800 Linggo (centr.) 16/06/’95 >5 570 Linggo (north) 1 1 600 Linggo (north) 1 500 Kroyakan 1. Linggo (centr.) refers to the area between Linggo and Mt. Lumping, Linggo (north) refers to the

lowland forests north of Linggo. See figure 8.1. 2. unconfirmed, see text. More direct observations were made in the western part of the study area. Groups of 2-13 individuals were seen on seven occasions. The smaller group sizes were probably a reflection of the difficulties in observing the complete group rather than


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the size of the group itself. On three occasions we had the impression that we could observe the whole troop, with group sizes of at least seven individuals, nine plus one neonate, and eleven plus two neonates. Two groups were detected by means of their characteristic vocalisations. In total at least six different groups inhabited the study area. On six occasions we observed a group of grizzled leaf monkeys within 50 m from the transect line. Assuming an average group size of seven individuals (cf. Supriatna et al., 1994) the population density was estimated at 28 individuals km-2. We observed the species between altitudes of 650 and 2565 m. Local inhabitants and officers of the forestry department reported it to be present north of Linggo (forests descends to c. 300 m) and also in the forests above Kroyakan (altitude c. 400 m). Grizzled leaf monkeys were recorded in primary forest and in secondary forest, both in edges and the interior. They were found in lowland forests, in forests on steep slopes and on hills and in upper montane forests. The ebony leaf monkey was the species observed most frequently. It was reported to be rather common on both on Mt. Prahu and the central part of the study area. In the western part we sighted groups on nine occasions and twice located a a group or individual by their characteristic vocalisation. In the forests above Kroyakan a group was also identified by means of vocalisation. Records come from the north-western part north of Linggo, to Mt. Lumping in the south and Kroyakan in the north-east, between altitudes of 500 and 1300 m (Table 8.1). At least eight groups of 3-19 individuals of ebony leaf monkey are present in the study area. Along the transect line groups were observed five times. Assuming an average group size of seven individuals (V. Nijman, unp. data) the density may be 23 individuals km-2. The habitat in which ebony leaf monkeys were observed included primary and secondary forest, both on the edges and in the interior. Population estimates Although preliminary, we present some information of the number of individuals of the two most endangered primate species --the Javan gibbon and the grizzled leaf monkey-- possibly present within the area. The Javan gibbon was observed between altitudes between c. 300 and 1300 m. It is likely to be distributed throughout the western half of the study area up to altitudes of c. 1600 m. This is considered to be the species' upper limit (Kappeler, 1984a) although it has been reported from higher altitudes (e.g., 2400 m on Mt. Pangrango: Doctors van Leeuwen, 1926; 1900 m on Mt. Tangkuban Perahu: R. Sözer, pers. comm. 1992). The most widely used method for estimating population sizes of Javan gibbons is by extrapolation based on the forest area inhabited by gibbons and their population density (e.g., Kappeler, 1984a, Kool, 1992; Supriatna et al., 1994; Asquith et al., 1996). Population densities vary with altitude (Kappeler, 1984a, Supriatna et al., 1994) and we followed the assumptions of Supriatna et al. (1994) which are comparable with those of Kappeler (1984a) and Asquith et al. (1996). The assumptions of Supriatna et al. (1994) are based on data derived from studies of the white handed (H. lar) and pileated gibbon (H. pileatus). They considered the edge effect (defined as the size of habitat on the


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forest periphery not occupied by gibbons) for Javan gibbons to be one km. Thus, suitable habitat for gibbons was calculated by subtracting the first kilometre of habitat from the available habitat. This area was multiplied by the gibbon population density for that altitudinal vegetation zone (Table 8.2). A population of over 500 individuals may be present in the area. Less is known about densities and altitudinal distribution of grizzled leaf monkeys than for the Javan gibbon. Reported densities vary from 4-5 individuals km-2 in Halimun National Park (Maitar in Supriatna et al., 1994) to 35 individuals km-2 in Patenggang (Ruhiyat, 1983). Our density estimate of 28 individuals km-2 is similar to the 25 individuals km-2 found by Sujatnika (1992; Sujatnika, pers. comm.) in Mts. Gede Pangrango National Park. According to Supriatna et al. (1994) grizzled leaf monkey do not inhabit the core of a forested area. Although tentative, if we, for reason of comparison only, follow the assumptions of Supriatna et al. (1994), i.e. grizzled leaf monkeys range in a band of 2 km around the perimeter of the area with a density of five individuals km-2, the available habitat totals c. 140-155 km2 and the total number of grizzled leaf monkeys present in the Dieng mountains may be c. 700-800 animals. Table 8.2 Estimates of the numbers of Javan gibbon present at the different vegetation zones on the

Dieng mountains and total number of gibbons present in the area, calculated following the assumptions of Supriatna et al. (1994).

Altitudinal vegetation zone (m) Size↑

(in km2)Edge

(in km2) Core

(in km2) Density↑↑ (ind. km-2)

Estimated number

Lowland (0-500m)

13-15

6-7

7-8

1-3

7-24

Hill (500-1000m) 90-100 20-23 70-77 7 490-539 Lower montane (1000-1500m) 17-20 6-8 11-12 2 22-24 Total 519-577 ↑ Size of natural forest area after RePPProT (1990), scale 1: 250,000: edge is defined as the first

kilometre of habitat on the forest periphery not occupied by gibbons, while core is calculated by subtraction of the area of the edge from the forest size (after Supriatna et al., 1994).

↑↑ Densities after Supriatna et al. (1994). DISCUSSION Even though we realise that some of our data are rather limited and based on few observations, we think that they allow comparison with other studies. Supriatna et al. (1994) concluded that there was an inconsistent and incomplete dataset available to estimate the sizes of wild gibbon and leaf monkey populations. In our attempts to estimate the number of Javan gibbon and grizzled leaf monkey present in the Dieng mountains, we largely followed the assumptions of Supriatna et al. (1994). Some of these assumptions however, are considered not to be valid in our study area, e.g., gibbons were heard frequently less than 100 m from the main road from Kayen to


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Peninggaran, and they were reported to be present in the lowland forest south-west of the road from Kroyakan to Doro, questioning the assumption that gibbons do not inhabit the first kilometre of the forest periphery. If we use the assumptions and densities estimated by Kappeler (1984a) and Asquith et al. (1995) to estimate the number of gibbons in the Dieng mountains, the results are similar to our own: 249-955 and 523-577, respectively (see Table 8.3). Table 8.3 Estimates of the numbers of Javan gibbon present in the different vegetation zones on the

Dieng mountains using the assumptions of Kappeler (1984) and Asquith et al. (1995).

Altitudinal vegetation zone (m)

Size↑ (in km2)

Density↑↑ (ind. km-2)

Estimated number

After Kappeler (1984) Lowland (0-500m)

13-15

1-13

52-195

Hill (500-1000m) 90-100 2-7 180-700 Lower montane (1000-1500m) 17-20 1-3 17-60 Total 120-135 249-955

After Asquith et al. (1984) Lowland (0-1000m) 77-85 6.5 501-553 Montane (1000-2000m; western part only) 11-12 2 22-24 Total 88-97 523-577

↑ Size of natural forest area after RePPProT (1990), scale 1: 250,000. ↑↑ Note that Asquith et al. (1994) took the edge effect into acount but that Kappeler (1984) did not. Furthermore, we do not agree with the assumption of Supriatna et al. (1994) that grizzled leaf monkeys are not found in the core of a forested area, and a density of 5 individuals km-2 seems rather conservative because our own estimate and those reported from other studies (e.g., Ruhiyat, 1983; Sujatnika, 1992) are considerably higher (see chapter 12). However, pending further research on the population density and habitat preferences of grizzled leaf monkeys, any further adjustment seems unwarranted. Despite the number of limitations and perhaps low level of accuracy we have presented our population estimates as it is believed that (i) even these rough estimates are useful in order to get some idea on population sizes and (ii) the estimates allow comparison with other areas and other studies which have been conducted so far. The only area, other than the Dieng mountains, where both grizzled leaf monkey and Javan gibbon are present in greater or similar numbers is Halimun National Park in West Java (360 km2 of forest between 500 and 1929 m, of which 80 per cent is above 1200 m; Kool, 1992). Most patches of strict lowland forest in Halimun National Park are discontinuous and are often situated outside the reserve boundaries (Whitten et al., 1996), so the area's protected status might create the illusion that populations of Javan gibbons and grizzled leaf monkeys are relatively secure, this is not necessarily the case. Population estimates of Javan gibbon for this


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area range from 852-1320 animals (Kool, 1992), 870 animals (Asquith et al., 1995) to 908 animals (Supriatna et al., 1994). Up to 720 grizzled leaf monkeys may be present (Supriatna et al., 1994), although Maitar (in Supriatna et al., 1994) reports very low densities of this species in the area and Kool (1992) was not able to obtain a density estimate because of the low number of sightings. During our surveys in the Dieng mountains we were repeatedly confronted with the fact that no one had recognised the high biological value of this area before. Therefore, and as our surveys were limited in time and did not cover the area as a whole, we highly recommend the area for those interested in studying Javan fauna and flora in more detail. In our survey for instance we observed or found traces of species like large flying fox Pteropus vampyrus, binturong Arctictus binturong, leopard Panthera pardus, pigs Sus scrofa and/or S. verrucosus, barking deer Muntiacus muntjak, and black giant squirrel Ratufa bicolor. The is still much to be discovered (see for a more complete listing of the mammals of the Dieng mountains Nijman & Setiawan, 2001). Scientific research would not only provide new information and better insight, it would also serve as a constant reminder of the conservation importance of the Dieng mountains. Contrary to MacKinnon (1987), we strongly believe that there is room for a further expansion of the reserve system on Java. In Central Java, currently scarsely any large terrestrial area has an adequate protected status, although several have been proposed as nature reserves or wildlife sanctuaries (MacKinnon et al., 1982). As conversion of the last remaining natural forest areas on Java is an ongoing process, resulting in an ever increasing fragmentation, it is of utmost importance to raise one or preferable more areas in the central part of the island to a higher conservation status. The Dieng mountains support relatively high numbers of two of Indonesia's most threatened primate species, the Javan gibbon and the grizzled leaf monkey, making it a top priority area for primate conservation. The area is amongst the most diverse left on Java, notably it is one of the few unprotected forests that covers the whole range from lowland to upper montane. It harbours 67 per cent of all bird species endemic to Java and Bali (20 of 30 species), and 70 per cent of the Javan Restricted Range forest birds (23 of 33 species; see Box 8.1). The creation of a reserve in the Dieng mountains would be of international importance for global biodiversity conservation. The area is probably sufficiently large to ensure the maintenance of viable populations of unique flora and fauna. Following Nijman & Sözer (1996) we suggest that the proposed wildlife sanctuary (MacKinnon et al., 1982) be extended to the north-west so as to include the lowland and lower montane forest of Linggo. In the central area, the boundary should follow the line between the summits of Mt. Rogojembangan and Mt. Kendalisodo. From Mt. Kendalisodo the boundary should run westwards -excluding the village of Petungkriyana- up to the Sengkarang River. From there the boundary should follow the eastern and southern slopes of Mt. Lumping. We recommended that the provincial or national authorities eassessed the feasibility of creating a nature reserve or national park in the Dieng mountains. If the reserve is to become a


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national park consideration should be given whether or not to include the Dieng plateau, with the three established lake nature reserves. The results of the present survey, and the proposals to extend the proposed wildlife sanctuary into the lowland zone, have been well received by the Directorate General of Forest Protection and Nature Conservation (PHPA), and currently gazettment is being processed. Table 8.4 Endemic and Restricted Range (R.R.) bird species recorded in the Dieng mountains.

Endemism is defined as being restricted to the Javan faunal region i.e. the islands of Java and Bali, while a Restricted Range species is a species which has a breeding range fewer then 50,000 km2 (Bibby et al., 1992; Sujatnika et al., 1995). Nomenclature and sequence follow Andrew (1992).

English name Scientific name Endemic R.R. Javan Hawk-eagle Spizaetus bartelsi • • Chestnut-bellied Patridge Arborophila javanica • • Pink-headed Fruit-dove Ptilinopus porphyreus • Yellow-throated Hanging-parrot Loriculus pusillus • Javan Kingfisher Halcyon cyanoventris • • Brown-throated Barbet Megalaima corvina • • Black-banded Barbet Megalaima javensis • Orange-fronted Barbet Megalaima armillaris • • Sunda Minivet Pericrocotus miniatus • Orange-spotted Bulbul Pycnonotus bimaculatus • Sunda Streaked Bulbul Hypsipetes viriscens • Sunda Blue Robin Cinclidium diana • White-breasted Babbler Stachyris grammiceps • • White-bibbed Babbler Stachyris thoracica • • Crescent-chested Babbler Stachyris melanothorax • • Grey-cheeked Tit-babbler Macronous flavicollis • • Javan Fulvetta Alcippe pyrrhoptera • • Javan Tesia Tesia superciliaris • • White-rumped Warbler Seicercus grammiceps • Rufous-tailed Fantail Rhipidura phoenicura • • White-bellied Fantail Rhipidura euryura • • Pygmy Tit Psaltria exilis • • White-flanked Sunbird Aethopyga eximia • • Violet-tailed Sunbird Aethopyga mystacalis • Grey-throated Darkeye Lophozosterops javanicus • • Sunda Serin Serinus estherae • ACKNOWLEDGEMENTS We thank the Indonesian Institute for Science (LIPI) for sponsoring our research and the Directorate General of Forest Protection and Nature Conservation (PHPA) for allowing us to conduct our fieldwork. BirdLife International Indonesia Programme is thanked for their support and especially the co-operation of Paul Jepson and Sujatnika is acknowledged. Sujatnika helped with preparing the map. Resit Sözer is


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thanked for his work during parts of the 1994 surveys, as are Iwan Setiawan and Andi Prima Setiadi. Drs Boeadi (Museum Zoologi Bogor) helped with identification of prey remains. Dr H. Albrecht, Dr P.J.H. van Bree, Dr J. Chapman and three reviewers commented on earlier drafts.

Distribution and Conservation of the Proboscis Monkey

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CHAPTER 9

DISTRIBUTION AND CONSERVATION OF THE PROBOSCIS MONKEY NASALIS LARVATUS IN KALIMANTAN, INDONESIA.

with Erik Meijaard, Biological Conservation 92: 15-24, 2000

ABSTRACT The proboscis monkey Nasalis larvatus is endemic to the island of Borneo. A review of the species' distribution reveals that it occurs throughout Kalimantan, the Indonesian part of Borneo, from the coastal areas to the headwaters of probably all major rivers. Proboscis monkeys are more widely distributed than has been thought previously, and were never confined to the coastal and downstream areas of rivers on the island of Borneo (including what is now Sabah, Sarawak, Brunei and Kalimantan) as has been assumed in some primate literature. Proboscis monkey habitat, i.e. riverine and coastal forest, is the most threatened of all vegetation types in Borneo, owing to conversion into agricultural land and logging. Another threat to their survival is hunting. The combination of these threats has reduced populations of N. larvatus in Sabah, Sarawak and East Kalimantan, and based on this it is expected that other populations elsewhere in Borneo are likewise threatened. Our study shows the present low efficiency of conservation programmes in Kalimantan, which adds to the problem of protecting N. larvatus. For the survival of the species the populations in Kalimantan are still of great significance, as they are considerably larger than those in Sabah, Sarawak, and Brunei. We therefore recommend the protection of some of the largest populations in order to ensure the long-term survival of the species. RINGKASAN Penyebaran dan konservasi Bekantan Nasalis larvatus di Kalimantan, Indonesia (bersama Erik Meijaard, Biological Conservation 92: 15-24, 2000): Bekantan Nasalis larvatus merupakan spesies endemik Pulau Borneo. Tinjauan ulang terhadap distribusi spesies ini menunjukkan bahwa spesies ini terdapat di seluruh Kalimantan, Borneo bagian Indonesia, dari daerah pesisir sampai hulu sungainya dari kemungkinan besar semua sungai-sungai besar. Bekantan ternyata tersebar lebih luas dibanding dengan yang diperkirakan sebelumnya, dan tidak hanya terbatas di pesisir dan kawasan hilir sungai-sungai di Pulau Borneo (termasuk Sabah, Sarawak, Brunei dan Kalimantan) seperti diperkirakan di beberapa literatur primata. Habitat bekantan, yaitu hutan di sepanjang aliran sungai dan pantai, merupakan tipe vegetasi yang paling terancam di Borneo, karena peralihan menjadi lahan pertanian dan penebangan kayu. Ancaman lainnya adalah perburuan. Gabungan ancaman-ancaman


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ini telah menurunkan populasi N. larvalis di Sabah, Sarawak dan Kalimantan Timur, dan berdasarkan hal tersebut diperkirakan bahwa populasi-populasi lainnya di Borneo juga terancam. Penelitian kami memperlihatkan rendahnya efisiensi program-program konservasi di Kalimantan, yang menambah permasalahan dalam perlindungan Bekantan. Untuk keberlangsungan hidup spesies ini populasi-populasi di Kalimantan masihlah penting sekali, di mana populasi-populasi itu sangat lebih besar dibandingkan dengan di Sabah, Sarawak, dan Brunei. Karena itu kami merekomendasikan perlindungan beberapa populasi yang terbesar untuk menjamin keberlangsungan hidup spesies ini. INTRODUCTION The proboscis monkey Nasalis larvatus (van Wurmb, 1787) is a large, sexually dimorphic Colobine, endemic to the island of Borneo. It is closely associated with waterways, returning to the water's edge in the evening, and rarely ranging far from rivers, generally <1 km (Bennett & Sebastian, 1988; Bennett & Davies, 1994; Yeager, 1991, 1993; see however Sebastian, 1994). N. larvatus is restricted to lowlands and is typically associated with coastal forest, including mangroves, and riverine, peat swamp and fresh water swamp forests. In Sarawak, one of the two Malaysian states in Borneo, the species is endangered, with an estimated population size of < 1,000 animals (Bennett et al., 1987). These populations were previously reported to be sparsely and patchily distributed (Payne et al., 1985). In Sabah the only large populations occur in the fresh water wetlands of the Kinabatangan flood plain, and around Dewurst Bay in the Eastern Deltas (Davies & Payne, 1982; Boonratana, 2000). The mangroves and estuaries in the Brunei and Padas Bay also support a population (Kawabe & Mano, 1972; MacDonald, 1982; Payne et al., 1985; Yeager, 1989). N. larvatus has rarely been recorded along Sabah’s north-eastern coast (Davies & Payne, 1982), nor on most of Sarawak’s north coast (K. Proud in Jeffrey, 1982; Salter & MacKenzie, 1985), isolating the population in Brunei Bay. Within Kalimantan, the Indonesian part of Borneo, N. larvatus occurs in many localities in all four provinces. The species is considered ‘Vulnerable’ according to the IUCN threat criteria (IUCN, 1996), and was given a ‘Very High’ conservation rating by Eudey (1987). MacKinnon (1987) estimated the total population size within Kalimantan to be > 250,000, with c. 25,000 protected inside reserves. Yeager & Blondal (1992) considered this last figure too high and made an adjustment to < 5,000 animals inside protected reserves. N. larvatus is protected by law throughout its range, and is listed on Appendix I of the CITES convention. The aim of this paper is twofold: (1) to provide information on the distribution of N. larvatus throughout Kalimantan in historic and present times, and (2) to provide information on threats facing the species.


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METHODS Information was obtained by direct observation and by interviewing local people on the status of N. larvatus: by the author EM from 1994-1997 in the course of a Kalimantan-wide orang-utan Pongo pygmaeus survey, and by VN in the framework of a WWF-Indonesia survey in 1996, which concentrated on Colobine monkeys. For the orang-utan survey a total of 78 field-checks involving 208 field days were made in Kalimantan. In addition 69 days were spent in towns and villages for official visits and interviews. During that period a total of almost 35,000 km were travelled by various means of transportation, including transects on foot. The surveys covered all major river systems of West, Central, and East Kalimantan, all main towns in Kalimantan, and mountainous areas in Central and East Kalimantan. The WWF survey was conducted between September and December 1996, totalling 78 field days, and covered the north-eastern part of East Kalimantan. Because of the limited means of transportation in Kalimantan, survey routes were mostly dictated by the course of rivers and roads and were not randomly chosen. Additionally, 32 days were spent in Sabah, Sarawak, and Brunei. Figure 9.1 shows the survey routes. Figure 9.1 Area covered during the 1994 - 1997 survey. Thick lines indicate the survey routes.


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Interviews were conducted in a semi-structured fashion. Questions were asked in Indonesian, which is also understood in the Malaysian states and Brunei. Interviews always started as an informal conversation, and if the informant knew about general wildlife subjects, the interviews became more specific. As the orang-utan was the main focus of the larger part of the survey, questions initially addressed that particular species, after which information about other wildlife species was collected, including proboscis monkeys. Questions mostly concerned absence or presence of the species and threats to its survival. The anecdotal information used in this survey provides only subjective data, and information on absence of proboscis monkeys was not recorded. We only include locations from where the species was reported by at least two independent sources (c.f. Salter & MacKenzie, 1985). Additional information was obtained from literature, and from biologists and conservationists working in Kalimantan. The Environmental Impact Assessment reports of Kalimantan's logging concessions also provided information on the present distribution of N. larvatus. A total of 115 reports were consulted. All N. larvatus records were given a latitude/longitude coordinate and entered in a computerized Geographic Information System (GIS), using PC ArcInfo and PC ArcView software. Other data layers contain information on the 1993 forest cover (World Conservation Monitoring Centre (WCMC) data base), and topography. Habitat was classified according to personal observation, data from literature, and via personal communication. The distance from the N. larvatus locations to the coast was calculated by proximity analysis in the spatial query builder of PC ArcView. For analysis we only included recent data. This was arbitrarily taken as records (published) after 1980. We have listed all information on the occurrence of N. larvatus, regardless of the numbers in which they may occur. For the 15 of what are probably the largest populations we give an indication of population sizes based on personal observation, personal communication, and information in the literature, taking into account the approximate extend of suitable habitat. Population sizes are classified as: 1: < 100; 2: 100-1000; and 3: >1000.

RESULTS Distribution Groups of N. larvatus were observed at 30 locations during the survey, and an additional 123 records were derived from literature and interviews (Fig. 9.2, Appendix 9.1). The species is scattered throughout Borneo from the mangroves and small islands in the coastal deltas, along virtually all major rivers to numerous inland sites. Eight percent (12/153) of the presence reports were > 200 km directly inland from the coast; 18 % (n = 28) between 100 and 200 km; 16 % (n = 25) between 50 and 100 km; and 58 % (n = 88) < 50 km from the coast. Distances to the coast following the course of the rivers are even larger, often > 300 km, and sometimes as much as 750 km. Our data suggest that N. larvatus does not occur at high altitudes. Over 90 % (n = 138) of the presence records were from altitudes < 200 m a.s.l., and


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the highest reports are from c. 350 m a.s.l. The occurrence of inland groups have sometimes been thought to consist of wandering males only (C. Yeager, pers. comm.). It is therefore important to note that our inland sightings included groups of N. larvatus comprising juveniles and females with dependent young. Figure 9.2 The 153 recent records of proboscis monkey Nasalis larvatus on Borneo as mentioned in the

text. The numbers 1-16 refer to priority areas for N. larvatus mentioned in the text and Table 9.1. Protected areas in Borneo are cross-hatched.

Within Kalimantan large populations have been reported from Danau Sentarum Wildlife Reserve (No. 3 in Fig. 9.2 and Table 9.1; c. 600, Sebastian, 1994), and from Gunung Palung National Park (No. 1; “several hundreds”, Yeager & Blondal, 1992), Tanjung Puting National Park (No. 5; c. 2000, Yeager & Blondal, 1992), and the Mahakam delta (No. 16; 600 - 900, Alikodra et al., 1992). Our data indicate that within Kalimantan a number of other areas remain where there are relatively large populations of N. larvatus. Notably, this includes the delta of the Sungai Sesayap


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(Sungai = River, hereafter abbreviated as ‘S’), S. Sembakung and S. Sebuku (No. 15), the Mahakam lakes area (No. 10), the fresh water and peat swamp forest areas of Central Kalimantan (No. 6), and the Kendawangan area (No. 2). Table 9.1 Priority areas for the protection of proboscis monkeys Nasalis larvatus in Kalimantan,

Indonesia. Noa Priority Areab Statusc Numbersd Habitat e Main threats Reference f 1

G. Palung

NP

2

F, P, Ri. LoD

Illegal logging

2, 3

2 Kendawangan NR 2-3 F, P Illegal logging 4, 5 3 Danau Sentarum WR 2-3 F, P, Ri Fire, hunting, logging 1, 6, 15 4 Sambas Paloh UNP 2 Ni, Ma, LoD, P Logging 1, 7, 8 5 Tanjung Putting NP 3 F, P, LoD Goldmining, logging,

hunting 1, 3

6 Central KalimantanRivers

NR/UNP 2-3 F, P, Ri Swamp reclamation 1

7 Lower S. Barito UNP 2 Ri Logging 1 8 P.Laut UNP ? Ri, LoD, F Logging 9 9 Balikpapan Bay UNP 1-2 Ri, Ma, F Logging 1 10 S. Mahakam and

Lakes UNP 2 Ri, F, P Logging, disturbance,

hunting 1, 5, 8, 14

11 S. Kedang Kepala NR/UNP 1-2 Ri, F, P Logging, fire 1 12 Kutai NP 1 Ri, F, P, LoD Logging, fire 1, 10, 11, 12 13 S. Kayan UNP 1 Ri, F, Ma, Ni Logging, hunting 1, 8 14 Sangkulirang UNP 1-2 Ri, F, Ma, Ni Logging 1, 13 15 S. Sesayap, S.

Sebuku, S. Sembakung

UNP 3 Ri, F, Ma, Ni Shrimp farming, logging

1, 5, 16

16 Mahakam delta UNP 2 Ma, Ni Shrimp farming, logging

17

(a) cf. Figure 9.2. (b) G.= Gunung (Mountain); P. = Pulau (Island); S. = Sungai (River). (c) NP = National Park; NR = Nature reserve; WR = Wildlife Reserve; UNP = Unprotected. (d) Indication of population sizes: 1<100 individuals; 2 100-1000 individuals 3>1000 individuals. See

text for details. (e) Mangrove forest (M), Freshwater swamp (F), Peat swamp (P), Riverine (Ri), Lowland Dipterocarp

(LoD), and Nipah palm (Ni). (f) 1 personal observation; 2 MacKinnon & Warsito, 1982; 3 Yeager & Blondal, 1992; 4 Noor &

Hanafia, 1994; 5. K.Jeanes, pers. comm.; 6 Sebastian, 1994; 7 McCarthy, 1997; 8 Silvius et al., 1987; W. Smits, pers. comm.; 10 Suzuki, 1984; 11 MacKinnon et al., 1994; 12 Rodman, 1978; 13 Wibowo pers. comm.; 14 R. Sözer, pers. comm.; 15 R. Dennis pers. comm.; 16 Momberg et al., 1998; 17 Alikodra et al., 1992.

Threats The only direct threat to the survival of N. larvatus recorded during this study was hunting. Hunting was reported at six locations during the three year surveys. In the northern Mahakam lakes, in East Kalimantan, N. larvatus is increasingly hunted to serve as bait for monitor lizards Varanus salvator, whose skins are highly valued.


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Further inland the species is hunted for food (R. Sözer, pers. comm). In the Danau Sentarum Wildlife Reserve, West Kalimantan, at least two proboscis monkeys were shot by army or police hunters in late 1996 (R. Dennis, pers. comm.). Iban people from the area north of the Reserve will opportunistically shoot the monkeys while on turtle hunting expeditions during the dry season, much to the annoyance of local Muslim fishermen (pers. obs.). Three instances of hunting along the S. Kayan and S. Pangean (where the species is rare) were reported by two Dayak hunters in 1996. Finally, it was reported by inhabitants of Tanjung Selor and its surroundings, East Kalimantan, that since the early 1990s the population of proboscis monkeys had declined dramatically due to hunting by non-Muslim Dayaks. Another threat to N. larvatus' survival is habitat destruction. Table 9.1 shows that in the 16 priority areas for protection, the main factors contributing to habitat destruction are logging (both legal and illegal), forest fire, gold mining, swamp reclamation and shrimp farming. Unfortunately, the proboscis monkeyís specialised habitat coincides with the areas on Borneo that are the first to be colonised, farmed, industrialised, and least protected by man. Table 9.2 shows that of the most important N. larvatus habitat types, only c. 39% has survived, of which 15% is protected. Hereby we need to note that the data in Table 9.2 are based on MacKinnon & Artha’s 1981 study, as no more recent data are publicly available. After almost two decades of a continuous logging regime (for reviews see Sunderlin & Resosudarmo 1996, and Rijksen & Meijaard 1999) considerably less habitat remains. Table 9.2 Proboscis monkey Nasalis larvatus habitat (km2) in Kalimantan (after MacKinnon et al.,

1996)

Vegetation type

Original area

Total remaining (<1981) (% of original area)

Total in reserves (% of total remaining)

Freshwater swamps 38,950 17,170 (44%) 3,620 (21%) Peat swamps 44,030 35,310 (80%)a 2,570 (7%)a

Mangrove forest 15,600 9,200 (59%) 780 (8%) Wet lowland forest (alluvium) 22,010 2,650 (12%) 160 (6%) Moist lowland (alluvium) 870 250 (29%) 0 Dry lowland forest (alluvium) 210 0 0

a. A total of 17,000 km2 of land, originally designated as protected forest will be used for agricultural

purposes in the Central Kalimantan province (Jakarta Post, 18 November 1996). The majority of this area consists of peat swamp forest. The total area of peat swamp forest in Kalimantan will be some 18,300 km2 or 42% of the original area, or 14% of the remaining total, will be inside a protected area.

During the survey only seven instances of proboscis monkeys held in captivity were reported or recorded (D. Kreb, pers. comm., W. Smits, pers. comm., R. Sözer, pers. comm., pers. observ.), and capturing for the pet trade does not appear to be a serious threat.


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DISCUSSION Distribution Early work on this species suggested that N. larvatus was dependent on mangrove forests for food and cover (e.g., Kawabe & Mano, 1972; Davies, 1962; Kern, 1962). Bennett & Gombek’s (1993) map showed the species to be largely restricted to coastal and nearby swamp forest, while Oates et al. (1994), Chivers & Burton (1988) and Bodmer et al. (1991) all considered it to be an essentially coastal species with rare individuals inland. However, it was certainly not just a coastal species in the past. The most detailed accounts of N. larvatus’ historic distribution are given by Zondag (1931) who includes all downstream parts of essentially all major rivers in what is now East, Central and South Kalimantan, but also several upstream areas: middle and upper S. Kahayan; middle and upper S. Kapuas (Central Kalimantan); middle S. Barito; middle S. Kayan; upper S. Sesayap. Upstream areas were also given by Westermann (1938), Gyldenstolpe (1920) and Pfeffer (1958): S. Kedang Kepala, upper Barito, S. Murung (the same S. Murung as in Chivers & Burton, 1987 and Bodmer et al., 1991), middle Mahakam, Tumbang Maruwe on the upper S. Barito, S. Liang, and S. Nggang. Other earlier upstream records were by Van der Aa (1884) and Jentink (1897). Our own records show that proboscis monkey populations are still present in the upstream parts of Borneoís rivers. Because of the small numbers observed inland, it appears that proboscis monkeys are most frequent in coastal areas, with the possible exception of the inland swamps surrounding the Danau Sentarum and Mahakam lakes. Owing to the nature of our study we cannot provide estimates of (a change in) population numbers. Threats In the interior of Borneo hunting appears to be an important supplement to rural peopleís diet and all primates including N. larvatus are hunted when the opportunity arises (Van der Aa 1884, and Pfeffer 1958). Additionally, N. larvatus is sometimes hunted for the highly valued bezoar stones which are sometimes found in the intestines of this and other Colobine species, and used in traditional Chinese medicine (Banks, 1931; Westermann, 1938). Jeffrey (1982), working in East Kalimantan, found that hunting and farming had eliminated proboscis monkeys from large areas of river and coast. Likewise, in Sarawak, Bennett (1988) reports hunting to be a major threat to N. larvatus. Davies & Payne (1982) mention an increase in hunting throughout the mangroves of Sabah's west coast, and in several localities the species is now rare or absent in places where they were once common. The decrease in abundance occurred markedly within the past 10 to 35 years, coinciding with guns and outboard motors becoming available to local people (Davies & Payne, 1982). The results of our survey indicate that N. larvatus is hunted both inland and in coastal areas. There is a possibility that hunting in the coastal areas is mainly limited to Dayak people and sport hunters, because for the Muslims, who predominate along the coast, consumption of monkeys is forbidden (Cleary & Eaton, 1992). Jentink


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(1897) already noted this along the S. Kapuas. There are indications (mainly information from interviewees) that hunting by indigenous people (especially since the availability of guns and outboard motors) has had a significant impact on populations of N. larvatus. Not only the larger rivers, but now also most smaller rivers have become easily accessible because of an extensive network of logging roads. The occurrence of N. larvatus close to waterways and its lower densities in inland areas have been explained by limited food availability, shortage of essential resources, and competition with other primates (e.g., Bennett & Sebastian, 1988). However, our data suggest that hunting might be a factor largely overlooked. Hunting has been, at least until recently, restricted to Borneo's interior, and may have reduced population densities and caused local extinctions. In those areas in Kalimantan's interior where hunting is traditionally forbidden for the local Muslim fishermen, e.g., Danau Sentarum and surroundings and the Mahakam lake area, the species thrives. Therefore it is worth noting that a hunting-related distribution pattern has also been found for the orang-utan, another lowland specialist primate on Borneo (Rijksen & Meijaard, 2000). Figure 9.3 The land use planning in Central Kalimantan, Indonesia, based on forest use classification

(TGHK) maps. The major cause for the recent decline of N. larvatus has undoubtedly been habitat destruction (MacKinnon, 1987; Wilson & Wilson, 1975; Salter & MacKenzie, 1985), since this primate frequents some of the riverine habitats most favoured by people for logging, cultivation, and village settlement. As an illustration (Figure 9.3) we show the planned land use in the province of Central Kalimantan. This indicates that almost all of the most suitable habitat, i.e. riverine forest is scheduled for


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conversion. Watershed protection forest and protected areas (with the exception of Tanjung Putting National Park) are situated in upland areas. Within the remaining habitat populations are being fragmented (Yeager & Blondal, 1992; Sebastian, 1994). The main factors limiting migration along and across rivers are the extensive use of waterways and river banks by humans and the severe degradation and conversion of the forest along the rivers. Furthermore, the species’ association with the riverine forest combined with the preference for low altitudes may limit migration between river systems. Finally, forest fires appear to be an increasingly serious threat to N. larvatus habitat. Fuller & Fulk (1998) report that fire hot spots during the 1997-1998 forest fires were more likely to occur near rivers. Yeager & Frederiksson (1998) state that proboscis monkey probably has the greatest proportion of its remaining habitat destroyed by fire of any primate in Kalimantan. Failing conservation in Kalimantan. Out of the 16 priority areas for conservation described in Table 9.1, seven are (partially) included in the protected area network system of Kalimantan. In at least four of these areas conservation measures seem to be completely inadequate for the long-term protection of the proboscis monkey populations. 1. Pulau Kaget (included in no 7 in Table 9.1), a 0,85 km2 reserve was gazetted on

this island in 1985, mainly for the preservation of a relatively large population of N. larvatus. When visited by E.M. in 1996 only c. 10 % of the reserve was covered with forest, 90 % was agricultural land. Many of the remaining trees had been ring-barked or poisoned and were dying. At that time, an estimated 300 proboscis monkeys remained (Purwasuka, pers. comm.). In 1999 it was reported that proboscis monkeys were dying due to lack of food and loss of habitat. The conservation authorities concluded that all monkeys had to be evacuated to nearby unprotected islands. So far 130 animals have been translocated and c. 60 have been brought to Surabaya Zoo on Java (Anonymous, 1999; Meijaard & Nijman 2000, chapter 10).

2. Tanjung Puting (no 5; 3,000 km2): This area contains the largest protected

population of N. larvatus. Nevertheless it has been badly affected by illegal logging, gold mining, and forest fires. Logging inside the park has left behind large patches of poorly regenerating fern wilderness on sand. Due to gold mining operations, north of the park, the original tea coloured waters of the black-water river of the park have permanently turned into thin mud solution containing >200 times the toxic level of mercury (Rijksen & Meijaard, 1999). River traffic has increased from c. 10-15 boats month-1 during 1984-1985 to an average of 27.5 boats day-1 in 1989, making it difficult for proboscis monkeys to cross the river (Yeager & Blondal, 1992). Burned freshwater forest in Tanjung Puting lost c. 75% of its tree stands in 1997 and almost all vegetation had been reduced to charcoal (Yeager, 1998).


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3. Kutai National Park (no. 12; 1,980 km2): This reserve was established in the 1930s. In the late 1960s however, a large sector of the reserve was given out as a timber concession, and the coastal lowlands were soon occupied by illegal settlers. In the 1970s two large industrial complexes were established in the reserve and a third of the area was degazetted (MacKinnon et al., 1994; Rijksen & Meijaard, 1999). Major forest fires occurred in this park in 1982-1983, 1987, and 1998, and an estimated 5% remains forested. For proboscis monkeys the area has lost its value.

4. Kendawangan Nature Reserve (no. 2; 650 km2): Although gazetted in 1981,

strengthened in 1982, and demarcated in 1992, the Kendawangan Nature Reserve does no longer appear on the official map of conservation areas in Indonesia. In 1997, conservation officials recommended that conservation efforts in the area should be halted as the reserve was too isolated and illegal logging was rampant.

The above mentioned examples demonstrate that in-situ conservation of proboscis monkeys on Kalimantan has been problematic. Conservation authorities seem to be failing at different fronts. Even though the species is legally protected, law enforcement is weak. During the survey, only once active law enforcement with reference to proboscis monkey was observed, when an animal trader was apprehended, although many illegal activities (including hunting, illegal logging, disturbance and capturing) were encountered and reported to the authorities. Within reserves the situation seems to differ little from areas outside the protected area network. It is important to note that law enforcement seems to be equally lax independent of the status of the area (National Parks, nature reserves or wildlife reserves), its remoteness, its size, and the time since its gazettement. For ex-situ conservation the odds do not seem to be any better. The species requires a specialised diet and is difficult to maintain in captivity (Collins & Roberts, 1978). Relatively few proboscis monkeys have been kept in international zoos, and in general these animals did not seem to thrive (Kern 1964). No European zoos hold the species at the moment, while in North America two males and a female remain in the Bronx Zoo, New York (K. Brouwer, in litt. Nov. 1997). A number of Indonesian zoos do have c. 70 animals on display (R. Sözer pers. comm., 1998; Anonymous, 1999). Neither the European nor the North American zoos have included the species in their Regional Collection Plans for primates. Considering the above, and, more importantly, in view of the lack of release sites (without a resident population), ex-situ conservation will contribute little to the survival of the species. We have demonstrated that N. larvatus has declined in parts of East Kalimantan, Sabah and Sarawak. For the other parts of the species range hard data are not yet available, but we expect the trend to be similar. Of the species potentially suitable habitat c. 39% remained in 1981, and possibly much less now. This study indicates that the distribution range was larger than previously assumed, and subsequently the reduction in population numbers must have been more drastic.


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Evidence is lacking, but, based on our study, the conservation authorities should seriously question whether the species can persist under the present conservation regime or that it is facing a nose dive to extinction. CONCLUSIONS It is beyond the scope of the present study to address the underlying causes of the failure of the Indonesian conservation authorities (and conservation NGOs) to safeguard either the proboscis monkeys or their habitat. What is clear however, is that if sufficiently large areas of habitat can be protected and persistent law-enforcement can be ensured, N. larvatus could survive. Because of their spectacular appearance and ease of observation in the wild the species is an excellent tourist attraction. If eco-tourism is well-guided and disturbance levels can be kept low, the species may serve as a flagship for many protected wetland sites. Several unprotected areas may still provide enough habitat for viable populations of N. larvatus. The improved protection of the following areas (see Fig. 9.2) would significantly increase the survival of this primate: (1) The extensive and largely pristine mangroves and peat swamp forests of the S. Sebuku, S. Sesayap and S. Sembakung delta; (2) The 80,000 ha area of little disturbed swamp forest to the north of the Mahakam Lakes and west of the Muara Kaman Nature Reserve; (3) Kendawangan Nature Reserve; (4) Danau Sentarum Wildlife Reserve; (5) Tanjung Puting National Park, and (6) Gunung Palung National Park ACKNOWLEDGEMENTS We thank the Indonesian Institute for Science (LIPI) for sponsoring our research and the Directorate General of Forest Protection and Nature Conservation (PHPA) for their cooperation. The help of Ir A. Rachmat (KSDA, Samarinda) is kindly acknowledged. WWF-Indonesia, and in particular Mr A. Purmono, Dr T.C. Jessup, Dr C. Eghenter, are thanked for their cooperation. Financial support was received from the Society for the Advancement of Research in the Tropics (VN), the Netherlands Foundation for International Nature Protection (VN, EM), the World Society for the Protection of Animals, World Wide Fund for Nature Netherlands, the Balikpapan Orang Utan Society and the Lucie Burgers Foundation for Behaviour Studies (EM). We want to thank all people who generously shared their proboscis monkey data with us, or otherwise provided information, amongst which Dr. W.T.M. Smits (Tropenbos-Kalimantan Programme), Dr R. Puri (East West Centre, Hawaii), G. Limberg (formerly WWF-IP), R. Sözer (ISP/ZMA, University of Amsterdam), D. Kreb (ISP/ZMA), R. Dennis (formerly ODA - Wetlands International), A. Erman (ODA - Wetlands International), G. Frederiksson (ISP/ZMA-Wanariset), S. van Balen (Wageningen Agricultural University); K. Jeanes (formerly ODA - Wetlands


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International), P. Jepson (formerly Birdlife International), Wibowo (Wetlands International), and K. Brouwer (European Association of Zoos and Aquariums). Finally, comments on earlier drafts were received from Dr H. Albrecht (Dept. Animal Behaviour, University of Amsterdam), Dr D. Kitchener (WWF Indonesia Programme), and S. van Balen. Dr B.N.K. Davis and two anonymous reviewers made constructive comments on the manuscript.


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APPENDIX 9.1 Localities (records published after 1980) where proboscis monkeys Nasalis larvatus have been recorded in Kalimantan, Indonesia, the Malaysian states of Sarawak and Sabah, and Brunei. (D = Danau = Lake; G. = Gunung = Mountain; S. = Sungai = River; P. = Pulau = Island; PT = Perseroan Terbatas = Inc. or Ltd. ) West Kalimantan Benua Martinus [112°25/1°07N]; Danau Sentarum WR [112°03/0°47 N]; G. Palung NP [110°05/1°06 S]; G. Senuju [109°29/1°30 N]; Hutan Sambas [109°26/1°43 N]; Muara Kendawangan [110°27/2°28 S]; PT Duadja Corporation II [110°49/0°50 S]; PT Erna Djuliawati [111°52/1°08 S]; PT Jamaker KalBar Bl. Nanga Sei [111°00/1°00 N]; PT Jamaker KalBar Blok S. Haji [109°30/1°40 N]; PT Jamaker KalBar Blok Unit 1 [109°30/1°50 N]; PT Jamaker KalBar Jaya Bl. Lanjak [112°25/1°00 N]; PT Jamaker KalBar S. Sentimau [109°36/1°25 N]; PT Sinar West Kalimantan Timber [110°43/2°37 S]; PT Sumber Jaya Baru Utama [110°30/1°05 S]; S. Bangkul Besar [110°25/2°45 S]; S. Blamban [110°14/2°43 S]; S. Embaloh [112°23/1°07 N]; S. Embaloh Ulu [112°32/1°23 N]; S. Membuluh [110°18/2°32 S]; S. Mentangan [110°41/2°47 S]; S. Seriang [111°56/0°56 N]; S. Tang [112°29/0°39 N]; Tanjung Satay [109°34/1°12 S]; upper S. Kapuas [112°54/0°56 N] Sources: MacKinnon and Artha, 1981; MacKinnon and Warsito, 1982; MacKinnon et al., 1996; Noor and Hanafia, 1994; Silvius et al., 1987; Sebastian, 1994; Yanuar et al., unp. data; R. Dennis, pers. comm.; S. van Balen pers. comm.; pers. observ. Central Kalimantan PT Bina Samaktha [112°00/2°25 S]; PT Bintang Arut [111°35/2°40 S]; PT Brata Jaya Utama [113°45/3°00 S]; PT Carus Indonesia [113°10/0°37 S]; PT Gadjah Seno Sakti [112°45/2°45 S]; PT Gunung Meranti [114°00/0°30 S]; PT Hutan Mulya [112°50/1°20 S]; PT Rathitara [113°30/1°30 S]; PT Sehati Barito, S. Bila [111°15/2°35 S]; PT Yusmin Trading [112°45/2°00 S]; S. Dason [114°58/0°07 N]; S. Gula [114°11/0°44 S]; S. Hanyu [114°02/0°58 S]; S. Kapuas Murung [114°25/2°25 S]; S. Mandau [113°53/0°43 S]; S. Mengkutup [114°15/2°05 S]; S. Murung PT LAAS [114°24/0°09 N]; S. Pinang [114°04/0°51 S]; Tanjung Penghujan [111°32/2°59 S]; Tanjung Puting extension [111°50/3°11 S]; Tanjung Puting NP [111°56/2°53 S]; Tumbang Mahub [112°21/1°02 S] Sources: Bodmer et al., 1991; Chivers and Burton, 1988; MacKinnon and Artha, 1981; MacKinnon et al., 1996; Payne et al., 1985; Silvius et al., 1987; Yeager and Blondal, 1992; Yanuar et al., unp. data; S. van Balen pers. comm.; pers. observ.


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South Kalimantan Hutan Bakau Pantai Timur [116°02/3°16 S]; Muara Muning [114°50/2°50 S]; P. Kaget [114°31/3°20 S]; P. Kembang [114°32/3°17 S]; P. Laut [116°13/3°48 S]; P. Pinang [115°03/3°05 S]; Pleihari Martapura [114°56/3°56 S]; Pleihari Tanah Laut [114°41/4°08 S]; S. Kacang [115°10/2°40 S]; S. Negara [114°56/2°47 S]; S. Tapin [115°15/2°55 S] Sources: MacKinnon and Artha, 1981; MacKinnon et al., 1996; Silvius et al., 1987; S. van Balen pers. comm.; pers. observ.; East Kalimantan Balikpapan Bay [116°43/1°03 S]; Balikpapan Bay, north [116°42/0°55 S]; Bunua Puhun, S. Mahakam [116°49/0°16 S]; D. Jempang [116°10/0°34 S]; D. Kendang Murung [116°35/0°23 S]; D. Wis [116°11/0°30 S]; D. Melitang [116°18/0°22 S]; D. Semayang [116°25/0°20 S]; Lamin Pulut [116°16/0°01 S]; Lower Mahakam delta [117°21/0°48 S]; Mahakam delta [117°27/0°40 S]; Miau Baru [116°57/1°15 N]; Muara Kayan [117°32/2°59 N]; Muara Sebuku [117°28/4°10 N]; PT Adindo Hutani Lestari [116°45/3°50 N]; PT Alas Helau [116°45/1°50 N]; PT Daisy Timber [118°40/1°15 N]; PT Dana Mula Bhakti [117°25/3°47 N]; PT ITCI-Weyerha¸ser [116°43/0°53 S]; PT Jaya Maha Kerta [117°10/4°05 N]; PT Rejosari Bumi [117°45/2°10 N]; PT Surya Hutani Jaya [117°08/0°05 N]; PT Timberdana [115°35/0°20 S]; PT Tungal Yudi Sawmill Plywood [115°35/0°30 N]; S. Alango Ulu [115°56/2°52 N]; S. Baai [117°38/1°15 N]; S. Bahau Long Alango [115°51/2°52 N]; S. Bahau Long Peleran [115°50/2°47 N]; S. Bulungan [117°30/2°55 N]; S. Jelau [115°52/0°26 S]; S. Kahala [116°21/0°05 S]; S. Karangan [117°51/1°14 N]; S. Kayan [116°43/2°48 N]; S. Kedang Kepala [ 116°41/0°04 N]; S. Kedang Rantau [116°45/0°01 N]; S. Kelai Long Lanuk [117°17/2°00 N]; S. Kendang [116°37/0°25 S]; S. Kendang Pahu [115°58/0°21 S]; S. Lurah [115°41/2°41 N]; S. Mahakam, Long Bagun [115°04/0°18 N]; S. Pangean [116°44/2°38 N]; S. Ratah [115°12/0°14 N]; S. Samboja [116°59/1°11 S]; S. Sebukuh [117°25/4°05 N]; S. Sebukuh [117°05/3°57 N]; S. Sembakung [117°20í/3°48í N] S. Sengatta, Kutai NP [117°26/0°26 N]; S. Sesayap [116°58/3°37 N]; S. Tubu [116°07/3°09 N]; S. Wahau [116°52/1°07 N]; Sangkulirang [118°31/1°00 N]; Senggata estuary [117°35/0°27 N]; S. Wain [116°47/1°05 S]; Tarakan [117°37/3°22 N]; Teluk Apar/ Teluk Adang [116°34/2°13 S]; Teluk Kaba [117°29/0°14 N]; Teratak, S. Mahakam [116°45/0°13 S]; Tubuan [116°18/0°11 S]; upper S. Senggata [117°12/0°36 N]; West of Muara Kaman NR [116°39/0°13 N] Sources: Alikodra et al., 1992; Azuma and Suzuki, 1984; Jeffrey 1982; MacKinnon and Artha, 1981; MacKinnon et al., 1996; Momberg et al., 1998; Silvius et al., 1987; Suzuki, 1984; Yanuar et al., unp. data; Yasuma, 1994; S. van Balen pers. comm.; G. Frederiksson, pers. comm.; D. Kreb, pers. comm.; G. Limberg pers. comm.; McCarthy, pers. comm.; R. Puri, pers. comm; R. Sözer, pers. comm.; P. Jepson, pers. comm.; pers. observ.


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Sarawak Bako NP [110°29/1°43 N]; Limbang mangroves [115°03/4°49 N]; S. Sarawak [110°27/1°39]; West of Miri (113°45/3°50 N); P. Bruit [111°21/2°34 N]; Rajang Delta [111°30/2°24 N]; Rajang Mangrove [111°21/2°13 N]; S. Maludam [111°14/1°28 N]; Samunsam wildlife sanctuary [109°35/1.52 N]; Trisu and Maludam peat swamps [111°05/1°37 N] Sources: Bennett, 1988; Bennett and Sebastian, 1987; Bennett et al., 1997; MacKinnon et al., 1996; Payne et al., 1985; Salter and MacKenzie, 1985; Salter et al., 1985. Brunei S. Brunei [115°00/4°58 N]; Brunei Bay [115°10/4°58 N] Sources: MacDonald, 1982; MacKinnon et al., 1996; Payne et al., 1985; Yeager, 1989. Sabah Cowle delta [117°55/4°25 N]; Danum Valley [117°47/5°02 N]; Eastern deltas [118°50/5°27 N]; Kabili-Sepilok Forest Reserve [117°59/5°49 N]; Kelompok G. Asuansang [109°35/1°43 N]; Kinabatangan [118°20/5°30 N]; Klias Peninsula [115°30/5°20 N]; Kulamba Wildlife Reserve [118°02/5°40 N]; Lawas Mangroves [115°27/4°55 N]; Maliau Basin [116°50/4°45 N]; Padas Bay [115°30/5°10 N]; P. Sebatik [117°55/4°25 N]; S. Sugut, middle reaches [117°29/6°17 N]; Salim Batu [117°20/3°00 N]; Samporna lowlands [118°26/4°28 N]; Sandakan peninsula [118°00/6°00 N]; Segama [118°23/5°14 N]; Sungut delta [117°43/6°25 N]; Tempasuk Plain [116°25/6°28 N]; Trusan-Sundar Mangroves [115°14/4°55 N] Sources: Davies and Payne, 1982; MacKinnon et al., 1996; Marsh, 1995; Payne et al., 1985.

The Local Extinction of the Proboscis Monkey in Pulau Kaget Nature Reserve

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CHAPTER 10

THE LOCAL EXTINCTION OF PROBOSCIS MONKEY NASALIS LARVATUS IN PULAU KAGET NATURE RESERVE,

INDONESIA

with Erik Meijaard, Oryx 34: 66-70 (2000)

ABSTRACT The population of the threatened proboscis monkey Nasalis larvatus, a Bornean endemic, in the South Kalimantan Pulau Kaget Nature Reserve of Indonesia is extinct. Until 1997 this small, isolated population, estimated at c. 300 animals, had been pushed towards the fringes of the reserve by illegal agricultural expansion. As food sources were depleted, the population apparently exceeded the decreasing carrying capacity of the reserve and was reported to be starving to death. As a solution, 84 animals were translocated to nearby, unprotected sites, resulting in 13 fatalities. An additional 61 animals were taken to a zoo where 60 per cent died within four months of their capture. There was neither a proper pre-translocation assessment of the suitability of the release sites, nor a proper post-translocation monitoring programme of the released animals. We conclude that the Pulau Kaget reserve and its proboscis monkeys have been poorly managed. To improve the effectiveness of conservation efforts in Indonesia we provide some suggestions. RINGKASAN Kepunahan lokal Bekantan Nasalis larvatus di Cagar Alam Pulau Kaget, Indonesia (bersama Erik Meijaard, Oryx 34: 66-70, 2000): Populasi Bekantan Nasalis larvatus suatu spesies endemik Borneo yang berstatus terancam, di Cagar Alam Pulau Kaget, Kalimantan Selatan, Indonesia telah punah. Sampai tahun 1997 populasi kecil dan terisolasi ini, diperkirakan sekitar 300 ekor, telah tersingkir ke pinggiran kawasan cagar alam oleh perambahan ilegal untuk pertanian. Karena sumber makanan telah dihabisi, populasi ini tampaknya melebihi daya dukung cagar alam dan dilaporkan mati kelaparan. Sebagai pemecahan masalahnya, 84 ekor ditranslokasikan ke daerah yang dekat, yang tidak dilindungi, mengakibatkan 13 kematian. 61 Ekor lain dibawa ke kebun binatang dimana 60% meninggal dalam kurun waktu 4 bulan dari penangkapannya. Sebelum translokasi, tidak ada penilaian terlebih dahulu yang memadai terhadap daerah pelepasannya, juga setelah translokasi tidak ada program monitoring yang tepat terhadap hewan pindahan itu. Kami berkesimpulan bahwa pengelolaannya Cagar Alam Pulau Kaget dan bekantannya telah sangat kurang. Untuk meningkatkan keefektifan usaha pelestarian di Indonesia kami memberikan beberapa saran.


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INTRODUCTION In 1976, 85 ha of the 247 ha large Pulau Kaget [3º26’S, 114º31’E] (pulau = island) was gazetted by Ministerial decree No. 701/Kpts/Um/11/1976 as a Strict Nature Reserve, which prohibits all human use of the reserve’s resources. The main reason for establishing the reserve was to protect its population of proboscis monkey Nasalis larvatus. The remainder of the island was designated for agricultural purposes. The island is situated in the middle of the Barito River delta, in South Kalimantan, only a few kilometres downstream from the provincial capital of Banjarmasin (Fig. 10.1). The area was a popular tourist destination because it was easy to see proboscis monkeys from the river. In 1993, the proboscis monkey was declared the provincial symbol of South Kalimantan, further adding to the apparent importance of Pulau Kaget Nature Reserve as a conservation site for this species. Figure 10.1 The island of Borneo (insert) and the location of Pulau Kaget and adjacent islands. The proboscis monkey, known as bekantan in the Indonesian language, is an endemic of the island of Borneo, where it inhabits riverine and coastal forest, including mangroves. It typically lives in one-male groups varying from 3-23 individuals, which may form large associations of up to 60 individuals (Bennett & Sebastian, 1988; Yeager, 1990, 1991, 1993; pers. observ.). Reported densities vary


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from 1.2 to 62.6 individuals km2 (Bennett & Sebastian, 1988; Alikodra et al., 1992; Yeager & Blondal, 1992). Proboscis monkey habitat is the most threatened of all vegetation types in Borneo, because of logging and conversion to agricultural land (Rijksen & Meijaard, 1999). Habitat destruction has been identified as the major threat to the survival of the proboscis monkey (Salter & MacKenzie, 1985; MacKinnon 1987; Meijaard & Nijman 2000, chapter 9), but other threats include hunting (Pfeffer, 1958; Meijaard & Nijman 2000, chapter 9), and, to a lesser extent, the illegal pet trade (Fig. 10.2). The combination of these threats has reduced proboscis monkey populations in several parts of Borneo (Davies & Payne, 1982; Salter & MacKenzie, 1985; Meijaard & Nijman 2000, chapter 9) and it is suspected that the species is in rapid decline (Meijaard & Nijman 2000 chapter 9). In 1990 the number of proboscis monkeys protected in reserves was estimated at some 5000 individuals (Yeager & Blondal, 1992). The proboscis monkey is classed as Vulnerable by IUCN (1996), and as early as 1987 it was given a ‘very high conservation rating’ by the Primate Specialist Group (Eudey, 1987). The species is listed on Appendix I of CITES and is protected by law throughout its range. Figure 10.2 Male proboscis monkey Nasalis larvatus in illegal private captivity (photo E. Meijaard)


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THE CASE OF THE PULAU KAGET PROBOSCIS MONKEYS When E.M. visited Pulau Kaget in November 1996, the central part of the island, including the reserve, had been cleared for agriculture, and only a c. 25-m-wide fringe around the central fields, was still forested. Proboscis monkeys were abundant in this strip of forest. On another part of the island, a similar narrow fringe of trees was still standing, but these trees had lost all their leaves and appeared dead (Fig. 10.3). In 1996 it has been estimated that 27% of all trees in the Pulau Kaget Nature reserve were dead (Bismark, 1999). Only c. 10% of the total land area of the reserve retained some tree cover (estimated at 5% in 1993 by Yeager (1996)). During E.M.’s visit no guards were present in the reserve. There appear to be several reasons for the habitat loss at Pulau Kaget. The reserve comprises rich agricultural soils, and farmers from outside the reserve have entered the area for many years to grow crops, apparently unhampered by the reserve’s fully protected status. According to local forestry officials, the farmers had ring-barked or poisoned many of the remaining trees, presumably to open up more land. An alternative explanation was upstream pollution from sawmills and wharves (cf. Bismark, 1999). Both the heads of the provincial Agency for the Conservation of Natural Resources and the regional office of the Forestry Department said that some 300 proboscis monkeys still survived in the remaining area, and that the present population was too large for the remaining habitat. This estimate was corroborated by Bismark’s (1999) count of 288 individuals in 1996 (but for a different view see Yeager (1996) who estimated the reserve’s population at 51 individuals). These population estimates suggest an over-capacity, which may have been a third reason for the defoliation. In 1996 the Governor of South Kalimantan and the Director General for Forest Protection and Nature Conservation also assessed the situation and promised further research. Short-term conservation measures were suggested, including the provision of leaves to the monkeys and the planting of some 5000 Sonneratia sp. seedlings, an important food source when fully grown. In the longer term, plans were put forward to downgrade the status of the area to a Wildlife Reserve, which would allow for other resource use besides conservation. According to an Indonesian newspaper report (Kompas, 5 Feb. 1999) rangers started to find dead proboscis monkeys on the island in 1997. In an attempt to prevent the local extinction of the proboscis monkeys, the conservation agencies decided that the remaining animals had to be translocated to the nearby, unprotected, islands of Burung (Tempurung Kecil), Tempurung Besar, Kembang and Bakut, all of which had extant proboscis monkey populations (Fig 10.2). However, according to official documents (Ministry of Forestry (MoF), 1999) between December 1996 and March 1997, before the translocations, there had already been six attempts to drive proboscis monkeys from the protected part of the island to the unprotected part. Unfortunately, the documents do not explain the logic behind these actions, which displaced a total of 205 animals into unprotected habitat (MoF, 1999). In early 1997 and late 1998, in two major capture efforts, some 84 proboscis monkeys,


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of which 13 died during capture, were translocated while an additional 61 were transported to Surabaya Zoo in Java (MoF 1999; Nursahid, 1999). The head of the provincial conservation authorities, Mr. Mar Purwasuka was quoted as saying: “the purpose of this relocation is to show the world that the South Kalimantan proboscis monkeys still exist, and have not become extinct, as has been rumored” (Kompas, 5 Feb. 1999). Post-translocation monitoring by the conservation authorities occurred 5 and 16 months after the two capture periods. This consisted of short visits to the islands during which suitable food trees were identified. Few proboscis monkeys were sighted, and most information on the species’ presence was obtained from local informants (MoF, 1999). No proboscis monkeys were encountered in the Pulau Kaget Nature Reserve, while on the unprotected part of the island a total estimated population of nine animals. According to our information no proper pre-translocation habitat assessments were conducted. Of the 61 animals that arrived in the zoo 24 were still alive after four months, resulting in a survival rate of less than 40 per cent (MoF, 1999; Nursahid, 1999). In addition to the officially removed animals an unknown number of proboscis monkeys were smuggled out on boats (Al Fatah, 1999). Confirmation for this was provided when the police confiscated four proboscis monkeys, which were on route to Surabaya in Java. They were purchased at Banjarmasin market on the mainland near Pulau Kaget for $US 25 each (Banjarmasin Post 27 June 1999). Table 10.1 indicates the significance of the translocation and capture of the Pulau Kaget proboscis monkeys in relation to the total protected population. Figure 10.3 Former prime proboscis monkey Nasalis larvatus habitat on Pulau Kaget (November 1996,

photo E. Meijaard)


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Table 10.1 Summary of the numbers of proboscis monkeys Nasalis larvatus involved in the Pulau Kaget translocation

Total protected population (1990) 5,000 Population at Pulau Kaget (1996) (percentage of total protected population) 288 (6%) Minimal number of translocated animals 84 Total number of animals taken to Surabaya Zoo 61 Number of Pulau Kaget animals that died in Surabaya Zoo or during translocations 50 Estimated population size of Pulau Kaget island after the translocations 9 Estimated population size of Pulau Kaget Nature Reserve after the translocations 0

DISCUSSION The translocation of proboscis monkeys from a protected to an unprotected area can hardly be considered an improvement to their survival prospects. The release sites all have high agricultural potential and are close to the town of Banjarmasin. Unless these sites are designated soon as part of the conservation area network, there is no reason to expect that the habitat in these sites will not experience the same deterioration witnessed on Pulau Kaget. Because little is known about the translocation of proboscis monkeys, we cannot predict the socio-ecological effects of the dispersal of a once contiguous population over several small islands, where the species occurred already. We maintain that this translocation could be justified only if everything possible had been tried to save the population in the original reserve. Considering that as early as 1993, primatologists warned the authorities of the deteriorating situation of Pulau Kaget (Yeager, 1996) and nothing constructive was done since then, we have to conclude that the situation was not handled adequately. If a translocation was the only feasible solution, it should have fulfilled at least the standard criteria (e.g., Vié, 1999; Yeager & Silver, 1999). It is clear that few of these conditions were met. The transfer of the remaining animals to Surabaya Zoo is also unlikely to contribute to the preservation of the species in the wild. Proboscis monkeys require a highly specialised diet and are difficult to keep in captivity (Collins & Roberts, 1978; K. Brouwer in litt., 12 November 1997). Relatively few proboscis monkeys are kept in captivity in international zoos, and mortality rates are high (K. Brouwer in litt., 12 November 1997). As long as habitat destruction cannot be controlled, ex-situ conservation will contribute little to nothing to the survival of the species in the wild. In our opinion, the conservation authorities have inadequately addressed the causes of habitat loss in Pulau Kaget Nature Reserve, leading to the demise of its proboscis monkey population. A possible solution would have been to restore the habitat or provide in situ support of the population, and buffer the populations from human impact by establishing and implementing no-access zone. However, the authorities instigated and executed the complete removal of the population from the Reserve.


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CONCLUSIONS The situation on Pulau Kaget is not exceptional as suitable proboscis monkey habitat is disappearing at a rapid rate throughout the species’s range. In five of the six protected areas in Indonesia where the species is represented by at least several hundred individuals, populations are in decline (Meijaard & Nijman 2000, chapter 9). It seems that the Indonesian conservation authorities are neither able to carry out species protection, nor protect the species’ habitat within reserves against the activities of plantation developers, timber concessions, farmers, and hunters (Rijksen & Meijaard, 1999). If these protective measures cannot be handled for a relatively small and accessible strict nature reserve, what can be expect for the extensive areas of unprotected habitat and remote reserves? Indeed, most of this unprotected habitat is scheduled for conversion into agricultural land and plantation, leaving almost none for the proboscis monkey (Meijaard & Nijman 2000, chapter 9). The reasons why the Indonesian authorities are failing to address conservation issues are complex. They include institutional deficiencies, a lack of funds, lack of knowledge, misconceptions on ecological issues and poorly integrated planning. Solutions have to be addressed in an integrated manner. They include: improvement of the legal framework; reorganisation and technical training of the responsible institutions; education and awareness campaigns; appropriate integration of development and conservation, expansion of the protected area network, and the alleviation of financial impediments (cf. Rijksen & Meijaard, 1999). What are needed most of all, however, are serious and effective commitment and political support, both nationally and internationally for solving conservation problems. Within the context of the present political and economic situation in Indonesia, the conservation community cannot rely solely on the present Indonesian conservation authorities to prevent the further decline of the proboscis monkey, and probably many other endangered species. A new approach is required, for instance, along the lines of the Orangutan Survival Programme (Rijksen & Meijaard, 1999) in which a dedicated, well-financed and fully mandated conservation body co-ordinates the work of conservation authorities, local government, non-governmental organisations, businesses, and international donors, with the specific aim of protecting species and its habitat. We hope that the current wave of openness and political reform in Indonesia will provide such opportunities for improved and effective conservation. ACKNOWLEDGEMENTS This communication stems from a plea by the head of the provincial Agency for Natural Resources to expose the situation on Pulau Kaget. We thank the Indonesian authorities, i.e. the Indonesian Institute of Sciences and the Directorate General of Forest Protection and Nuture Conseervation, for granting permission to conduct our research, and for providing us with data. We thank Koen Brouwer (European


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Association of Zoos and Aquariums) for providing data on captive proboscis monkeys. Thanks due to Ed Colijn (Indonesian Nature Conservation Database) for making geographical information available. Arne Mooers (Zoological Museum Amsterdam), Tim O’Brien and Margaret Kinnaird (Wildlife Conservation Society – Indonesia) commented on a draft document. Two anonymous referees are thanked for their comments on the manuscript.

Patterns of Primate Diversity on Borneo

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CHAPTER 11

PATTERNS OF PRIMATE DIVERSITY ON BORNEO, AND SELECTION OF CONSERVATION PRIORITY AREAS

with E. Meijaard

ABSTRACT We assessed the spatial patterns of primate diversity in terms of species richness and endemism for Borneo, and evaluate this in relation to patterns of human land-use and setting of the protected area network. Based on an extensive data set of locality records for all thirteen species present on the island (n=1414, range 26-273 per species), combined with data on the ecology of the respective species and with the aid of a Geographic Information System, we prepared detailed distribution maps, and overlayers. Tropical wet evergreen forest below 500 m a.s.l. was identified as the most species rich habitat, with in fact, all species occurring in it. Secondly, peat swamp forest came out as a numerically important habitat for primates on Borneo, whereas the smallest number of primate species occur in mangrove forest. The most species-rich area, with eleven species co-existing, was the tropical wet evergreen forest near large rivers in central-eastern East Kalimantan, Indonesia, covering a land surface of some 30,000 km2. The most endemic species-rich area comprises essentially the same area albeit slightly larger. Studies on other animals and plant groups almost invariably identified northern Borneo (i.e. the Malaysian state of Sabah) as richest in species and endemics. The newly identified hotspot is situated in one of the most densely populated areas of Borneo, the remaining forests are inadequately included in the protected area network, and the area has suffered severely from the great forest fires in 1982-1983 and 1997-1998. Three large protected areas situated in central-eastern East Kalimantan, each once home of >70% of all species and between 80-100% of all the endemics, have most if not all of their forest destroyed by a combination of illegal logging, mining, encroachment, and the forest fires. Two proposed conservation areas in the area are inhabited by the Punan, a (formerly) nomadic hunter-gather tribe, which makes effective species protection in these areas difficult. RINGKASAN Pola keanekaragaman primata di Kalimantan, dan pemilihan daerah konservasi yang berprioritas (dengan E. Meijaard): Pola-pola keanekaragaman primata kami tentukan dengan menggunakan kekayaan jenis dan keendemikan untuk Kalimantan, dan ini kami tinjau kembali sehubungan dengan pola-pola tataguna tanah dan jaringan


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kawasan konservasi. Peta-peta yang terperinci, dan overlayers kami siapkan untuk semua 13 jenis yang ada di pulau tersebut, berdasarkan data set dari catatan lokasi (n=1414, 26 sampai 273 per jenis), digabung dengan data ekologi masing-masing jenis, dengan menggunakan Sistem Informasi Geografi (GIS). Pertama hutan tropis di bawah 500m d.p.l. ditentukan sebagai habitat yang paling kaya jenis, di mana sebetulnya semua jenis dapat ditemukan. Kedua, hutan rawa gambut ternyata habitat penting untuk primata dari segi jumlah jenis, sedangkan jumlah primata paling sedikit dapat ditemukan di hutan bakau. Hutan tropis di dekat sungai besar di Kalimantan Timur sebelah timur-tengah adalah wilayah paling kaya akan jenis, dengan sepuluh sampai sebelas jenis yang hidup berdampingan, dan melingkupi kawasan seluas sekitar INTRODUCTION The purpose of a conservation network is ultimately to ensure persistence of valued biodiversity (Frankel & Soulé, 1981). Persistence is affected by processes depending on intrinsic (e.g., ecological, demographic, and genetic) and extrinsic (e.g., habitat clearance and degradation, over-exploitation, introduced species) factors (Araújo & Williams, 2000). From the early 1980s onwards conservationists have recognised the importance of regional concentrations of species (hotspots) as a tool for identification of sites for the preservation of biodiversity (e.g., Terborg & Winter, 1983; Myers, 1988; Prendergast et al., 1993; Pressy et al., 1993; Scott et al., 1993; Dobson et al., 1997; Mittermeier et al., 2000; Harcourt, 2000). If hotspots coincide for a great many taxa, in theory, the less area needs conserving to protect biodiversity and in turn the more likely biodiversity is protected. However, the hope that areas of high diversity overlap for different taxa, soon appeared to be vain in many cases (e.g., Prendergast et al., 1993; van Jaarsveld et al., 1998; Harcourt 2000), and the hotspot approach has moved more strongly to identifying complementary sites (Pressy et al., 1993, Williams et al., 1997; Howard et al., 1998). Since rarely data on all species are available, it is common practice to select a small, relatively well known group as representative for all species (Bibby et al., 1992; Hacker et al., 1998; Sluys, 1999). Selection of conservation priorities can then be based on the patterns (endemism, species-richness, etc.) found in these particular groups. By comparison with many other taxa, the order Primates consists of mostly large, easily observable species, with the possible exception of the nocturnal, generally smaller, ones. They are thus relatively well-studied (Rowe, 1996), and we probably have as good information on the global distribution of primate taxa as we do for any other tropical taxon (Harcourt, 2000). Primates thus could be good indicator species in biodiversity assessments for countries with less opportunity for biological surveys than others, and understanding their diversity could therefore be especially useful. Recently, Harcourt (2000) assessed the distribution patterns of


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primates world-wide. Nevertheless at smaller scale, the knowledge we have on the distribution of primates is often imprecise. Borneo is a case in point. MacKinnon (1986ab; 1987) assessed the distribution of primates in the Indo-Malayan region, including Borneo. Other general distribution maps of Bornean primates are given by e.g., Oates & Davies (1994: Colobines), Geissmann (1995: gibbons), and Niemietz (1984: tarsiers). These maps are generally imprecise and in the case of Borneo data on the occurrence in the interior or the southern (Indonesian) three-quarters of the island are lacking for many taxa (e.g., Meijaard & Nijman, 2000). Seven out of thirteen species of primates on Borneo are included in the IUCN listing of threatened species (see Table 11.1). Area selection is a relevant aspect of conservation planning in primates on Borneo, since habitat loss and site protection are widely seen as the key issue in the conservation of primates, and their wide appeal may make them ideal flagships for tropical ecosystems. The northern part of Borneo (consisting mainly of the Malaysian state of Sabah) is more mountainous than other parts, and according to the Pleistocene refugium hypothesis (Haffer 1969) the area remained covered in wet forest even during the driest part of the Pleistocene (e.g., Brandon-Jones, 1996; Taylor et al., 1999; for a critique see Meijaard, in prep.). The area has been long identified as a hotspot for many taxa. Myers (1988; 1990) included it as one of 18 global hotspots on the basis of vascular plants. Restricted parts of northern Borneo have been identified as centers of endemism and as particularly species rich for a number of taxa (see Table 11.2). Also for insect groups such as cicadas the northern part of Borneo appears to be particularly species rich, although this might be an artefact of biased sampling (J.P. Duffels, pers. comm.). Importantly, few other areas on Borneo have been identified as centres of endemism, other than those associated with particular habitat types (e.g., caves, lime stone regions, and kerangas forest: see MacKinnon et al., 1996). Table 11.1 Centers of endemism or species-richness in northern Borneo

Area Group Source Around north-eastern highland region Endemic mammals Groves, 1994 North-west Endemic plants Heywood, 1987 Colobines Taylor et al., 1999 Endemic mammals Groves, 1994 Mountains Endemic and non-endemic plants Heywood, 1987 moths Holloway, 1978 Endemic birds MacKinnon et al., 1996 Restricted range birds Sujatnika et al., 1995

In an attempt to assess the spatial patterns of primate diversity in terms of species richness and endemism, we compiled a data set of locality records of all primates on Borneo. Combined with data on the ecology of the respective species (habitat preference, altitudinal distribution), we prepared detailed distribution maps. In the


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present study we evaluate patterns of endemism and species richness of primates on Borneo in relation to patterns of land-use by humans and settings of (proposed) conservation areas. Hotspots and their characteristics are identified. METHODS Study area The island of Borneo with a size of 746,305 km2 is the third largest island in the world (after Greenland and New Guinea). Administratively it is divided in the four Indonesian provinces of West, Central, East, and South Kalimantan (covering some three quarters of the island's total area), the two autonomous Malaysian states Sabah and Sarawak and the Brunei Sultanate. Borneo mainly consists of relatively low-lying areas (over half of the island lies below 150 m a.s.l.), with running from south-west to the north-east a central chain of higher hills and mountains. Borneo's highest mountain is Mt. Kinabalu in Sabah, which is, with its 4101 m, the highest peak between the Himalayas and the mountains of New Guinea. Borneo is dissected by many large rivers such as the Kapuas River (1143 km), the Barito River (900 km), and the Mahakam River (775 km). Mountain ranges and rivers on Borneo act as faunal barriers (MacKinnon et al., 1996; Rijksen & Meijaard, 1999). Borneo supports the largest expanse of lowland evergreen rain forest in the Sundaic region, with some 60% of the land surface still under natural forest (MacKinnon et al., 1996) although this percentage has dropped significantly since then and may be as low as 45% at present (pers. observ.). Timber is a major source of revenue for the Malaysian states and Kalimantan; oil-rich Brunei has less need to exploit its forest for timber. Besides for timber production, every year vast areas are cleared for agriculture, plantations, human settlements, and transmigration. Fire is increasingly acting as a major threat to forest on Borneo, especially in the Indonesian parts of the island. Coinciding with El Niño Southern Oscillation events, during dry years, vast areas are set alight and millions of hectares of forest have already been affected (e.g., Fuller & Fulk 1998; Suhartoyo & Toma, 1999). Especially lowland forests are directly threatened by these practices due to their accessibility and their higher soil fertility compared to higher altitude forests. Less than ten per cent of the forest on Borneo is formally protected as conservation forest, and most of this area is concentrated in the mountains (MacKinnon et al., 1996; Sujatnika et al., 1995). Study species The island of Borneo harbours 13 species of non-human primates from five different families (Table 11.2). The majority (11 species) is diurnal, and only the slow loris Nycticebus coucang and the western tarsier Tarsier bancanus lead a nocturnal life. Five species are endemic to the island, four of them are colobines (subfamily Colobinae) and the fifth is a gibbon. Although the orang-utan on Borneo is sometimes considered a separate species (Seuanez et al., 1979; Karesh et al., 1997),


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differing from the one from Sumatra, for the present analysis it is considered to be not endemic to the island. Table 11.2 Habitat and altitudinal limits of the primates of Borneo Family Species

IUCN Status

Number of records

Habitat types Alt. limit

Notes

Loridae Slow loris Nycticebus coucang

LR3(lc)

67

TWE, PSF, FWS

1000

Tarsidae Western tarsier Tarsius bancanus

LR3(lc)

61

TWE

1000

Cercopithecidae Long-tailed macaque Macaca fascicularis

LR2(nt))

219

All, excluding TME

1000

Pig-tailed macaque Macaca nemestrina

VU A1(c)(d) 106 TWE, TME, PSF --

Banded leaf monkey Presbytis femoralis

LR2(nt) 26 TWE 1000

Bornean leaf monkey Presbytis hosei

LR3(lc) 84 TWE, TME -- Endemic

Red leaf monkey Presbytis rubicunda

LR3(lc) 190 All, excluding MF, FWS -- Endemic

White-fronted leaf monkey Presbytis frontata

DD 72 TWE 1000 Endemic

Proboscis monkey Nasalis larvatus

Vu A2(c) 153 PSF, FWS, MF, RF 500 Endemic

Silvered leaf monkey Trachypithecus cristatus

LR2(nt) 100 PSF, FWS, MF, RF 500

Hylobatidae Agile gibbon Hylobates agilis

LR2(nt)

70

TWE, PSF, FWS

1000

Bornean gibbon Hylobates muelleri

LR2(nt) 164 TWE, PSF, FWS 1000 Endemic

Hominidae Orang-utan Pongo pygmeus

Vu A1 (c)(d) C1

273

All, excluding MF

500

Key: MF = Mangrove forest; FWS = Freshwater swamp; PSF = Peat swamp forest; TWE = Tropical wet

evergreen forest; TME = Tropical montane evergreen forest; RF = Riverine forest. IUCN status after Eudey 1996/1997.

Data collection and analysis Information on the occurrence of primates was obtained by direct observations by E.M. from 1994-2000, and V.N. in 1996 and 1999-2001. This survey covered all major river systems of West, Central, and East Kalimantan, and the mountainous areas of Central and East Kalimantan. Several visits were made to the Malaysian states of Sabah and Sarawak and to Brunei. Total survey effort was more than 400 days. Additionally, we conducted semi-structured interviews with local people


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(often hunters) in Bahasa Indonesia, which is also understood in the Malaysian states and Brunei. Information from local people was included only when at least two independent sources indicated the presence of a particular species in an area. Environmental Impact Assessment reports of Kalimantan's logging concessions also provided information on the present distribution of primates. A total of 115 reports were consulted. The collections of the zoological museums of Amsterdam, Leiden, Bogor, London and Singapore were consulted. Additional information was obtained from the literature (excluding generalised distribution maps in the primate reference books) and through biologists and conservationists working in the area. All records were entered into a computerised Geographic Information System (GIS), using PC ArcInfo and PC ArcView software. Other data layers contain information on the mid-1993s forest cover and vegetation types (World Conservation Monitoring Centre (WCMC) data base), topography, cities and villages, and established and proposed conservation areas. The resulting GIS provides information on the habitat types and altitudinal limits of primates associated with the records available on their presence. Habitat was classified as Mangrove forest (MF), Freshwater swamp (FWS), Peat swamp forest (PSF), Tropical wet evergreen forest (TWE) and Tropical montane evergreen forest (TME). Riverine forest (RF) is normally included in the tropical wet evergreen forest, but for species that show a strong association with riverine forest, we created a separate category. Riverine forest is defined as the forest within 2 km of a large river and situated below 500 m a.s.l. Using the PC ArcView Spatial Analyst software (demo version), we converted the forest distribution from a vector to a raster map, which allowed for an accurate overlay of the forest type distributions and the primate presence locations. Based on forest types, associated with the primate species (see Table 11.1) and their presence locations, relative accurate distribution range maps could be produced for each species. Subsequently, these ranges were overlaid to determine the areas where the species’ ranges overlap. Thus, we created various combinations, such as the area with most endemic species, the areas with 11 overlapping species, etc. RESULTS Distribution We documented 1414 locality records for the thirteen species combined, ranging from 26 locality records for the banded leaf monkey to 273 records for the orang-utan. The average number of locality records per species is 122. As an illustration, figure 11.1 to 11.3 give the distribution of three of the endemic primates of Borneo. The white-fronted leaf monkey Presbytis frontata (Fig. 11.1) is mostly restricted to the central part of the island, with an isolated population near Gunung Palung National Park (J.M. Lammertink, in litt.). Whether or not the species is indeed absent from the intervening area is at present not clear. The species does occur in the central part of the island despite the fact that it was widely


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believed to have a disjunct distribution with populations in Sarawak separated from those in East and South Kalimantan (Eudey, 1987; Oates & Davies, 1994; Rowe, 1996). In fact, the central part of the island (e.g., Lanjak-Entimau, Batang Ai, Betung-Kerihun, confluence of the Kapuas and the Mahakam), seems to be the only area where the species is common (Blouch, 1997; J.K. Gurmaya, pers. comm.; chapter 13). The Bornean leaf monkey Presbytis hosei is confined to the northern part of Borneo, and supports the assumption that (many) species on Borneo are restricted to this part of the island (see Table 11.1). The southern boundary runs somewhere north of the Mahakam lakes and south of the Apo Kayan. The Mahakam River itself runs significantly south of this southern boundary, and there does not seem to be a clear geographical barrier to explain the species’ distribution. Figure 11.1 Geographical distribution of white-fronted leaf monkey Presbytis frontata


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Figure 11.2 Geographical distribution of Bornean leaf monkey Presbytis hosei The Kapuas and the Barito rivers form the boundaries for the Bornean gibbon Hylobates muelleri: it is only found in the area north and east of these two large river systems. The remaining part of Borneo is inhabited by the agile gibbon H. agilis, a species that also occurs on Sumatra and the Malay peninsula. At the head-waters of the Barito river an apparent stable hybrid population occurs (Mather, 1994).


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Figure 11.3 Geographical distribution of Bornean gibbon Hylobates muelleri The gross habitat preferences of primates are listed in Table 11.1. The largest number of species occur in tropical wet evergreen forest below 500 m a.s.l. In fact all species have been recorded in this habitat type (note that riverine forest is part of tropical wet evergreen forest). The listing also points to the relative importance of peat swamp forest as a habitat for primates on Borneo. The smallest number of primate species occur in mangrove forest, and those that do either have specialised adaptations to cope with the rather low nutritious mangrove leaves (proboscis monkey Nasalis larvatus and silvered leaf monkey Trachypithecus cristata) or supplement their diet by feeding on animal matter (long-tailed macaque Macaca fascicularis).


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Altitudinal distribution of primates is, at least in part, related to the productivity and availability of food sources, and, for arboreal species, the physiognomy of the forest. Primate densities generally decrease with increasing altitude (see also e.g., Davies & Payne, 1982). Table 11.1 also includes the altitudinal limit (if any) of each species. We hereby have to note that for many species we found a higher than 'normal' altitudinal record for Mt. Kinabalu. Occurrence of primates on these higher altitudes may be in part due to the Massenerhebung-effect, in which on high mountains or in the central parts of mountain ranges, the vegetation zones are broader than on small isolated mountains (van Steenis, 1972). Since Mt. Kinabalu (4101 m a.s.l.) is considerable higher than any other mountain on Borneo and very few mountains reach above 3000 m, for analysis we restricted certain species to altitudes lower than the highest altitudinal record. Again, those species that are able to make a living above the 1000 m line, generally occur at (considerable) lower densities than in the lowlands. Few species are able to persist above 2000-2500 m altitude (although some of them are occasionally recorded at these altitudes); for the analysis the total land surface above this altitude was so small that it was ignored. Pattern of species richness The largest number of species occurring in a single area is eleven. This area is totally enlosed and included in the areas where ten species occur sympatrically. Figure 11.4 Pattern of primate diversity on Borneo. The map shows those areas where 10 or 11 species

occur sympatrically, in relation to the protected area network.


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The area where the highest number of species, coexist is in the tropical wet evergreen forest near large rivers in central-eastern East Kalimantan. It covers a land surface of some 30,000 km2. The area where at least ten species occur is considerably larger and encompasses, besides central-eastern East Kalimantan, also the south-eastern part of Sabah and northernmost East Kalimantan. Sarawak and Brunei are less species rich, and only in small areas do nine species co-exist. The province of South Kalimantan is in terms of primate species richness the least interesting part of Borneo. The area where the five endemic primates co-exist, essentially comprises the same area as the most species rich area (i.e. central-eastern East Kalimantan). Inclusion of the orang-utan as an endemic species does not change the spatial pattern drastically, apart from the fact that the northern boundary of the eastern hotspot now runs slightly more to the south. The most species rich areas are all situated in the lowlands, below 500 m a.s.l. The mountain areas of Borneo are considerably less species-rich. Figure 11.5 Pattern of endemic primate diversity on Borneo. The map shows those areas where the five

endemic primates occur in sympatry, in relation to the protected area network.


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Conservation area selection If we compare the hotspots of primate species richness and endemism with the positioning of national parks (including greater forestry parks) and nature reserves (strict nature reserve, wildlife reserve, virgin jungle reserves), it becomes clear that there is little overlap. Most of the largest reserves are situated in areas that are not particularly rich in primate species. In fact, few contain more than eight sympatric species. Five reserves (> c. 500 km2) provide refuge for nine or more species, in three more than ten species have been recorded, and only one (Kutai National Park) is home to the maximum number of eleven sympatric species (Table 11.3). An analysis of the endemic species leads to a similar reserve listing. Few reserves harbour population of more than four sympatric endemics and in reserves that do, often one or two are very rare (e.g., Danum Valley and Gunung Palung). The only reserve that has populations of all five endemics within its boundaries is again Kutai National Park. The real tragedy is, however, that of the five most species-rich reserves, three have been almost completely destroyed by a combination of illegal and legal logging, mining, encroachment, and the forest fires of 1982-1983 and 1997-1998 (MacKinnon et al., 1994, Rijksen & Meijaard, 1999, Suhartoyo & Toma, 1999, Jepson et al., 2001). Additionally, law enforcement with respect to logging, extraction of non-timber products, hunting, capturing of wildlife etc. is virtually absent; primates are not exempt. Table 11.3 List of large reserves that rank(ed) among the highest in primate species richness↑ Reserve Size

(km2) Number of

species (13 is 100%)

Number of endemics

(5 is 100%)

Notes

Kutai 2000 11 5 Forest largely, if not completely, destroyed Muara Kaman 625 10 4 Forest largely, if not completely, destroyed Gunung Palung 900 10 3 P. frontata rare and restricted to the eastern part Bukit Suharto 710 9 4 Forest largely, if not completely, destroyed Danum Valley 438

(2476)↑↑ 9 4 N. larvatus rare

↑ Within the reserves many species show a restricted distribution, and may even be more common

outside the reserve proper. ↑↑ The larger figure represents the Ulu Segama commercial forest reserve of which Danum Valley

forms a part. In theory, all species can be included in the protected area network if in addition to (part of) the central-eastern part of East Kalimantan, parts of West and / or Central Kalimantan south of the Kapuas River (to include the agile gibbon Hylobates agilis) and the low-lying regions of Sarawak (to include the banded leaf monkey Presbytis femoralis) are added.


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Few reserves have been proposed in the region most rich in primates, those of significance include the proposed south-eastern extension Kayan Mentarang National Park (Ulu Kayan Mutlak 3500 km2) and Sangkulirang Peninsula (Mangkilat-Kelompok Kapur Sangkulirang 2000 km2). However, unfortunately, in both of these areas densities of primates are generally low, in part due to the efforts of the Kenyah Dayaks and especially the (formerly) nomadic Penan and Punan. With their formidable hunting skills these tribes are able to assure that all but the smallest primates remain rare. DISCUSSION The number of locality record holds little information on the actual abundance of the majority of species. Proboscis monkeys are less common than the number of records (n=153) indicate (see Meijaard & Nijman, 2000), but their striking appearance and their occurrence near waterways makes them particularly easy to see and identify. In contrast, the two nocturnal species are possibly more common then the data suggest but they are rarely recorded because of their activity pattern and silent behaviour. The large number of records for the orang-utan (n=273) largely derives from the fact that one of us (E.M.) has been conducting surveys to document the distribution of this very species (see Rijksen & Meijaard, 1999); survey efforts were concentrated in those areas where the species was expected to occur. In fact, the orang-utan is among the rarest primate in Borneo. The banded leaf monkey (n=26) is probably genuinely rare on Borneo for at least two reasons. First, it has the most restricted distribution of any primate, and second, it is confined to tropical wet-evergreen forest below 1000 m a.s.l in an area that is largely deforested. Likewise, long-tailed macaques (n=219) are genuinely common as they occur all over the island, in a large range of habitat types and are quite tolerable to habitat disturbance. Red leaf monkey (n=190), on the contrary, have a much more restricted range of habitats in which they occur, but they are found almost over the entire island. Both species are also easily identified and quite vocal which also facilitates identification. The present study reconfirms the importance of the tropical wet evergreen forest below 500 m a.s.l., and especially near rivers as one of the most important habitats for wildlife. For primates, including many of the endemics, this habitat type is of prime importance. Peat swamp forest comes out as an habitat of importance as well, although less so for most of the endemics. Of the two most threatened species (the orang-utan and the proboscis monkey) considerable populations do occur in the peat swamp forests (Meijaard & Nijman, 2000; Meijaard, 1997). Only small amounts of this forest type have so far been included in the protected area network, despite the fact that some considerably large area still remain. Restricted parts of northern Borneo have been identified as centers of endemism and as particularly species rich for a number of taxa including vascular plants, insects, birds, and mammals. Whether these patterns are a true reflection of


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the distribution of these taxa or that it reflects a strong research bias remains to be seen. However, quite illustrative are recent findings for birds. Until recently, a great number of species was considered to be confined to Mt Kinabalu or the northern mountains (Smythies, 1981; MacKinnon & Phillipps, 1993). Field work in mountain regions in Kalimantan and in the interior, however, revealed that the 'northern mountain endemics' are neither confined to the north nor to the heighest mountains (Wilkinson et al., 1991; Van Balen 1997, 1999a, 2000) and in fact some species have been recorded as far as the Schwaner range (Rice, 1989), Mt Niut (Prieme & Heeregaard, 1988), and the Meratus mountains (Davidson, 1997). Expert ornithologists can identify most species by sighting or call and there is generally no need to collect specimens. Hence fairly complete species lists can be made with relatively little effort. Many other taxa (including small mammals, insects, and plants) can only be identified when collected and preserved, and so far, intensive collections have been made more in northern Borneo than in any other part of Borneo. Although progress is made in uncovering the distribution patterns of even the most elusive of animals, e.g., the bay cat Catopuma badia (Meijaard, 1997), biologically, large areas of the island remain virtually a terra incognita. For primates, we found a centre of species richness and endemism in the central eastern part of East Kalimantan. To our knowledge this has not previously been recognised as such. This finding derives in part from more detailed distribution maps of especially three colobines viz. proboscis monkey, silvered leaf monkey, and white-fronted leaf monkey, and the orang-utan. The notion that eastern-central East Kalimantan is a centre for primate endemism is only in part related to the taxonomic position taken. Including the orang-utan as an endemic species only emphasises the importance of the area, albeit smaller in size. A change of the taxonomy of the banded leaf monkeys Presbytis femoralis, however, would put more emphasis on northern Sarawak as a centre for primate endemism. Populations of this species on Borneo are generally considered to be congeneric with taxa occurring on the Natuna Islands, southern Malay Peninsula and eastern Sumatra (Brandon-Jones, 1984). However, the populations on Borneo do differ in their pelage characteristics from populations from other islands (most pronounced in P. f. cruciger from northern Sarawak), and in fact the banded leaf monkey may comprise several species (V. Nijman, unp. data; cf. Eudey, 1987). The fact that central-eastern East Kalimantan is a hotspot for primate diversity illustrates the invalidity of high diversity overlap for different taxa, and points to the importance of identifying complementary sites (cf. Pressy et al., 1993, Williams et al., 1997; Howard et al., 1998). It is expected that for a number of other taxa, especially with a high level of frugivory, this area will turn out to be of equal importance. From a conservation perspective our findings are gloomy as well as sobering. The regions identified as of prime importance are among the least protected in Borneo. Large parts of the east-central hotspot have suffered from the large forest fires both in 1982-1983 and 1997-1998 (Goldammer et al., 1999). Forest that has


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burned twice is of little importance to primate conservation (pers. observ.). In theory, forest areas that have burned once can regenerate and, given the fact that even in the worst affected areas some small patches of 'good' forest with some primate groups remain, these areas can be of potential importance for primate conservation. However, unless one takes an unrealistically positive view, in practice, most if not all of these forests will burn again in the next El Niño Southern Occilation Event; the large amount of dead wood makes them extremely fire-prone. The remaining patches of unburned forest are few and far in between. Unless these areas are actively protected during the next dry years it is feared that these will be seriously affected by forest fires as well. Given the amount of active forest protection that was given during the previous forest fires and their succes rate, it has to be feared that most forests will disappear within the next ten to twenty years. The remaining unprotected forest is all earmarked for conversion or selective logging; actually, the total area of consession is considerably larger that the remaining forest (Rijksen & Meijaard, 1999). Selective logging will make the forest more fire-prone. Conservation of primates in the region's protected area network offers little more hope for optimism. For example, if not for the signs indicating entering Kutai National Park or Bukit Suharto Greater Forestry Park it would be hard to note one enters a conservation area. Like Muara Kaman Nature Reserve, both areas are almost completely deforested (pers. observ.). Combined these areas originally included almost 3500 km2 of prime primate habitat but at present they are of hardly any value for primate conservation. ACKNOWLEDGEMENTS The surveys were conducted in co-operation with the Directorate General for Forest Protection and Nature Conservation (PKA, formerly PHPA), the Ministry of Forestry and Estates Crops (MOFEC formerly MOF) and under sponsorship of the Indonesian Institute for Sciences (LIPI). Steph B.J. Menken (IBED, University of Amsterdam) is thanked for comments on previous versions of this paper.


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Re-Assessment of IUCN Conservation Status of the Endemic Primates

CHAPTER 12

RE-ASSESSMENT OF IUCN CONSERVATION STATUS OF THE ENDEMIC PRIMATES OF JAVA AND BORNEO

ABSTRACT A re-assessment of the IUCN status of the endemic primates of Java and Borneo was made on the basis of a study from 1994-2001 and additional data from the literature. Five (or six) of the nine (or ten) endemics have their current status changed. Fuscous leaf monkey Presbytis frederica is currently classed as Data Deficient, but the species is here synonymised with grizzled leaf monkey P. comata. This species is currently classed as Endangered and this status remains unchanged in the re-assessment. Bornean leaf monkey P. hosei and Bornean gibbon Hylobates muelleri are currently both classed as Lower Risk but on the basis of a sharp reduction of available habitat aggravated by hunting, both species are more appropriately classed as Vulnerable. The white-fronted leaf monkey Presbytis frontata is currently classed as data Deficient, but on the basis of low population densities over the greater part of its range, and the sharp reduction of its lowland forest habitat it is classed as Vulnerable. The proboscis monkey Nasalis larvatus is currently classed as Vulnerable, but given a sharp reduction in available habitat and inadequate protection inside reserves, it is more appropriately classed as Endangered. Finally, the Javan gibbon Hylobates moloch is currently classed as Critically Endangered, but given a less dramatic decrease of remaining forest on Java as suggested, and the finding of significant populations in Central Java, the species is more appropriately classed as Endangered. RINGKASAN Peninjauan kembali mengenai status konservasi menurut IUCN dari primata endemik di Jawa dan Kalimantan: Peninjauan kembali kami buat mengenai status IUCN dari primata endemik di Jawa dan Kalimantan berdasarkan hasil sebuah penelitianlapangan dan survai pada tahun 1994-2001 ditambah data pustaka. Lima (atau enam) dari sembilan (atau sepuluh) jenis kera telah berubah status konservasinya saat ini. Rekrakan Presbytis fredericae saat ini diklasifikasi sebagai Kurang Data, tetapi jenis ini dianggap kami sejenis dengan Surili P. comata. Jenis ini dianggap Genting saat ini, dan status ini tidak berubah pada tinjauan kembali kami. Baik Bangat P. hosei maupun Kelawat Hylobates muelleri saat ini diklasifikasi Berisiko Rendah, tetapi kedua jenis ini lebih tetap diklasifikasi sebagai Rentan, berdasarkan penyusutan drastis dari habitat yang ada, yang diperburuk oleh pemburuan. Lutung dahi putih Presbytis frontata saat ini diklasifikasi sebagai

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Forest (and) Primates Kurang Data. Tetapi statusnya kami anggap sebagai Rentan, berdasarkan kepadatan rendah di bagian terbesar wilayah penyebarannya. Bekantan Nasalis larvatus adalah satu jenis saat ini diklasifikasi Rentan tapi terbatas pada kantung-kantung terakhir dari hutna tropis dataran di pingir sungai dan hutan bakau, lebih tetap diklasifikasi bagai Genting. Terakhirnya, Owa Jawa H. moloch adalah satu jenis diklasifikasi Kritis tetapi kerena masih ada beberapa populasi yang cukup besar di Jawa Barat dan Jawa Tengah, lebih tetap diklasifikasi bagai Genting. INTRODUCTION In the following section a re-assessment of the IUCN conservation status of the endemic primates of Java and Borneo is presented. It is based on data presented in the previous chapters of this thesis, additional and as yet unpublished results from the study, and published data. Firstly, for each species its legislative status is given, i.e. whether or not it is protected by Indonesian and / or Malaysian law. When the species is included on Appendix I or II of the Convention on International Trade in Endangered Species (CITES) this is indicated. Secondly, its present IUCN listing (based on Eudey, 1996/1997) is given with the criteria according to which it is included in that particular category. This is followed by the suggested IUCN listing and its criteria. Finally, the justification of the changes (if any) are presented. RESULTS AND DISCUSSION Grizzled leaf monkey Presbytis comata Legislative status: Protected by Indonesian Law as Presbytis aygula (Surat Keputusan Menteri Pertanian No 247/Kpts/Um/4/1979, Undang-undang No. 5 / 1990, Surat Keputusan Mentri Kehutanan No 301/KPT-II/1991 and No. 882/KPT-II/1992). Included on Appendix II of the Convention on International Trade in Endangered Species (CITES). Present IUCN status: Endangered based on criteria: A1(c): A reduction of at least 50% over the last three generations (<35 years –

inferred from life history data of colobine monkeys in Rowe [1996]) based on a decline in area of occupancy, extent of occurrence, and / or quality of habitat.

C2(a): Population estimated to number less than 2500 mature individuals and a continuing decline, observed, projected, or inferred, in numbers of mature individuals and population structure in the form of severely fragmented sub-populations (i.e. no sub-population estimated to contain more than 250 mature individuals).

Suggested IUCN status: Endangered based on criterion A1(c).

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Re-Assessment of IUCN Conservation Status of the Endemic Primates Justification: The distribution range is larger than previously assumed, with substantial populations occurring in central Java (chapters 6 and 8). No large changes in the extent of habitat have occurred as compared to previous assessment. The total population is significantly larger than assumed under C2(a). The most recent estimate of 2285 individuals as obtained during a PHVA (Supriatna et al., 1994) is unrealistic for at least four reasons: (i) It is based on an incomplete data set (only seven of 33 areas known to be

inhabited by the species were included in the analysis); (ii) It is based on wrong assumptions. The species would prefer a narrow

altitudinal zone between 1200 and 1800 m a.s.l., rarely occurring below 1200 m a.s.l. In fact it occurs from sea level to 2500 m a.s.l., most likely attaining its highest densities in the lowlands (Nijman, 1997; chapter 6);

(iii) During the data compiling process there must have been confusion between the two Javan leaf monkeys. Grizzled leaf monkey would have a preference for ecotones, edges and riverborders, and would not occur inside the core of a forested area. This description in all likelihood refers to ebony leaf monkey Trachypithecus auratus and certainly not grizzled leaf monkey. During the PHVA meeting the two endemic leaf monkey were often mixed up. In fact the participants were invited to attend a meeting on the Javan gibbon and silver leaf monkey Trachypithecus auratus [=ebony leaf monkey] (Anonymous, 1994) and not a meeting on Javan gibbons and grizzled leaf monkey Presbytis comata. The handbook with background information (Anonymous 1994) even explains that the silver leaf monkey consists of three subspecies, again suggesting the workshop deals with Trachypithecus auratus of which there are three subspecies as opposed to Presbytis comata of which two subspecies have been described. In this same handbook a summary is given of the diet and feeding behaviour of ebony leaf monkeys, again suggesting that the meeting deals with ebony leaf monkey. Finally, in the proceedings of the workshop (Supriatna et al., 1994) photographs of ebony leaf monkeys are included but not of grizzled leaf monkey.

(iv) Under-estimation of population densities. Supriatna et al. (1994) used a population density of four individuals km-2 corresponding with one group per 1.75 km2. Indeed in a number of areas the species is known to be rare (e.g., Ujung Kulon) or to show a patchy distribution within reserves (e.g., Tukung-Gede). However, data from Table 12.1 and comparisons with data from other Presbytis species (Oates et al., 1994) suggests densities between 10 to 20 individuals km-2 to be more typical.

Data presented in table 12.1 also suggest large differences between the two methods employed for censussing this primate. Density estimates obtained with the line transect method are typically a fifth of those obtained with the range mapping method. Reported group sizes for grizzled leaf monkeys from line transects (average 4.0 individuals: Sugarjito et al., 1997; 4.8 individuals: Sugarjito & Sinaga, 1999; 2.0 individuals: Gurmaya et al., 1995; but 7.0: Nijman & van Balen, 1997) are also

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Forest (and) Primates generally smaller than reported from range mapping studies (average: 4.8 individuals: Harjanti, 1996; 5.8 and 6.0 individuals: Ruhiyat, 1991: 7.0 individuals: Sujatnika, 1992). In all likelihood the elusive nature of the species makes it difficult to detect, leading to an under-estimate of true densities during line transect surveys. The range mapping method invariably has been employed in ecological studies and hence the study areas were selected as to contain a fair number of grizzled leaf monkey groups, precluding extrapolation to densities over large areas. Table 12.1 Estimates of densities of grizzled leaf monkey Presbytis comata in Java

Locality

Altitude (m asl)

Density (ind. km-2)

Method Source

Ujung Kulon 0-400 1.3↑ Line-transect Gurmaya et al., 1995 Mt. Tukung Gede 40-400 4.3↑↑ line-transect Melish & Dirgayusa, 1996 Mts. Halimun 600-1200 8.2↑↑↑ line-transect Sugarjito et al., 1997 Mts. Halimun 1200-1750 2.1 line-transect Sugarjito et al., 1997 Mts. Halimun 600-1200 2.6 line transect Sugarjito & Sinaga, 1999 Mts. Halimun 1200-1400 0.4 line transect Sugarjito & Sinaga, 1999 Mts. Halimun 1400-1750 1.4 line transect Sugarjito & Sinaga, 1999 Mts. Halimun 900-1200 4-5 -- Maitar in Supriatna et al., 1994 Mt. Gede 1300-1500 25 mapping Sujatnika, 1992; pers. comm. Mt. Patuha 2000-2200 10-15 mapping Harjanti, 1996 Kamojang 1400-1600 10-12 mapping Ruhiyat, 1983; 1991 Patenggang 1600-1800 35-36# mapping Ruhiyat, 1983; 1991 Mts. Dieng 650-850 28 line-transect Nijman & van Balen, 1998

↑ Estimate might be rather low as parts of the reserve that are known not to be inhabited by grizzled

leaf monkeys were included in the survey (K.J. Gurmaya, pers. comm.); Melish & Dirgayusa (1996) report that, according to park wardens, the population has decreased over the last two decades.

↑↑ Line-transect was situated along the forest fringe and densities in forest interior may differ (Melish & Dirgayusa, 1996).

↑↑↑ The two studies by Sugarjito et al. (1997) and Sugarjito & Sinaga (1999) seem to be based on the same data set, yet density estimates from the second study are about a third of the first. The reason for this discrepancy is unknown.

# Ruhiyat (1991) reports that the relatively high density in Patenggang was at least partially caused by previous logging operations and/or the recent opening of parts of the forest for tea cultivation, both limiting the amount of forest available.

Bornean leaf monkey Presbytis hosei Legislative status: Not protected by Indonesian Law (although there is room for speculation as P. comata is listed as P. aygula; P. hosei was formerly considered to be included in this taxon), not protected by Malaysian Law (Sarawak and Sabah); legislative status in Brunei not known. Included on Appendix II of the Convention on International Trade in Endangered Species (CITES). Present IUCN status: Lower Risk 3 (least concern).

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Re-Assessment of IUCN Conservation Status of the Endemic Primates Suggested IUCN status: Vulnerable based on criterion:

A1(c): A reduction of at least 20% over the last three generations (<35 years) based on a decline in area of occupancy, extent of occurrence and / or quality of habitat.

Justification: The species has a restricted range distributed over three countries. It is inadequately included in the protected area net work, although a substantial population is present in the Kayan Mentarang National Park. The species is common in certain areas (e.g., Kayan Mentarang National Park: Nijman 1997, S. Wulfraat, pers. comm.; Dent Peninsula, Sabah: Davies & Payne 1982), but rare in others (Sepilok: Bennett & Davies 1994). Apparently it is especially rare in those areas where red leaf monkeys are common (Payne et al., 1985). Highest densities are reached in lowland rain forest (Davies & Payne 1982), a habitat that is becoming increasingly rare. The species is able to survive in disturbed forest (secondary forest, selectively logged forest) but at significantly lower densities (Nijman 1997; Johns 1992). The species used to be common in the Kutai regions (Rodman 1978) but has lost most of its habitat due to the forest fires (Suzuki, 1994) and illegal logging. A survey in 2000 failed to find a single individual in the eastern region of the Kutai National Park (V. Nijman unp. data). All of its habitat outside the protected area network in Kalimantan has been earmarked for conversion or has been handed out as concession. Throughout its range it is hunted for food and for its valued bezoar stones (visceral concretions used in traditional medicine and sometimes found in this and other Presbytis species). Hunting is often associated with inland settlements, the timber industry and the demand for bezoar stones. In Sarawak the three leaf monkey species (Presbytis frontata, P. rubicunda, and P. hosei) account for at least one percent of all mammals hunted, which may account for some 20,000 monkeys annually (Bennett et al., 1987). Hunting for bezoar stones seems to be concentrated to restricted areas (Nijman 1997; Pfeffer 1958), but can have a severe impact on local populations. The demand for bezoar stones can lead to excesses such as the killing of dozens of Bornean leaf monkeys near the southern border of the Kayan Mentarang National Park by adding poison to sungans (salt-water springs) (A. Rachmat, pers. comm.). Fuscous leaf monkey Presbytis fredericae Legislative status: Protected by Indonesian law as P. aygula (see under P. comata). Included under P. comata on Appendix II of the Convention on International Trade in Endangered Species (CITES). Present IUCN status: Data Deficient Suggested IUCN status: Endangered as Presbytis comata

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Forest (and) Primates Justification: Presbytis fredericae is synonymised with Presbytis comata (chapter 5) and as such no IUCN status is justified. Populations of P. comata in the eastern part of its range are all found in unprotected forest areas. White-fronted leaf monkey Presbytis frontata Legislative status: Protected by Indonesian Law (Surat Keputusan Menteri Pertanian No 247/Kpts/Um/4/1979, Undang-undang No. 5 / 1990, Surat Keputusan Mentri Kehutanan No 301/Kpts-II/1991 and No. 882/Kpts-II/1992). Not protected by Malaysian Law (Wild Life Protection Ordinance 1958). Included on Appendix II of the Convention on International Trade in Endangered Species (CITES). Present IUCN status: Data Deficient Suggested IUCN status: Vulnerable based on criterion: A1(c): A reduction of at least 20% over the last three generations (<35 years)

based on a decline in area of occupancy, extent of occurrence and / or quality of habitat.

Justification: The species’ distribution range is larger than previously assumed (chapter 11) and the species is not restricted to low altitude forest below 300 m a.s.l. as suggested by Medway (1970). It is present in large parts of Borneo but probably confined to lowland forest (<1000 m a.s.l.). White-fronted leaf monkey attains its highest density in the central part of its range from where it was previously assumed to be absent (e.g., Oates et al., 1994; MacKinnon, 1984; Rowe, 1996; see Table 12.2). Table 12.2 Densities of white-fronted leaf monkey Presbytis frontata at different localities in Borneo Locality Density

groups km-2 Individuals km-2

Group size

Reference

Lanjak-Entimau south central north

2.10 1.94 1.20

8.88 8.20 5.09

4.23 Blouch, 1997

Batang Ai 1.16 -- -- Meredith, 1993 in Blouch, 1997 Kapuas-Mahakam 12.5 43.7 3-4 Istiadi et al., 1994 Kutai National Park 0.06 0.06 1 Suzuki, 1992 Berau 0.2-0.7 1.2-1.7 2-6 Yanuar et al., 1995 Gn Palung Kembera Selinsing

0.4-0.5 0.4-0.5

1.9-2.4 0.4-0.5

5 1

J.M. Lammertink, in litt.

Sungai Wain 0.3-0.4 1.1-1.4 3-5 V. Nijman, unp. data Indication of density Barito Ulu rare 2-3 Mather, 1994 Long Bia rare 3-4 V. Nijman, unp. data Bukit Suharto rare -- Yasuma & Alikodra, 1990 Betung Kerihun common -- J.K. Gurmaya, pers. comm.

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Re-Assessment of IUCN Conservation Status of the Endemic Primates The density estimate obtained by Istiadi et al. (1994) is considerably higher than from any other region. This might be due to methodological differences, but their results clearly indicate that the species is common in the Kapuas-Mahakam region (cf. information from local inhabitants of the S. Rata region, V. Nijman, unp. data). Central populations are adequately included in the protected area network as significant population are present in the Lanjak Entimau, Batang Ai, and Betung Kerihun reserves (Blouch, 1997; J.K. Gurmaya, pers. comm.), but eastern and western populations are largely located outside reservesIn West Kalimantan white-fronted leaf monkey is probably patchy distributed with (isolated?) populations near Gunung Palung National Park. In East Kalimantan it is probably present throughout the province, but only locally and in small numbers. Given the species' occurrence at (very) low population densities over a fairly large area, it might be nomadic (Medway 1970), at least in parts of its range. The species is hunted for bezoar stones, whereas hunting for food is widespread throughout the interior of Borneo. Red leaf monkey Presbytis rubicunda Legislative status: Protected by Indonesian Law (Surat Keputusan Menteri Pertanian No 90/Kpts/Um/2/1977, Undang-undang No. 5 / 1990, Surat Keputusan Mentri Kehutanan No 301/Kpts-II/1991, and No. 882/Kpts-II/1992). Not protected by Malaysian Law, legislative status in Brunei not known. Included on Appendix II of the Convention on International Trade in Endangered Species (CITES). Present IUCN status: Lower risk 3 (least concern) Suggested IUCN status: Lower risk 3 (least concern) Justification: The species is endemic to Borneo and Karimata Island, off the west coast of Borneo. On Karimata the species is common (Yanuar et al., 1993). It is the most widespread of the Bornean colobines, occurring throughout most of the lowlands, hills, and mountains (Yanuar et al., 1995). The species occurs in secondary forest albeit in lower numbers. It occurs mainly below 1500 m a.s.l. (MacKinnon, 1987), although records from Mt Kinabalu suggest occurrence below 2000 m a.s.l. Red leaf monkeys are present in most of the larger reserves and the present protected area network seems to be adequate for the species. As other Presbytis species it is frequently hunted in the interior, both for its bezoar stones and for food. Ebony leaf monkey Trachypithecus auratus Legislative status: Protected by Indonesian Law (Surat Keputusan Menteri Kehutanan dan Perkebunan No 733/Kpts-II/1999). Included on Appendix II of the Convention on International Trade in Endangered Species (CITES).

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Forest (and) Primates Present IUCN status: Vulnerable based on criteria: A1(c): A reduction of at least 20% over the last three generations (<35 years)


B2(c)(d): Extent of occurrence estimated to be less than 20,000 km2 or area of occupancy estimated to be less than 2000 km2, and estimates indicating a continuing decline, inferred, observed or projected, in area, extent and/or quality of habitat, and number of locations or sub-populations.

Suggested IUCN status: Vulnerable based on criterion A1(c). Justification: Ebony leaf monkeys show a restricted distribution range with a large number of isolated fragments on three islands; the extent of occurrence as estimated under B2 is a considerable under-estimate. Although the species is quite tolerable to a certain degree of habitat disturbance and can be found in a large variety of forest types, including man-made, it is dependent on forest cover of some sort. In plantations it is normally restricted to those parts where more natural forest (e.g., along river stretches) is still present (Nijman, 2000; chapter 7). Probably most safe in mountain habitats, but population densities are lower at higher altitudes than in lowland forests. Local populations in mangrove areas have gone extinct (Supriatna et al., 1988) or are inferred to have become extinct on the basis of total destruction of habitat (Nijman 2000; chapter 7). Some small isolated populations are probably not viable in the long run. Overall the species' habitat is severely fragmented and this greatly limits dispersal between populations. The species is not present on the Kangean islands as has been suggested (e.g., de Iongh et al., 1982; Bergmans & van Bree 1986). Ebony leaf monkeys are well included in the present protected area network (it is present in most of the larger protected areas on Java, Bali, and Lombok), although active protection of the species in these areas or active protection of their habitat is often absent. Trade may turn out to be an increasing problem, as the species is heavily traded on Java. For the province of east Java alone it has been estimated that some 227 individuals are traded per month (Anonymous 2000). Ebony leaf monkeys are often one of the most common primate species found on bird markets. The erythristic pelage morph is more expensive than the more common melanic pelage morph. Trade of ebony leaf monkeys occurs over long distances, and the erythristic pelage morph is commonly seen on West Javan bird markets (Nijman 2000; chapter 7). Proboscis monkey Nasalis larvatus Legislative status: Protected by Indonesian Law (Peraturan Perlindungan Binatang Liar 1931 No. 266, Undang-undang No. 5 / 1990, Surat Keputusan Mentri Kehutanan No 301/Kpts-II/1991, and No. 882/Kpts-II/1992). Protected by Malaysian Law (Wild Life Protection Ordinance 1958), legislative status in Brunei

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Re-Assessment of IUCN Conservation Status of the Endemic Primates not known. Included on Appendix II of the Convention on International Trade in Endangered Species (CITES). Present IUCN status: Vulnerable based on criteria: A2(c): A reduction of at least 20% projected or suspected to be met within the

next three generations (<45 years) based on a decline in area of occupancy, extent of occurrence and / or quality of habitat.

C2(a): Population estimated to number less than 250 mature individuals and a continuing decline, observed, projected, or inferred, in numbers of mature individuals and population structure in the form of severely fragmented sub-populations (i.e. no sub-population estimated to contain more than 250 mature individuals).

Suggested IUCN status: Endangered based on criterion: A1(c): A reduction of at least 50% over the last three generations (<45 years)


Justification: Although the distribution range of the species is larger than previously assumed, with populations occurring far inland, it is under severe threat from hunting and habitat loss. Many inland populations are already severely diminished in size and number and it is expected that many local populations have become extinct. Hunting is widespread in the interior, and with many people moving from the interior to coastal areas as well as people from areas with few restrictions to hunting primates (e.g., Sulawesi, Sumatra) migrating to Borneo, hunting in coastal areas is increasing. Proboscis monkey probably has the greatest proportion of its remaining habitat destroyed by the 1997 forest fires of any primate species in Kalimantan (Yeager & Frederiksson 1998): fire hot spots during the 1997-1998 forest fires were more likely to occur near rivers (Fuller & Fulk 1998). The species is restricted to forest in low-lying areas (mostly below 300 m a.s.l.) which is also most favoured by people for logging, cultivation, and village settlement. The protected area network is far from adequate. In five of the six protected areas in Indonesia where the species is represented by at least several hundred individuals, populations are declining (Meijaard & Nijman 2000, chapter 9). The largest population of the species occurs in Kalimantan where active species management or active management of proboscis monkey's habitat is inadequate. In Sabah, the only area where the species still seems to be common is the Lower Kinabatangan (Boonratana 2000), whereas it occurs in a few areas of Sarawak where it is generally rare (Bennett et al., 1987). A small isolated population occurs in Brunei. The suggestion that proboscis monkey might be better classed as endangered as opposed to vulnerable has also been made by Eudey (1996/1997).

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Forest (and) Primates Javan gibbon Hylobates moloch Legislative status: Protected by Indonesian Law (Peraturan Perlindungan Binatang Liar 1931 No. 266, Undang-undang No. 5 / 1990, Surat Keputusan Mentri Kehutanan No 301/Kpts-II/1991 and No. 882/Kpts-II/1992). Included on Appendix I of the Convention on International Trade in Endangered Species (CITES). Present IUCN status: Critically endangered based on criteria: A1(c): A reduction of at least 80% over the last three generations (45 years:

Supriatna et al., 1994) based on a decline in area of occupancy, extent of occurrence and / or quality of habitat.

C2(a): Population estimated to number less than 250 mature individuals and a continuing decline, observed, projected, or inferred, in numbers of mature individuals and severely fragmented population structure (i.e. no sub-population estimated to contain more than 50 mature individuals).

Suggested IUCN status: Endangered based on criterion: A1(c): A reduction of at least 50% over the last three generations (45 years)


Justification: The distribution range is larger than previously assumed (Nijman 1995, Nijman & Sözer 1995; Nijman & van Balen 1997). The inferred decline of 2400-7900 gibbons in 1978 to 400 gibbons in 1994 (Supriatna et al., 1994) is largely based on differences in methodology used, i.e. extrapolation based on geographic area inhabited and density at different altitudinal zones (Kappeler 1981, 1984) vs. number of individuals actually observed in a few areas (Supriatna et al., 1994). I assume that this inferred decline was the main reason for listing the species as critically endangered. The lower estimate has been questioned (Asquith 1995, 2001), and data from the present study makes it increasingly unlikely to be held true. As an example, the central Javan populations would consist of 17 individuals (confined to Gn Slamet) according to Supriatna et al. (1994), whereas probably over 800 individuals are present. Table 12.3 lists the number of gibbons present on Java, broken down to 15 forest areas that are inhabited by more than 50-100 gibbons. From this listing it becomes apparent that the total number of gibbons in Java is more likely to be in the order of 4000 individuals, i.e. an order of magnitude larger than previously estimated (Supriatna et al., 1994). Estimates of the number of gibbons in one area (Halimun national park) have remained fairly constant over the last 20 years, despite various reports on the loss of habitat at both the lower regions of this park as from the enclave in the center of the park (Whitten et al., 1996). Thus, Kappeler (1981) estimated the population of the park to be between 600-1800 individuals in 1978, Kool (1992) at 852-1320 individuals in 1989, Asquith et al. (1995) at 870 in 1994, and finally, Sugarjito & Sinaga (1999) at 864-936 individuals in 1997.

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Re-Assessment of IUCN Conservation Status of the Endemic Primates Table 12.3 Estimated number of Javan gibbons Hylobates moloch present in Java Area Status1 Alt. range Forest area2 Total

number Number of adults3

Source

Ujung Kulon (Gn Honje & Tanjung Tereleng)

NP 0-480 85 560 339 a, b

Gn Halimun NP 400-1929 270 850-1320 515-800 a, c, d Gn Salak Unp. 800-2210 70 140 85 a Telaga Warna – Megamendung NR / unp. 500-1600 30 >50? >30? b Gede Pangrango NP 500-3019 50 100 61 b, e Sangabuana Unp. 250-1280 50 100 61 a, b Burangrang - Tangkuban Perahu NR / unp. 900-2081 40 >50? >30? b Gn Simpang NR 400-1816 140 600 364 a Gn Tilu NR 900-2434 30 100 61 a Gn Papandayan NR 700-2622 120 250 152 a Gn Wayang Unp. 500-1830 85 300 182 a Peg. Pembarisan Unp. 300-1351 120 >50? >30? b, f Gn Slamet Unp. 700-3428 40 100? 61? b, f Gn Lawet – Cupu-Simembut- Jaran Unp. 700-1100 20-30 >50? >30? b Peg. Dieng Unp. 300-2565 120-135 519-577 315-350 b, g Total population 1270-1295 4019-4397 2436-2665

1 Status: NP= national park (taman nasional); NR= strict nature reserve (cagar alam); unp. = not protected as conservation forest: smaller sections might be protected as strict nature reserve.

2 Habitat is the approximately available habitat inhabited by gibbons. Forest above 1500 m a.s.l. is not included.

3 Number of adults is based on an average group size of 3.3 individuals, of which two are adult; floaters are not included in any of the above estimates.

4 a = Asquith et al. 1995; b = Nijman unp. data; c = Kool 1992; d = Sugarjito et al. 1997; e = Harris 1996; f = Nijman 1995; g = Nijman & Van Balen 1997.

The new total population estimate is unlikely to be an over-estimate, as overall a conservative population density of less than one gibbon group km-2 has been used (i.e. 4000 gibbons in 1300 km2 forest). Furthermore, the species is known from at least 11 other (mostly small and sometimes fragmented) forest areas (viz. Gn Jayanti-Tangkuban Perahu, Lengkong, Gn Porang, Cisolok, Bojongpicung, Pasir Susuru, Gn Malang, Gn Halu, Leuweung Sancang, Gn Masegit-Kareumbi, Gn Manglayang, and possibly Gn Sawal and Gn Ciremai), from which few data on forest size or number of gibbons present are currently available. Asquith et al. (1995) reported the apparent extinction of nine local gibbon populations, mostly due to loss of habitat. Two of these forest areas (Telaga Warna and Tangkuban Perahu-Burangrang) in fact are still inhabited by gibbons (pers. observ.). Given the overall loss of forest in west and central Java, many more gibbon populations have undoubtedly suffered from habitat loss over the last few decades. Large scale deforestation on Java dates back to the first half of the 19th century, when the Dutch colonial government imposed the so-called ‘cultuurstelsel’ which forced farmers to grow cash crops on communal grounds (often forest). During the following 100 years, large areas of forest were lost and many became fragmented. Over the last 50 years or so, however, large scale deforestation has slowed down (see e.g., Whitten et al., 1996). Hence, there does not seem to be a justification for

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Forest (and) Primates inferring a loss of 80% of the Javan gibbon population (or their habitat) over the last 50 years as assumed under criterion A1(c). Likewise, there seem to be at least eleven forest areas with an estimated population of a 100 gibbons (corresponding to at least 60 mature individuals) or more, and four areas with over 500 gibbons each. Listing the Javan gibbon as critically endangered under criterion C2(a) hence becomes questionable. Bornean gibbon Hylobates muelleri Legislative status: Protected by Indonesian Law (Peraturan Perlindungan Binatang Liar 1931 No. 266 and Undang-undang No. 5 / 1990 and Surat Keputusan Mentri Kehutanan No 301/Kpts-II/1991 and No. 882/Kpts-II/1992). Protected by Malaysian Law (Wild Life Protection Ordinance 1958), but specified therein by invalid scientific name, which may subvert prosecution. Legislative status in Brunei not known. Included on Appendix I of the Convention on International Trade in Endangered Species (CITES). Present IUCN status: Lower Risk 2(near threatened) Suggested IUCN status: Vulnerable based on criterion: A1(c): A reduction of at least 20% over the last three generations (<45 years)


Justification: Bornean gibbon is endemic to the area north of the Kapuas River and East of the Barito River. Its range encompasses three countries. The species is confined to altitudes below 1250, and attains its highest density in the lowlands (Davies & Payne 1982). Lowland forest is becoming increasingly rare on Borneo. All of its habitat outside the protected area network in Kalimantan has been earmarked for conversion or has been handed out as concession. Bornean gibbons are present in a number of large reserves in the island’s interior (including Kayan Mentarang, Lanjak Entimau, Batang Ai, Betung Kerihun), but formerly significant populations in Kutai National Park and Bukit-Suharto have almost completely disappeared. The species is able to survive in disturbed forest (secondary forest, selectively logged forest) but at lower densities (Nijman 1997; Johns 1992). Large parts of its range have been negatively affected by the forest fires of the last decades, and it is anticipated that parts of its remaining habitat will be lost with the next forest fires. Burned-over forests offers little, if any, room for the species to survive. Throughout its range it is hunted for food; hunting often being associated with inland settlements and the timber industry.

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Re-Assessment of IUCN Conservation Status of the Endemic Primates LEGISLATIVE STATUS OF PRIMATES IN INDONESIA As became clear from the above listing there is little consistency in the protective status of primates in Indonesia. Some of the species with a very restricted range within Indonesia, and often World-wide are not protected by law, whereas other, more wide-ranging and common species, are protected. This even becomes more apparent when all primates, and not just the ones endemic to Java and Borneo are included. Many primate species are identifiable by specialists only, often on characters like vocalisation or minor differences in pelage characteristics. When prioritising which species deserves legal protection, this should explicitly taken into consideration. This might be illustrated by the different Presbytis taxa that occur in Indonesia, and their protective status. The leaf monkeys of Sumatra, Java and Borneo occur in a great variety of colours from almost completely white to black, and in all sorts of different pelage patterns. If we take a closer look at the grey-backed leaf monkeys only, we end up with populations of at least five species, i.e. Sumatran leaf monkey P. thomasi, southern populations of P. melalophos on Sumatra, some populations of P. femoralis also on Sumatra, the western populations of P. comata on Java, and Bornean leaf monkey P. hosei. At present only P. thomasi and P. comata are protected by Indonesian law, yet it will be very difficult to distinguish the different taxa once encountered at a bird market or when in illegal captivity. The same is true for the Trachypithecus leaf monkeys where T. auratus is protected but T. cristata is not, yet to the non-specialist both species may appear very similar. Another caveat in protecting primates in Java is the use of outdated nomenclature in the legislative literature. Primate taxonomy in Indonesia is a discipline in motion, and with the use of molecular systematics and other techniques, and better understanding of evolutionary relationships between taxa, new taxa are being described regularly, and the geographic boundaries recognised between allopatric species shift regularly. These difficulties in identifying and distinguishing protected from non-protected species, and changes in nomenclature, may, and indeed do, create a loop-hole for malevolent keepers and may promote illegal trade. The easiest solution to this problem is to protect either all primates, or protect primates by genus. The gibbons are already included as such, thus all hylobats are protected by Indonesian law (see above). This system can easily be adopted for the other primates are well. Thus the different leaf monkeys, the proboscis monkey and the pig-tailed langur, can all be protected as colobines. Indeed proposals as these have been submitted to the compilers at the Workshop on Keeping Wild Protected Animals (Lokakarya Penanganan Satwa Liar Peliharaan yang Dilundungi) held in Bogor at 20-21 July 2000.

179


180

General Discussion

181

CHAPTER 13

GENERAL DISCUSSION In this last chapter some general points from the three sections of this dissertation, viz., background information and research methodology, conservation and ecology of the endemic primates of Java, and conservation and ecology of the endemic primates of Borneo, will be discussed briefly, as will be the conservation of primates in the Sundaic region. Thereafter, a few suggestions for conservation-related research will be given. RESEARCH METHODOLOGY The first section dealt in part with testing the validity of various census techniques in a number of areas and under different conditions. Monitoring programmes often rely on changes in densities of single species to indicate an ecosystem's health. A comparison was made between three commonly used census techniques for estimating population densities (and biomass) of single species. Mapping is generally considered to provide the most accurate approximation of true density, not just for rainforest primates but for many other species groups as well (NRC, 1981; Skorupa, 1987; Bibby et al, 1992a). Because of the three-dimensional structure of the closed canopy forests, many arboreal species are difficult to locate, and locating all individuals in a certain area may prove to be difficult, if not impossible. Range mapping, on the other hand, is time consuming and labour intensive, and only applicable in relatively small, accessible areas. The greatest source of error in the range mapping technique probably derives from the so-called edge effect, viz., the error in determining whether groups (or individuals) on the edges of the census area are inside or outside that area (Sen, 1982; Krebs, 1989). This error increases as the ratio of edge to area increases, and is thus affected by the census area (error increases with a decreasing census area), configuration of the census area (the error is smallest in circular census areas and greatest in an irregularly shaped one), and the number of groups present in the census area (the error decreases with increasing group density). Often, only the ranges of one or two groups are accurately mapped and this is taken as the closest approximation of 'true densities' against which other methods are tested (e.g., Brugiere & Fleury, 2000). Since there is no a priori reason to assume range mapping to be more accurate than either line transects, fixed point counts or any other census technique, and given the potential sources of error (including or excluding groups, drawing the boundaries of the mapping area, estimation of group sizes, etc.), the perceived superiority of range mapping as a technique for estimating 'true densities' seems unfounded (contra, e.g., Reynolds et al., 1980; Brugiere & Fleury, 2000).


182

The most commonly used technique of estimating population densities of rain forest animals is the (repeated) line transect (NRC, 1981; Whitesides et al., 1988; Buckland et al., 1993; Bibby et al., 1992a). The merits and pitfalls of the technique and various analytical methods of data analysis are discussed in length by Burnham et al. (1980) and in part in chapter 2. It suffices here to say that although there are a great number of sources of error it is often the only technique applicable, given the amount of time and resources available. Caution is needed, however, in the interpretation of the data, especially when comparing data sets collected by different researchers, with different sampling regimes and efforts, in different areas, or at different times (see also chapter 2). One particular source of bias that became apparent during the present study (chapter 2) was the use of ridges and spurs for positioning transects. As recommended by amongst others Burnham et al. (1980), transects should be placed randomly or through a stratified random technique and should follow a straight line, and not follow geographic features or roads. Many primates show a preference for ridges or rivers, at least for parts of the day (Nijman, unp. data; chapter 2), and by censussing along ridges, spurs, and crests only, population densities will be over-estimated or under-estimated, depending on the species involved. Fixed point counts are frequently used in ornithological studies often in the form of 'variable circular plot counts' (e.g., Reynolds et al., 1980; Bibby et al., 1992). Although certain primates do vocalise frequently and predictably, the technique has only rarely been used in primatological studies. The clear advantage of estimating densities over relatively large areas in a short time span justifies that more effort should be put in testing the accuracy of this technique in comparison to more commonly used techniques. The largest source of bias is the variation in the calling rates (cf. Brockelman and Ali, 1987). Even within species, this varies greatly between groups, between days (in part this is related to weather conditions), between seasons, and between populations. The influence of human disturbance on calling behaviour of primates has been noted (Johns, 1985c; Berenstain et al., 1986; chapter 3), yet it is rarely appreciated. In chapter 4 we tried to improve the fixed point count technique by identifying individual groups of Javan gibbons in a relatively small area. Identification of individual groups on the basis of their vocal output is reliable and consistent in this species (Dahlmann & Geissmann, 2001; chapter 4), and it is anticipated that fixed point counts as a technique for density estimation and detailed longitudinal studies can be applied more broadly than at present. In general, behavioural studies have been considered to be of limited value for conservation because of the discordance in the level of focus between behavioural (individuals and populations) and conservation biologists (populations and ecosystems) (Clemmons & Buchholz, 1997). Yet, in monitoring programmes often single species or species groups are used as indicators for the health of an ecosystem (Van der Hoeven et al., 2000, and references therein). As indicated above in the case of the Javan gibbon (chapter 4) census techniques can be improved by incorporating behavioural information. Primates often alter their behaviour under the influence of human disturbance, and this alteration can have an influence on the outcome of

General Discussion

183

density estimations (chapter 3). Primates and most likely many other animals as well (e.g., terrestrial birds and mammals), do respond differently to the presence of humans, including surveyors, in disturbed habitats as compared to undisturbed ones (cf. Johns, 1985a; 1986). This has to be taken into account when comparing the results of surveys in habitats differing in their degree of disturbance and in monitoring programmes where disturbance levels change over time. Habitat disturbance often has an effect on density (lowered carrying capacity of the forest, lowered fecundity, higher mortality, changed rates of immigration or emigration) and this introduces additional behavioural changes in the groups under study. Although the magnitude in which animals change their behaviour may not necessarily reflect the susceptibility to habitat disturbance (Gill et al., 2001), species-specific data or detailed case studies on how to determine a proper measure of susceptibility to habitat disturbance, are lacking. The results of chapters 2 and 3 seriously question the validity of directly comparing estimates obtained by different census techniques from different areas, especially if these areas differ in their level of disturbance. For example, in the present study differences in density estimates in the order of 10-30% were attributed to the interaction between census methodology and study area. When sites additionally differ in their level of disturbance, it is likely that density estimates may differ in the order of 50%, yet true densities are the same. There seems to be an increased need for understanding how the underlying assumptions of various census and monitoring techniques are affected by the behavioural plasticity of the species under study, the effects of inter-observer variability (Mitani et al., 2000), and the area in which the study is conducted. CONSERVATION AND ECOLOGY OF PRIMATES ON JAVA An accurate description of its range of occurrence is essential for the proper assessment of a species’ conservation status as well as for monitoring changes in abundance, range, and status, yet detailed information on the distribution of primates is rarely published (Brockelman & Ali, 1987). Asquith (2001; in litt.) reported on a dichotomy present in the small group of people that focus on the conservation and management of Javan gibbons Hylobates moloch. A Population and Habitat Viability Analysis (Supriatna et al., 1994) focussed almost entirely on genetic management as the strategy to reduce the threats for this species, whereas field researchers consistently proposed forest management and protection as the right approach. Little effort has been put in accurately assessing the distribution of the Javan gibbon. Kappeler (1984) and Asquith et al. (1994) surveyed Javan gibbons and found the species to be present mainly in the west Javan province. Kappeler (1984) did survey the central Javan province but found only two small populations on Gn Slamet and Gn Lawet. Asquith et al. (1994) apparently assumed the species to be confined to West Java and did not survey in Central Java. Yet one of the most unexpected findings of the present study was the


184

recording of substantial populations of not only the Javan gibbon but also the grizzled leaf monkey in Central Java (chapter 8). Javan gibbon was recorded in three areas, viz., the southern slopes of Gn Segara (Pembarisan mountains), the southern slopes of Gn Slamet, and the Dieng mountains. An indication of population sizes for the two first mentioned areas is difficult to present as limited time was spent in the area (Pembarisan mountains) or the surveys covered limited ground (Gn Slamet), yet by taking into account the altitudinal range of the forest (gibbon densities decrease with increasing altitude) and its size we can make some educated guesses. Although gibbons may be present in the north-eastern part of the Pembarisan mountains only (Kappeler [1984] reports the species to be absent from Gn Pojok in the central part), the size, the altitudinal range (300-1351 m a.s.l.), and the relatively good condition of the forests suggest a significant population. Likewise, estimates of forest areas at different altitudinal zones on Gn Slamet (40 km2 between 700-1000 m a.s.l. and 60 km2 between 1000-1500 m a.s.l.: Nijman & Sözer, 1996) and consistent observations of gibbons on locations between 700 and 1200 m a.s.l. (Seitre & Seitre, 1990; Linsley & Nawimar, 1994; Martarinza, pers. comm.; Sugihartono and F. Nargata, pers. comm.; pers. observ.) suggest that the number of Javan gibbons on this mountain may range in the dozens if not hundreds. For the Dieng mountains an estimate of some 500-600 individuals was reached (chapter 8). With the (smaller and isolated) populations on Gn Lawet (Kappeler, 1984), Gn Cupu-Simembut (M. Linsley, pers. comm.), and Gn Jaran (pers. observ.), the central Javan population of Javan gibbons may total some 700-800 individuals (chapter 12). This is opposed to 17 individuals for central Java reached at during the PHVA, and is about twice the estimate of the total wild population (Supriatna et al., 1994). It is concluded that properly designed and executed surveys can add substantially to our knowledge of endangered species, and that too often intrusive management actions are suggested without the proper base-line data available. Prior to the present study, the knowledge we had of the geographical and altitudinal distribution of the grizzled leaf monkey Presbytis comata was limited. It was mostly considered to be confined to West Java but as with the Javan gibbon, considerable populations were found in the Central Javan province (chapter 6). The altitudinal range of the species is not as narrow as Supriatna et al. (1994) indicated. Given the limited amount of forest that remains in the lowlands on Java it is fortunate that grizzled leaf monkey does occur at altitudes between 1000-2500 m a.s.l., although in all likelihood densities in montane areas are (considerably) lower than in lowland areas. Little is known about the ecology of the grizzled leaf monkey, although it has been studied in some detail in a few montane areas (Ruhiyat, 1983, 1991; Sujatnika, 1992; Harjanti, 1996; M. Wedana, pers. comm.); no detailed studies have been conducted in lowland forests, however. Ebony leaf monkeys Trachypithecus auratus have been studied at a number of lowland sites in Java and Bali (Brotoisworo, 1983; Kartikasari, 1986; Djuwantoko, 1991; Kool & Croft, 1992; Kool, 1993; T. Voght, pers. comm.). Most studies focused on the feeding and ranging behaviour and most were restricted to relatively

General Discussion

185

dry forest types (teak plantations, deciduous forest). The species is abundant in many of the wetter forest types, but possibly because it is considerably more difficult to study them in these environments, we have limited knowledge on its ecology in these forest types (cf. Bennett & Davies, 1994). CONSERVATION AND ECOLOGY OF PRIMATES ON BORNEO Primates are often considered as ideal flagships for species conservation in tropical areas because of their high appeal to humans (Rowe, 1996; Cowlsihaw & Dunbar, 2000). Yet on Borneo even the two most spectacular primate species, viz., the orang-utan and the proboscis monkey, are in great danger of extinction. The conservation status of the orang-utan on Borneo is well documented by Rijksen & Meijaard (1999), and in chapters 9 and 10 an attempt was made to assess the conservation status of the proboscis monkey. The proboscis monkey was selected because of its striking appearance (and hence it would rank high on the list of species that people –including conservation authorities- would like to preserve) and as an example of an endemic species with a narrow niche. Like other species that are confined to the low-lying forests of Borneo it is severely affected by habitat alteration, logging, and increasingly by forest fires. In those areas from where it would be expected to be secure from these threats, viz., conservation areas, it is declining, possibly as fast as in the unprotected forests. The case study of the local extinction of proboscis monkeys from the Pulau Kaget nature reserve served to illustrate how local populations of legally protected species can disappear within a few years even from within protected areas. In chapter 11 we assessed the spatial patterns of primate diversity in terms of species richness and endemism for Borneo. As expected, the tropical wet evergreen forest below 500 m a.s.l. was identified as the most species rich habitat, with all species occurring in it, with peat swamp forest as second best. Unexpectedly, perhaps, was the finding that not northern Borneo, i.e., the Malaysian state of Sabah, came out as the most species-rich area, but central-eastern East Kalimantan. In an area of some 30,000 km2 more than 80% of all primate species, and all the endemics, co-exist sympatrically. Sobering, however, is the realisation that the newly identified hotspot is situated in one of the most densely populated areas of Borneo. The remaining forests are inadequately protected and the area has suffered severely from the great forest fires in 1982-1983 and 1997-1998. Only a small fraction is included in the protected area network, but deforestation in these protected areas is probably as severe as in non-protected areas. The three most species-rich protected areas have most, if not all, of their forest destroyed by a combination of illegal logging, mining, encroachment, and the forest fires, whereas two proposed conservation areas in central-eastern East Kalimantan are inhabited by the Punan, a (formerly) nomadic hunter-gatherer tribe, which makes effective species protection in these areas difficult.


186

Inadequate species protection and inadequate protection of conservation areas, and a sharp reduction of the amount of forest over the last decades throughout most of Borneo, justifies that four of the five endemic primates had their current IUCN threat status changed (chapter 12). Prior to the present study, very little was known about the white-fronted leaf monkey P. frontata. In chapter 11 we prepared a detailed distribution map and collected autecological data. Combined with data on its density (chapter 12) the assessment reveals that the species is probably best considered Vulnerable according to IUCN threat criteria. Bornean leaf monkey P. hosei and Bornean gibbon Hylobates muelleri were both considered at Lower Risk of extinction, but on the basis of a sharp reduction of available habitat, aggravated by hunting, both species are more appropriately classed as Vulnerable. As already indicated above, the proboscis monkey is inadequately protected inside reserves and has experienced a sharp reduction in available habitat. Hence, it should be classed as Endangered. As a corollary of the above-mentioned problems, the conservation of primates on Borneo is, and has been, complex. It seems that the Indonesian conservation authorities are neither able to carry out species protection, nor to protect the species’ habitat within reserves against the activities of plantation developers, timber concession holders, farmers, and hunters (Rijksen & Meijaard, 1999; chapters 9, 10, and 11). Most of the unprotected habitat is scheduled for conversion into agricultural land and plantation, leaving almost none for the forest-dependent primates. As indicated in chapter 9, the reasons why the Indonesian authorities are failing to address conservation issues are complex. We have mentioned among other things, a lack of funds, lack of knowledge, misconceptions on ecological issues, poorly integrated planning, and lack of serious and effective commitment and political support, for solving conservation problems. Given the (lack of) success of species and habitat conservation in the Malaysian parts of Borneo, the underlying deficiencies are probably fairly similar to those in Kalimantan. Solutions have to be found nationally and internationally in an integrated manner. For an area in transition such as Borneo (Padoch & Peluso, 1996) in times of political reform, decentralisation, and economic hardship (more so in Indonesia than in Malaysia), species and habitat conservation may not be high on the agenda. However, it is the plight of the authorities on Borneo, the central governments of Indonesia and Malaysia, and indeed the international community to safeguard the biological wealth of the island. There are still opportunities to do so as none of the Bornean primate species have become extinct yet, and none of the populations are too small to be beyond recovery. Although the current wave of openness and political reform in Indonesia might provide such opportunities for improved and effective conservation, at present the decentralisation process has been far from smooth and in in fact quite often has jeopardised the status of both wildlife and wildlands.

General Discussion

187

EXTINCTION OF PRIMATES IN THE SUNDAIC REGION FROM AN ISLAND-BIOGEOGRAPHICAL PERSPECTIVE Small areas, be it islands or reserves, are expected to harbour less species than large areas. Since the 1920’s ecologists have tried to fit equations to such species-area relations. The most powerful model that has been in use since the 1960's (e.g., Preston, 1960, 1962) is a power function model, usually expressed as a double logarithmic transformation: log S = log k + z · log A (equation 13.1) in which S represents the number of species, A is the island area, and k and z are fitted parameters that describe intercept and slope. The power function is derived from a log normal distribution of species abundance, and the theory that support the use of this type of function (e.g., Preston, 1960, 1962; MacArthur & Wilson, 1967) contains an implicit assumption of equilibrium. The values of k and z can be established empirically by determining a best fit line for the data set. Soon conservationists realised that the theory of island biogeography was useful to interpret extinction processes and could aid in conservation management (Frankel & Soulé, 1981; Meffe & Carroll, 1994).

Log area

Log (number of species+1)

Java

Borneo

.4

.5

.6

.7

.8

.91

1.11.21.3

1.41.5

2.5 3 3.5 4 4.5 5 5.5 6 6.5

Figure 13.1 Relationship between island size (log Area) and number of primate species in the Sundaic

region, with 95% confidence intervals. The relationship is described by Log(N+1)=0.242A-0.248, R2=0.78, p<0.01, where N=number of species and A=Area.


188

If we examine the relationship between land area and the number of primates for eight different 'islands' in the Sundaic region (from small to large: Mentawai Islands, Belitung, Bali, Bangka, Java, Peninsular Malaysia, Sumatra, Borneo, and Sundaland as a whole) (Fig. 13.1) we see that both Bali and Java have fewer primates than can be expected from their area. In fact, from the regression equation we can predict that Java is short of some three to four primate species, and Bali is short of at least one species. Borneo with some 13 species is not short of any primates, nor does it seem to be particularly species rich. Van Balen (1999b) reports a similar finding for birds: compared to the other islands in the Sundaic region, Java (but not Bali) is short of a number of bird species, whereas Borneo is not. log(number of endemics+1)

Java

Borneo

-.2

0

.2

.4

.6

.8

1

1.2

1.4

2.5 3 3.5 4 4.5 5 5.5 6 6.5 Figure 13.2 Relationship between island size and number of endemic primate species in the Sundaic

region, with 95% confidence intervals. The relationship is described by Log(E+1)=0.207logA-0.575, R2=0.25, p>0.10, where E=number of endemic species and A=Area.

If we take a closer look at the number of endemic primates (Fig. 13.2), it turns out that both Java and Borneo are not short in endemics. Bali does not harbour an endemic primate, as can be expected from the endemic-area curve. Both Sundaland as a whole and the Mentawai Islands show up as particularly species-rich. The relationship in Figure 13.2 is weak but this is probably not due to an inappropriate set of island sizes. In order for a mammal the size of a primate to evolve in situ a minimum population size and hence a minimum area is needed. This suggests that surface area alone is not a good predictor for the level of endemism (indeed isolation seems to be an important factor, the Mentawai Islands are separated from mainland Sumatra by a deep trench, whereas most of the other smaller islands are situated on the shallow Sunda Shelf). In conclusion it seems that Java has lost three to four, most likely non-endemic (see Fig 13.2), primates, and Bali just one. Interestingly, three species of non-

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endemic primates are known from prehistoric deposits from Java, viz., orang-utan Pongo pygmeus, siamang Symphalangus syndactylus, and pig-tailed macaque Macaca nemestrina (Whitten et al., 1996). All three species are still extant in other parts of Sundaland. Little is known about the fossil fauna of Bali, but large parts of the island experience a significantly longer dry season than other islands on the Sunda Shelf, and the island may have never harboured a true rain forest primate community. The pig-tailed macaque is known to inhabit dry deciduous forest in the northern parts of its range (e.g., Thailand: Lekagul & McNeely, 1988) and hence, may have occurred on Bali. Island species are widely believed to be more vulnerable to extinction than their congeners on the mainland (Brooks et al., 1997; Cowlishaw & Dunbar, 2000), and indeed a disproportionate large number features on lists of threatened species (Groombridge, 1994; Cowlishaw & Dunbar, 2000; Collar et al., 2001). Locally, however, paleo-endemics may be expected to be better adapted to their environment than their wide-ranging congeners. This may be in part related to the so-called insular syndrome (Krebs, 1994). A primary attribute of this syndrome is the higher densities often reached by island populations compared to continental populations in similar-sized areas (Krebs, 1994). This may be due to lower competitive interactions and reduced intra-specific aggression or territorial defence (Stamps & Buenchner, 1985). A second component of the insular syndrome is niche expansion, mostly documented as an increase in niche breath (Blondel, 1985; Krebs, 1994). Returning to the extant number of species and the available habitat, we can explore whether or not these are in equilibrium (an implicit assumption of the theory of biogeography: MacArthur & Wilson, 1967), and whether or not the primate community of the respective islands have already reached the so-called relaxation phase. According to Brooks et al. (1997), the number of species present in the remaining forest can be predicted by: Sn2 = So2 · (Fn/Fo)z (equation 13.2) where So2 is the number of expected species for an area as derived from a species-area curve (Figure 13.1), Sn2 is the number of predicted species on the basis of the remaining forest, Fo is the original and Fn is the remaining forest area, and z is the slope of the regression line (0.242: Figure 13.1). For lowland forest on Java, Bali, and Borneo these values are, respectively: So2 = 8.9, 3.6, and 13.9, Fo =123,270 km2, 4520 km2, and 656,776 km2, Fn =5,230 km2, 880 km2, and 308,684 km2 (data from MacKinnon et al. 1982, MacKinnon & Artha 1982, RePPProT, 1990). Filling in the equations for each of the islands, it turns out that on the basis of present forest cover Java should have four primate species (i.e., one less than at present), Bali two, and Borneo eleven or (possibly) twelve. Lowland forest was chosen as all the primate species occur there (chapters 1 and 11), at probably their highest density, and none of the species occurs in montane forest only. Including all forest (i.e., lowland and montane) in the equation, however, does not alter the results for any of the islands. Data on the current extent of remaining


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forest on Borneo vary widely, and the most recent data available (MacKinnon et al., 1996) are already outdated. E. Meijaard (in litt.) estimates that only some 45% of the forests of Borneo remains. This would leave room for no more than eleven species, i.e., two less than at present. The most likely candidates for extinction on Borneo are the banded leaf monkey Presbytis femoralis (see chapter 11), the proboscis money Nasalis larvatus (chapter 9), and the orang-utan Pongo pygmeus (Rijksen & Meijaard, 1999). While filling in equation 13.2 there was the implicit assumption that the primates are evenly distributed over the entire (lowland) forest area, both in the present and in the past. Data presented in chapters 6-8 and 12 showed that this is an invalid assumption, i.e., western Java and central-eastern East Kalimantan contain more species that other parts of the respective islands. Hence loss or conservation of forest areas in these parts will have a disproportional effect on the number of species that (theoretically) can persist in the remaining forest on both islands. Likewise, fragmentation per se will have its effect on the composition and number of the remaining species. Precisely these two key principles can be used as guiding principles in habitat and species conservation as it allows to maximise results with the limited resources available. As already mentioned in the first chapter, Java (and to a lesser extent Bali) represents an area where little forest remains, where the pressure on the remaining populations of primates dates back several centuries, and where many people are no longer directly dependent on the forest, whereas Borneo represents an area in transition. Although still largely covered with forest, rapid changes in land-use and changing human attitudes will greatly aggravate the pressures wildlife populations are facing. With respect to the extinction of primates on Java and Borneo, probably the former island has already reached its relaxation phase, whereas the latter has not. Hence, we can expect some local extinctions on Borneo even if the present forest cover remains unchanged. The history of deforestation on Java will most likely repeat itself on the other Sundaic islands, e.g., Sumatra and Borneo and possibly other parts of South-east Asia (in particular Indo-China). These areas have a much higher number of primate species (Rowe, 1996), including some of the rarest primates in the World (Eastern black crested gibbon Hylobates sp. cf. nasutus (Geismann & Than, 2001) and Cat Bai leaf monkey Trachypithecus poliocephalus (Nadler & Long, 2000). SUGGESTIONS FOR FURTHER RESEARCH 1. Strengthening the link between behavioural biology and conservation Recently two books have appeared in which the link between behavioural biology and conservation was explored, viz., Behavioral approaches to conservation in the wild edited by Clemmons & Buchholz (1997) and Behaviour and conservation edited by Gosling & Sutherland (2000). From the various studies in these books it becomes apparent that a better understanding of animal behaviour can greatly

General Discussion

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contribute to increase the success of conservation projects and, reversibly, how lessons learned from conservation can contribute to an increase in our knowledge of animal behaviour. Behavioural variation between populations of a species can have great conservation implications. Meijaard & Nijman (2000; chapter 9) showed that in the interior of Borneo, local populations of proboscis monkeys have diminished in number and extent of occurrence, and in all likelihood the species has disappeared from many of its former haunts. Hunting was considered a major factor in these local extinctions. One of the reasons why proboscis monkey may be more vulnerable to extinction due to hunting than other primates is their river-refuging behaviour: in most areas proboscis monkeys return to the water's edge in the evening (Bennett & Sebastian, 1988; Bennett & Davies, 1994; Yeager, 1991a, 1993). Here they congregate in bands, comprising several groups, which may total up to some 50-60 individuals (Yeager, 1990, 1991a; pers. observ.). Given that boats on Borneo are the main mode of transportation, and waterways are essentially the highways in the interior, it is not surprising that this predictable behaviour of proboscis monkeys, their large size and, locally, large numbers, make them easy targets for hunters. Information from interviewees confirmed the ease to hunt them, and although many individuals will flee once the first individual(s) is (are) shot, it was reported that not rarely will they return to the same spot the next day, and the next, until essentially the group is is wiped out. However not all proboscis monkey populations express this river-refuging behaviour. Sebastian (1994) reported that in Danau Sentarum proboscis monkeys did not always choose to sleep near the water's edge. Instead, during the dry season, groups were found to use dry riverbeds within the forest and sleep on trees along these dry open areas. The role that bio-acoustics can play in conservation studies is clearly a field worth exploring. Individual recognition, including sexing individuals by their call, allows longitudinal studies without any intrusive techniques being employed, and allows future detailed study without habituation or severe intrusion into the habitat of the species under study. Especially for rare and endangered species, in this era of instability where animals are not safe even inside ‘protected’ areas, the decision of whether or not to study the animals of interest by frequent intrusion into their habitat (and the often associated establishment of trail systems) and especially whether or not animals are to be habituated to human observers, should be taken very carefully. 2. Increase knowledge of year-round ranging patterns of primates Some primates are strictly sedentary and will not range far, even when local conditions have worsened (Johns, 1985c). Others, as for instance the pig-tailed macaque, will range habitually over large areas, often in response to local abundance of fruit. And in yet other species, e.g. the orang-utan, a certain proportion of the population may be strictly sedentary, whereas others wander over great distances (Rijksen & Meijaard, 1999). Sebastian (1994) reported substantial local movements of proboscis monkeys within and outside the Danau Sentarum reserve in response to the changing water levels. These seasonal movements may not be restricted to this


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area, and may have important implications for the design of protected areas. It is important to explicitly take the ranging patterns of animals (not just primates) into consideration when formulating conservation priorities. For instance, Momberg et al. (1998) made boundary proposals for a new to be gazetted national park in the Sebaka-Sembukung region. The proposed boundary was situated c. 5 km away from large rivers, as to include vital proboscis monkey habitat. Although this 5-km strip may provide enough habitat for the species, with limited knowledge of ranging patterns of this and other species, especially in relation to less favourable seasons, it would be worthwhile to collect more data on the ranging behaviour of species during lean periods. Although a greater insight in the biology, including behaviour, of target species can greatly help in effective conservation, there has to be a will to use this knowledge wisely. The case of the local extinction of the proboscis monkeys of the Pulau Kaget Nature Reserve (chapter 10) demonstrates this clearly.

3. Increase knowledge of the general ecology of endemic primates For many of the endemic primates of Java and Borneo basic information on their biology is lacking. For a fair number of species we have detailed lists of dietary items, e.g., grizzled leaf monkey (Ruhiyat, 1991; Sujatnika, 1992; Wedana, 1993; Harjanti 1996), ebony leaf monkey (Kartikasari 1986; Supriatna et al., 1989; Kool 1989, 1993; Djuwantoko et al., 1994), Javan gibbon (Kappeler 1981, 1984b; Rinaldi 1999), proboscis monkey (Salter et al., 1985; Yeager, 1989b; Bismark, 1994; Woods, 1995), red leaf monkey (Supriatna et al., 1986; Davies, 1988; Davies et al., 1988), and Bornean gibbon (Rodman, 1978; Leighton, 1987), yet for others it is completely lacking (white-fronted leaf monkey, Bornean leaf monkey). More importantly, from both a conservation and an ecological and evolutionary perspective, we have very few insights into how food selection (and dietary preferences) varies over different habitats, over altitude, with season, etc. Yet, in a changing environment, this information may be vital if we are to develop a sound management system for the conservation of species.

4. Assess the geographical distribution of target species In the present study we attempted to accurately assess the geographical distribution of the endemic primates of Java and Borneo. However, especially for the Bornean species the data should only be seen as a first attempt. We have limited information on the different densities at which these species occur throughout their range. The white-fronted leaf monkey, for instance, seems to be sparsely distributed and genuinely rare throughout most of its range, yet in north West Kalimantan and south Sarawak it seems to be much more common (chapter 11 and 12). We do not know whether the individuals that have repeatedly been observed in two areas east of Gunung Palung National Park are part of an isolated population or whether the distribution range of the species does extend far into West (and Central?) Kalimantan. White-fronted leaf monkeys are probably patchily distributed near Gunung Palung as Blundell (1996) did not include it in a list of mammals occurring in the park based on >110 months of observation effort. Likewise more information

General Discussion

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about the inland populations of the proboscis monkeys and the banded leaf monkey in West Kalimantan is badly needed. 5. Assess the effects of hunting on wildlife populations In the introduction it was already mentioned that the attitudes of humans towards primates in the Sundaic region differ greatly. The one extreme is seen on Bali where Hindus regularly provide offerings for primates, whereas the other extreme can be found in interior Borneo where almost all of the primate species are hunted when the occasion arises. The effects of hunting on populations of primates are not sufficiently known. The last years it became apparent that hunting in tropical areas often is unsustainable. Attempts to harvest natural resources sustainably inevitably lead to over-exploitation often to the point of collapse or extinction of the target species (Robinson & Bennett, 2000). The data on proboscis monkeys (chapter 9) and the orang-utan (Rijksen & Meijaard, 1999) indirectly pointed to hunting as one of the factors, perhaps even the main factor, to explain the absence of these species from parts of interior Borneo. Generally, however, there are insufficient or no data on the long-term intrinsic population dynamics of many rainforest species (including primates) in the absence of hunting. Likewise, the impact of hunting on most target species is unknown, let alone the impact on non-target species. On Borneo hunters often hunt opportunistically and take certain non-target species only upon encounter. Hunting in tropical areas is often associated with other types of disturbances (logging, settlements, road construction etc.) and the relative impact of hunting versus other disturbances is virtually unknown. In order to obtain these data long-term monitoring research is essential. Without understanding these above-mentioned deficiencies, future attempts to estimate and develop sustainable harvests or attempts to conserve protected populations and areas will be greatly handicapped and imprecise. Instead of assuming that indigenous tribes do hunt sustainably, it is imperative to conduct tightly controlled experiments on hunting impacts. These experiments should be conducted outside the protected area network, however, and on species not protected by law.


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Summary: Forest (and) Primates

SUMMARY

FOREST (AND) PRIMATES: ECOLOGY AND CONSERVATION OF THE ENDEMIC PRIMATES OF JAVA AND BORNEO

For primates, the Sundaic region is one of the most species-rich areas in the World. Depending on the taxonomy followed it harbours some 18-20 species endemic to the area. On two of the larger islands in the region, namely Java and Borneo, three and five single island endemics are found, respectively. Six of these are colobine monkeys whereas the remaining two are gibbons. Most of these endemic primates for their survival are dependent on natural forest. Java is a densely populated area and has a long history of deforestation, whereas Borneo is a sparsely populated island in transition and altering land-use is rapidly changing the appearance of the island; until a few decades ago Borneo was still largely covered in forest. The present study aimed at collecting data on the ecology and conservation of the endemic primates of Java and Borneo. Hereto studies were conducted and surveys executed over the period 1994-2001. The first part of the study focussed largely on testing census techniques used in primatological studies and to assess the effects of behavioural changes in the target-species brought about by various kinds of disturbance on census results. It was found that density estimates varied considerably between techniques and sites and concluded that caution is needed when comparing census data from different sites, collected by different techniques and by different researchers. Primates may alter their response to human observers in response to (habitat) disturbance and it seems likely that this in turn will have its effect in monitoring programmes, leading to either under- or overestimation of the true densities. The second part of the study focussed on the endemic primates of Java. Firstly, it was found that the eastern populations of one of the endemics, the grizzled leaf monkey Presbytis comata, were not diagnosably distinct from those in the west. Hence, there is no support for treating these eastern populations (described as P. c. fredericae) as a separate species. Secondly, the distribution and conservation status of the endemic primates of Java was assessed. The ebony leaf monkey Trachypithecus auratus occurs throughout Java, Bali, and Lombok but, contrary to previous reports, not on the Kangean Islands. On the basis of its limited range and highly fragmented populations, and some capturing for trade, it should be considered Vulnerable according to the IUCN threat criteria. The grizzled leaf monkey is confined to the rainforests of West and Central Java and occurs from sea level to c. 2500 m a.s.l. Significant populations were found in Central Java, beyond its expected range, but given the high degree of fragmentation of its population the species is Endangered according to the IUCN threat criteria. The grizzled leaf monkey shares its habitat throughout most of its range with the Javan gibbon

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Hylobates moloch. Being confined to the last remnants of floristically rich lowland forest on this densely populated island, it is the rarest of the three Javan endemics. However, population numbers have been severely under-estimated in the past and with some 4000-4500 individuals remaining it is Endangered according to the current IUCN threat criteria. The third part of the study focussed on the endemic primates of Borneo. The distribution and conservation status of one of the most charismatic primates of South-east Asia, the proboscis monkey Nasalis larvatus, was assessed. It was found not only in coastal areas and downstream parts of large rivers, as assumed previously, but throughout the Bornean interior as well. Generally, populations in the interior were small and thinly spread, a pattern most readily explained by more intense hunting in the interior than in coastal areas. The species is not adequately protected and most of the larger populations included in the protected area network are in decline. Next, we assessed the spatial patterns of primate diversity in terms of species richness and endemism for Borneo, and evaluated this in relation to patterns of human land-use and positioning of the protected area network. The tropical wet evergreen forest near large rivers in central-eastern East Kalimantan, Indonesia, covering a land surface of some 30,000 km2, was the richest area both in terms of absolute species number (up to eleven sympatric species) and in the number of endemics (up to five endemics). There is hardly any overlap between the areas most rich in primates and the protected area network. Of the five protected areas most rich in primates (including endemics), three are almost completely devoid of forest, mostly due to a combination of illegal logging, mining, encroachment and arson. Two of the primates endemic to the northern three-quarters of the island, the Bornean gibbon H. muelleri and the Bornean leaf monkey P. hosei are Vulnerable to extinction according to the IUCN threat criteria, on the basis of a sharp reduction in available habitat over the last decades, aggravated by hunting. The white-fronted leaf monkey P. frontata is an enigmatic species. Its distribution range was found to be significantly larger than previously assumed, but over large parts of its range it seems to be one of the rarest primates, occurring at low densities. Given these findings, and given a sharp reduction of its lowland habitat over the last decades it is Vulnerable to extinction. Conservation of primates and their forest both on Borneo and Java has proven to be problematic largely due to a lack of funds, lack of knowledge, misconceptions on ecological issues, poorly integrated planning, and lack of serious and effective commitment and political support, locally, nationally as well as internationally. If we are to conserve the endemic primates of the Sundaic region it is imperative that solutions have to be addressed in an integrated manner. Future research should focus on collecting ecological and behavioural data much needed to accurately address conservation issues, preferably through long-term monitoring programmes.

Ringkasan: Hutan (dan) Primata

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RINGKASAN

HUTAN (DAN) PRIMATA: EKOLOGI DAN PELESTARIAN PRIMATA ENDEMIK DI JAWA DAN KALIMANTAN

Wilayah Sondaik adalah salahsatu kawasan terkaya di dunia untuk keanekaragaman primata di mana 18 jenis terbatas penyebarannya pada kawasan ini. Di Jawa dan Kalimantan, yang termasuk pulau-pulau yang terbesar, terdapat tiga dan lima jenis endemik yang terbatas pada satu pulau saja. Enam jenis di antaranya tergolong suku kera sub-suku Colobinae, sedangkan dua jenis tergolong suku owa. Kelestarian dari kebanyakan kera ini tergantung pada pelestarian hutan. Pulau Jawa adalah wilayah yang padat penduduknya di mana hutan ditebang sejak lama, sedangkan Kalimantan adalah pulau yang berada pada masa peralihan di mana perubahan tataguna tanah secara cepat mulai mengkonversikan permukaan pulau ini. Jawa sudah sangat sedikit hutannya sejak dulu, sedangkan Kalimantan masih ditutupi hutan luas sampai beberapa dasawarsa yang lalu. Tujuan penelitian ini ialah mengumpulkan data mengenai ekologi dan pelestarian primata endemik di Jawa dan Kalimantan. Untuk ini studi-studi dilaksanakan di mana survai lapangan berlangsung selama perioda 1994-2001. Bagian pertama studi ini berfokus pada pengujian mengenai tehnik sensus pada penelitian primata yaitu bermaksud untuk menentukan dampak terhadap hasil sensus dari perubahan perilaku jenis-jenis sasaran yang disebabkan oleh gangguan lingkungan di sekitar primata tersebut. Sebagai hasil penelitian ditemukan bahwa penaksiran kepadatan cukup bervariasi di antara berbagai tehnik dan lokasi. Kesimpulannya adalah bahwa kita perlu sangat berhati-hati jika membandingkan data sensus dari berbagai lokasi yang dikumpulkan oleh berbagai peneliti dengan menggunakan berbagai tehnik. Primata mungkin mengubah responsnya terhadap manusia yang mengamatinya sebagai reaksi terhadap gangguan habitatnya. Tidak mustahil ini ada dampaknya dalam program peninjauan dan sebagai hasilnya mengurangi atau melebihi taksiran kepadatan yang sebenarnya. Bagian kedua studi ini berfokus pada primata di Pulau Jawa. Pertama, ditunjukkan bahwa populasi dari salahsatu kera endemik, yaitu Rekrakan Presbytis comata fredericae, yang terdapat di Jawa sebelah timur tidak dapat dipisahkan secara jelas sebagai jenisnya sendiri dari populasi di sebelah barat. Kedua, penyebaran dan status kelestariannya dari primata endemik di Jawa ditentukan. Lutung Jawa atau budeng Trachypithecus auratus ditemukan di seluruh Jawa, Bali dan Lombok, akan tetapi tidak ditemukan di Kepulauan Kangean, meskipun pernah ada laporannya. Berdasarkan penyebarannya yang terbatas dan populasi-populasinya yang sangat terpencar, ditambah penangkapan untuk dijual-belikan, jenis kera ini seharusnya dianggap Rentan menurut kriteria ancaman yang disusun IUCN. Surili itu terbatas pada hutan tropis di Jawa Barat dan Tengah dari permukaan laut sampai sekitar 2500m dpl. Populasi yang cukup besar ditemukan di Jawa Tengah, di luar penyebaran yang diduga sebelumnya. Meskipun demikian jenis


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ini dianggap Genting menurut kriteria acaman IUCN karena derajat terpecahnya populasi ini. Surili ini membagi habitatnya dengan Owa Jawa Hylobates moloch di sebagian terbesar wilayahnya. Jenis terakhir ini adalah terjarang dari ketiga kera endemik di Jawa karena terbatas pada kantung-kantung terakhir dari hutan tropis dataran Bagian ketiga dari studi ini berfokus pada primata endemik di Kalimantan. Penyebaran dan status kelestariannya ditentukan untuk salahsatu primata paling karismatik di Asia Tenggara, yaitu Bekantan Nasalis larvatus. Ternyata jenis ini tidak terbatas pada daerah pesisir dan kawasan hilir dari sungai besar, seperti diduga sebelumnya, namun terdapat juga di seluruh pedalaman Kalimantan. Secara umum populasi-populasi di pedalaman kecil dan tersebar berjauhan, sebuah pola yang dapat diuraikan karena pemburuan yang lebih intensif dibanding dengan keadaannya di daerah pesisir. Jenis ini tidak dilindungi secara memadai dan kebanyakan dari populasi-populasinya yang besar sedang menurun jumlahnya Walaupun berada dalam kawasan konservasi. Selanjutnya kami menentukan pola-pola spasial dari keanekaragaman primata dalam arti kekayaan jenis dan keendemikan untuk Kalimantan, serta mengevaluasikan ini berhubung dengan pola-pola tataguna tanah oleh manusia, dan tataruang jaringan kawasan konservasi. Hutan tropis sepanjang sungai besar di Kalimantan Timur sebelah timur-tengah yang menutupi kawasan berukuran 30,000 km2, adalah kawasan terkaya, baik dari segi jumlah jenis absolut (sampai sebelas jenis yang hidup berdampingan di sini), maupun dari segi jumlah jenis endemik (sampai lima jenis terdapat di sini). Dari kelima kawasan konservasi yang terkaya akan jenis (termasuk yang endemik), tiga di antaranya hampir habis hutannya. Ini terutama disebabkan oleh penggabungan antara penebangan ilegal, penambangan, pelanggaran tapal batas, dan pembakaran. Dua di antara primata yang endemik untuk bagian tigaperempat dari pulau Kalimantan bagian utara, yaitu Kalawat Hylobates muelleri dan Banggat Presbytis hosei adalah Rentan Punah menurut IUCN. Pelestarian dari primata beserta hutannya, baik di Kalimantan maupun di Jawa, terbukti ada masalahnya terutama karena kekurangan kelembagaan, dana yang kurang, pengetahuan yang tidak memadai, salah-pengertian mengenai isyu-isyu ekologis, perencanaan yang kurang pemaduannya, dan kurangnya komitmen yang sungguh-sungguh serta efektif dan dukungan politik, baik setempat, nasional dan internasional. Pemecahan masalah-masalah tersebut dengan pendekatan secara integral merupakan syarat mutlak, jika kita ingin melestarikan primata endemik di Wilayah Sondaik. Penelitian di masa depan seharusnya berfokus pada pengumpulan data-data ekologi dan perilaku yang begitu dibutuhkan untuk menanggapi isyu-isyu konservasi, dan sebaiknya berlangsung melalui program peninjauan jangka panjang.

Samenvatting: Bos (en) Apen

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SAMENVATTING

BOS (EN) PRIMATEN: ECOLOGIE EN BESCHERMING VAN DE ENDEMISCHE PRIMATEN VAN JAVA AND BORNEO

Voor primaten is het Sunda-gebied één van de meest soortenrijke gebieden in de wereld. Het herbergt ongeveer 18 endemische soorten, dat wil zeggen soorten die alleen in dat specifieke gebied voorkomen. Op twee van de grootste eilanden in het gebied, Java en Borneo, komen respectievelijk drie en vijf endemische primaten voor. Daarvan behoren er zes tot de groep van de slankapen en de overige twee zijn gibbons. De meeste van deze endemische primaten zijn voor hun voortbestaan afhankelijk van de instandhouding van het bos. Java is een dichtbevolkt eiland met een lange geschiedenis van ontbossing, terwijl Borneo een dunbevolkt eiland in overgang is en een intensivering van het landgebruik het eiland in snel tempo verandert. Java is grotendeels ontbost, terwijl tot enkele tientallen jaren geleden Borneo nog grotendeels bedekt was met tropisch regenwoud. Deze studie had tot doel om gegevens te verzamelen over de ecologie en bescherming van de endemische primaten van Java en Borneo. Hiertoe werden studies uitgevoerd gedurende de periode 1994-2001. Het eerste deel van de studie richtte zich grotendeels op het testen van censustechnieken die gebruikt worden in primatologische studies en het in kaart brengen van de effecten die gedragsverandering in primaten ten gevolge van verstoring kunnen hebben op censusresultaten. Afhankelijk van de gebruikte technieken werd gevonden dat dichtheidsschattingen behoorlijk varieerden en er werd geconcludeerd dat voorzichtigheid is geboden bij het vergelijken van censusdata vanuit verschillende onderzoeksgebieden. Primaten veranderen hun reactie naar onderzoekers ten gevolge van (habitat) verstoring en het lijkt waarschijnlijk dat dit op zijn beurt weer een effect heeft op monitoringprogramma’s, daar het leidt tot onder dan wel overschatting van dichtheden. Het tweede deel van de studie richtte zich op de endemische apen van Java. Eén van de eerste resultaten was dat de oostelijke populaties van de Javaanse Langoer Presbytis comata niet diagnostisch verschillen van populaties in het westen en de hypothese dat de oostelijke populaties (beschreven als P. c. fredericae) een aparte soort vormen werd verworpen. Vervolgens werd de verspreiding en de status van de endemische apen van Java in kaart gebracht. De Javaanse Mutslangoer Trachypithecus auratus komt verspreid voor over Java, Bali, en Lombok, maar, in tegenstelling tot eerdere aanwijzingen, niet op de Kangean eilanden. Naar aanleiding van het beperkte verspreidingsgebied van de soort, het voorkomen in een groot aantal gefragmenteerde populaties en in beperkte mate het wegvangen voor de handel, dient de Javaanse Mutslangoer volgens de criteria van de IUCN als een 'kwetsbare soort' beschouwd te worden. De Javaanse Langoer is beperkt in zijn verspreiding tot de regenwouden van West en Midden Java, waar de soort voorkomt van zeeniveau tot ca. 2500 m boven zeeniveau. Belangrijke populaties werden


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gevonden in Midden Java, oostelijk van het tot dan toe bekende verspreidingsgebied, maar de grote mate van fragmentatie van populaties rechtvaardigt de classificatie van 'bedreigd' volgens de criteria van de IUCN. De Javaanse Langoer deelt zijn habitat met de Javaanse Gibbon Hylobates moloch. Alleen voorkomend in de laatste stukjes onverstoord laagland bos die nog te vinden zijn op het dichtbevolkte eiland, is dit de meest zeldzame soort van de drie Javaanse endemen. Ondanks dat het populatieaantal van deze soort recentelijk sterk onderschat is (slechts 400 individuen in het wild) en als 'ernstig bedreigd' werd beschouwd, moet met de huidige populatieschatting van ongeveer 4000-4500 gibbons, de status van de soort nog steeds als 'bedreigd' worden opgevat. Het derde deel van de studie richtte zich op de endemische apen van Borneo. De verspreiding van één van de meest charismatische apen van zuidoost Azië --de Neusaap Nasalis larvatus-- werd in kaart gebracht. Er werd gevonden dat de soort niet alleen in kustgebieden en langs de benedenloop van de grote rivieren voorkwam, maar ook ver in de binnenlanden. Over het algemeen waren de populaties in het binnenland klein in aantal en dun verspreid, iets wat te verklaren is door de hogere jachtdruk in de binnenlanden vergeleken met de kustgebieden. De Neusaap is niet adequaat beschermd en de meeste van de grotere populaties in beschermde gebieden vertonen een dalende trend. Vervolgens zijn de ruimtelijke patronen van de diversiteit (zowel soortenrijkdom als endemisme) van apen op Borneo in kaart gebracht en is dit in verband gebracht met het landgebruik van de mens en de situering van natuurreservaten en nationale parken. Het tropisch regenwoud aan beide zijden van de grote rivieren in een betrekkelijk klein gebied van ca. 30.000 km2 in het centrale deel van oostelijk Oost Kalimantan, is het meest soortenrijk (11 sympatrische apensoorten) en bevat de meeste endemen (vijf soorten). Een combinatie van illegale houtkap, mijnbouw, landbouw, en het ongecontroleerd afbranden van bos, heeft ertoe geleid dat er in drie van de vijf meest soortenrijke beschermde gebieden (natuurreservaten en nationale parken) vrijwel geen bos meer over is. Twee van de primaten, endemisch voor het noordelijke deel van Borneo, de Borneo Gibbon H. muelleri en de Borneo Langoer P. hosei, zijn 'kwetsbaar' daar de laatste decennia het beschikbare habitat zeer sterk is afgenomen en de jachtdruk onverminderd hoog is gebleven en mogelijk zelfs toegenomen. De Witvoorhoofdlangoer P. frontata is een raadselachtig dier. Er werd gevonden dat zijn verspreidingsgebied beduidend groter is dan werd aangenomen, maar over grote delen hiervan komt de soort in zeer lage dichtheden voor en is het één van de meest zeldzame primaten. Dit in ogenschouw nemende, aangevuld met de kennis dat het beschikbare habitat drastisch is gereduceerd over de laatste decennia, maakt dat deze soort kwetsbaar is voor uitsterven. Uit de studie komt naar voren dat de bescherming van endemische primaten en hun bos op zowel Borneo als Java problematisch is. Dit komt door institutionele gebreken, een tekort aan financiële middelen, misopvattingen over ecologische processen, slecht geïntergreerde planning, een gebrek aan serieuze en effectieve betrokkenheid en politieke steun, zowel lokaal, nationaal als internationaal. Als we willen dat de endemische primaten van het Sunda-gebied behouden blijven, dan is

Samenvatting: Bos (en) Apen

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het noodzakelijk dat oplossingen in een geïntegreerde manier worden behandeld. Vervolgonderzoek zou zich kunnen richten op het verzamelen van ecologische en ethologische data die nodig zijn voor beschermingsdoeleinden en dit dient bij voorkeur te gebeuren in lange termijn onderzoeksprogramma's.


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