Palmar dermatoglyphics as a means of identifying individuals in a baboon population

International Journal of Primatology, Vol. 7, No. 5, 1986

Palmar Dermatoglyphics as a Means of Identifying

Individuals in a Baboon Population

Jane E. Phillips-Conroy, ~.3 Clifford J. Jolly, 2 and Pia Nystrom 3

Received October 25, 1985; revised May 9, 1986

Dermatoglyphic patterns provide a reliable, permanent means o f identifying individual primates in wild populations. Unlike the conventional marking techniques applied in wildlife biology, they are not prone to fading, loss, or distortion. Nonetheless, they have not been previously used for identification in primate field studies. We report here two simple techniques for recording dermatoglyphs in the field and describe an application o f the method to a long-terin study o f population dynamics among baboons (Papio hamadryas, sensu lato) in central Ethiopia. Members o f a baboon population were live-trapped, and replicas made o f their palmar dermatoglyphics, in 1973, 1982, 1983, and 1984. By comparing the 1973 set with the later samples, we were able to identify four animals, two o f each sex. All had been subadult or newly adult in 1973, as determined by dental eruption. Eleven years after their first capture, both females were still members o f the same troop, although this had apparently amalgamated with a neighboring group. Both males had migrated. One had moved from one olive baboon group to another; the other (a hybrid) had moved from the hybrid zone described by Nagel (1973) into an olive troop. Ten animals were identified in both the 1983 and the 1984 samples, and one o f these had previously been recorded in both 1982 and 1973. Establishing identity by means o f dermatoglyphics promises to be a useful tool in studies where sampling episodes are widely separate in time.

KEY WORDS: dermatoglyphics; baboons; marking; migration.

~Department of Anatomy and Neurobiology, Washington University Medical School, 660 South Euclid Avenue, St. Louis, Missouri 63110.

ZDepartment of Anthropology, New York University, New York, New York 10003. 3Department of Anthropology, Washington University, St. Louis, Missouri 63130.

0164-0291/86/1000-0435505.00/0 (D 1986 Plenum Publishing Corporation

436 Phillips-Conroy, Jolly, and Nystrom

INTRODUCTION

Recognition of individual animals is an essential part of most biological fieldwork, and finding reliable individual markers is a recurrent problem. Among mammals in general, and primates in particular, there is no standard- ized way of marking individuals comparable to the leg bands used on birds or the gill-tags of fish. Some noninterventive studies of large mammals capitalize on individual variation in hide color and pattern (giraffe), distribu- tion and patterning of vibrissae (lion), wrinkles on the nose (gorilla), and trunk creases and wrinkles (elephant) (Ashton, 1978), but such natural markers are rare in most primate species. The most common and easily seen natural markers are likely to be ear notches and other evidence of past wounds and injuries, but these are susceptible to alteration and thus prove inade- quate in the long term. Of course, many field-workers who spend long periods of time observing their animals become so familiar with them that they easily recognize individuals by facial shape, posture, or general demeanor. Such identifications are quite reliable as long as the study is continuous but are notoriously difficult to maintain if observation is interrupted for any length of time or if observers are replaced.

Live capture, followed by tranquilization and release, permits animals to be artificially marked. Representative methods of marking include tat- tooing, freeze-branding, ear-notching, and applying a tag, usually to the ear (Stonehouse, 1978). However, in some situations, as when animals are being exhibited in a national park, authorities may be unwilling to permit ob- vious markers to be applied. In any case, these methods are variably successful. Over time, artificial ear-tags and notches suffer from the same disadvantage as natural marks--they are only as permanent as the ear to which they are attached. Even tattoos become faded or distorted and usually need to be repeated (Ingrain, 1978). In our study of baboons in Ethiopia, an interval of 9 years separated the initial trapping in 1973 from the yearly trapping that recommenced in 1982. Although each animal was photographed in 1973, inevitable changes in external appearance during this time made it impossible to recognize individuals when they were retrapped. As reported in this paper, we employed a previously unused data set for identifying individuals: their palmar dermatoglyphics. This method depends on the fact that baboons, like humans and other higher primates, display on their paimar and plantar surfaces dermatoglyphic patterns that are in detail unique to the individual and persist unchanged throughout life. [We did not record or examine the dermatoglyphics of the terminal digital pads in this study; it is our impression, however, that in cercopithecoids the patterns on these p a d s - fingerprints in the strict sense-are less variable, and less suitable for use in identification, than those of humans and other hominoids (Midlo and Cum- mins, 1942).]

Palmar Dermatoglyphics for Marking Baboons 437

The dermatoglyphics of primates have a long history of study (Midlo and Cummins, 1942), with the past two decades witnessing a burgeoning in- terest (Biegert, 1961; Froehlich and Thorington, 1982; Newell-Morris 1979; Newell-Morris and Kerr, 1974; Newell-Morris et al., 1982). These studies have used dermatoglyphs primarily as a phenotypic measure of genetic distance, evolutionary relationship, or developmental stress. No previous study has used dermatoglyphic details [the minutiae of Galton (1882)] to identify individuals.

MATERIALS AND METHODS

Our data are derived from a long-term, repeated, cross-sectional study of olive, hamadryas, and hybrid baboons in the Awash National Park, Ethiopia. Its focus is on the demographic and genetic structure of the hybrid zone and the ways in which this responds to the vagaries of climate in the region (Brett et al., 1977; Phillips-Conroy, 1978; Phillips-Conroy and Jolly, 1981a, h, 1986). An important aspect of the study concerns the nature and frequency of migration of animals between groups, into and out of the hybrid zone, and across the species' border. Information about migration is provided by repeated census of the membership of known troops, which requires that animals be individually identified. The baseline study, carried out in 1973 by a team led by F. L. Brett, involved 534 animals, which were caught, examined and released. They comprised the majority of the members of 10 troops (labeled A through K; Fig. l), 8 of which (B through J) had contiguous ranges along the Awash River.

Having been caught in a cage-type live-trap, each animal was tranquilized with Sernylan, weighed, and photographed, and blood samples, tooth casts, and hair samples were taken. From about 350 animals (not, unfor- tunately, including Troop D), the investigators recorded the palmar dermatoglyphics of both hands. In June and July of 1982, 1983, and 1984, shorter field seasons were devoted to trapping animals from the area previously occupied by groups D, E, and F. By 1982, only two groups were discerni- ble in this area. The combined ranges of E and F were occupied by a single troop, which we called E/F. In 1982, eight animals, all adult males, were sampled from this group. In 1983 and 1984, we caught and examined 34 and 49 animals, respectively, drawn from both groups and all age and sex classes, although males still predominated (Table I).

Various means have been used to record the dermatoglyphics of living nonhuman primates. Impressions on ink pads or presensitized paper may be used, as with humans (Sivadjian, 1970). Other studies have used dental impression material to make a negative mold of the palm or sole (Tips et al., 1964). Still others have used photographs (Jolly and'Peterson, 1984).


TRAPPING LOCALITIES OF THE NEW YORK UNIVERSITY ~ EXPEDITION ~ K

~Lctesy F Brett) ~ t ( . ~ , , ~

"-... , . \ .-/.

Fig. 1. Map of the study area, Awash National Park, Ethiopia, showing the approximate ranges, along the Awash River, of the troops trapped in 1973. The larger letters (A-K) are the labels applied by the 1973 expedition. The smaller characters 0 -3 , HQ, CI-C6) are the labels used for the same troops by Nagel 0973).

None of these methods is without drawbacks, and we now prefer a transfer technique that offers a number of advantages in cost and convenience in the field.

In the present study, two methods were used to record dermatoglyphic patterns of animals while they were tranquilized. The first, photography, was used in 1973, 1982, and 1983. The second, using an adhesive-tape transfer, was introduced in 1983 and used exclusively in 1984. For both methods, the palm is first carefully cleaned and thoroughly dried. For the photographic method, talcum powder is applied to the clean surface and then wiped off,

Table !. Baboons Trapped in the Awash, 1982-1984 ~

Young Old Young Old Year Group males males females females Total

1982 E /F 2 6 0 0 8 1983 E /F 7 4 1 0 12 1983 D 13 8 1 0 22 1984 E/F l0 4 9 2 25 1984 D 10 4 7 3 24

"Old" means having an estimated data of birth in or before 1972 and, therefore, being old enough to be included in the 1973 sample, uYoung" animals were born in 1973 or later.


so as to highlight the ridges. The palm is then photographed, using black- and-white film. The tape-transfer method follows Aase and Lyons (1971). After cleaning the palm, one smears the surface sparingly with powdered graphite, using a cosmetic sponge. A strip of 4-in. cellophane adhesive tape (3M products, Scotch Tape No. 821 or Scotch Book Tape No. 845) is then applied to the graphite-covered palm. Care must be taken to press the tape onto all prepared surfaces, including the valleys between the palmar pads. The tape strip is then carefully peeled off and immediately stuck onto a plain 5 • 8-in. index card, labeled with the animal's ID number.

As well as being clear and easy to read, graphite transfers have a number of other advantages over other methods. They are much cheaper to produce than photographs and require no further processing in the form of develop- ing and printing. Furthermore, the transfer procedure can be quickly and easily repeated in the field until a satisfactory result is obtained. In contrast, defects in dermatoglyphic photographs may well go undetected until the film is developed and printed, by which time they cannot be corrected. Being immediately available, graphite transfers can be compared in the field with reference sets from previous seasons, permitting rapid cross-identification. A final practical advantage of this technique is that graphite transfers can be reproduced simply and accurately by photocopying to yield a duplicate data set (Figs. 2b and c).

Traditional ink-pad techniques and molds made with impression material also offer the advantage of immediate results but have other disadvantages. Ink pads are hard to use without the cooperation of the subject and are made more so by the high relief on the palms and soles of most nonhuman primates. Impression material reproduces details excellently, but the technique is comparatively time-consuming, messy, and, above all, very expensive if used on any but the smallest species. Furthermore, the resulting replica has all the disadvantages of any three-dimensional object when it comes to storage, copying, and analysis.

After experimenting with methods of coding palm-prints by pattern type, we resorted to simple visual comparison as a means of matching in- dividtrals from one sample to another. Each print from the 1982, 1983, and 1984 series was compared, respectively, with each print from each of the other series-about 34,000 comparisons in all. The process was less tedious than it might seem, however, since most matches could be ruled out within a second or two by spotting an incompatibility of pattern type in one of the major palmar regions. All comparisons were performed "blind" with respect to the age, sex, and taxonomic affiliation of the animals. Not only was this blind comparison approach less time-consuming than presorting, but, more importantly, it provided a set of checks on the validity of the matches. All matches were checked by several observers, working independently.


Fig. 2a

Fig. 2b


Fig. 2c

Fig. 2. Detail of the ulnar mid/palmar region of the left hand of a female baboon trapped in 1973 and 1984. (a) Photograph of 73-129; (b) graphite transfer of the same animal in 1984, now 84-047; (c) Xerox copy of 2b.

RESULTS

In all, 15 matches were made. Prints from four animals (two each in 1982 and 1984) were matched in the 1973 sample, and nine animals trapped in 1983 were reidentified in 1984. One animal was recognized in all four samples.

Several lines of evidence reinforce our confidence in these identifications. First, there is the ease with which most nonmatches can be recognized; it is rarely necessary to examine more than the major configuration of the pattern in one or two regions. In contrast, in the cases recognized as matches, all visible minutiae (details o f ridge-branching, islands, core patterns, and so on) corresponded exactly (Figs. 2 and 3). There were, in other words, no "borderline" cases that appeared similar but could be eliminated by a few minutial details. Second, in all matches there was concordance by sex and taxon; in spite of the "blind" procedure, no male was matched with a female print, for example, or an olive with a hamadryas. Third, and most telling, was the consistency of the dental evidence. Throughout the study, a cast was made of the left upper quadrant of each animal's dentition, and notes were taken on the state of the rest o f the dentition. From these data, we were able to show that both the dentally determined age of the animal and the details


Fig. 3a

Fig. 3. Palmar prints of the left hand of a female baboon trapped in 1973 and retrapped in 1984. Distal is toward the top. (a) Photograph of 73-129, proximal palm; (b) 73-129, distal palm; (c) 84-047, graphite transfer. In c, note the callousing that partially obscures the dermatoglyphics o f the distal pads.


Fig. 3b


Fig. 3c

Palmar Dermatoglyphics for Marking Baboons

of dental morphology, trauma, and loss tended to confirm the identifications. For example, the screening yielded two identified males from 1973: 73-379 was the same animal as 82-005, while 73-009 was the same as 82-006, 83-002, and 84-013. In 1973, both these males were subadult, with second molars newly erupted; 73-379 had both permanent premolars erupted, while 73-009 still retained the deciduous third premolar and deciduous canine. Such dentitions are consistent with ages between 4 and 4.5 years (Reed, 1965; Bramblett, 1969). Nine years later, in 1982, both animals had dentitions consistent with an age of 13 to 13.5 years, as estimated from patterns of dentine exposure on the occlusal surface of the postcanine teeth (Phillips-Conroy, 1978). The animal trapped four times (73-009= 82-006=83-002=84-013) showed progressive dental wear consistent with increasing age.

Of the two females, the younger had in 1973 a dentition complete apart from third molars, indicating an age of between 4.5 and 6 years. The amount of occlusal wear suggested the upper end of this range. In 1984, her age was estimated, from occlusal wear, at approximately 16 years. The older female had, in 1973, just erupted the third upper molar, yielding an estimated age of 7 years. In 1984, her occlusal wear was consistent with an age of about 18 years.

Nine matches were made between the 1983 and 1984 samples, all in- volving adult males. In five cases, the tooth impressions and notes in- disputably confirm the match, with idiosyncratic wear patterns, missing and broken teeth, and, in one case, a distinctively large interval between the lower right central and the lateral incisors. In the remaining cases, the dental impressions showed no clearly distinctive features but exhibited patterns of wear consistent with the match.

DISCUSSION

If, as we are convinced, the identifications established here are sound, they iUustrate the value of using palmar dermatoglyphics to ensure long-term identification of individual animals. Unlike other external features, they are unique and remain unaltered by maturation, growth, and aging. We recom- mend that whenever animals are repeatedly trapped and tranquilized as part of a field study, dermatoglyphics should be recorded, as a supplement to the more traditional-and, initially, more visible-marking techniques. A dermatoglyphic record is likely to be especially useful in studies where years in- tervene between periods of fieldwork. In the present research climate, the desirability of long-term studies and large data sets is being emphasized, while, at the same time, it is becoming harder to finance continuous field observation. It is likely that strictly observational, longitudinal studies of comparatively limited populations will be increasingly supplemented by successive,


comparatively short but intensive, multidisciplinary studies that involve hands-on techniques and encompass larger sample populations. In such cir- cumstances, field-workers cannot hope to learn to recognize all their animals consistently by the traditional method, and the need for a reliable, objective means of identification in the hand becomes imperative. The dermatoglyphic technique described here has proved valuable in our long-term study, involv- ing hundreds of animals in widely separated time frames, and has enabled us to document both male migration and long-term female tenure in Awash olive and hybrid baboon groups (Jolly and Phillips-Conroy, in preparation).

ACKNOWLEDGMENTS

We would like to acknowledge the collaboration and assistance of members of the Biology Department of Addis Ababa University, particular- ly Dr. Amha Belay, Dr. Tewoldeberhan G. Egziabher, Tsirha Adefris, Shimelis Beyene, Goetom Redda, and Hanna Abera. We thank Ato Tashome Ashine, Director, and the staff of the Wildlife Conservation Organization for their assistance and for permission to work in the Awash National Park; the Chief Wardens, Awash National Park, Ato Hagos Yohannes and, more recently, Ato Abbay Tadessa, for facilitating many aspects of the study; our colleagues F. L. Brett and R. G. Cauble, who collected the dermatoglyphics during the 1973 study; and Ann Peterson, Nancy Fulton, Nina Weissberg, and Laurie Matthews, who helped print the negatives and carried out many of the comparisons.

The 1973 research was supported by Grant GS-35177 from the National Science Foundation, the 1982 field season by Don Meier Productions during the filming of a Wild Kingdom segment, and the 1983 and 1984 fieldwork by Earthwatch Field Grants. We thank our many able Earthwatch volunteers for their assistance during these seasons.

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Palmar dermatoglyphics as a means of identifying individuals in a baboon population

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