Transactions of the Western Section of The Wildlife Society TWS Transactions_low res.pdf · of the Transactions of the Western Section ... of The WesTern secTion of The Wildlife socieTy

Transactions of the Western Sectionof

The Wildlife Society

2008Volume 44

TRANSACTIONS OF THE WESTERN SECTIONOF

THE WILDLIFE SOCIETY2008 - Volume 44

An official publication of the Western Section of the Wildlife Society

Editor:John Harris

Production:Mary Auth

Copies are available from: The Western Section of the Wildlife Society,P.O. Box 13543, San Luis Obispo, CA 93406-3543

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EDITOR’S NOTE

I am happy to bring you the 2008 volume of the Transactions of the Western Section of The Wildlife Society. This is Volume 44 of the annual series, which was first published in 1966. The Transactions is the scientific publication of record for the Western Section and is an important benefit of Section membership. The success and value of the Transactions is dependent on annual submissions of quality manuscripts by wildlife biologists and other environmental professionals. The Transactions is a peer-reviewed publication with an open submission policy. Manuscript submission guidelines are published at the end of this volume and are based on the publication guidelines for the Journal of Wildlife Management, published by The Wildlife Society.

The Transactions includes paper on a wide variety of topics related to wildlife conservation and management including papers from the Section’s Annual Conference and other research and review papers. Preliminary data sets, reviews and critiques are welcome. The Transactions is uniquely suited for studies focused on wildlife management and conservation conducted by public agencies, environmental consulting firms, and undergraduate

and graduate students. Benefits of publishing in the Transactions include: (1) rapid turnaround time of less than one year from submission to publication; (2) no page costs for Section members; (3) hardcopy publication and posting on the Section’s web site; (4) electronic archives on the Section’s web site; (5) a continuous publication history for >40 years; (6) distribution to Section members and many libraries and bibliographic programs. Most Section members receive the Transactions in an electronic form and it is my goal to further exploit the potential of electronic publication. Photographs and color maps are examples of features that can more easily be accommodated in electronic form. This year, we will be providing supplementary web-based material for one of the papers in this volume.

I thank Mary Auth for her work in formatting and producing this volume. I would also like to thank Dave Germano, Brian Cypher, Jeff Single, and Steve Kohlmann for their assistance in producing this volume.

John H. Harris, Editor31 December 2008

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TABLE OF CONTENTS

2008 Contributed Papers

TEMPERATURE TESTS FOR DIURNAL LIVE TRAPPING SHADE CONFIGURATIONS .......................... ..................................................Howard O. Clark, Jr., Darren P. Newman, Charles J. Randel, Marc D. Meyer EFFECT OF CATTLE GRAZING ON LIZARD DIVERSITY IN MANAGED CENTRAL CALIFORNIA GRASSLANDS.....................................................................................................David L. Reinsche

CURRENT STATUS OF THE MOHAVE GROUND SQUIRREL............................................Philip Leitner

THE USE OF SCIENCE-BASED LITERATURE FOR PREDATOR CONTROL TO ENHANCE BIG HORN SHEEP, MULE DEER AND PRONGHORN IN NEVADA..........................Jim D. Yoakum

BIRD USE OF LONE OAK TREES IN VINEYARD VS. SAVANNA IN CENTRAL-COASTAL CALIFORNIA OAK WOODLAND—A PILOT STUDY .....................................................................................................................................................................................Joseph Michael and William Tietje

Western Section Notes

ANNUAL MEETINGS OF THE WESTERN SECTION OF THE WILDLIFE SOCIETY

WESTERN SECTION OF THE WILDLIFE SOCIETY AWARDS

OFFICERS OF THE WESTERN SECTION OF THE WILDLIFE SOCIETY

INSTRUCTIONS FOR CONTRIBUTORS TO THE TRANSACTIONS OF THE WESTERN SECTION OF THE WILDLIFE SOCIETY

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TEMPERATURE TESTS FOR DIURNAL LIVE TRAPPING SHADE CONFIGURATIONS

Howard o. Clark, Jr.,1 H. T. Harvey & associates, 7815 North Palm avenue, Suite 310, Fresno, Ca 93711-5511, USa.

darrEN P. NEwMaN, H. T. Harvey & associates, 7815 North Palm avenue, Suite 310, Fresno, Ca 93711-5511, USa.

CHarlES J. raNdEl, III, Sapphos Environmental, Inc., 430 North Halstead Street, Pasadena, Ca 91107, USa.

MarC d. MEYEr, H. T. Harvey & associates, 7815 North Palm avenue, Suite 310, Fresno, Ca 93711-5511, USa.

ABSTRACT: Diurnal live trapping in desert environments requires thermal protection from high temperature extremes. However, internal trap temperatures under cardboard shades have not been reported in the literature. We tested 3 shade designs commonly used by biologists during diurnal trapping: two A-frame designs with different cardboard colors, brown and white, and a cardboard box tube. Trap shade treatments were tested from 21 April to 7 July 2007 with temperatures (°C) recorded hourly with a datalogger. There was no difference in internal trap temperatures between the shade configurations when ambient air temperatures reached approximately 30°C, but as the trapping season progressed, residual heat stored in the desert landscape led to higher internal live trap temperatures.

TransacTions of The WesTern secTion of The Wildlife socieTy 44:1-3

Key words: diurnal trapping, shade configuration, temperature

1 [email protected]

Diurnal trapping for rodent species in desert ecosystems typically involves the use of Sherman live traps (7.5 x 9.5 x 30.5 cm; H.B. Sherman Traps, Tallahassee, FL) placed in grids or linear transects and covered with a cardboard A-frame shelter or equivalent non-metal structure to provide shade. The covers are especially critical during the summer months when daytime temperatures can be extremely high. Hourly temperature monitoring at each grid site during trapping is usually required by the California Department of Fish and Game (2003).

There are no published reports of the microclimate temperatures within traps under cardboard shelters, as described in some diurnal live trapping protocols (e.g., California Department of Fish and Game 2003). Critical attention must be given to ambient air temperature during diurnal live trapping of desert rodents to prevent heat stress and heat-related mortality of captured individuals. Once daytime temperatures reach a critical point, diurnal mammal activity patterns adjust in order to compensate, but for animals sequestered inside a trap, temperature coping behaviors are limited (Drabek 1973, Schwanz 2006, Vispo and Bakken 1993). Here we present our results of microclimate temperatures within 3 different shade treatments.

METHodS aNd MaTErIalSWe established a transect with 3 traps under different

shade treatments in a Mojave creosote scrub community (Holland 1986), 10 km northwest of Hesperia, San Bernardino County, California (34° 29’ 30” N, 117° 25’ 45” W, NAD83/WGS84; 990 m). We placed shade treatments in areas of comparable vegetative cover and shade regimes. Two shade treatments were A-frame cardboard shelters, one white and the other brown, made from standard corrugated cardboard measuring 60 x 90 cm. We folded the cardboard pieces in half to form an isosceles triangle and secured the edges by folding the outside 10 cm of cardboard upward and placing sand and rocks on the upper surface to hold the shades in place. The third shade treatment was a 60 x 90 cm brown cardboard piece folded into a rectangular, open-ended box that surrounded the trap’s four sides. We secured the box shelter by driving wooden lath stakes along 2 sides.

We centered each trap within the shelters in a north-south orientation of the long axis using a standard military grade lensatic compass (Stocker and Yale, Inc., Beverly, MA) with the declination compensated 13.5° west with the entrance of each trap closed and facing north. We positioned a Hobo® datalogger (Onset Computer Corp.,

2 Shade Configuration Temperature Testing ● Clark et al. TRANS.WEST.SECT.WILDL.SOC. 44:2008

Bourne, MA) within each trap. We programmed the dataloggers to record an hourly temperature until the end of the trapping season. We placed a fourth datalogger as a control within a goldenhead shrub (Acamptopappus spp.) to collect the ambient air temperature within a shade microhabitat.

We used a one-way, model I ANOVA to test the null hypothesis that internal trap temperature was similar among trap shade treatments when ambient temperature was between 30 and 34°C; 32°C is the ambient temperature at which traps must be closed according to some protocols (e.g., California Department of Fish and Game 2003) to avoid heat-related injury to desert rodents. Data for this analysis were evaluated for normality with the Kolmogorov-Smirnov test and for homoscedasticity with Levene’s test (Zar 1999).

We used a linear regression to evaluate the relationships between spring calendar date (21 April to 7 July 2007) and internal trap temperature. We conducted this test to examine whether variation in internal trap temperature increased as the trapping season progressed from mid-spring to early summer. We evaluated regression variables for normality, homoscedasticity, and independence of residuals. For all analyses, we used only a single internal trap temperature value for each trapping date (selecting the value that was closest to 32°C) in order to maintain independence among samples. All analyses were conducted with Statistica 6.0 (StatSoft Inc., Tulsa, OK) using an α level of 0.05.

rESUlTSEach datalogger collected 1,534 temperatures

from 21 April to 7 July 2007 (76 consecutive days). There was no difference in internal trap temperature among the three shade treatments (F2,191 = 0.091, P = 0.913). There was a weak positive relationship between calendar date and internal trap temperature (β= 0.040 ± 0.067 [SE], F1,62 = 5.752, R2

adj = 0.070, P < 0.001). Figure 1 is an X-Y scatter of diurnal ambient control temperature in °C versus shade treatment temperature. Ambient temperature and internal trap temperature under the cardboard shade were similar during temperatures between 5°C and 20°C. However, when the diurnal ambient temperature was higher than 30°C, the temperature within the cardboard-covered trap varied +/- 10°C. Points above the regression line were typically recorded during the latter part of the season, and points below the regression line were recorded during the early part of the season.

dISCUSSIoNWe found no significant difference in microclimate

temperature between the configurations: white and brown A-frame cardboard shades, and a brown cardboard box tube. Our analysis of the microclimate temperatures within traps under cardboard shades suggests these shelters are fairly effective in reducing internal trap temperatures during late season, hot midday periods; however, internal trap temperature variation increased as the season progressed. During April and May, the internal microclimate had a low average of 28.5°C, and during June and July, the microclimate had a high average of 31.5°C. Higher trap temperatures observed throughout the season suggest accumulative residual heat stored in the substrate and released throughout the night, in which the shades had little influence. Daytime heating of the trap occurred much faster under these conditions and potentially provides more risk of heat stress to captured individuals.

aCkNowlEdGMENTSWe thank S. I. Hagen for reviewing the manuscript

and providing helpful editorial comments. E. Kentner provided additional statistical support. H. T. Harvey & Associates provided funding to purchase the dataloggers.

Figure 1. X-Y scatter of ambient control temperature versus shade treatment temperature. Nighttime temper-atures were excluded; times included range from 0600 to 1800.

lITEraTUrE CITEdCalifornia Department of Fish and Game. 2003.

California Department of Fish and Game Mohave Ground Squirrel Survey Guidelines. California Department of Fish and Game, Sacramento, CA, USA.

Drabek, C. M. 1973. Home range and daily activity of the round-tailed ground squirrel, Spermophilus tereticaudus neglectus. American Midland Naturalist 89:287-293.

Holland, R. F. 1986. Preliminary description of the terrestrial natural communities of California. California Department of Fish and Game, Sacramento, CA, USA.

Schwanz, L. E. 2006. Annual cycle of activity, reproduction, and body mass in Mexican ground squirrels (Spermophilus mexicanus). Journal of Mammalogy 87:1086-1095.

Vispo, C. R., and G. S. Bakken. 1993. The influence of thermal conditions on the surface activity of thirteen-lined ground squirrels. Ecology 74:377-389.

Zar, J. H. 1999. Biostatistical Analysis, 4th ed. Prentice-Hall International, Inc., Upper Saddle River, New Jersey, USA.

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EFFECT OF CATTLE GRAZING ON LIZARD DIVERSITY IN MANAGED CENTRAL CALIFORNIA GRASSLANDS

daVId l. rIENSCHE, East Bay regional Park district, 2950 Peralta oaks Court, P.o. Box 5381, oakland, Ca 94605.

ABSTRACT: Management of vegetation in undeveloped lands, especially those at the interface with urban landscapes, is critical to the maintenance of plant and animal species diversity and public safety. Research can help develop vegetation management strategies to achieve fire safety goals, support ranching programs and provide suitable grassland habitat for special status and other wildlife species. I studied how the abundance of lizards was affected by grazing and how different levels of residual dry matter (RDM) are associated with lizard densities. Lizard density was significantly greater in grazed areas than ungrazed grasslands. Lizard population densities, on average, were 2.75 times higher in these managed grazed grasslands than in ungrazed grasslands. Lizard densities decreased with increased vegetation height and thatch density (RDM levels). Relatively low, moderately grazed, RDM levels, 2200 - 5530 kg/ha, appear to support the highest lizard population densities. In particular, adult Western fence lizard (Sceloporus occidentalis) populations averaged three times greater density in grazed areas than ungrazed grasslands. These results help managers understand some of the effects of grassland management on Central California lizard populations.


Throughout history climatic variation, fires, burrowing rodents and native herbivores comprised natural disturbance factors influencing grassland ecology. Wildlife managers often attempt to simulate these ecological forces, fire or herbivory, to manipulate vegetation to meet management goals. For more than 50 years, the proper role of livestock in wildlife habitat management has sparked controversy. For example, Fitch (1948) and Howard et al. (1959) suggested that the California ground squirrel (Spermophilus beecheyi) competed with livestock for green forage. Those studies, conducted at the San Joaquin Experimental Range in Madera County, California, justified suppression of ground squirrel populations until Schitoskey and Woodmansee (1978) showed that cattle and ground squirrels feed on different plants during the green forage season (February, March and April).

Relationships between livestock grazing and wildlife populations are difficult to define because grazing intensity, time, and distribution often differs (Kirsch et al. 1978). Numerous studies on western rangelands have assessed the effects of livestock grazing and the resulting changes to plant species. Heavy livestock grazing reduces biomass and diversity of annual forbs and grasses, and changes shrub species composition (Brown and Schuster 1969, Laycock 1967, Potter and Krenetsky 1967, Ellison 1960, Byldenstein et al. 1957). In contrast, based on a 55-year study, species richness and diversity in shortgrass prairie were higher in moderately grazed plots than in ungrazed plots (Hart 2001). Likewise, plots in Nevada showed few changes in species composition, cover, density and production inside or outside herbivory exclosures over a 65-year

period, indicating that recovery rates were similar under moderate grazing and on grazing exclusion sites (Courtois et al. 2004). Additionally, species richness and cover of native annual forbs at a site in California were higher in grazed sites, and this effect was concomitant with decreased vegetation height and litter depth (Hayes and Holl 2003).

Only a few studies have addressed effects of grazing on reptile populations. At a Mojave Desert site in Southern California, plots without heavy sheep grazing had twice the number of lizards and three times the plant biomass of grazed plots (Busack and Bury 1974). Pianka (1966) documented that vegetative communities with more plant structure supported more desert lizard species than those with less plant structure. Also, changes in vegetation structure due to overgrazing reduced overall lizard abundance and diversity in the Sonoran Desert scrub Jones (1981a). However, not all 23 species of lizards decreased in number, and heavy grazing may in fact increase the abundance of some species. Grazing can cause reduction in debris heaps, which offer important sources of food and cover for the western terrestrial garter snake (Thamnophis elegans) inhabiting high elevation riparian habitat, and may result in the species decline Szaro et al. (1985). In contrast, there is a general trend of greater abundance of small vertebrates with decreasing levels of residual dry matter in arid areas of the San Joaquin Valley of California (Germano et al. 2001). This study showed that heavy growth of non-native grasses in average and above-average rainfall years seemed to depress populations of a variety of lizards and rodents, including the endangered blunt-nosed leopard lizard (Gambelia sila), giant

kangaroo rat (Dipodomys ingens), and the threatened San Joaquin antelope squirrel (Ammospermophilus nelsoni). The invasion of non-native grasses has been a significant cause for the decline of lizard species in brushland and dune habitats in the Great Plains (Scott 1996). Likewise, successive years of increasing plant biomass started to decrease blunt-nosed leopard lizard survival (Germano and Williams 2005). Thick herbaceous plant cover impeded the leopard lizard’s ability to run, making it possible to capture adult lizards by hand, something they could never do when the ground was more open (Germano and Williams 2005). In Nebraska, the abundance of lesser earless lizards (Holbrookia maculata) was positively associated with cattle grazing and soil disturbance (Ballinger and Jones 1985, Ballinger and Watts 1995). Furthermore, the lesser earless lizard was more abundant on Gunnison’s prairie dog (Cynomys gunnisoni) colonies than off, suggesting that the rodent burrows act as a refuge from predators (Davis and Theimer 2003).

The work presented here is the first study to compare lizard populations within managed grasslands of Central California. The primary goal of this study was to compare how vegetation mass and structure affects lizard species densities under year-long grazed, seasonally grazed, and ungrazed situations. The second goal of this study was to systematically document different grassland RDM and their associated effects on adjacent lizard species densities. The third goal of this study was to compare grazing treatments on the density of Western fence lizard by size class, as this species was the most common lizard in the study area and represents a major food resource for the endangered Alameda whipsnake (Masticophis lateralis euryxanthus).

STUdY arEaI studied lizard densities at Garin Regional Park in

Hayward and Sunol Regional Wilderness near Sunol, California. Both properties are part of the East Bay Regional Park District, a two-county special district with about 38,850 ha in Alameda and Contra Costa Counties. I selected the precise coordinates of sampling sites with a random number table to reduce bias and increase statistical validity. All sites possessed similar topography, rainfall, and elevation to minimize the effects of natural environmental factors. I used a Global Positioning System (GPS) receiver to find sites on the ground.

Annual grassland is the predominant plant community at both locations. The vegetation is composed primarily of non-native annual grasses and herbs with scattered oak trees. Non-native grasses, which were introduced to California by early settlers, are the major component of the region’s grassland flora.

Common non-native grasses at the study sites included wild oats (Avena fatua), rye grass (Lolium multiflorum), annual bluegrass (Poa annua), foxtail barley (Hordeum jubatum), and ripgut brome (Bromus diandrus). Other introduced species included black mustard (Brassica nigra), poison hemlock (Conium maculatum), sweet fennel (Foeniculum vulgare), and wild radish (Raphanus sativus). These weedy species may be expanding their populations over time to dominate ungrazed sites.

METHodSLizard species richness at Garin Regional Park and

Sunol Regional Wilderness is low with only the Western fence lizard, Western skink (Eumeces skiltonianus), California whiptail (Aspidoscelis tigris mundus) and Southern alligator lizard (Elgaria multicarinata) comprising the majority of the species in this area. I used 35 trapping arrays, each with multiple trapping sessions, throughout three summer seasons: 2002, 2003 and 2004. I characterized 14 year-long grazed sites by the existence of cattle trails and the presence of livestock year round. The seven sites I characterized as being seasonally grazed had cattle trails but cattle were only present December through June each year. The 14 ungrazed sites had not been grazed by livestock for > 15 years. At each lizard trap site, I collected daily air temperature, weather conditions, number of each lizard species captured, number of recaptured individuals, age, sex, snout to vent length (SVL) of each individual, and the identification of other trapped vertebrate species. I toe-clipped each lizard with a unique pattern for later identification (Tinkle 1967), and drew a colored numeral on the ventral surface of the body using a non-toxic felt marker. Each lizard was released at its point of capture after handling.

I also recorded the characteristics of each site and the RDM each field season. I measured RDM by collecting three samples at each trap array site. At each site, I clipped herbaceous vegetation 13 mm from the ground within 0.1 m2 plots. Loose plant material that could be easily picked up was included in the sample. The dry samples were air dried and weighed using a gram scale (Davis 1976, Hormay 1942, Frost 1988, Heady 1994, NRC 1994, UCCE 1994).

To capture lizards, I used drift fences in combination with pitfall traps, following a design by Jones (1981a, b). Each trap array had three drift fences (7.3 m) and four buckets (substituting 15 l for recommended 19 l) comprised each trap array. I sheltered traps from direct sunlight using 13-mm thick plywood. A trap-cover locking system was attached to the drift fence system to prevent predation in the pitfall traps over night. In addition, I placed a small, damp, nontoxic sponge in the bottom of each trap to reduce the risk of amphibian

TRANS.WEST.SECT.WILDL.SOC. 44:2008 Effect of Cattle Grazing on Lizard Diversity ● Riensche 5

mortality, and I drilled 6-8 holes in the sides of the traps to allow water drainage. I checked temperatures in these covered pitfall traps during the mid afternoon heat to make sure that the critical thermal maximum (44–45 oC) for the Western fence lizard would not be exceeded. Also, I placed “Safe-houses” modified from the design by Padgett-Flohr and Jennings (2001) in the bottom of each pitfall trap to reduce the risk of harm to nocturnal mammals. During the sampling period, I checked traps once every 24 hours; the traps were opened at 0730 and were checked the following morning. The sampling periods consisted of a maximum of three consecutive days in June, July, and August for three field seasons (2002, 2003, and 2004). I tightly covered all bucket traps between sampling periods and removed the buckets at the conclusion of the study.

Lizard density was calculated as the number of lizards caught within 24 hours in one array approximately 1000 m2 (one lizard array night). In addition, 25 out of the 616 lizards were recaptures among all 35 trap arrays during this three year study. Lizards caught more than once were not included more than once in the density estimate. Densities were calculated for lizard species on grazed, seasonal grazed and ungrazed study sites. The test for statistically significant differences between managed grassland conditions was based on the Mann-Whitney U-test at the 95% confidence level. I compared the relationships between RDM and lizard density using the Kendall’s coefficient of ranked correlation. In addition, I compared lizard size classes among the three grazing treatments, using the Kruskal-Wallis test, at the 95% confidence level.

rESUlTSThe number of Western fence lizards and Western

skinks differed in grazed managed grasslands, as compared to ungrazed managed grasslands (Fig. 1). These two species were three times denser in these two moderately grazed regions than ungrazed sites. California alligator lizards were significantly denser in ungrazed managed grasslands compared to grazed areas (Fig. 1). The density of California whiptails were not significantly different between grazed and ungrazed sites (Fig. 1). In addition, there was a significant inverse relationship between density of lizards and RDM levels over a range of 389 – 34,650 kg/ha (t > 3.3, P < 0.05, R2 = 0.12; Fig. 2). The Kruskal-Wallis test revealed a highly significant difference for male (df = 2, tied p < 0.001; Figure 3) and female (df = 2, tied p < 0.001; Figure 3) Western fence lizard size class abundance and their use of the three grazing treatments. The Kruskal-Wallis test showed no statistically significant nor nearly significant difference for juvenile Western fence lizards in their use of the three grazing treatments (df = 2, tied p = 0.36; Figure 3).

dISCUSSIoNWildlife habitat in the San Francisco Bay area has

changed dramatically in the past three centuries. As Brown and McDonald (1995) point out, though, we can not go back to pre-European times, and therefore, we need to find a way to manage communities now dominated by exotic plant species. Diverse audiences are interested in the management of vegetation where undeveloped lands meet the urban expanse of homes and other buildings. Multiple perspectives are held on how best to manage this unique boundary commonly referred to as the urban-wildland intermix. Prevention of dangerous wildfires and potential loss of life and

6 Effect of Cattle Grazing on Lizard Diversity ● Riensche TRANS.WEST.SECT.WILDL.SOC. 44:2008

Figure 1. The densities of lizard species in grazed man-aged grasslands versus ungrazed managed grasslands. Western fence lizards and western skinks exhibit a sig-nificant difference in abundance (Mann-Whitney U-test, n = 616 lizards among 35 sites, tied p < 0.001) and may be 3 x more abundant in grazed versus ungrazed regions.

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Figure 2. The Kendall’s coefficient of ranked correlation revealed a statistically significant inverse relationship between lizard density (lizards/array/24 h) and residual dry matter (RDM) levels over a range of 389 – 34,650 kg/HA (Tied p < 0.001 for 35 traps).

property is something that most people agree on. Local research is needed to help shape vegetation management strategies so that resource agencies can achieve acceptable fire safety goals, prevent weed invasion, and provide habitat for the region’s diverse flora and fauna. Cattle grazing, even if light, is one method that can decrease grassland fire intensity and might help reduce non-native grasses.

Pianka (1966) reported that structural richness of various vegetative communities was important in determining lizard species richness. In theory, communities with greater structural diversity (plant heights, and possibly RDM) would support greater abundance and diversity of lizard species. In Sonoran Desert scrub communities, cattle reduce short plants by totally consuming perennial grass and severely reducing the composition of palatable shrubs, leading to reduced lizard numbers (Jones 1981a,b). In contrast, I found that adult male and female Western fence lizards are more abundant in grazed grasslands compared to ungrazed grasslands. It is possible that adult fence lizards are selecting these open, moderately disturbed areas to improve their reproductive success. In a three-year study in the northern Arizona ponderosa pine forest, the reproductive success and hatching abundance of the sagebrush lizard (Sceloporus gracious) were consistently highest in the most open cover (meadow) and stand (savannah) types, and lowest in forest cover types, especially high density ponderosa forests (Germaine and Germaine 2003). Andrews and Wright (1994) and Overall (1994) have suggested that habitat favorability

for reptile species often is strongly dependent on the site’s favorability for the species’ egg stage. Courtship displays also might be more effective in more open areas.

For many lizard species, horizontal vegetation structure (leaf, log, and limb debris) determines species composition more often than that of vertical vegetation structure (Pianka 1966, Jones 1981a, b). This trend results primarily from the lizards’ foraging and thermoregulation needs (Brattstrom, 1965). Jones (1981a) demonstrated that grazing–induced vegetative structural changes reduced overall lizard abundance and diversity in the Western Arizona desert scrub, although not all lizards were adversely affected, and that heavy grazing in fact favored lizards that foraged while sitting on trees and downed tree limbs.

The Western fence lizard, a sit-and-wait species who forages while on rock outcrops, log piles, and down trees, appears to be favored by moderate grazing. Abundance of fence lizards increased with lower RDM levels and moderate grazing. The Western skink, which searches for invertebrate prey beneath dense grass and leaf litter, also appears to be favored by moderate grazing. Kie and Loft (1990) predicted that livestock might improve habitat values for Western fence lizards, side-blotched lizards (Uta stansburiana), and Western pond turtles (Actinemys marmorata) by providing a mix of grasses and forbs in a herbaceous assemblage.

As stated earlier, much of California has been invaded by exotic plant species during the past 100 to 300 years. Large grazing native mammals probably have been depleted for even longer periods. It is generally believed that livestock and early settlers introduced non-native grasses in California. Germano et al. (2001) suggested that these introduced grasses and forbs create impenetrable thickets for small ground-dwelling native vertebrates, such as the giant kangaroo rat (Dipodomys ingens), San Joaquin kangaroo rats (Dipodomys nitratoides), San Joaquin antelope squirrels (Ammospermophilus nelsoni), and the blunt-nosed leopard lizards (Gambelia sila). Their research shows that these desert-dwelling threatened and endangered species are negatively affected by thick herbaceous cover. In some years, moderate to heavy grazing by livestock might be the best way to decrease the dense cover created by exotic annual grasses in order to prevent the further declines of these threatened and endangered species (Germano et al. 2001). These authors argued that these native desert-dwelling species are adapted morphologically, behaviorally, and physiologically to inhabit relatively open habitats and therefore are ill-equipped to live in dense grass.

Impacts of habitat alterations are not just limited to species inhabiting California’s San Joaquin Valley. For

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Figure 3. The Kruskal-Wallis test revealed a highly significant difference for adult male (df = 2, tied p < 0.001) and adult female (df = 2, tied p < 0.001) Western fence lizard density (lizards/array/24 h) and their use of the three grazing treatments. Adult Western fence liz-ard populations average three times greater density in grazed grasslands compared to ungrazed grasslands.


example, Ballinger and Watts (1995) reported declines in abundance of the Lesser earless lizard and the Eastern fence lizard (Sceloporus undulatus) in the Sand Hills region of Nebraska when cattle grazing was stopped and the associated vegetation was allowed to increase, resulting in a denser grass community on the short-grass prairie. Absence of a natural disturbance factor such as fire has demonstrated that lizard populations can decline (Greenberg et al. 1994). Norbury and Norbury (1996) reported that little or no grazing in semiarid, exotic-dominated short-tussock grasslands in New Zealand can be detrimental to some native species. Also, Jaggi and Baur (1999) suggest that overgrowing vegetation (brushes and trees) may degrade the habitat quality for the asp viper (Vipera aspis), a threatened species in the northern Swiss Jura Mountains, which may lead to the local extinction of this snake and probably other reptiles as well. The results of a two-year study in northwest Spain by Galan (2004) showed that the lacertid lizard (Podarcis bocagei) population declined, largely due to a rapid decline in habitat favorability when dense vegetation colonized the site. Research in southeastern Australia on the broad-headed snake (Hoplocephalus bungaroides), a rock-dwelling nocturnal serpent, suggested that thermally suitable retreat sites are limiting resources, and that local increases in vegetation density might contribute to the decline of this endangered species (Pringle et al. 2003). The vegetation and soil disturbances created by black-tailed prairie dog (Cynomys ludovicianus) colonies in the short-grass prairie biome of western Kansas was reported by Kretzer and Cully (2001) to enhance landscape heterogeneity and contributes to greater reptile and amphibian diversity.

The effects of the livestock industry on wildlife are complex, and the analyses made by this research are limited to some degree. The critical time of year for wildlife in central California’s annual grasslands depends on the wildlife species of specific interest. My findings suggest that the seasonal, managed consumption of grasses by moderate cattle densities in Central California’s annual grasslands tends to create favorable conditions for the Western fence lizard and Western skink. While my research has emphasized the importance of cattle grazing on the lizard species evaluated during typical to heavy rainfall, it is obvious that other resource management issues must also be considered. They may include, but are not limited to, wildland fire management, pest management, providing opportunities for the “consumptive use of renewable wildlife resources,” watershed quality, aesthetics, and the protection of special status species under the Endangered Species Act or other state or federal agency designation. The implementation of a grazing management plan to

enhance wildlife needs an interdisciplinary approach, which includes knowledge of plant community dynamics and the habitat requirements of affected wildlife species (Vavra 2005). A grassland mosaic that includes all succession stages may be necessary to maximize wildlife species diversity and abundance. Patches of different habitats and management strategies across the landscape may be optimal. Hopefully others will contribute towards this effort, helping to develop an ecosystem perspective towards the management of Central California grasslands.

aCkNowlEdGMENTSFunding and support for this research was provided

by the East Bay Regional Park District, Regional Parks Foundation, Alameda County Fish and Wildlife Commission, and the Bick Hooper Foundation. A special thanks goes to all those listed below who helped guide the research and analysis, reviewed the manuscript, and assisted with the field work: B. Beckett, D. Bell, G. Bloom, S. Bobzien, A. Bohorquez, R. Canright, J. DiDonato, C. High, H. High, K. High, S. High, C. Kitting, D. Larson , S. McGinnis, J. Mena, J. Norton, S. Opp, B. Pinomaki, T. Pinomaki, M. Riensche, S. Riensche, D. Riensche, N. Riensche, R. Riensche, M. Schynert, E. Suess, H. Thomas, P. Thompson, P. Thompson, E. Wildy and S. Wiley.

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CURRENT STATUS OF THE MOHAVE GROUND SQUIRREL

PHIlIP lEITNEr,1 Endangered Species recovery Program, department of Biological Sciences, California State University-Stanislaus, Endangered Species recovery Program, one University Circle, Turlock, Ca 95382, USa

ABSTRACT: The Mohave ground squirrel (Spermophilus mohavensis) is found only in the western Mojave Desert of California. Although it is listed as Threatened by the State of California, there is little published information regarding its current distribution and status. I have assembled a comprehensive database covering unpublished field studies, surveys, and incidental observations conducted over the 10-year period from 1998-2007. This database contains records of 1140 trapping sessions, only 102 of which were successful in capturing >1 Mohave ground squirrels. In addition, there are 96 incidental observations in which the species was detected. An analysis of these 198 positive records identifies 4 core areas that continue to support relatively abundant Mohave ground squirrel populations and 4 other areas in which there are multiple recent records of the species. Although the southern portion of the range has been most intensively sampled, the only recent occurrences there are from a single core population on Edwards Air Force Base plus an additional 4 detections from Victor Valley. There are extensive areas within the geographic range where the status of the species is unknown, especially on the China Lake Naval Air Weapons Station and Fort Irwin. I present recommendations for surveys in areas where no recent studies have been carried out. I also identify potential corridors between known populations and recommend studies to determine if these connections are actually occupied by the species. Finally, I indicate conservation measures needed to ensure that known populations and corridors are adequately protected from habitat loss and degradation.


Key words: Mohave ground squirrel, Spermophilus mohavensis, California, Mojave Desert, threatened species, core populations, corridors, conservation

1 [email protected]

The Mohave ground squirrel (Spermophilus mohavensis) is found only in the western Mojave Desert of California (Best 1995). Its historic range (Figure 1) totaled about 20,000 km2 (Gustafson 1993). It has been found from the area of Palmdale and Victorville in the south to Owens Lake in the north. The eastern escarpment of the Sierra Nevada forms much of the western boundary of its range, while in the east its distribution extends to the Mojave River Valley and to the Fort Irwin military reservation. This region has experienced rapid growth over the past few decades. Urban development in the Antelope Valley, Indian Wells Valley, and along the Mojave River from Victorville to Barstow has resulted in a human population in excess of 700,000. Three large military bases conduct extensive training and testing operations. Much of the western Mojave Desert is used for motorized outdoor recreation, mining, and livestock grazing. There is an expanding transportation infrastructure, including highways, railroads, airports, pipelines, and electric transmission lines. Recent government policies have stimulated great interest in siting renewable energy facilities in this region, especially wind farms and solar installations.

Because of these multiple development pressures, there has been significant and on-going loss of wildlife habitat in the western Mojave Desert as well as widespread habitat degradation and fragmentation.

There has been concern about the conservation status of the Mohave ground squirrel since 1971, when it was first listed as Rare under the California Endangered Species Act (CESA). After the reauthorization of CESA in 1984, the species was classified as Threatened. Its subsequent regulatory history has been highly controversial. In 1993, the California Fish and Game Commission acted to remove it from the list of threatened species, a decision that was set aside in 1997 following judicial review. A petition to list the Mohave ground squirrel under the federal Endangered Species Act (ESA) was rejected by the US Fish and Wildlife Service in 1995. The US Fish and Wildlife Service is currently (2008) reviewing a new petition to list the species as endangered under the ESA.

In 2006, the US Bureau of Land Management (BLM) approved the West Mojave Plan, which was designed to conserve a number of sensitive species throughout the western Mojave Desert, with special emphasis on the desert tortoise (Gopherus agassizii) and Mohave ground squirrel (Bureau of Land Management 2006). The alternative version of the plan as adopted established a Mohave Ground Squirrel Conservation Area consisting of 6,988 km2 of public lands managed by the BLM. (Fig. 1) These conservation measures do not apply to private and military lands within the historic range of the species.

11

Figure 1. The historic range of the Mohave ground squirrel in the western Mojave Desert of California, with important place names indicated. The Mohave Ground Squirrel Conservation Area is shown as established in the West Mojave Plan (U.S. Bureau of Land Management (2005)).

12 Current Status of Mohave Ground Squirrel ● Leitner TRANS.WEST.SECT.WILDL.SOC. 44:2008

Although the Mohave ground squirrel has been designated as a state-listed species since 1971 and has been the focus of a major conservation planning effort by the BLM, there is still little published information on its distribution, abundance, and population trends. Brooks and Matchett (2002) reviewed 19 reported studies of the species, covering the period from 1918 to 2001. Only 2 of these studies were published in scientific journals. Since this review by Brooks and Matchett, a great deal of new information has become available, most of it unpublished. Two radiotelemetry studies describing home range dynamics and juvenile dispersal were recently published in peer-reviewed journals (Harris and Leitner 2004, 2005). Several state and federal agencies, as well as private conservation groups, have sponsored field research designed to determine the status of the species in particular areas. In addition, the California Department of Fish and Game (CDFG) requires trapping surveys at proposed development sites according to a prescribed protocol (CDGF 2003).

This paper brings together the data from unpublished field studies and surveys conducted during the 10-year period from 1998-2007. I have obtained reports for all sponsored research surveys and have received information on protocol trapping surveys from many consulting biologists. The information presented here includes both positive records documenting Mohave ground squirrel occurrence and negative results from trapping surveys in which the species was not detected. The objectives of this review are to:

1. Document the geographic distribution of Mohave ground squirrel occurrences,

2. Summarize the distribution and relative intensity of survey efforts,

3. Identify important areas and corridors for conservation based on available occurrence data, and

4. Recommend areas where additional survey effort is needed.

METHodSI utilized 4 sources of information regarding the

distribution and occurrence of the Mohave ground squirrel during the period 1998-2007: the California Natural Diversity Database, regional field studies, protocol trapping at proposed development sites, and incidental observations as reported by field biologists.

The California Natural Diversity Database (CNDDB) is a state-wide inventory of the status and locations of rare species and natural communities. The CDFG produces and regularly updates this computerized catalog, which contains records of occurrence submitted by state and federal agencies, consulting firms, and individual biologists. It contains positive records of

occurrence only and generally does not include data documenting the absence of a species from a particular locality.

The CNDDB contained a total of 293 occurrence records for the Mohave ground squirrel as of August 4, 2007 (CNDDB 2007). Twenty-eight new occurrences were submitted during the period from 1998-2007 and there were also 2 new records at previously known locations for the species. These records were obtained from regional field studies, protocol trapping, and incidental observations. I incorporated these 30 records into the data base used in this analysis.

A number of regional field studies have been conducted during the past 10 years, many of them funded by public agencies and private conservation groups. I have reviewed 19 unpublished reports that describe the results of such trapping surveys and have also obtained data from several biologists whose surveys have not been documented in formal reports (Appendix A).

The third source of data was trapping surveys carried out at proposed development sites, as required by the CDFG (CDFG 2003). The CDFG guidelines specify that surveys be conducted on proposed project sites that support desert scrub vegetation and are within or adjacent to the Mohave ground squirrel geographic range. The surveys must be carried out by a qualified biologist operating under authority of a Memorandum of Understanding (MOU) with CDFG. The protocol mandates an initial visual survey of the project site. If no Mohave ground squirrel is detected visually, live-trapping is required for up to 3 sessions of 5 consecutive days each. The trapping sessions must be conducted during the periods March 15-April 30, May 1-31, and June 15-July 15. Trapping grids normally consist of 100 traps arranged in a 4x25 array (linear projects) or in a 10x10 array (other projects).

If a Mohave ground squirrel is detected on the site, the project proponent must apply to CDFG for an Incidental Take Permit and provide compensation, usually in the form of mitigation lands. If no Mohave ground squirrel is observed or captured, it is not necessarily evidence that the site is unoccupied or is not potential habitat. Nonetheless, CDFG will stipulate for a period of 1 year that the project site harbors no Mohave ground squirrels. Most protocol surveys carried out in recent years have not resulted in detection of the species.

In order to obtain the results of protocol trapping surveys for the period 1998-2007, I contacted all biologists who were known to possess an MOU authorizing take of Mohave ground squirrels. The great majority responded by providing their survey data, including dates of trapping sessions, coordinates of grid centers, number of trap-days of sampling effort, and

TRANS.WEST.SECT.WILDL.SOC. 44:2008 Current Status of Mohave Ground Squirrel ● Leitner 13

whether or not Mohave ground squirrels were detected. Although I have not obtained data for all protocol trapping efforts, I have collected a total of 943 records that represent 426,615 trap-days of sampling. I estimate that I obtained records for >95% of the total protocol trapping effort for the period 1998-2007.

I have classified as incidental observations all reports by biologists who observed or captured Mohave ground squirrels incidental to other field studies. This category includes visual and auditory detections, captures made while trapping for other species, and highway mortalities.

For regional and protocol surveys, a record is defined as a single trapping session, usually consisting of 5 successive days. Records from trapping surveys can be negative, with no Mohave ground squirrel captures, or positive, indicating a session with at least 1 capture. On the other hand, records from incidental observations were always positive, indicating the detection of at least 1 Mohave ground squirrel at a specific location. Table 1 lists the number of records obtained for this review from regional surveys, protocol trapping, and incidental observations. The regional and protocol trapping surveys provided a total of 1,038 negative records, as compared to only 102 trapping sessions in which at least 1 Mohave ground squirrel was captured. Although the regional studies involved only 21.6% of the total trapping effort, they accounted for 69.6% of the positive records. On

the other hand, the protocol surveys made up 78.4% of trapping effort, but contributed only 30.4% of Mohave ground squirrel detections.

I entered data from all sources into an Excel spreadsheet and then imported that into an Access database. This permitted data to be manipulated and extracted through the query process. A series of base maps covering the geographic range of the Mohave ground squirrel was developed using Geographic Information System (GIS) techniques. All records, both positive and negative, were plotted on these digital maps for visual analysis. In this way, the distribution of Mohave ground squirrel occurrences for the last 10 years could be visualized in relation to the distribution of sampling effort.

rESUlTS

General distribution of Mohave Ground Squirrel records

The geographic distribution of both positive and negative Mohave ground squirrel records over the period 1998-2007 is shown in Figure 2. There has been no attempt at either systematic or random range-wide sampling and the records tend to be concentrated in certain well-defined regions. The great majority of trapping effort has been conducted in the southern part of the geographic range, south of State Route 58. In spite of this very intensive sampling, Mohave ground squirrels have been detected in only 2 areas south of State Route 58, one on Edwards Air Force Base and the other in the vicinity of Victorville. The northern part of the geographic range is in Inyo County, where almost all trapping has been conducted in the Coso region on China Lake Naval Air Weapons Stations (China Lake NAWS) and in the vicinity of Olancha and Haiwee Reservoir. Outside of these 2 areas, there have been only 5 widely scattered detections in the entire northern part of the range over the past 10 years. In the central part of the range, from Ridgecrest south to State Route 58, most positive records have been concentrated in 6 distinct regions. Trapping in the vicinity of Ridgecrest has resulted in the capture of a number of Mohave ground squirrels and there are abundant records for the extensive valley (Little Dixie Wash) between Inyokern and Red Rock Canyon State Park. To the south, there is a cluster of detections associated with the Desert Tortoise Natural Area (DTNA) and another in the Pilot Knob region east of Cuddeback Dry Lake. There are many records from the broad plateau that lies north of Barstow (Coolgardie Mesa and Superior Valley) and there are also several detections in the area just north of Boron.

It is clear that there are extensive areas within the range of the Mohave ground squirrel that have not been


Table 1. A summary of the data sources used for this review. For regional and protocol surveys, a record is defined as a single trapping session (usually 5 days) at a specific grid location. If no Mohave ground squirrels were detected, such records were considered negative, while a positive record was a trapping session in which >1 Mohave ground squirrels were captured. For inci-dental observations, all records are positive. Each record indicates the detection of >1 Mohave ground squirrels at a particular location. The sampling effort for regional and protocol surveys is calculated as the number of traps operated per day times the number of days per trapping session summed over all trapping sessions.

Type of Data Total Positive Records Trap-days

Regional Surveys 197 71 111,710

Protocol Surveys 943 31 426,615Incidental Observations 96 96 N/A

Totals 1,236 198 538,325


Figure 2. The geographic distribution of all Mohave ground squirrel records for the period 1998-2007. A total of 1,236 records are plotted, which include 1,140 trapping sessions conducted for regional and protocol surveys and 96 incidental observations. Solid triangles and squares represent locations of trapping grids at which >1 Mohave ground squirrels were captured. Crosses show sites of the 96 incidental observations at which >1 Mohave ground squirrels were detected.

effectively sampled. Figure 3 shows a 10x10 km sampling frame superimposed on the geographic range, with the sampling units color-coded to indicate the number of records (both positive and negative) for each unit during the period 1998-2007. It can be seen that sampling efforts have been heavily concentrated in the southern part of the range, especially to the west and north of Victorville, in the Palmdale-Lancaster area, around Barstow, and in the vicinity of the town of Mojave. Approximately 67% of all trapping efforts have been located in the region from State Route 58 south. The lack of recent data on Mohave ground squirrel occurrence in the northern part of the range is obvious, but there are also large gaps in our knowledge in the central part of the range. Except for the Coso area, there have been no surveys on either the north or south ranges of China Lake NAWS during the past 10 years. The Western Expansion Area of Fort Irwin has been well sampled using a randomized method of selecting trapping sites. However, only 1 trapping attempt has been recorded elsewhere on Fort Irwin over the period 1998-2007. In contrast, Edwards Air Force Base has sponsored extensive surveys on a randomized sampling basis, so that the distribution of the species is known there in great detail.

regional analysis of Mohave Ground Squirrel records

In this section, I present detailed information on Mohave ground squirrel distribution and abundance during the period 1998-2007 for a number of regions within the geographic range. This regional analysis is supported by a series of 7 maps that are available as Supplemental Online Material at the website of The Western Section of The Wildlife Society: http://tws-west.org/transactions/TWSWS_Transactions_directory.htm

Inyo County. — Inyo County includes the northernmost region occupied by Mohave ground squirrels. Records are concentrated in the area between Olancha and Haiwee Reservoir and in the Coso Range, within the China Lake NAWS. The species has been detected at 5 protocol trapping grids to the south of Olancha, beginning in 2002. Mohave ground squirrel populations at 2 sites in the Coso Range have been monitored by regular spring trapping sessions. Animals have been captured on both grids at every trapping occasion. In 2007, a Mohave ground squirrel was captured at Lee Flat just inside the boundary of Death Valley National Park, which marks the northernmost record for the species. The other 4 records for Inyo County are incidental observations, including an individual that was stuck by a vehicle in northern Panamint Valley, several kilometers east of the generally-accepted limits of the range.

Ridgecrest Area.—Trapping has been conducted at 10 grids in the vicinity of Ridgecrest, with Mohave ground squirrels detected at 5 of these sites. In addition, protocol trapping at 10 grids along State Route 178 east of Ridgecrest in 2006 yielded captures at 6 locations. However, no Mohave ground squirrels were captured in 2002 at 2 sites in the Spangler Hills southeast of Ridgecrest.

Little Dixie Wash.—The Little Dixie Wash region is a broad valley extending from Inyokern southwest to Red Rock Canyon State Park. Two extensive trapping studies have detected Mohave ground squirrels throughout this region. In 2002, the species was captured at 6 of 7 grids widely scattered across this valley. There have been more than 20 incidental observations as well, suggesting that Mohave ground squirrels are widely distributed here. In 2007, a visual sighting established the first record to the west of the mountain crest in the Kelso Creek drainage.

Fremont Valley to Edwards Air Force Base.—The Fremont Valley extends northeast from the vicinity of Cantil toward Garlock and Johannesburg. No Mohave ground squirrels have been detected here during the past 10 years, despite trapping efforts at 6 grids. There are 13 positive records around the periphery of the DTNA and out a few kilometers to the east. No trapping has been carried out in the interior of the DTNA, but it is likely that Mohave ground squirrels are present there as well. Two incidental records exist for the area just to the north and east of the town of Mojave, but repeated protocol trapping efforts here have been unsuccessful. Finally, there are 10 trapping records and incidental observations in the area to the north of Boron and Kramer Junction. These records suggest a fairly widespread population across this region.

Wind Farm Area Southwest of Mojave.—Protocol trapping surveys have been conducted at 24 grids located on wind energy development sites southwest of the town of Mojave. Although this area is outside the generally-accepted boundaries of the geographic range, much of the habitat here seems suitable for the species. To date, no Mohave ground squirrels have been detected during these trapping efforts. Two recent visual observations are listed in the CNDDB, but confirmation through trapping is needed.

Edwards Air Force Base.—Edwards Air Force Base has been carrying out an extensive monitoring program to document the distribution of Mohave ground squirrels within the military reservation. From 2003 through 2007, trapping has been conducted at 40 randomly-located grids across the base, resulting in detection of the species at 6 of these sites. In combination with other trapping efforts and incidental observations, this program has clearly defined the area in which Mohave ground squirrel populations are present.



Figure 3. The distribution of sampling effort throughout the historic range of the Mohave ground squirrel for the period 1998-2007. A 10 x 10 kilometer sampling frame is set over the region and the total number of records (both positive and negative) are indicated for each 10 x 10 km block. These records are the trapping sessions conducted for regional and protocol surveys. Incidental observations are not plotted here.

Los Angeles County.—Protocol trapping has been conducted at 52 grid locations in the desert portion of Los Angeles County during the period 1998-2007, but no Mohave ground squirrels have been detected by this method. The only positive records in Los Angeles County have been 4 detections in a small area near Rogers Dry Lake on Edwards Air Force Base.

Victor Valley to Barstow.—Intensive protocol trapping has been conducted in the Adelanto area and on the western outskirts of Victorville, resulting in the capture of Mohave ground squirrels at 3 separate locations. The 2 trapping records north of Adelanto plus a visual sighting just to the west suggest the presence of a residual population in this area. Capture of a juvenile female well to the south near the intersection of US 395 and I-15 indicates that another population may exist here as well. There have been no records east of the Mojave River since 1955 but, as shown in Figure 2, this area has not been effectively sampled in the last 10 years. Three major trapping studies have been conducted from El Mirage Dry Lake north and east toward Barstow. There have been no detections of Mohave ground squirrels over this extensive area.

Barstow Area.—There were only 3 Mohave ground squirrel records in the Barstow area during the period 1998-2007. In 2005, a Mohave ground squirrel was observed about 6 km south of Barstow near the city landfill, in an area outside the generally-accepted range boundary. Two other occurrences were documented in 2007 to the west of Barstow. Mohave ground squirrels were detected at the edge of an alfalfa field near Harper Dry Lake and 1 was trapped about 10 km west of Hinkley near State Route 58.

Coolgardie Mesa and Superior Valley.—To the north of Barstow is a broad, gently-sloping plateau that extends from Coolgardie Mesa in the south to Superior Valley in the north. Three trapping studies have been conducted in this region over the past 10 years and all have documented Mohave ground squirrel occurrences. There have also been at least 7 incidental observations.

Pilot Knob Area.—Trapping studies in the Pilot Knob area, from Cuddeback Dry Lake east to the boundary of China Lake NAWS, have detected Mohave ground squirrels at 5 different sites.

Contact Zone with round-tailed Ground SquirrelThe Mohave ground squirrel and the round-tailed

ground squirrel (Spermophilus tereticaudus) are closely related (Hafner and Yates 1983). The 2 species are very similar in general appearance, the most obvious difference being the much longer tail of the round-tailed ground squirrel. The round-tailed ground squirrel is found throughout the eastern Mojave Desert of California and its geographic range adjoins that of the Mohave

ground squirrel. The contact zone between the 2 species extends from Lucerne Valley along the Mojave River to Barstow and then northeast through Fort Irwin (Fig. 4). During the period 1998-2007, a total of 30 round-tailed ground squirrel occurrences have been recorded in this contact zone. Round-tailed ground squirrels are common in the area around Barstow, especially in disturbed habitats. The species has also been observed in Lucerne Valley, near Hodge on the Mojave River, near Coyote Dry Lake, and on the eastern side of Fort Irwin. In addition, round-tailed ground squirrels have been detected in 2 areas well within the historic range of the Mohave ground squirrel. There have been 5 reports from the Western Expansion Area of Fort Irwin, as much as 24 km inside the generally-accepted boundary of the Mohave ground squirrel range. The other area of interest is west of Barstow along State Route 58, where round-tailed ground squirrels were trapped at 8 sites in 2006 and 2007. Individuals of both species were captured on a grid about 20 km west of the range boundary. Lack of historical baseline data makes it impossible to determine if the round-tailed ground squirrel is actively extending its distribution at the expense of the Mohave ground squirrel.

dISCUSSIoN

General distribution of Mohave Ground Squirrel records

It is important to be clear about the significance of positive records that indicate Mohave ground squirrel presence during the past 10 years. These positive records are highly concentrated in just 8 distinct areas, in which 93.4% (185/198) of all Mohave ground squirrel occurrences have been documented (Fig. 5). It is of interest that there are at least some Mohave ground squirrel records prior to 1998 in each of these 8 areas, suggesting that recent trapping effort has focused on areas with historic records. However, much of the Mohave ground squirrel range has never been surveyed. This is especially true in Inyo County, which includes large areas where no surveys or protocol trapping have ever been carried out. The situation is similar, although not as extreme, in the central part of the range. There are 6 areas here where recent evidence indicates the presence of Mohave ground squirrel populations. However, little trapping has been conducted outside the areas that support these known populations. In the southern part of the range, south of State Route 58, there has been much greater trapping effort and the sampling has been much more widely distributed. Even here, there are still a few relatively restricted areas that have not been surveyed since 1998. In all 3 sections of the Mohave ground squirrel range, additional populations may well



Figure 4. The contact zone between the Mohave ground squirrel and the round-tailed ground squirrel. This shows the distribution of trapping sessions conducted for regional and protocol surveys, as well as incidental observations of Mohave ground squirrels. Circles show sites where round-tailed ground squirrels have observed or captured. These data cover the period 1998-2007.


Figure 5. The geographic locations of currently known Mohave ground squirrel populations, including 4 identified core populations and 4 other populations.

exist outside the 8 areas in which recent positive records are concentrated.

The significance of negative records must be interpreted carefully as well. When regional surveys or protocol trapping fail to detect Mohave ground squirrels, it is important to keep in mind that this in itself cannot be used as evidence that the species is absent or that the area does not provide habitat for the species. There are a number of other circumstances that could result in lack of captures, such as locating a trapping grid in a small patch of marginal or unsuitable habitat, abundance of natural foods that reduce the attractiveness of the bait, low population density due to a series of dry years, or trapping early in the season before juveniles begin their dispersal movements. If trapping grids are not randomly sited, it is not valid to infer from a lack of captures at the grid sites that Mohave ground squirrels are absent in the surrounding habitat. Any conclusions would apply only to the grid sites themselves. In general, the most that can be concluded from lack of captures is that the negative results provide no evidence that the species is present. However, if repeated trapping efforts over a period of several years fail to detect Mohave ground squirrels, it becomes more and more probable that the species is very rare, if not absent, from the study area.

The distribution of trapping effort among private, military, and public land ownerships has been distinctly uneven over the past 10 years. Almost all protocol trapping surveys have been conducted on private lands or on highway rights-of-way, because of the regulatory requirement to determine presence or absence of the Mohave ground squirrel on proposed project sites. Military lands make up about 37% of the land surface

within the range boundaries, but have been the locations for only 7.4% of all trapping records (Table 2). While Edwards Air Force Base and the Western Expansion Area of Fort Irwin have been sampled intensively, very little trapping effort has been expended on the remainder of Fort Irwin or on China Lake NAWS.

Core areasData collected over the past 10 years has made

it possible to identify 4 areas within the range of the Mohave ground squirrel that still support relatively abundant and widespread populations. These core areas are defined by 3 criteria. First, there must be evidence that Mohave ground squirrel populations have persisted for a substantial period of time, on the order of 2-3 decades. Second, the species must be currently found at a minimum of 6 locations throughout the area. Third, the total number of individuals detected since 1998 must be >30. The 4 areas that are currently known to satisfy these criteria are Coso/Olancha, Little Dixie Wash, Coolgardie Mesa/Superior Valley, and Edwards Air Force Base (Fig. 5). These 4 core areas total about 1,672 km2, or about 8.4% of the entire historic range (Table 3). During the period 1998-2007, there have been 135 positive records in core areas, accounting for 68.2% of the total 198 positive records. It is important to emphasize that these identified core areas are simply the only important population centers that have been identified thus far. There are very likely to be other core areas in parts of the geographic range that have not been adequately sampled in the last 10 years.

Coso/Olancha Core Area.—China Lake NAWS sponsored field studies of the Coso Hot Springs area


Table 2. An analysis of trapping effort on military lands within the range of the Mohave ground squirrel (MGS) during the period 1998-2007. The number of sites refers to the number of distinct trapping grid locations, while the number of records is the total number of trapping sessions at all sites, regardless of whether Mohave ground squirrels were captured.

Military Base Area (km2) % MGS Range No. Sites No. Records % Records

China Lake NAWS 4400 22% 2 20 1.8%

Fort Irwin 1800 9% 18 19 1.7%

Edwards AFB 1200 6% 43 43 3.9%

Totals 7400 37% 63 82 7.4%

in 1978 that detected 35 Mohave ground squirrels at a number of sites through trapping and visual observations (Zembal and Gall 1980). In the following year, trapping was carried out at 8 sites throughout the Coso Range and in Rose Valley to the west (Leitner 1980). A total of 124 individual Mohave ground squirrels were captured at 7 of the 8 trapping grids. A monitoring program in the Coso Range and Rose Valley from 1988 through 1996 resulted in the capture of over 1400 juvenile and adult Mohave ground squirrels (Leitner and Leitner 1998). Aardahl and Roush (1985) failed to trap the species at a site near Olancha in 1980, but did observe several individuals in the same general area.

During each of the past 7 years (2001-2007), Mohave ground squirrels have been trapped at 2 permanent grids in the Coso Range (Leitner 2001, 2006, 2008). A total of 89 adults have been captured over this period. The species has also been detected regularly in the Olancha area, where 29 adult captures were recorded at 5 sites from 2002 to 2005. The Coso/Olancha area clearly qualifies as an important core area, based upon the persistence of Mohave ground squirrel populations here for 30 years, the presence of the species at many sites, and the number of animals detected.

Little Dixie Wash Core Area.—Mohave ground squirrels were first recorded in the Little Dixie Wash region in 1931 and 1932, when specimens were collected at Freeman Junction and on the east side of Walker Pass (CNDDB Occ. #21 and #52). Trapping surveys by the BLM in 1974 and 1975 resulted in 17 captures at 7 localities in Dove Springs Canyon and Bird Spring Canyon (CNDDB Occ. #84, #174, #175, and #191-194). Aardahl and Roush (1985) reported capturing a total of 94 individuals (both adults and juveniles) at 6 grids in the Little Dixie Wash area from April-July 1980. Finally, trapping at 2 sites in 1994 yielded a total of 12 Mohave ground squirrels (Scarry et al. 1996). Additional occurrences were documented at 10 other locations in this region during the period 1974-

1990. Thus, Mohave ground squirrels were recorded at 27 locations in the Little Dixie Wash area from 1931 through 1996.

Recent field studies have been conducted in the Little Dixie Wash area during the period 2002-2007. In 2002, a total of 19 adult Mohave ground squirrels were captured at 6 of 7 grid locations (Leitner 2008). This was followed by more intensive studies at the Freeman Gulch site, with a total of 108 adults and 101 juveniles recorded from 2003 through 2007. Pit-fall trapping for reptiles in the Dove Springs Open Area resulted in the incidental capture of 6 Mohave ground squirrels at 4 different locations. Finally, a trapping survey in 2007 yielded 7 adults at 4 grids near the northern boundary of Red Rock Canyon State Park (Leitner 2008). The Little Dixie Wash core area has supported Mohave ground squirrel populations for over 70 years and recent records confirm that the species is abundant and widespread here.

Coolgardie Mesa/Superior Valley Core Area.—Mohave ground squirrels were first discovered in 1977 north of Barstow on the plateau that stretches from Coolgardie Mesa north to Superior Valley (Wessman 1977). The species was detected at 9 locations, with 1-3 individuals reported at each site. In 1980, Aardahl and Roush (1985) trapped 2 grids in Superior Valley, capturing 24 individuals (both adults and juveniles). A total of 24 Mohave ground squirrels were subsequently recorded at 5 sites in 1981 and 1982 (CNDDB Occ. #206-210). In 1994, 4 individuals were captured at 2 trapping grids in this area (Scarry et al. 1996).

Two recent surveys have been carried out in the Coolgardie Mesa/Superior Valley area. Trapping at 4 sites in 2002 yielded Mohave ground squirrel captures at each location for a total of 14 adults. A more extensive survey of the Western Expansion Area of Fort Irwin in 2006 and 2007 resulted in 36 individuals captured at 10 of 12 trapping grids. There is clear evidence that Mohave ground squirrels have persisted here for at


Table 3. The estimated sizes of the 4 identified core areas, as measured in square kilometers and in acres. The number of positive Mohave ground squirrel records for the period 1998-2007 is given for each core area.

Core Area Name Area (km2) Area (acres) Number of Positive Records

Coso / Olancha 452 111,690 33

Little Dixie Wash 393 97,172 44

Coolgardie Mesa / Superior Valley 516 127,450 23

Edwards Air Force Base 311 76,761 35

least 30 years. Recent surveys have documented that the species was present at 14 of 16 trapping sites and in several cases a substantial number of individuals was captured. This core area is at the eastern edge of the range and several captures or observations of animals that appear to be round-tailed ground squirrels have been recorded here. The potential for hybridization in this area between these 2 closely related species should be carefully investigated.

Edwards Air Force Base Core Area.—A number of surveys have documented the past occurrence of Mohave ground squirrels on Edwards Air Force Base, with most records located to the north, east, and south of Rogers Dry Lake. The earliest observations were made during the period 1973-1977 in the area south of Rogers Dry Lake (CNDDB Occ. #265). Seventeen Mohave ground squirrels were trapped in 1988 at 3 sites northeast of Rogers Dry Lake (ERC Environmental and Energy Services Company 1989). Additional trapping in 1993 in this same area resulted in captures of many adults and juveniles (Deal et al. 1993, Mitchell et al. 1993). Surveys at Mt. Mesa to the southeast of Rogers Dry Lake yielded 9 Mohave ground squirrels in 1992 (U.S. Fish & Wildlife Service 1993) and over 30 individuals in 1993 (Deal et al. 1993, Mitchell et al. 1993). A total of 13 Mohave ground squirrels were trapped in 1994 at 4 sites in halophytic saltbush scrub to the south and southwest of Rogers Dry Lake (Buescher et al. 1995). The species was recorded at 4 additional locations to the east of Rogers Dry Lake during the period 1981-1991.

Recent field studies have clearly delineated a core area on Edwards Air Force Base, with all Mohave ground squirrel records since 2000 localized to the east and south of Rogers Dry Lake. Trapping surveys were conducted at 19 grids in this area during the period 2000-2005, with a total of 29 adults and 4 juveniles captured at 8 of the study sites (Vanherweg 2000, Leitner 2003, Air Force Field Test Center 2004 and 2005, Leitner 2008). Although no captures were recorded at the 8 grids south of Rogers Dry Lake in 2005, Mohave ground squirrels are known to be present here, based upon 6 incidental observations. Mohave ground squirrel populations have been known in this core area for over 30 years and the large numbers of recent records demonstrate that the species is still well-distributed here. To date, this is the only core area known to exist in the southern part of the range.

Connectivity between Core areasThe 4 core areas are isolated from each other by

distances ranging from 48-80 km. It will be an important conservation goal to ensure sufficient connectivity between them to allow gene flow. Figure 6 shows the

locations of the core areas with possible habitat corridors illustrated.

The potential corridor between the Coso/Olancha core area and Little Dixie Wash follows a narrow strip of public land between the Sierra escarpment and the boundary of China Lake NAWS. It is not clear that this corridor is effective because of its minimal width (1-4 km) and because there is no firm evidence that it is currently occupied. There may well be an alternative corridor through China Lake NAWS, but the U.S. Navy cannot guarantee permanent protection and, again, there is no proof that continuous Mohave ground squirrel populations exist here.

Connectivity between the Little Dixie Wash core area and Edwards Air Force Base is most likely to be achieved by protection of a north-south habitat corridor along US Highway 395. This linkage appears to provide the highest quality habitat connection between these 2 core areas. It would also help to provide connectivity among other known populations in the Ridgecrest area, the DTNA, Pilot Knob, and the Boron region. There are no recent Mohave ground squirrel records along much of this corridor, so it is not clear that it is currently occupied.

The most effective corridor linking the Coolgardie Mesa/Superior Valley core area with other populations is probably thorough the Pilot Knob region. This connection is relatively short and crosses apparently good quality habitat. Although the most direct route is across a corner of the China Lake NAWS, public lands just to the south could also provide connectivity. An alternative linkage would be to the southwest toward Edwards Air Force Base across the broad valley centered on Harper Dry Lake. However, this route is lower in elevation, receives less rainfall, and habitat here is of lesser quality.

The lack of data concerning the existence or status of Mohave ground squirrel populations in these potential corridors is a serious problem. While these routes may seem geographically appropriate in providing linkages between populations, it will be important to conduct field studies to determine whether or not they are actually occupied.

MaNaGEMENT rECoMMENdaTIoNS

The database of Mohave ground squirrel records that has been assembled for this analysis should be maintained by CDFG or another suitable public agency and made available for on-line access by interested researchers, agency staff, consultants, and conservation organizations. An interactive mapping system should be developed in conjunction with the database, so that



Figure 6. Map of potential habitat corridors that may provide connectivity between identified core areas and other known Mohave ground squirrel populations.

users could obtain map displays of areas of interest. As recommended by Brooks and Matchett (2002), a system should be developed to collect both positive and negative data on a continuing basis from biologists, agency staff, and consultants. It would be desirable to issue an annual report with appropriate maps to provide updated information on Mohave ground squirrel occurrences.

It is clear that additional field surveys are urgently needed to provide a more comprehensive picture of Mohave ground squirrel occurrence and status throughout its range. It is also clear that surveys to date have been seriously inadequate in documenting patterns of Mohave ground squirrel distribution because trapping sites have for the most part not been selected according to a randomized scheme. In the absence of a randomized sampling procedure, the results of such surveys apply only to the trapping site and cannot be extrapolated to the general region. It is recommended that a range-wide survey be conducted, with sampling locations determined on a randomized basis. Since this would be an expensive and logistically difficult undertaking, it

may be more realistic to develop a survey plan that could be implemented gradually over several years as funding becomes available. The first step could be to establish a sampling frame covering the entire Mohave ground squirrel range, with the area divided into sampling units, perhaps 10 x 10 km or smaller. When a survey is planned for a particular region, trapping grids could be sited in sampling units chosen at random. This system would be quite flexible, since it could be implemented at different scales as appropriate for the purposes of the sponsoring organization. It is recommended that the Mohave Ground Squirrel Technical Advisory Group develop such a range-wide randomized sampling plan and submit it to the CDFG, BLM, and military installations for consideration.

It appears to be of critical importance to acquire more data concerning the status of the species in the northern and central parts of its range (Fig. 7). Surveys should be carried out on both the north and south ranges of China Lake NAWS, on Fort Irwin, and along the corridor north from EAFB to Ridgecrest. There has


Figure 7. Potential survey areas in the northern and central portions of the Mohave ground squirrel range, showing their geographic relationship to survey efforts during the period 1998-2007.

been little or no sampling during the period 1998-2007 in these 4 extensive areas. A careful study plan should be developed to ensure adequate survey coverage within each area.

It is also recommended that field surveys be conducted in key areas within the southern range of the species in order to determine whether viable populations still remain outside of EAFB (Fig. 8). The trapping surveys could focus on public lands, but a serious attempt should be made to obtain permission for surveys on private lands as well. Because of the pace of development within the southern portion of the Mohave ground squirrel range, this exploratory work needs to be carried out with urgency.

The region southwest of the town of Mojave was identified in the West Mojave Plan (BLM 2003) as the Kern County Study Area. The West Mojave Plan recommended that Mohave ground squirrel trapping surveys be conducted here on public lands. The possibility was left open that the boundary of the Mohave

Figure 8. Potential survey areas in the southern portion of the Mohave ground squirrel range, showing their geo-graphic relationship to survey efforts during the period 1998-2007.

Ground Squirrel Conservation Area could be modified to include these public lands if justified by survey results. A number of protocol trapping surveys have recently been carried out on private land in this area in connection with proposed wind energy projects. Although no Mohave ground squirrels have been trapped thus far, there have been 2 reported visual detections. It is recommended that additional trapping surveys be authorized on both public and private property, especially in areas that have not yet been investigated.

More information is needed about the relationship between the Mohave ground squirrel and its sibling species, the round-tailed ground squirrel. There are recent reports of round-tailed ground squirrel occurrences well inside the historic Mohave ground squirrel range to the west of Barstow and in the Western Expansion Area of Fort Irwin. Round-tailed ground squirrels seem well-adapted to land disturbance in agricultural areas and on the outskirts of towns. It is possible that hybridization is occurring where the 2 species come in contact. It is


recommended that surveys be carried out to determine the current eastern limits of the Mohave ground squirrel range and establish a baseline so that future westward movement of round-tailed ground squirrels could be detected. It is also recommended that genetic studies be undertaken in the contact zone to investigate the extent of hybridization where the 2 species co-occur.

Although trapping is the most effective method of identifying areas that support Mohave ground squirrel populations, it is recommended that certain modifications of current trapping procedures be tested. Trained wildlife dogs could be used to screen large areas and help focus trapping efforts on the most promising sites. Most trapping efforts to date have used large 100-trap grids. It would be of interest to try other trap configurations, such as more numerous small grids (for example, arrays of 20 traps) and long (>1000 meter) linear transects. Finally, such alternative trap configurations could be used in combination with adaptive cluster sampling (Thompson et al. 1998), which would allow for increased effort adjacent to a sampling unit where a Mohave ground squirrel is detected.

It is essential to protect BLM lands within the Mohave Ground Squirrel Conservation Area by enforcing the 1% limitation on ground disturbance (Fig. 1) called for under the West Mojave Plan (BLM 2005). In addition, acquisition of private lands that are included within the boundaries of the Conservation Area should be pursued aggressively, especially land that is included within known core areas. Finally, there may be important Mohave ground squirrel populations outside the Conservation Area that could protected by acquisition of private lands and careful management of BLM lands. The area stretching from the DTNA southeast toward Boron may be a good example of such a conservation opportunity.

aCkNowlEdGMENTSThis review was funded by Edwards Air Force Base

through a subcontract with Tetra Tech, Inc. I am very grateful to Shannon Collis and Donald Clark for their support and guidance throughout this project. Carrie Munill provided outstanding assistance with the GIS mapping effort. A number of biologists generously contributed their data, including Mark Allaback, Patrick Kelly, Tom Kucera, David Laabs, Denise LaBerteaux, Steven Myers, Michael O’Farrell, William Vanherweg, and Ryan Young. The following agencies and organizations gave permission to include data collected in studies that they sponsored: California Department of Fish and Game, California Department of Parks and Recreation, California Department of Transportation, Desert Tortoise Preserve Committee, Edwards Air Force Base, Fort Irwin, and US Bureau of Land Management.

I greatly appreciate the helpful comments on the manuscript by B. Cypher, J. Harris, and 1 anonymous reviewer.

lITEraTUrE CITEdBest, T. L. 1995. Spermophilus mohavensis. American

Society of Mammalogists, Mammalian Species No. 509: 1-7.

Brooks, M. L., and J. R. Matchett. 2002. Sampling methods and trapping success trends for the Mohave ground squirrel, Spermophilus mohavensis. California Fish and Game 88:165-177.

Buescher, K., D. R. Mitchell, B. Ellis, J. Sawasaki, D. M. Laabs, and M. Allaback. 1995. Mohave ground squirrel studies at Edwards Air Force Base, California. Air Force Flight Test Center, Environmental Management Office, Edwards Air Force Base, California, USA.

California Department of Fish and Game. 2003. Mohave ground squirrel survey guidelines. California Department of Fish and Game, Sacramento, California, USA.

California Natural Diversity Database. 2007. Rarefind. California Department of Fish and Game, Biogeographic Data Branch, Sacramento, California, USA.

Deal, W., T. Bridges, and M. Hagan. 1993. Mojave ground squirrel trapping at two sites within Edwards AFB, California. Edwards Air Force Base, California, USA.

Gustafson, J. R. 1993. A status review of the Mohave ground squirrel (Spermophilus mohavensis). California Department of Fish and Game, Nongame Bird and Mammal Section, Sacramento, California, USA.

Hafner, D. J., and T. L. Yates. 1983. Systematic status of the Mojave ground squirrel, Spermophilus mohavensis, subgenus Xerospermophilus. Journal of Mammalogy 64:397-404.

Harris, J. H., and P. Leitner. 2004. Home-range size and use of space by adult Mohave ground squirrels, Spermophilus mohavensis. Journal of Mammalogy 85:517-523.

_____. 2005. Long distance movements of juvenile Mohave ground squirrels, Spermophilus mohavensis. Southwestern Naturalist 50:188-196.

Leitner, P. 1980. Survey of small mammals and carnivores in the Coso Geothermal Study Area. Report IV in Field Ecology Technical Report on the Coso Geothermal Study Area. Prepared for U.S. Department of the Interior, Bureau of Land Management, Bakersfield, California, USA.


Scarry, P. L., P. Leitner, and B. M. Leitner. 1996. Mohave Ground Squirrel Study in West Mojave Coordinated Management Plan Core Reserves, Kern and San Bernardino, May-June 1994 and April-May 1995. Prepared for California Department of Fish and Game, Region 4, Fresno, California, USA.

Thompson, W. L., G. C. White, and C. Gowan. 1998. Monitoring Vertebrate Populations. Academic Press, Inc., San Diego, California, USA.

U.S. Bureau of Land Management. 2003. Draft Environmental Impact Report and Statement for the West Mojave Plan. U.S. Bureau of Land Management, California Desert District, Moreno Valley, California, USA.

U.S. Bureau of Land Management. 2005. Final Environmental Impact Report and Statement for the West Mojave Plan. U.S. Bureau of Land Management, California Desert District, Moreno Valley, California, USA.

U.S. Bureau of Land Management. 2006. Record of Decision, West Mojave Plan, Amendment to the California Desert Conservation Area Plan. U.S. Bureau of Land Management, California Desert District, Moreno Valley, California, USA. p.

Zembal, R. L., and C. Gall. 1980. Observations on Mohave ground squirrels, Spermophilus mohavensis, in Inyo County, California. Journal of Mammalogy 61:347-350.


APPENDIX 1UNPUBlISHEd rEPorTS oF rEGIoNal

TraPPING STUdIES CoNdUCTEd dUrING THE PErIod 1998-2007

Air Force Flight Test Center. 2004. Inventory for Presence of Mohave Ground Squirrel at Edwards Air Force Base, California. 26 pp. + appendices.

Air Force Flight Test Center. 2005. Inventory for Presence of Mohave Ground Squirrel at Edwards Air Force Base, California. Draft Report. 16 pp. + appendices.

Air Force Flight Test Center. 2006. Inventory for Presence of Mohave Ground Squirrel at Edwards Air Force Base, California. Draft Report. 23 pp. + appendices.

Leitner, Philip. 2001. Report on Mohave ground squirrel monitoring, Coso geothermal power generation facility, 2001. Prepared for Coso Operating Company, LLC, Inyokern, CA. 16 pp. + appendix.

Leitner, Philip. 2001. California Energy Commission and Desert Tortoise Preserve Committee Mohave ground squirrel study. Final report 1998-2000. Prepared for Desert Tortoise Preserve Committee, Inc., Riverside, CA. 33 pp. + appendix.

Leitner, Philip. 2003. Inventory for presence of Mohave ground squirrels at Edwards AFB, California. Prepared for TYBRIN Corporation, Fort Walton Beach, FL. 13 pp. + appendices.

Leitner, Philip. 2005. Mohave ground squirrel trapping survey in the region between U.S. Highway 395 and the Mojave River, San Bernardino County, 2004. Prepared for Desert Tortoise Preserve Committee, Inc., Riverside, CA. 16 pp.

Leitner, Philip. 2005. Trapping survey for the Mohave ground squirrel in the DTNA Eastern Expansion Area, 2003. Prepared for Desert Tortoise Preserve Committee, Inc., Riverside, CA. 19 pp.

Leitner, Philip. 2006. Mohave ground squirrel monitoring, Coso geothermal power generation facility, 2006. Prepared for Coso Operating Company, LLC, Inyokern, CA. 11 pp. + appendix.

Leitner, Philip. 2007. Mohave ground squirrel survey, El Mirage Off-Highway Vehicle Open Area, 2002 and 2004. Prepared for USDI Bureau of Land Management, California Desert District, Moreno Valley, CA. 17 pp.

Leitner, Philip. 2007. Mohave ground squirrel surveys at the Western Expansion Area of the National Training Center and Fort Irwin, California. Prepared for ITS Corporation, San Bernardino, CA. Endangered Species Recovery Program, California State University, Stanislaus, Fresno, CA. 26 pp. + appendices.

Leitner, Philip. 2008. Mohave ground squirrel surveys at Red Rock Canyon State Park, California. Prepared for California Department of Parks and Recreation, Tehachapi District, Lancaster, CA. Endangered Species Recovery Program, California State University, Stanislaus, Fresno, CA. 26 pp. + appendices.

Leitner, Philip. 2008. Exploratory trapping surveys for the Mohave ground squirrel in three regions of the western Mojave Desert 2002. Prepared for California Department of Fish and Game, Habitat Conservation Planning Branch, Sacramento, CA and Eastern Sierra and Inland Deserts Region, Ontario, CA. Endangered Species Recovery Program, California State University, Stanislaus, Fresno, CA.

Leitner, Philip. 2008. Mohave ground squirrel trapping surveys in the Spangler Hills OHV Open Area and the Western Rand Mountains ACEC. Prepared for California Department of Fish and Game, Habitat Conservation Planning Branch, Sacramento, CA and Eastern Sierra and Inland Deserts Region, Ontario, CA. Endangered Species Recovery Program, California State University, Stanislaus, Fresno, CA. 20 pp.

Leitner, Philip. 2008. Monitoring Mohave ground squirrel populations in the Coso region, 2002-2005. Prepared for California Department of Fish and Game, Habitat Conservation Planning Branch, Sacramento, CA and Eastern Sierra and Inland Deserts Region, Ontario, CA. Endangered Species Recovery Program, California State University, Stanislaus, Fresno, CA. 20 pp + appendices.

Recht, Michael A. 1998. Chapter VIII, Small Mammal Surveys. In: Biological Surveys at Proposed Land Acquisition Sites in the Paradise Range and Superior Valley, 1998. Prepared for U.S. Army National Training Center, Fort Irwin, CA. Dominguez Hills Corporation, Carson, CA. 4 pp. + appendix.

Starr, Michael J. 2001. Population Distribution and Abundance of Antelope Ground Squirrels (Ammospermophilus leucurus) and Mohave Ground Squirrels (Spermophilus mohavensis), in the Western Mojave Desert, Spring 2001. 9 pp. + appendix.

Starr, Michael J. 2006. Population Distribution and Abundance of Antelope Ground Squirrels (Ammospermophilus leucurus) and Mohave Ground Squirrels (Spermophilus mohavensis), in the Western Mojave Desert, Spring 2006. 10 pp. + appendix.

Vanherweg, William J. 2000. Mohave ground squirrel study at the new OB/OD site, Edwards Air Force Base, California. 7 pp.


THE USE OF SCIENCE-BASED LITERATURE FOR PREDATOR CONTROL TO ENHANCE BIGHORN SHEEP, MULE DEER AND PRONGHORN IN NEVADAJIM D. YOAKUM, Western Wildlife, Post Office Box 369, Verdi, Nevada 89439-0369, USAABSTRACT: A bill was introduced in the Nevada Legislature during 2007 to consider increasing finances for the predator control program to enhance wild ungulate populations and other wildlife. The Assembly bill evoked much public interest, however, technical based information relative to predator-prey relations was not readily available. Consequently, conservation organizations requested a concise but comprehensive review of science-based literature regarding the influence of predator control programs on bighorn sheep (Ovis canadensis), mule deer (Odocoileus hemionus), and pronghorn (Antilocapra americana) in Nevada and adjacent states. Therefore, this report was accomplished documenting more than 50 technical publications of predation relations with large native wild ungulates. Case histories, findings, and management strategies were provided for predator control programs to enhance large wild ungulates.


Key Words: Bighorn sheep, bobcat, coyote, cougar, golden eagle, mule deer, Nevada, political services, predator control programs, pronghorn, science-based wildlife management literature.

INTrodUCTIoNPublic interest regarding predator relations to big

game in Nevada increased during 2007. For example, 8 articles were published in the Reno Gazette-Journal newspaper (Rice 2006, 2007a, 2007b, 2007c, 2007d, Lent 2007, Heath 2007, and Molde 2007). Also, the Nevada Bighorns Unlimited News printed a lengthy article regarding the objectives and results of various predator control programs (Mason 2007). The state legislature became involved with Assembly Bill Number 259 that proposed major changes in the management of cougars (Felis concolor), and increased funds for lethal control of predators (Nevada Legislature 2007).

With the above events, there was an accelerated demand by the public for sound wildlife management information. Therefore the objectives of this paper are: (1) to provide a concise review of science-based publications regarding the effects of predators on wild ungulates, (2) to assess the results of recent predator control strategies to enhance wild ungulates in Nevada, and (3) to make these findings readily available to conservation organizations and other interested sources.

SCIENCE IN wIldlIFE MaNaGEMENT TodaYModern “wildlife management” has been hailed as

a major conservation endeavor for the enhancement of natural resources in North America. In their book Return of Royalty: Wild Sheep of North America, Toweill and Geist (1999) traced the history of this success to U.S. President Theodore Roosevelt’s leadership some 100 years ago. While president, he gave a unique twist to the North American philosophy of wildlife conservation, one that bears his name to date: The Roosevelt Doctrine. This Doctrine proclaimed that the management of

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wildlife was to be based on the best science available. Information in this article emphasizes science-based studies because these findings remain the foundation for applying wildlife management strategies today (Sinclair 1999).

CaSE HISTorIESNumerous publications have reported the influences

of predators on large wild ungulates. These documents will be reviewed for pronghorn (Antilocapra americana), mule deer (Odocoileus hemionus), and bighorn sheep (Ovis canadensis).

Pronghorn antelopeMore than 30 studies during the past 60 years have

evaluated the effects of predators on pronghorn in Canada, Mexico and the United States (O’Gara and Shaw 2004, Yoakum et al. 2004). These investigations substantiated that adult pronghorn were seldom victims of predation as they have the ability to outrun predators. However, fawns less than 3 months old were frequent prey for golden eagles (Aquila chrysaetos), bobcats (Lynx rufus), and especially coyotes (Canis latrans). Within the last decade, cougars (Felis concolor) have been added to the list of minor predators (Yoakum et al. 2004). These studies verified that predators frequently kill small fawns, but none reported predator control practices to increase fawn recruitment resulted in increased wild free-roaming pronghorn numbers (Yoakum et al. 2004). The following long-term investigation supports this assessment.

Hart Mountain National Antelope Refuge (HMNAR) The HMNAR is located in Oregon within sight of

the Nevada northwestern border. During severe winters,

pronghorn travel from Hart Mountain to crucial habitats in Nevada. A decade ago it was assumed predators were responsible for low fawn recruitment and thus limiting population numbers on the HMNAR (Greg et al. 2001).

To clarify the influences of predators on fawns, the U.S. Fish and Wildlife Service initiated a field study at the HNNAR in 1996 (Dunbar and Valarde 1998, Greg et al. 2001). New-born fawns were caught, instrumented with radio mortality transmitters and released for 3 months of continuous monitoring. This project was the only long-term (more than 10 consecutive years) instrumented fawn mortality research project conducted for free-living native pronghorn in western North America. Results indicated that neonate mortality rates from predation ranged from some 10 to 90 percent; however, the average loss to predation per annum was close to 50 percent (Yoakum et al. 2004). This mortality rate appeared high, but pronghorn females generally produce 2 fawns per year; a higher rate than generally needed to maintain adequate fawn recruitment for population numbers (O’Gara 2004). The major finding for this HMNAR study was that a 10-year average of 50 percent loss annually was attributed to predation; however, population numbers almost doubled during the investigation. Evidently, high predation losses were not sufficient to limit pronghorn population increases for this study. This 10-year research study alluded to the ascertainment that vegetation conditions were relatively healthy; thus the herd increased in spite of the lack of a predator control program (Yoakum et al. 2004). Similar long-term studies are needed for other pronghorn habitats.

Additional Pronghorn StudiesHess (1986) analyzed 38 years of fawn survival

data for the interstate region of California, Nevada and Oregon. He concluded “Fawn predation, starvation, abandonment, and weak fawn syndrome are symptoms of DD (density dependence) in the Great Basin, not causes of low fawn survival. With the pronghorn population >4X that of the 1950s, it is questionable if fawn predation is a real biological problem.” These findings were supported by a 2-year research project conducted on the Sheldon National Wildlife Refuge, Nevada (McNay 1980). The study was designed to determine the cause of low fawn recruitment. Results indicated vegetation condition and not predation was the predominant factor influencing fawn survival. More recently in 2002, the Nevada Department of Wildlife reported that their limited coyote control program had no discernable benefit for pronghorn fawn:doe ratios (Hack and Menzel 2002).

The Pronghorn Management Guides (Autenrieth et al. 2006) provide a compilation of ecological and

management findings for Canada, Mexico, and the United States. The Guides were produced during the last 30 years by representatives from state/provincial and federal government agencies, universities, wildlife consultants, conservation organizations, and interested persons. Regarding the interactions of pronghorn and predators, it was recognized that predators could be deleterious to wild free-living pronghorn herds when pronghorn numbers were low and predator numbers were high. Although pronghorn were subject to predation annually, it was generally not a factor limiting herd numbers. Rather, habitat conditions were reported as the major agent.

An additional benefit of conducting lengthy quantitative studies of predation on pronghorn was experience gained regarding how to effectively determine whether a carcass was possibly killed by a predator or died from other causes and later scavenged by predators (Fig. 1). Guides for such diagnostic procedures are now available (O’Gara 1978, O’Gara and Shaw 2004).

Mule deerSome 50 years ago, the Nevada Legislature

employed professor Starker Leopold from the University of California, Berkeley, to evaluate mule deer issues in Nevada (Leopold 1959). Leopold concluded that forage conditions in general were not in quality condition and were responsible for limited deer numbers. Predators were not identified as a major mortality problem. Leopold and colleagues conducted other investigations of mule deer for interstate herds between Nevada and California (Longhurst et al. 1952). They concluded that nutrition intake of deer during critical seasons determined productivity and mortality. Starker Leopold concluded “Putting all this in much simpler form, good forage ranges generally have many deer; poor ranges have few. All other influences are secondary” (Leopold 1966:57).

More recently, the Nevada Department of Wildlife published Biological Bulletin number 14 regarding current trends in mule deer populations (Wasley 2004). The report states “There is no question that coyotes eat fawns. However, if coyote predation of fawns were limiting mule deer populations, fawn ratio data and coyote harvest data should display some type of cause and effect relationship. Although a general trend consistent with this hypothesis exists for a period, data fail to substantiate the hypothesis, especially over the last 10 years” (Wasley 2004:27).

Another comprehensive report regarding the influences of predation on mule deer was completed in 2003 by a team of wildlife biologists for western state wildlife agencies (Ballard et al 2003). Their findings stated that while predation occurred in all mule deer

TRANS.WEST.SECT.WILDL.SOC. 44:2008 Use of Science Based Literature for Predator Control ● Yoakum 31

populations, in most cases, predation had little impact on population. The importance of predation depended on the relation of deer herds to habitat carrying capacities. When deer populations were low and habitat conditions were poor, predation could limit population growth. Wildlife management agencies were often asked to implement predator reduction programs. To be effective, these programs needed to be well planned and implemented only when predation had been documented as the factor suppressing the mule deer population. The authors concluded most mule deer and predator studies were short-term (3 years), conducted in relatively small areas, and few actually demonstrated increased fawn recruitment resulting in subsequent larger harvests by humans. Also, conditions that led to a particular deer population being limited by predation were poorly documented. In addition, the authors reported that a recent survey of state/provincial wildlife agencies found few agencies had predator control programs to benefit ungulate populations.

Predation studies using radio telemetry to document mule deer neonate mortality have been limited (Linnel et al. 1995, Ballard et al. 2003). One in Colorado stated the primary reason why some western states have lost half their peak mule deer populations during the past 2 decades was because mule deer were suffering from poor nutrition and disease created by deteriorating forage quality (Saile 2000). While predation and other factors contribute to mule deer decline, their effects are less than those of deficient and poor quality forage. “Coyotes are often portrayed as muley killers. But in a recent study of fawn mortality in Colorado, state researchers found that only 21 percent of fawn deaths could be linked to coyotes, and in some cases, the carcass-feeding may have occurred after the fawn died” (Saile 2000:12).

Persons interested in other reports pertaining to mule deer production and mortality may find a wealth of information in the following literature: Hornocker (1970), Tueller and Monroe (1976), Connolly (1978), Salwasser et al. (1978), Smith and LeCount (1979),

Figure 1. Pictured here is an adult pronghorn carcass found on the Hart Mountain National Antelope Refuge in Or-egon. An autopsy disclosed the animal had apparently not been killed by predators but died of other causes. Evidently a bobcat found the carcass, consumed parts, and then attempted to bury with surrounding vegetation. Bobcats charac-teristically cover their food cache as an attempt to conceal the carcass from other predators or scavengers. (Photo by Jim D. Yoakum, Verdi, Nevada).

32 Use of Science Based Literature for Predator Control ● Yoakum TRANS.WEST.SECT.WILDL.SOC. 44:2008

Connolly (1981), Walimo (1981), Russo (1984), Gruell (1986), Skogland (1991), Clements and Young (1997), Salle (2000), Spalinger (2000), Ballard et al. (2001) and (2003).

Bighorn SheepThe Desert Bighorn Council published recommended

management guides for bighorn sheep occupying arid habitats (Wilson et al. 1980). Regarding predation, early reports verified predation by coyotes, bobcats, golden eagles, and cougars, but predation was not deemed a limiting factor for free-living bighorn populations having adequate cover (Blaisdell 1961. Elliot 1961, Jantzen 1961, Weaver 1961). The qualifier “free-living” is inserted here for certain bighorn transplants during the 1950s-1960s placed transit animals in small fenced enclosures. Such enclosures on the HMNAR in Oregon and the Sheldon National Wildlife Refuge in Nevada were successful, however, the site near Hawthorne, Nevada experienced major mortality problems as it apparently had been constructed in a cougar travel corridor.

Compared to pronghorn or mule deer, few instrument monitoring studies of neonatal mortality were conducted for bighorn on deserts, and these studies

were with low numbers of lambs (Linnell et al. 1995). More recently, cougars in various southwestern states have been implicated as major predators on recently translocated bighorn (Ernest et al. 2002, Kamler et al. 2002, Rominger et al. 2005) (see Table 1). These studies used telemetry to monitor released animals. When bighorn losses to cougars were verified, management commenced removal of mountain lions until the herd had grown large enough to sustain predation (Kamler et al. 2002).

During 1999, a 4-day meeting was conducted in Reno, Nevada for the Second North American Wild Sheep Conference with attending representatives from the Northern Wild Sheep and Goat Council (Alaska, Canada and northwestern United States), and the Desert Bighorn Council (Mexico and southwestern United States). These international wild sheep groups meet periodically to report ecological and management strategies. A subsequent 470 page report for the Conference documented technical papers presented and business meeting accomplishments (Thomas and Thomas 2000).

A major section of the conference transactions reported on management practices conducted to enhance wild sheep by state agencies in the United States.

State Wildlife Agency Rocky Mt. Bighorn California Bighorn Desert Bighorn

Arizona No No

California No No

Colorado No No

Idaho No No

Montana No

Nebraska No

New Mexico Yes** Yes**

Nevada No No No

Oregon No No

South Dakota No

Texas Yes** Yes**

Utah Yes** No Yes**

Washington No No

Wyoming No

** Denotes cougars killed bighorns, and that permits were issued to hunt cougars in area.

Table 1. Results of questionnaire survey to state wildlife agencies reported in the 2nd North American Wild Sheep Conference Transactions (Thomas and Thomas 2000). These responses were to the question: Did you use predator control to benefit bighorn?


Table 1 provides a review of findings regarding the use of predator control programs reported to benefit bighorn (generally cooperative control programs with Animal Damage Control or Animal and Plant Health Inspection Services in the federal government). From these findings, it appeared that (1) predator control practices to benefit wild sheep were not a major management activity, (2) most wildlife programs that used predator control were southwestern States where ecological carrying capacities were inherently low, and (3) successful predator control programs were conducted after documentation that cougars were killing bighorns following translocation projects. A review of papers in the Desert Bighorn Council Transactions since 2000 indicated predator control programs were being used prior to, during, and immediately following translocation endeavors. Apparently predator control programs for bighorn enhancement were most frequently implemented where low bighorn numbers existed following translocation projects.

THE lEoPold aNd oTHEr rEPorTS oN PrEdaTor CoNTrol

During 1963, a panel of senior wildlife biologists reviewed the objectives and effectiveness of the Predator and Rodent Control Branch of the U.S. Fish and Wildlife Service (Leopold 1964). The panel charged the predator controllers with catering to the livestock industry, ignoring science, and wasting taxpayer’s dollars by unnecessarily killing thousands of wildlife. The committee concluded: “It is the unanimous opinion of this Board that control as actually practiced today is considerably in excess of the amount that can be justified in terms of total public interest” (Leopold 1964:29).

The 1964 report was one of the first published review and evaluation of United States federal government wildlife control programs. Since then, 3 more reports have been accomplished to assess the values, procedures, expenditures, and results of predator control on wildlife (Cain et al. 1972, Phillips and Jonkel 1975, and U.S. Fish and Wildlife Service 1978). The 2007 North American Wildlife and Natural Resource Conference conducted an all day workshop pertaining to “Predators and Prey”, and plan to publish a compendium of technical papers presented.

CoNClUSIoNS aNd SUMMarYDuring 2007, much interest and activity emerged

regarding the justification, procedures, results, and values of predator control programs to enhance wild ungulates in Nevada. However, conservation organizations noted the paucity of science-based literature to inform

the public of effective practices facing predator/prey management strategies. This resulted in the assessment of more than 50 publications that contributed to the following findings and conclusions:

1. Wild predators have preyed on native large ungulates for centuries, and this will continue for centuries to come, for this is a natural phenomena of ecological carrying capacities.

2. Predator relations to wild prey and effective predator damage control programs for enhancing wildlife are highly controversial management concepts in North America. Apparently reasons for some of these controversial attitudes include lack of field training and experience to justify predator control programs for enhancing wildlife species based on best science-based data by some wildlife biologists and managers. Also, certain hunters, political delegates, conservationists and other public interest sources at times lack technical training in science-based programs, and mix personal opinion with science findings--matters that may not contribute to effective wildlife management goals.

3. Predator control programs are generally under the administration of state and federal wildlife management agencies today. Before wildlife damage control programs are undertaken, careful assessment should be made of the problem, a management plan developed, and assurance provided that the control technique(s) to be used will be effective and biologically and socially appropriate.

4. The majority of science-based publications within the last 25 years have indicated that wildlife predation generally had not been and were not now the limiting factor controlling most free-living ungulate populations.

5. These publications have provided data indicating that the primary factor limiting populations of bighorn, mule deer and pronghorn were the quality and quantity of forage and survival vegetation cover conditions. All other factors were generally secondary.

6. These reports support the contention that one of the most effective expenditure of current public wildlife management funds should generally be to improve vegetation conditions for forage and security cover instead of predator control.

aCkNowlEdGMENTSThe services of Fred Wright, Dave Rice, Don

Klebenow, Steve Kohlmann, Marsall White and Reg Barrett are greatly appreciated for reviewing early drafts of this report.


lITEraTUrE CITEdAutenrieth, RE., D.E. Brown, J. Cancino, R.M. Lee,

R.A. Ockenfels, T.M. Pojar, and J.D. Yoakum. Compilers. 2006. Pronghorn management guides. Pronghorn Workshop and North Dakota Game and Fish Department. Bismarck, North Dakota, USA.

Ballard, W.B., D. Lutz, T.W. Keegan, L.H. Carpenter, and J.C. deVos, Jr. 2001. Deer-predator relationships: A review of recent North American studies with emphasis on mule and black-tailed deer. Wildlife Society Bulletin 29:99-115.

Ballard, W.B., T.W. Keegan, D. Lutz, L.H. Carpenter, and J.C. deVos, Jr. 2003. Deer-predator relationships. Pp. 177-218 in J.C. deVos, M.R. Conover, and N.E. Headrick. Mule deer conservation: Issues and management strategies. Western Association of Fish and Game Wildlife Agencies and Jack H. Berryinan Institute, Logan, Utah, USA.

Blaisdell, J.A. 1961. Bighorn-cougar relationships. Transactions Desert Bighorn Council 5:42-46.

Cain, S.A., J.A. Kadlec, D.L. Allen, R.A. Cooley, N.G. Hornocker, A.S. Leopold, and F.H. Wagner. 1972. Predator control-l97l. Institute for Environmental Quality, University of Michigan, Ann Arbor, Michigan, USA.

Clements, C.D. and J.A. Young. 1997. A viewpoint: Rangeland health and mule deer habitat. Journal of Range Management 50:129-138.

Connolly, G.E. 1978. Predators and predator control. Pp. 369-394 in J.L. Schmidt and D.L. Gilbert, editors. Big game of North America. Stackpole Books, Harrisburg, Pennsylvania, USA.

_____ 1981. Limiting factors and population regulation. Pp. 245-285 in O.C. Wallmo, editor. Mule and black-tailed deer of North America. University of Nebraska, Lincoln, Nebraska, USA.

Dunbar, M.R. and R. Velarde. 1998. Health evaluation of pronghorn (Antilocapra americana) on Hart Mountain National Antelope Refuge in southeastern Oregon: 1996-1997. National Wildlife Health Center technical report 98-01. U.S. Geological Survey, Madison, Wisconsin, Wisconsin, USA.

Elliot, H.N. 1961. Bobcats and bighorn sheep. Transactions Desert Bighorn Council 5:38-41.

Ernest, H., E. Rubin, and W. Boyce. 2002. Fecal DNA analysis and risk assessment of mountain lion predation on bighorn sheep. Journal of Wildlife Management 66(l):75-85.

Gregg, M.A., M. Bray, K.M. Kilbride, and M.R. Dunbar. 2001. Birth synchrony and survival of pronghorn fawns. Journal of Wildlife Management 65(1):19-24.

Gruell, G.E. 1986. Post-1900 irruptions in the Intermountain West: Principal cause and influence. General Technical Report INT-206, United States Department Agriculture, Forest Service, Ogden, Utah, USA.

Hack, M.A. and K. Menzel. 2002. Pronghorn state and province status reports: 2001. Proceedings Pronghorn Workshop 20:6-16.

Heath, R. 2007. Predator control column omitted results of studies. Letters to the Editor 11C, Reno Gazette-Journal Newspaper, Reno, Nevada, USA. April 14, 2007.

Hess, M.L. 1986. Density dependent summer pronghorn fawn survival ratios in the interstate antelope population. Proceedings Pronghorn Antelope Workshop 12:53-54.

Hornocker, M.G. 1970. An analysis of mountain lion predation upon mule deer and elk in the Idaho Primitive Area. Wildlife Monographs Number 21: 29 pages.

Jantzen, R.A. 1961. Bighorns and golden eagles. Transactions Desert Bighorn Council 5:47-50.

Kamler, J.R., R.M. Lee, J.D. deVos, Jr., W.D. Ballard, and H.A. Whitlaw. 2002. Survival and cougar predation of translocated bighorn sheep in Arizona. Journal of Wildlife Management 66:1267-1272.

Lent, G.A. 2007. Managing predators is based on science. Opinion 9a, Reno Gazette-Journal Newspaper, Reno, Nevada, USA. February 23, 2007.

Leopold. A.S. 1959. Big game management. Pages 85-99 in Nevada Legislative Council Bureau. Survey of fish and game problems in Nevada. Bulletin number 36, Nevada Legislature, Carson City, Nevada, USA.

_____ 1964. Predator and rodent control in the United States. Transactions North American Wildlife and Natural Resources Conference 29: 27-49.

______. 1966. Adaptability of animals to habitat changes. Pp. 66-75 in F.F. Darling and J.P. Milton, editors. Future environments of North America. Doubleday and Company, New York, New York, USA.

Linnell, J.D.C., R. Annes, and R. Anderson. 1995. Who killed Bambi? The role of predation in the neonatal mortality of temperate ungulates. Wildlife Biology 1(4):209-223.

Longhurst, W.M., A.S. Leopold, and R.F. Dasmann. 1952. A survey of California deer herds: Their ranges and management problems. Game Bulletin number 4, California Department of Fish and Game, Sacramento, California, USA.

Molde, D. 2007. Predators haven’t been given a pass. Letters to the editor l3E, Reno Gazette-Journal Newspaper, Reno, Nevada, USA, April 23, 2007.


Mason, R. 2007. Predation management. Nevada Bighorns Unlimited News 22(1):6-7, 19.

McNay, N.E. 1980. Causes of low pronghorn fawn/doe ratios on the Sheldon National Wildlife Refuge, Nevada. Thesis, University of Montana, Missoula, Montana, USA.

Nevada Legislature. 2007. AN ACT relating to wildlife, classifying a wild mountain lion as an unprotected mammal; designating the Department of Wildlife as the Department of Fish and Game; placing the Department under the control of the Board of Wildlife Commissioners; authorizing the Commission to adopt regulations for the hunting, killing, or nonlethal control of mountain lions from an aircraft; revising certain provisions relating to the use of a spring gun, set gun or other device for the destruction of a mountain lion; making an appropriation; and providing other matters properly relating thereto. Assembly Bill number 259 entered March 7, 2007, Nevada Legislature, Carson City, Nevada, USA.

O’Gara, B.W. 1978. Differential characteristics of predator kills. Proceedings Pronghorn Antelope Workshop 8:380-393.

_____ 2004. Reproduction. Pp. 275-298 in B.W. O’Gara and J.D. Yoakum. Pronghorn: Ecology and management. University Press Colorado, Boulder City, Colorado, USA.

O’Gara, B.W. and H.A. Shaw. 2004. Predation. Pp. 337-378 in B.W. O’Gara and J.D. Yoakum. Pronghorn: Ecology and management. University Press Colorado, Boulder, Colorado, USA.

Phillips, R.L. and C. Jonkel, editors. 1975. Proceedings of the 1975 predator symposium. Montana Forest and Conservation Experiment Station, Missoula, Montana, USA.

Rice, D. 2006. Predators good for healthy wildlife populations Sports Section D2, Reno Gazette-Journal Newspaper, Reno, Nevada, USA. November 24, 2006.

_____. 2007a. Killing natural predators does little good. Sports Section D2, Reno Gazette-Journal Newspaper, Reno, Nevada, USA. February 9, 2007.

_____. 2007b. Predator—control debate based on many complex factors. Reno Gazette-Journal Newspaper, Reno, Nevada, USA. March 3, 2007.

_____. 2007c. The best protection is understanding social habits. Sports Section D2, Reno Gazette-Journal Newspaper, Reno, Nevada, USA. March 30, 2007.

_____. 2007d. Assembly bill to label lions as unprotected is all wrong. Sports Section D2, Reno Gazette-Journal Newspaper, Reno, Nevada, USA. April 6, 2007.

Roininger, E.M., F.S. Winslow, E.J. Goldstein, D.W. Weybright, and W.C. Dunn. 2005. Cascading effects of subsidized mountain lion populations in the Chihuahuan Desert. Transactions Desert Bighorn Council Conference 48:56-66.

Russo, J.P. 1984. The Kaibab north deer herd--its history, problems, and management. Bulletin number 7, Arizona Game and Fish Department, Phoenix, Arizona, USA.

Saile, B. 2000. Where have all the mule deer gone? Field and Stream, June, page 12.

Salwasser, H., S.A. Hall, and G.A. Ashcraft. 1978. Fawn production and survival in the North Kings River deer herd. California Fish and Game 64:38-52.

Sinclair, A.R.E. 1991. Science and practice of wildlife management. Journal of Wildlife Management 55:767-773.

Skogland, P. 1991. What are the effects of predators on large ungulate populations? Okikos 61:401-411.

Smith, N.S. and A. LeCount. 1979. Some factors affecting survival of desert mule deer fawns. Journal of Wildlife Management 43:657-665.

Spalinger, D.E. 2000. Nutritional ecology. Pp. 108-139 in S. Demariais and P.R. Krausman, editors. Ecology and management of large mammals in North America. Prentice Hall, Upper Saddle River, New Jersey, USA.

Thomas, A.E. and H.L. Thomas, editors. 2000. Transactions of the 2nd North American Wild Sheep Conference. April 6-9, 1999, Reno, Nevada, USA.

Toweill, D.E. and V. Geist. 1999. Return of royalty: Wild sheep in North America. Boone and Crockett Club and Foundation for North American Wild Sheep, Missoula, Montana, USA.

Tueller, P.T. and L.A. Monroe. 1976. Management guidelines for selected deer habitats in Nevada. Publication number R 104. Agriculture Experiment Station, University of Nevada, Reno, Nevada, USA.

U.S. Fish and Wildlife Service. 1978. Predator damage in the west: A study of coyote management alternatives. U.S. Fish and Wildlife Service, Washington D.C., USA.

Wallmo, O.C. 1981. Mule and black-tailed deer in North America. University Nebraska Press, Lincoln, Nebraska, USA,

Wilson, L.O., J. Blaisdell, G. Welsh, R. Weaver, R. Brigham, W. Kelly, J. Yoakum, M. Hinks, J. Turner, and J. DeForge. 1980. Desert bighorn habitat requirements and management recommendations. Transactions Desert Bighorn Council 23:1-7.

Yoakum, J.D., H.G. Shaw, T.M. Pojar, and R.H. Barrett. 2004. Pronghorn neonates, predators, and predator control. Proceedings Pronghorn Workshop 21:73-95.


BIRD USE OF LONE OAk TREES IN VINEYARD VS. SAVANNA IN CENTRAL-COASTAL CALIFORNIA OAk WOODLAND—A PILOT STUDY

JoSEPH MICHaEl and wIllIaM TIETJE, department of Environmental Science, Policy, and Management, University of California, Berkeley, Ca 94720

ABSTRACT: During the vineyard expansion on the California central and north coasts the past decade, many growers left individual trees within newly established vineyards. Recent research in several habitat types worldwide has documented the ecological contributions of lone or residual trees to habitat structure, connectivity, and aesthetics in the highly-modified landscape. During spring, 2008, we used point counts and behavioral observations to compare bird diversity and abundances from three replicate vineyards at 17 valley oak (Quercus lobata) trees within the vineyards vs. 17 valley oaks of similar size in adjacent oak savanna. Our measurements of bird species diversity and abundances were similar in both treatments, including on those of several insectivorous bird species potentially beneficial to growers. Several bird species, however, that may be sensitive to development were detected substantially more in savanna or were unique to savanna. To further evaluate the costs to the grower and the contribution to biodiversity of lone trees in the vineyard landscape, we are using the results of this pilot study to develop an expanded study, including more replication, a measure of bird reproductive fitness, experimental habitat enhancement, and cost-benefit analyses.


Key words: oak woodland, vineyard, Quercus spp., bird diversity, habitat management, pest management, agroecosystem.

37

INTrodUCTIoNAs the amount of woodland in California, and

elsewhere, is modified by land use, it becomes increasingly important to understand how biodiversity can be managed in agroecosystems. During the vineyard expansion on the central and north coasts during the last decade, many growers left individual oak trees (Quercus spp.) on the margins of vineyards and even within the planted vines. Today, these trees incur a cost to grape production and are perceived by many growers as encouraging vineyard pests. Without economic and ecologic valuing of these trees, they will decline and not be replaced. With value, growers will maintain the trees, with mostly unknown benefits to biodiversity and agriculture.

The ecological and aesthetic value of lone trees has been of increasing research interest the past decade. They have been implicated as keystone structures (sensu Manning et al. 2006) in otherwise impoverished landscapes. Several contributions to species diversity have been attributed to lone trees. They may function as foci of activity for several taxa of animals (Dean et al. 1999, Dunn 2000). The lone tree may also provide a link or connection between isolated woodland patches, thereby increasing landscape level connectivity as described by Hilty and Merenlender (2004) for riparian corridors in California oak woodland. Interestingly, bird diversity was correlated with the level of isolation in grass fields of Willamette Valley, Oregon, the most isolated oak trees harboring the most diversity (DeMars 2008).

Here we report the results of a spring 2008 pilot study on lone valley oak architectural attributes and breeding bird use of these oaks within three replicate vineyards in San Luis Obispo County, compared to the same measurements on valley oak trees of similar size and spacing in adjacent oak savanna. This pilot study was prompted by our desire to use the information to design a well-replicated and longer-term study with cost-benefit and experimental components. Our longer term objective is to provide growers and other land-use managers with information on the balancing of agricultural production with the maintenance of biodiversity.

STUdY arEaDuring April to June, 2008, we used GIS satellite

maps and field reconnaissance to select study trees within three vineyards and the adjacent oak savanna. The vineyards are located in north San Luis Obispo County near Templeton and Paso Robles, California, and a minimum of 10 km apart (Figure 1). The study sites comprised approximately 210 ha of planted vines and support facilities, and 129 ha of oak savanna. Topography in the vineyard-savanna mosaics varies from flat to gently rolling to fairly steep (<20%). The climate of the study sites is Mediterranean, characterized by cool, wet winters and warm, dry summers. Mean annual temperature is 15.3 C°. Total annual precipitation occurs mostly as rain between November and March and averages approximately 38 cm (66 year range = 11 to 74 cm. (Western Regional Climate Center 2001).

The predominant trees within vineyards are valley oak, with occasional to rare instances of coast live oak (Quercus agrifolia) and blue oak (Q. douglasii). These remnant oaks occupy circular areas approximately 30 m in diameter (approx. 0.07 ha) within the vines. Annual grasses and several species of forbs, including milkweed (Asclepias spp.), Italian thistle (Carduus pygnocephalus), and milk thistle (Silybum mariamum), are the only ground cover within these circular areas. Bare ground is common. Cover crops are planted and maintained in the vineyard rows. In the adjacent portions of oak savanna habitat, an overstory of valley oak dominates, with a small but consistent contribution of coast live oak and blue oak. Understory along these rolling savannas is an array of exotic annuals, including ripgut brome (Bromus diandrus), star-thistle (Centaurea spp.), and avena (Avena spp.). Ground cover beneath the canopies of savanna oaks is comprised of similar proportions of the same exotic species occurring beneath vineyard oaks, but generally of greater densities and with poison oak (Toxicodendron diversilobum) occasionally occurring under the canopy of an individual savanna tree.

METHodSHabitat Measurements

Because valley oak was the dominant species within and outside of vineyards, we selected only valley oaks for our study. Our criteria for selection of a study

tree follows: ≥50 m from the vineyard edge, ≥5m from a neighboring tree, ≥50 cm dbh, and ≥18 m tall. We measured both the distance from vineyard’s edge to the base of each sample tree, and the distance to the nearest neighboring tree using GIS maps. We measured dbh with a D-Tape and height using a clinometer. To assess the architecture of vineyard and savanna trees, we took the following measurements: Crown Diameter, the average of the maximum and minimum crown diameters projected on the ground; Crown Density, the percent of light blocked by branches, assessed ocularly following the method of Zarnoch et al. (2004); and Live Crown Ratio, the percentage of the tree height supporting live green foliage (e.g., 45 ft of foliage/60-ft tree = 75%), assessed ocularly. Finally, we counted all clumps of oak mistletoe (Phoradendron villosum), recorded all dead limbs ≥13 cm basal diameter and ≥0.7 m long that we calibrated with measurements of dead branches of similar size on the ground (Garrison et al. 2002), and counted nesting cavities ≥3 cm diameter using binoculars from three viewpoints around the oak.

Bird MeasurementsTo survey avian diversity and abundance, we counted

only individuals perched within the tree, or perched on the ground within the crown diameter. During official sunrise to ≤1100 and following the protocol of Ralph et al. (1995), we conducted five 10-minute point counts per study tree on five separate days, each at a location within 15 m of the trunk that afforded good visibility of the crown. If necessary, for ≤5 minutes after counts, we confirmed species identifications and the presence of active nests. We recorded the following indicators of breeding status: copulations, nest visits (cavity or cup), wing begging, parents feeding young, fledgling molt patterns, fecal sac removal, and nesting vocalizations. We did not conduct point counts on windy or rainy days, or when heavy fog interfered with visibility. We rotated count times among study trees to avoid the potential for declining bird detections during later morning hours.

Data AnalysesWe calculated means, ranges, 95% confidence

intervals (CI), and standard errors (SE) for tree size and selected architectural attributes (n=17 vineyard oaks and 17 savanna oaks), and bird species detections. We report the number of detections of birds from both vineyard and savanna trees as means of the total count of detections and as percentages of each sample. We also compared treatments by linear regression to determine if comparable numbers of cavity nesting species were using similar numbers of suitable cavities.

Figure 1 – Location of 3 study sites comprising approxi-mately 339 ha of vineyard (striped) and oak savanna (stippled) habitat, used to assess vegetative and avian diversity in northern San Luis Obispo County, Califor-nia, spring 2008. Study sites enlarged (not to scale) to illustrate shape and composition.

38 Bird Use of Lone Oak Trees ● Michael and Tietje TRANS.WEST.SECT.WILDL.SOC. 44:2008

rESUlTSLone Trees

Tree size and architecture were similar between vineyard and savanna trees, with a slight but consistent trend toward larger trees among savanna oaks. Savanna oaks also tended toward higher crown densities, higher live crown ratios, and fewer clumps of mistletoe, but the overlapping 95% CI’s indicate that these differences are not statistically significant (Figure 2).

BirdsLesser goldfinch (Carduelis psaltria), European

starling (Sturnis vulgaris), Bullock’s oriole (Icterus bullockii), and western bluebird (Sialia mexicana) were substantially more abundant in vineyard oaks than their savanna counterparts, while white-breasted nuthatch (Sitta carolinensis) and oak titmouse (Baeolophus inornatus) were notably more abundant in savanna trees (Figure 3). House finch (Carpodacus mexicanus) appeared on both sets of trees in similar proportions, and was detected in much higher numbers than any other species. House finch, lesser goldfinch, and European starling comprised 51.7% of vineyard detections, compared to 40.7% within savanna. White-breasted nuthatch and oak titmouse comprised a higher proportion of detections in the savanna (21.7%) compared to vineyard (9.4%) (Figure 3). Mean numbers of species, active nests, and active breeders were also similar (Table 1). Cavity nesters from both savanna and vineyard were detected in increasing numbers within those oaks with larger numbers of cavities (25 of 34 oak trees) (Figure 4).

Lark sparrow (Chondestes grammacus), lazuli bunting (Passerina amoena) American robin (Turdus migratorius), black-headed grosbeak (Pheucticus melanocephalus), Cooper’s hawk (Accipiter cooperii), and loggerhead shrike (Lanius ludovicianus) were unique to vineyard, whereas house sparrow (Passer domesticus), Lawrence’s goldfinch (Carduelis lawrencei), red-winged blackbird (Agelaius phoeniceus), spotted towhee (pipilo maculatus), western scrub-jay (Aphelocoma californica), western meadowlark (Sturnella neglecta), great-horned owl (Bubo virginianus), California quail (Callipepla californica), and Wilson’s Warbler (Wilsonia pusilla) were unique to savanna (Table 2).

Figure 2 – CI (95%) comparing selected valley oak ar-chitectural attributes on vineyard and oak savanna study sites. No characteristic’s mean was significantly differ-ent (P ≥0.05) based on our sampling.

Figure 3 – Percent of all detections for vineyard oaks (562) and savanna (466) oaks. Both treatments were sampled with equal effort (17 trees, 5 counts/tree). These 13 species comprise approximately 90% of the sample (927 of 1,028 detections), with each species represent-ing ≥1.5% of the total.

Figure 4 – Regression between the number of cavities counted and the number of cavity nesters detected per oak tree at 3 vineyard and 3 savanna sites in north San Luis Obispo County. Two data points are represented by points 1,0 and 1,3. Similar r² values indicate similar usage rates of cavities by cavity nesters on both treat-ments.

TRANS.WEST.SECT.WILDL.SOC. 44:2008 Bird Use of Lone Oak Trees ● Michael and Tietje 39

dISCUSSIoNOur data indicate that the composition and numbers

of bird species using isolated oak trees in our vineyard and oak savanna sites are comparable (respectively, 26 vineyard vs. 29 savanna species; 562 vs. 466 detections; 10 vs. 14 breeding species). Number of nesting cavities and breeding activity were also similar in vineyards and savanna. House finches were notably and similarly abundant in vineyard and in savanna and, although less abundant, we detected similar numbers of individuals in the two treatments for most bird species. However, not surprisingly, there are several notable differences that the data suggest. Four additional species not observed breeding in vineyards were observed breeding in savanna. Several species, most notably lesser goldfinch, European starling, Bullock’s oriole, and western bluebird showed a preference for vineyards, whereas white-breasted nuthatch and oak titmouse preferred savanna. These preliminary findings are in line with species preferences that studies have documented for the spectrum of undeveloped woodland, to semi-developed, to urbanized (Blair 1996, Bolger et al.1997). Overall, differences in bird responses between vineyard and savanna sites may result from factors other than trees per se, including the proximity to other vegetative characteristics, anthropogenic activities, and the behavioral inclinations of each species. These factors were not assessed in this pilot study.

European Starlings are closely associated with human habitations (Rising 2001) and specialize in ground foraging for insects that may be readily accessible on bare or only lightly vegetated vineyard soil (Purcell and Stephens 2006). We observed most communally nesting starlings at large decadent oaks with large numbers of cavities and sparse canopy foliage, suggesting that starlings may become more common in vineyards as the trees decline. House finches, western bluebirds, and lesser goldfinches similarly prefer widely spaced woodland edges over interior forest (Groth 2001). Western bluebirds readily

utilize nesting boxes in vineyards and savanna almost equally and successfully (Fiehler et al. 2006). Boxes were often in close proximity to oaks in our study vineyards, potentially accounting for higher detection rate of bluebirds in vineyards. Bullock’s orioles are leaf gleaning insectivores, and this should discount any concerns growers have over their presence. California quail, although not detected often in or under trees, were seen in substantial numbers along rows of vines. Cover provided by the vines may rival that of savanna in terms of what quail prefer. Our observations suggest that oak trees in vineyard or savanna with abundant grass and forb ground cover provided more detections of ground foragers such as western meadowlarks, red-winged blackbirds, western scrub-jays, mourning doves (Zenaida macroura), and California towhees (Pipilo crissalis). Oaks in vineyards with little to no ground cover harbored less avian diversity.

The birds that we recorded using vineyard trees occupy various foraging niches. Starlings forage for insects on the ground, woodpeckers and nuthatches probe the bark, Bullock’s orioles and others are foliage gleaners, and others, such as violet-green swallows (Tachycineta thalassina) sally for insects above the vines. Some birds eat grapes causing either pluck (removal of grapes) or peck (non grape removal) damage, the European starling and house finch being the primary culprits. For the grower, it may be a situation of “take the good with the bad”; surely, providing habitat for the more rare native birds provides some ecological and political values.

This study provides preliminary evidence that even the single, isolated oak tree in the vineyard can be a focus of bird diversity. Further quantification is needed if the trends indicated from this study are to be used for guidelines for the conservation of bird diversity in the agroecosystem. The study pointed out additional areas for study, such as cost-benefit analyses of the maintenance of lone trees; comparison of lone trees within the vines with those on the margin of the


──────────────────────────────────────────────────── Vineyard Savanna ─────────────── ───────────────Per Tree Measure Mean 95% CI Range Mean 95% CI Range────────────────────────────────────────────────────No. of species 8.1 0.9 4 - 12 7.5 1.3 3 - 11No. of detections 33.1 6.1 14 - 53 27.4 7.5 7 - 77No. of active nests 0.5 0.4 0 - 2 0.5 0.3 0 - 2No. of breeding species 1.4 0.5 0 - 3 1.2 0.5 0 - 3────────────────────────────────────────────────────

Table 1 ─ Numbers of species, detections, active nests, and breeding species in vineyard oaks vs. savanna oaks within 3 study sites in central-coastal California, spring 2008.

Species Mean SE Breeding Species Count Mean SE BreedingHouse Finch (Cardopacus mexicanus) 8.4 1.78 X House Finch 138 8.1 3.83 XLesser Goldfinch (Carduelis psaltria) 5.4 1.07 X White-breasted Nuthatch 61 3.6 0.88 XEuropean Starling (Sturnus vulgaris) 3.4 1.31 X Oak Titmouse 40 2.4 0.66 XBullock's Oriole (Icterus bullockii) 3.1 0.71 X Bullock's Oriole 31 1.8 0.49 XWhite-breasted Nuthatch (Sitta carolinensis) 1.9 0.66 X Lesser Goldfinch 29 1.7 0.63 XWestern Bluebird (Sialia mexicana) 1.8 0.6 X European Starling 23 1.4 0.53 XWestern kingbird (Tyrannus verticalis) 1.5 0.63 X Acorn Woodpecker 17 1.0 0.43Acorn Woodpecker (Melanerpes formicivorus) 1.5 0.38 X Western kingbird 16 0.9 0.44 XOak Titmouse (Baeolophus inornatus) 1.2 0.54 X Mourning Dove 16 0.9 0.76Ash-throated Flycatcher (Myiarchus cinerascens) 0.8 0.23 Western Bluebird 11 0.6 0.36 XMourning Dove (Zenaida macroura) 0.8 0.34

House Sparrow (Passer domesticus) * 11 0.6 0.65 X

Nuttall's Woodpecker (Picoides nuttallii) 0.6 0.44 X

Lawrence's Goldfinch (Carduelis lawrencei) * 10 0.6 0.44 X

Violet-green Swallow (Tachycineta thalassina) 0.6 0.37 Violet-green Swallow 9 0.5 0.26Northern Mockingbird (Mimus polyglottos) 0.4 0.26 Dark-eyed Junco 8 0.5 0.27 XCalifornia Towhee (Pipilo crissalis) 0.4 0.24 Ash-throated Flycatcher 6 0.4 0.15Lark Sparrow (Chondestes grammacus) * 0.4 0.19 California Towhee 6 0.4 0.26Steller's Jay (Cyanocitta stelleri) 0.2 0.24 Nuttall's Woodpecker 5 0.3 0.14 XDark-eyed Junco (Junco hyemalis) 0.2 0.13

Red-winged Blackbird (Agelaius phoeniceus) * 4 0.2 0.14

Lazuli Bunting (Passerina amoena) * 0.1 0.08

Bushtit (Psaltriparus minimus) 3 0.2 0.13

Anna's Hummingbird (Calypte anna) 0.1 0.08

Red-tailed Hawk (Buteo jamaicensis) 3 0.2 0.18 XSpotted Towhee (Pipilo maculatus) * 3 0.2 0.10Western Scrub-Jay (Aphelocoma californica) * 3 0.2 0.10

Northern Mockingbird 3 0.2 0.13

Steller's Jay 2 0.1 0.12Western Meadowlark (Sturnella neglecta) * 2 0.1 0.08

Anna's Hummingbird 2 0.1 0.08Great-horned Owl (Bubo virginianus) * 2 0.1 0.12 X

Total Count 562 Total Count 466

* Species unique to either vineyard or savanna with a total individual count (from 170 visits) greater than one.

Savanna OaksVineyard Oaks

2

7

7

6

4

3

13

11

10

30

25

25

21

14

2

Count

143

91

57

53

32

Table 2 – Species most abundant by landscape type (species included were those detected ≥2 times). We calculated total count as the number of individuals identified over all 170 visits to oak trees. Mean and standard error (SE) are based on the five visits to 17 oaks at each of the three vineyards and savannas. We counted 562 individuals in vineyard oaks and 466 individuals in savanna oaks. Specific breeding activity (X) included variables mentioned previously in the text.

TRANS.WEST.SECT.WILDL.SOC. 44:2008 Bird Use of Lone Oak Trees ● Michael and Tietje 41

vineyard, and with individual trees within the woodland (in addition to the savanna comparison done here); experimentation, perhaps by use of nest boxes or plantings; and the assessment of relative fitness of birds in all treatments. LeBuhn and Fenter (2008) recorded similar abundances of bumble bees (Bombus spp.)within vineyards and in the surrounding landscape. In like manner in our future study of lone trees, a possible covariate of value is arthropod abundances and richness on lone trees. Our longer-term goal is to provide the grower of grapes with some recommendations for optimizing diversity (of native birds) in the vineyard setting, that is, to help the grower maintain and even enhance biodiversity of wildlife while also conducting an economically profitable agricultural enterprise.

aCkNowlEdGMENTSWe thank the personnel at Mesa Vineyard

Management, and J. McCollough, and M. Wyss for allowing access for study purposes. In addition, we thank D. Merrill, K. Merrill, and G. Hibbits for their individual efforts and navigational assistance. For their support on all aspects of the study design, we thank C. DeMars, M. Bartsch, and J. Zingo. The study was funded by the UC Integrated Hardwood Range Management Program, UC Berkeley.

lITEraTUrE CITEdBlair, R.B. 1996. Land use and avian species diversity

along an urban gradient. Ecological Applications 6(2): 506-519.

Bolger, D.T., Scott, T.A, and Rotenberry, J.T. 1997. Breeding bird abundance in an urbanizing landscape in coastal southern California. Conservation Biology 11(2): 406-421.

Dean, W.R.J., S.J. Milton, F. Jeltsch. 1999. Large trees, fertile islands, and birds in arid savanna. Journal of Arid Environments 41: 61-78.

DeMars, C.A. 2008. Conserving avian diversity in agricultural systems: the role of isolated Oregon white oak legacy trees. Thesis, Oregon State University, Corvallis, USA. 123 p.

Dunn, R.R. 2000. Isolated trees as foci of diversity in active and fallow fields. Biological Conservation 95: 317-321.

Fiehler, C.M., W.D. Tietje, and W.R. Fields, W.R. 2006. Nesting success of western bluebirds (Sialia mexicana) using nest boxes in vineyard and oak-savannah habitats of California. The Wilson Journal of Ornithology 118(4): 552-557.

Garrison, B.A., R.L. Wachs, T.A. Giles, and M.L.

Triggs. 2002. Dead branches and other wildlife resources on California Black Oak (Quercus kelloggii). Pages 593-604 in W.F. Laudenslayer, Jr., P.J. Shea, B.E. Valentine, C.P. Weatherspoon, and T.E. Lisle, technical coordinators. Proceedings of the symposium on the ecology of dead wood in western forests. 2-4 November 1999; Reno, NV. Gen. Tech. Rep. PSW-GTR-181. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. 949 p.

Groth, J. 2001. Finches and allies. Pages 552-560 in The Sibley guide to bird life and behavior, C. Elphick, J.B. Dunning, Jr., and D.A. Sibley, editors. Alfred A. Knoph, New York, N.Y., USA. 588 p. + Index.

Hilty, J.A. and A.M. Merenlender. 2004. Use of riparian corridors and vineyards by mammalian predators in northern California. Conservation Biology 18(1): 126-135.

LeBuhn, G. and C. Fenter. 2008. Landscape context influences bumble bee communities in oak woodland habitats. Pages 301-306 in A. Merenlender, D. McCreary, and K. Purcell, technical editors. Proceedings of the sixth California oak symposium: today’s challenges, tomorrow’s opportunities. Gen. Tech. Rep. PSW-GTR-217. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 677 p.

Manning, A. D., J. Fischer, and D.B. Lindenmayer 2006. Scattered trees are keystone structures − implications for conservation. Biological Conservation 132: 311-321.

Purcell, K.L. and S.L. Stephens. 2006. Changing fire regimes and the avifauna of California oak woodlands. Studies in Avian Biology 30: 33-45.

Ralph, C.J., S. Droege, and J.R. Sauer. 1995. Managing and monitoring birds using point counts: standards and applications. Pages 161-181 in C.J. Ralph, J.R. Sauer, and S. Droege (technical editors). Monitoring bird populations by point counts. Gen. Tech. Rep. PSW-GTR-149. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. 187 p.

Rising, J.D. 2001. Starlings and mynas. Pages 475-477 in The Sibley guide to bird life and behavior, C. Elphick, J.B. Dunning, Jr., and D.A. Sibley, editors. Alfred A. Knoph, New York, N.Y., USA. 588 p. + Index.

Zarnoch, S.J., W.A. Bechold, and K.W. Stolte. 2004. Using crown condition variables as indicators of forest health. Canadian Journal of Forest Research 34: 1057-1070.



Year location

1954 ................................Davis, California 1955 ................................Fresno, California 1956 ................................Davis, California 1957 ................................San Luis Obispo, California 1958 ................................Davis, California 1959 ................................Fresno, California 1960 ................................Sacramento, California 1961 ................................Davis, California 1962 ................................San Jose, California 1963 ................................Sacramento, California 1964 ................................* 1965 ................................* 1966 ................................Reno, Nevada 1967 ................................Anaheim, California 1968 ................................Sacramento, California 1969 ................................Berkeley, California 1970 ................................Fresno, Califonria 1971 ................................Sacramento, California 1972 ................................San Luis Obispo, California 1973 ................................Lake Tahoe, Nevada 1974 ................................Monterey, California 1975 ................................Sacramento, California 1976 ................................Fresno, California 1977 ................................San Jose, California 1978 ................................Lake Tahoe, Nevada 1979 ................................Long Beach, California 1980 ................................Redding, California 1981 ................................San Luis Obispo, California 1982 ................................Reno, Nevada 1983 ................................Anaheim, California 1984 ................................Sacramento, California 1985 ................................Monterey, California 1986 ................................Sparks, Nevada 1987 ................................Fresno, California 1988 ................................Hilo, Hawaii 1989 ................................Redding, California 1990 ................................Sparks, Nevada 1991 ................................Sacramento, California 1992 ................................San Diego, California 1993 ................................Monterey, California 1994 ................................Maui, Hawaii

TRANS.WEST.SECT.WILDL.SOC. 44:2008 ANNUAL MEETING LOCATIONS 43

1995 ................................Rohnert Park, California 1996 ................................Sparks, Nevada 1997 ................................San Diego, California 1998 ...............................Sacramento, California 1999 ................................Monterey, California 2000 ................................Riverside, California 2001 ................................Sacramento, California 2002.................................Visalia, California 2003.................................Irvine, California 2004 ................................Rohnert Park, California 2005.................................Sacramento, California 2006.................................Sacramento, California 2007.................................Monterey, California 2008.................................Redding, California.

* Those individuals with information concerning the Western Section of the Wildlife Society meeting locations for 1964 and 1965 please contact the Transactions Editor.


Year location

44 ANNUAL MEETING LOCATIONS TRANS.WEST.SECT.WILDL.SOC. 44:2008

OUTSTANDING CONTRIbUTIONS TO WILDLIFE AWARD

Year Winner

1955 .......................................................................................................................... F.P. Cronemiller 1956 ................................................................................................................................Seth Gordon 1965 ....................................................................................... Raymond Dasmann, Eugene McAteer 1966 .......................................................................................................................J. Harold Severaid 1967 ............................................................................................................................ Walter Putnam 1968 ................................................................................................................................ Jim Yoakum 1969 ....................................................................................................................... William Dasmann 1970 ..............................................................................................................................Pauline Davis 1971 ............................................................................................................................... Gene Kridler 1972 .............................................................................................................................Howard Leach 1973 .................................................................................................................................... Unknown 1974 ..................................................................................................................... A. Starker Leopold 1975 ................................................................................................................................... Not Given 1976 .................................................................................................... Dan Anderson, Edwin Z’Berg 1977 .................................................................................................................................Peg Frankel 1978 ................................................................................................... Robert Nelson and Vern Smith

RAYMOND F. DASMANN CONSERVATIONIST OF PROFESSIONAL OF THE YEAR AWARD THE YEAR AWARD

Year Winner Year Winner

1979 ........................................... Robert Nelson 1979 ............................................. Vern Smith 1980 .......................................Eldridge G. Hunt 1980 ........................................Daniel Chapin 1981 ......................................... Richard Teague 1981 ................................Glenn W. Sudmeier 1982 ....................................William Longhurst 1982 ......................................... David Gaines 1983 ....................................Richard A. Weaver 1983 .......................Ray and Marion Conway 1984 ..................................................Not Given 1984 .............................................. Not Given 1985 .......................................Vernon C. Bleich 1985 .................................. William McIntyre 1986 .......................................... James Yoakum 1986 .........................................Marvin Wood 1987 .............................................James Jeffres 1987 .................................... Hank Doddridge 1988 ........................................David Woodside 1988 .........................................Kelvin Taketa 1989 ...................................Reginald H. Barrett 1989 ....................................William Grenfell 1990 ....Michael T. Chapel, Terry M. Mansfield 1990 ....................... Felix Smith, Dan Chapin 1991 ..................... William F. Laudenslayer, Jr. 1991 ..........................................Brian Walton 1992 .................................... Ronald D. Rempel 1992 ................................... Susan Baughman 1993 .................................. Gordon I. Gould, Jr. 1993 ........................................... Rick Hewett 1994 ............................................... John G. Kie 1994 ................... Fern Duvall, Gary Sprinkle 1995 ............................................. Larry Saslaw 1995 ........................ Amigos De Bolsa Chica 1996 ............................................. Don DeLong 1996 ........................................ Larry Johnson 1997 .........................................Walter Howard 1997 ....................................... John Anderson 1998...........................................Brad Valentine 1998 ..........................................Elsie Dupree 1999 ................................................ Ken Mayer 1999 ..................................... Stephen Geddes

TRANS.WEST.SECT.WILDL.SOC.44:2008 WESTERN SECTION TWS AWARDS 45

2000 ..................................... Richard Anderson 2000 . Center for Natural Lands Management 2001 ..................................................Ron Jurek 2001 ..................................... Daniel Williams 2002 ................................................Jon Hooper 2002 ....................................... John R. Mount 2003 .............................................. Jared Verner 2003 . Riparian Brush Rabbit Recovery Team 2004 ........... C. John Ralph, Robert C. Stebbins 2004 ......................... Desert Tortoise Council 2005..........................................Peter H. Bloom 2005....................................David F. DeSante 2006...................................Archie S. Mossman 2006...........California Waterfowl Association 2007......................................Daniel C. Pearson 2007............................Yolo Basin Foundation 2008........................................Dr. Bill Zelinski 2008................Conservation Biology Institute

RAYMOND F. DASMANN CONSERVATIONIST OF PROFESSIONAL OF THE YEAR AWARD THE YEAR AWARD

Year Winner Year Winner

JAMES D. YOAKUM AWARD FOR OUTSTANDING SERVICE

Year Winner

1998......................................................................Jim Yoakum 1999......................................................................... Bill Clark2000 ..................................................................Rick Williams2001.........................................................................Not Given2002.........................................................................Not Given2003.........................................................................Not Given2004.........................................................................Not Given2005...................................................................Brad Valentine2006.................................................................Michael Chapel2007..........................................................................Not Given2008............................................................................Marti Kie

46 WESTERN SECTION TWS AWARDS TRANS.WEST.SECT.WILDL.SOC.44:2008

TRANS.WEST.SECT.WILDL.SOC.44:2008 WESTERN SECTION TWS OFFICERS 47

OFF

ICER

S O

F TH

E W

ESTE

RN

SEC

TIO

N O

F TH

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LIFE

SO

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Year

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hapt

er R

eps t

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tive

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ion

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ncil

1954

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pold

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gor

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1956

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1957

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ann

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r, Jr

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elly

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each

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gor

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1958

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tler

H. L

each

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Ada

ms,

R. R

udd,

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each

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asm

ann

1959

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jers

man

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J. H

iehl

eA

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done

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Ada

ma,

H. L

each

, W. E

vans

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ann

1960

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ning

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ns, E

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ning

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1962

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ning

M. R

osen

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er, H

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l, A

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anc

W. L

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urst

1963

D. K

elle

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. Lea

chP.

Are

ndR

. Mal

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H. H

all,

A. Z

ajan

c, B

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lette

W. L

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1964

H. L

each

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egas

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rend

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hom

pson

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ng, E

. Sm

ithR

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l, D

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ntos

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W. L

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1965

L. H

endr

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P. A

rend

J. Yo

akum

F. K

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lJ.

Yoak

umB

. Bro

wni

ng, E

. Sm

ith,

R. M

all,

D. M

cInt

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J. Se

vera

id

1966

P. A

rend

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ning

E. D

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osen

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akum

E. S

mith

, R. H

ubba

rd, R

. Mal

l,D

. McI

ntos

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raid

1967

B. B

row

ning

S. H

arris

R. L

aurs

enJ.

Ber

nard

J. Yo

akum

J. C

owan

, R. H

ubba

rdJ.

Yoak

um

1968

S. H

arris

J. C

owan

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aurs

enJ.

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ston

J. Yo

akum

J. M

iner

, F. W

inte

r,E.

Dom

an, J

. Yoa

kum

J. Yo

akum

1969

J. C

owan

J. Yo

akum

J. K

eith

J. H

ewst

onJ.

Yoak

umE.

Dom

an, P

. Tue

ller,

D L

arso

nH

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ch

1970

J. Yo

akum

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M. W

hite

J. Sp

ruill

J. Yo

akum

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uelle

r, D

. Lar

sen

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each

1971

M. R

osen

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hite

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all

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ning

J. Yo

akum

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elvi

e, J.

Ski

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Hew

ston

, R. T

eagu

e, R

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s,D

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on, I

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1972

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on, R

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48 WESTERN SECTION TWS OFFICERS TRANS.WEST.SECT.WILDL.SOC.44:2008

OFF

ICER

S O

F TH

E W

ESTE

RN

SEC

TIO

N O

F TH

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WS

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ncil

1973

R. L

aurs

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gue

R. J

urek

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eer

J. Yo

akum

D. K

itche

n, R

. Wat

son,

J. L

ight

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ores

ter,

C. F

oshe

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LIFE

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ctSe

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50 WESTERN SECTION TWS OFFICERS TRANS.WEST.SECT.WILDL.SOC.44:2008

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iden

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iden

t/Pr

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Ele

ctSe

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Trea

sure

rN

ewsl

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rE

dito

rTr

ansa

ctio

nsE

dito

rC

hapt

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oE

xecu

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boa

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Sect

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Rep

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Cou

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N O

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tV

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Ele

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cret

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sure

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ewsl

ette

rE

dito

rTr

ansa

ctio

nsE

dito

rC

hapt

er R

eps t

oE

xecu

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boa

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ion

Rep

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Cou

ncil

2003

L. D

iller

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ull,

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een

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z,T.

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J. M

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a

INSTRUCTIONS FOR CONTRIBUTORS TO THETRANSACTIONS OF THE WESTERN SECTION OF THE WILDLIFE SOCIETY

General Policy: Original papers in the field of wildlife ecology and management, habitat management, conservation biology, and related natural resource topics are published in the Transactions of the Western Section of The Wildlife Society. All papers of interest to Western Section members will be considered for publication, regardless of whether the papers were presented at the annual meeting of the Western Section TWS. Pages charges will be charged for all pages for non-members of the Section. For members, pages exceeding 8 in published form will be charged to the author unless waived by the Editorial Committee.

Technical Papers and General Papers: Technical papers present and analyze data in a rigorous manner similar to ar-ticles in the Journal of Wildlife Management. Their format must follow the latest issue of Unified Manuscript Guidelines of the Wildlife Society Peer-Reviewed Publications (http://www.wildlife.org/publications/wild-70-01.guide_304%20320_ebook1.pdf). Papers that clearly make no attempt to fulfill these guidelines will be summarily rejected by the Editor and returned to the author without any further review. General papers include keynote addresses, review papers, policy papers, panel discussions, and other presentations. For general papers, the same guidelines should be followed but no abstract is required.

Copy: Type the manuscript double-spaced throughout with 1 1/2-inch margins all around on good quality paper 8 1/2 x 11 inches. Number pages in upper right-hand corner. Proceed from a clear statement of purpose through proce-dures, results, and discussion. Sequence of contents is: abstract, introduction, study area, methods, results, discussion, acknowledgments, literature cited, tables and figures. Type the author’s complete address on upper left-hand corner of first page. The author’s name and affiliation follows the title. Present address, if different, should be indicated in a footnote on the first page. Otherwise, avoid footnotes by incorporating such material in the text.

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Title: The title should be concise, descriptive, and not more than 10 words in length. Avoid scientific names in titles if possible.

Acknowledgments: Include acknowledgments as a separate section immediately preceding the Literature Cited sec-tion.

Scientific Names: Vernacular names of plants and animals are accompanied by appropriate scientific names based on the most current and generally accepted taxonomy the first time each species is mentioned in the abstract, and again the first time each is mentioned in the text.

Abstract: An abstract should accompany all technical papers. The abstract should be an informative digest of sig-nificant content. It should summarize specific findings, and not simply describe what was done. The abstract should stand alone as a brief statement of the conclusions of the paper.

Literature Citations: Literature citations are listed alphabetically by authors’ last names in the Literature Cited. Use initials only for given names of authors. Cite books as follows: authors, date, title, publisher, place and paging. Spe-cific page numbers must accompany direct quotes and paraphrased passages. When necessary it is permissible to cite unpublished reports. Include source, paging, kind of reproduction (type-written, mimeographed, or photocopied), and place where filed. DO NOT ABBREVIATE CITATIONS; SPELL OUT COMPLETELY (e.g., “Journal of Wildlife Management”, not “J. Wildl. Manage.”).

Tables: A good table should be understandable without references to the text. Long tables are rarely of general interest. Conversely, short lists, with pertinent comments, should be included in the text rather than as a separate table. Tables should be in MS Word format, using the MS Word “table function” (do not use “tabs” to separate columns). All tables should include a title, which should be in the first row of the table.

52 INSTRUCTIONS FOR CONTRIBUTORS TRANS.WEST.SECT.WILDL.SOC.44:2008

Illustrations: Illustrations should be suitable for photographic reproduction without retouching or redrawing. Illus-trations exceeding 7 x 10 inches are not acceptable. Line drawings or graphs should be in India ink on white drawing paper. All figures should be converted to a .jpeg format and submitted electronically, separately from manuscript. A resolution of 300 dpi is recommended to assure quality reproduction.

Submission procedure: Manuscripts can be submitted to the Transactions Editor at any time. HOWEVER, MANU-SCRIPTS MUST BE SUBMITTED BY 1 MAY OF A GIVEN YEAR TO ENSURE PUBLICATION IN THE VOLUME FOR THAT YEAR. Manuscripts submitted after 1 May will be reviewed, but may not be published until the following year. Electronic submissions are highly encouraged and preferred over paper copies. Electronic submissions must be of files in MS Word format with any tables imbedded in the text file. Figures may imbedded in the MS Word file, but must also be submitted separately. An electronic version of a cover letter introducing the paper must also be included with the electronic submission. Zipped files are advised when files exceed 1,000 kb. If submitting paper copies, please submit 3 copies of the text, tables, and figures along with a cover letter introducing the manuscript. Submit good quality photocopies of the figures; do not submit originals. Finalized versions of the manuscripts must be submitted as electronic versions once reviews are complete and your manuscript has been accepted. Please submit manuscripts to:

John Harris Transactions Editor Biology Department Mills College 5000 MacArthur Boulevard Oakland, CA 94613 For inquires: E-mail: [email protected] Phone: 510-430-2027 Fax: 510-430-3304

Editorial Policy: All manuscripts submitted for publication will be peer-reviewed by qualified referees. The Transac-tions Editor reserves final right to accept or reject manuscripts.

John Harris, Transactions Editor

TRANS.WEST.SECT.WILDL.SOC.44:2008 INSTRUCTIONS FOR CONTRIBUTORS 53

Transactions of the Western Section of The Wildlife Society TWS Transactions_low res.pdf · of the Transactions of the Western Section ... of The WesTern secTion of The Wildlife socieTy

Documents

Transactions of the Western Section of The Wildlife Society TWS Transactions_low res.pdf · of the Transactions of the Western Section ... of The WesTern secTion of The Wildlife socieTy