Robert A. Garrott

Analysis of wildlife radio-tracking data

Preliminaries. Design of Radio-Tracking Studies. Effects of Tagging on the Animal. Estimating Animal Locations. Designing and Testing Triangulation Systems. Simple Movements. Home Range Estimation. Habitat Analysis. Survival Rate Estimation. Population Estimation. Data Analysis System. Appendices. Each chapter includes references. Index.

Assessment Of Prey Vulnerability Through Analysis Of Wolf Movements And Kill Sites

Within predator-prey systems behavior can heavily influence spatial dynamics, and accordingly, the theoretical study of how spatial dynamics relate to stability within these systems has a rich history. However, our understanding of these behaviors in large mammalian systems is poorly developed. To address the relationship between predator selection patterns, prey density, and prey vulnerability, we quantified selection patterns for two fine-scale behaviors of a recovering wolf (Canis lupus) population in Yellowstone National Park, Wyoming, USA. Wolf spatial data were collected between November and May from 1998-1999 until 2001-2002. Over four winters, 244 aerial locations, 522 ground-based telemetry locations, 1287 km of movement data from snow tracking, and the locations of 279 wolf kill sites were recorded. There was evidence that elk (Cervus elaphus) and bison (Bison bison) densities had a weak effect on the sites where wolves traveled and made kills. Wolf movements showed a strong selection for geothermal areas, meadows, and areas near various types of habitat edges. Proximity to edge and habitat class also had a strong influence on the locations where elk were most vulnerable to predation. There was little evidence that wolf kill sites differed from the places where wolves traveled, indicating that elk vulnerability influenced where wolves selected to travel. Our results indicate that elk are more vulnerable to wolves under certain conditions and that wolves are capable of selecting for these conditions. As such, vulnerability plays a central role in predator-prey behavioral games and can potentially impact the systems to which they relate.

Prey Risk Allocation In A Grazing Ecosystem

Understanding the behaviorally mediated indirect effects of predators in ecosystems requires knowledge of predator-prey behavioral interactions. In predator-ungulate-plant systems, empirical research quantifying how predators affect ungulate group sizes and distribution, in the context of other influential variables, is particularly needed. The risk allocation hypothesis proposes that prey behavioral responses to predation risk depend on background frequencies of exposure to risk, and it can be used to make predictions about predator-ungulate-plant interactions. We determined non-predation variables that affect elk (Cervus elaphus) group sizes and distribution on a winter range in the Greater Yellowstone Ecosystem (GYE) using logistic and log-linear regression on surveys of 513 1-km2 areas conducted over two years. Employing model selection techniques, we evaluated risk allocation and other a priori hypotheses of elk group size and distributional responses to wolf (Canis lupus) predation risk while accounting for influential non-wolf-predation variables. We found little evidence that wolves affect elk group sizes, which were strongly influenced by habitat type and hunting by humans. Following predictions from the risk allocation hypothesis, wolves likely created a more dynamic elk distribution in areas that they frequently hunted, as elk tended to move following wolf encounters in those areas. This response should dilute elk foraging pressure on plant communities in areas where they are frequently hunted by wolves. We predict that this should decrease the spatial heterogeneity of elk impacts on grasslands in areas that wolves frequently hunt. We also predict that this should decrease browsing pressure on heavily browsed woody plant stands in certain areas, which is supported by recent research in the GYE.

Contrasting Effects of Wolves and Human Hunters on Elk Behavioral Responses to Predation Risk

Abstract Prey behavioral responses to predation risk in wolf–ungulate–plant systems are of interest to wildlife managers. Using Global Positioning System data collected from telemetry-collared elk (Cervus elaphus) and wolves (Canis lupus), we evaluated elk behavioral responses to spatial and temporal variation in wolf- and human-predation risk on a winter range in the Greater Yellowstone Area, USA. We found elk changed grouping patterns and increased movement rates as predation risk increased and that these behavioral changes were habitat dependent. Elk behavioral responses to wolf- and human-predation risk were similar; however, responses to human-predation risk were stronger than responses to wolf-predation risk. These results suggest that predation risk from wolves or human hunters may result in elk spending more time on private rangelands away from public-land winter ranges, which may exacerbate problems of landowner tolerance of elk on livestock pastures. However, increased movement and changing grouping patterns on winter ranges may also disperse elk grazing impacts and lessen elk impacts on any one area.

Opinion Projecting the effects of environmental change on Antarctic seals

Abstract We consider how Antarctic seals may respond to changes in climate, realizing that anthropogenic alteration of food webs will influence these responses. The species considered include the ice-obligate - crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii), Ross (Ommataphoca rossii) and leopard (Hydrurga leptonyx) seal - and the ice-tolerant Antarctic fur seal (Arctocephalus gazella) and southern elephant seal (Mirounga leonina). The data analysed are from long-term censuses of Weddell seals in McMurdo Sound (1997–2006), and of Weddell, fur and elephant seals at Arthur Harbour, Antarctic Peninsula (1974–2005). After considering their responses to recent changes in environmental features, as well as projected and current changes to their habitat our conclusions are that the distribution and abundance of 1) crabeater and Weddell seals will be negatively affected by changes in the extent, persistence and type of annual sea ice, 2) Ross and leopard seal will be the least negatively influenced by changes in pack ice characteristics, although, as may be the case for crabeater and Weddell, population size and distribution may be altered through changes in food web dynamics, and 3) southern elephant and fur seals will respond in ways opposite to the pack ice species, but could also be influenced most immediately by changes in their food resources due to factors other than climate.

Survival of mule deer in Northwest Colorado

Survival of mule deer (Odocoileus hemionus) in Piceance Basin, Colorado, was measured with radio telemetry for 3 years on 1 study area and 4 years on another. Survival rates for deer >6 months old were estimated for yearly intervals beginning 1 December. Male and female fawns had similar (P = 0.254) survival, as did adult and yearling females (P = 0.567). There were significant differences (P 6 months old, yearling female, and adult female mule deer; (2) identify the timing and causes of mortality for ach age class; and (3) use a Cox model analysis to test for relationships between fawn size and overwinter survival. Financial support was provided by the U.S. Dep. Energy Contract W-7405-ENG-36 to Los Alamos Natl. Lab. and DE-FG02-85ER60297 to Colorado State Univ. Supplemental funding was provided by Colo. Fed. Aid Wildl. Restor. Proj. FW 26P and Cathedral Bluffs Shale Oil Co. We thank D. A. Garrott, M. A. Sovada, and D. L. Weybright for field assistance and the Bur. Land Manage. and local ranchers for their coop ration. B. L. Dupire, J. E. Morris and many other Colo. Div. Wildl. personnel aided in innumerable ways. Special thanks to T. E. Hakonson during the formulation of this study and K. V. Bostick for administration and logistic expertise. We appreciate the cooperation of T. H. Pysto of Cathedral Bluffs Shale Oil Co. in facilitating access to the shale oil lease tract and in helping trap deer. Numerous individuals participated in the annual trapping sessions. D. J. Freddy, T. M. Pojar, and W. D. Snyder reviewed the manuscript.

Aerial mark-recapture estimates of confined mule deer in pinyon-juniper woodland

Counts from a helicopter of known numbers of marked (radio-collared) and reasonably well known numbers of unmarked mule deer (Odocoileus hemionus hemionus) in 4 58-70-ha pastures were used to calculate 114 Lincoln-Petersen estimates of population size. Three approaches to combine Lincoln-Petersen estimates were explored: simple arithmetic mean, median, and joint hypergeometric maximum likelihood. Compared to individual estimates, all 3 produced narrower confidence intervals and increased the percentage of confidence intervals that covered true population values. The median was least sensitive to outliers, but the joint hypergeometric maximum likelihood provided -40% smaller confidence intervals. About the same percentage of confidence intervals for all 3 estimators (64-73%) overlapped at least part of the ranges of true population size. For all 3 estimators, a large proportion (>45%) of a small population should be marked to obtain more reliable estimates and greatest confidence interval coverage. However, there is still high probability that mean population estimates will be low. J. WILDL. MANAGE. 51(1):41-46 Testing Petersens mark-recapture method (Petersen 1896, Lincoln 1930) using aerial sampling has received scant attention with regard to big game population estimates. Woolf (1973) used the technique to estimate size of a confined white-tailed deer (0. virginianus) population in Pennsylvania, and Rice and Harder (1977) initially evaluated the technique with known numbers of confined white-tailed deer in Ohio. To our knowledge, research to assess accuracy of the technique to estimate size of mule deer populations is lacking. During tests of aerial counting accuracy with mule deer in fenced enclosures (Bartmann et al. 1986), considerable numbers of unmarked deer were present along with radio-collared deer that were stocked, thus presenting a unique opportunity to test aerial mark-recapture estimation procedures. In the experimental protocol used in this study, animals are marked with radio collars so that the number of marked animals in an area can be determined with biotelemetry prior to an aerial survey. Since unmarked animals sighted during an aerial survey are not marked (radio-collared) for subsequent surveys, the Schnabel-Darroch multiple recapture protocol (Model M, of Otis et al. 1978) is not applicable for this situation. Rather, multiple applications of the Lincoln-Petersen estimator are computed where the initial marking (radio collaring) of animals constitutes the 1st sample, and the numbers of marked and unmarked animals counted during the aerial survey provide the 2nd sample. Each aerial survey then produces a new Lincoln-Petersen estimate. Our objective in this paper is to evaluate performance of 3 procedures (simple arithmetic mean, median, and joint hypergeometric maximum likelihood estimate) to combine repeated Lincoln-Petersen estimates using aerial markrecapture data where total numbers of deer were reasonably well known. This research was funded by Colo. Fed. Aid Wildl. Restor. Proj. FW 26P, and by the U.S. Dep. Energy, Contract W-4305-36 to Los Alamos Natl. Lab. and DE-FG02-85ER60297 to Colorado State Univ. We thank D. R. Anderson for critically reviewing the manuscript. STUDY AREA AND METHODS Four contiguous 58-70-ha pastures on pinyon pine (Pinus edulis)-Utah juniper (Juniperus osteosperma) winter range in Piceance Basin, northwestern Colorado, were stocked with a total of 48 mule deer in November and December 1983. Each deer was fitted with a radio transmitter mounted on a white collar 5.1 cm wide. Deer were not marked for individual identification during aerial surveys, as this was 1 Present address: Department of Fisheries and Wildlife, University of Minnesota, St. Paul, MN 55108.

Arctic fox home range characteristics in an oil-development area

Spring and summer home ranges and local movements of arctic foxes (Alopex lagopus) were studied from 1975 to 1977 at the Prudhoe Bay oil-development area in northern Alaska. Twenty-seven adult and 62 juvenile foxes were captured, marked, and released. Nine adults and 5 juveniles were equipped with radio collars and monitored during 1976 and 1977. Home range size was 20.8 +/- 12.5 (SD) km/sup 2/ for 4 adult foxes and 3.7 +/- 1.7 km/sup 2/ for 5 juveniles. Home range configuration was similar for all marked members of individual families. Adult foxes were nocturnal and territorial. Foxes used oil-development sites for feeding, resting, and denning. Use of these became more comon late in the rearing season, as juveniles became more mobile. A major fluctuation in the availability of natural foods did not appear to alter ues of developed areas by foxes. The number of juvenile foxes observed at Prudhoe Bay decreased from 1976 to 1977, but the decrease was less pronounced than in a nearby undisturbed area.

Northern Yellowstone elk after wolf restoration

Abstract We analyzed counts, vital rates, and limiting factors for northern Yellowstone elk (Cervus elaphus) before and after wolf (Canis lupus) restoration in 1995–1996 to evaluate predictions that elk numbers would move to a lower equilibrium point with corresponding density-related changes in vital rates. Elk counts decreased from approximately 17,000 in 1995 to 8,335 in 2004. Pregnancy rates for prime-age females (3–15 years) during 2000–2003 were high (0.90) and similar to those during 1950–1967 when elk density was 30% lower (5–9 elk/km2). The survival rate for prime-aged females was 0.85 (95% CI = 0.81–0.87) compared to 0.99 when harvests were low and wolves absent. The proportions of elk harvested each year increased as elk numbers decreased during 1990–2002 but departed from this anti-regulatory trend as permit levels were reduced in 2003–2004. Snow pack strongly influenced elk vulnerability to hunting by increasing migration to lower elevations. Thus, harvests removed a relatively constant proportion (27±5%) of animals that migrated out of the park each year, primarily prime-aged females with high reproductive value. Conservative estimates of wolf off-take (>1,000 elk) exceeded harvests by 2003, with wolves primarily selecting calves and older elk with lower reproductive value. Recruitment decreased as the ratio of wolves to elk increased, and wolves maintained high kill rates and rapid population growth despite a 50% decrease in elk counts. Elk numbers likely will continue to decrease until 1) levels of harvest and predation decrease sufficiently, 2) there is sufficient time for recruitment of calves to prime breeding age, and 3) there is a numerical response of wolves to fewer elk. We recommend that managers quickly adjust antlerless permit quotas to population size in a density-dependent manner so that harvests do not accelerate the decrease in elk numbers.

A Seventy-Year History of Trends in Yellowstone's Northern Elk Herd

Abstract We analyzed counts of northern Yellowstone elk (Cervus elaphus) in Yellowstone National Park, Wyoming, USA, over 70 years to evaluate the effects of changing management on population trends. Population reduction efforts and hunter harvests during 1932–1968 removed 71,330 elk and decreased estimated abundance from 16,000 to 6,000 elk. Abundance increased to approximately 17,000 elk (λ = 1.19) when removals ceased and harvests were very small during 1969–1975. Moderate to liberal hunter harvests of antlerless elk outside the Park during 1976–2004 removed a relatively consistent proportion (26 ± 0.1 [SD]%) of females that migrated outside the park, mostly from prime-age (3–15 yr) classes with high reproductive value. Substantial winterkill was infrequent (1989, 1997), but it significantly reduced calf survival when it occurred. Wolves (Canis lupus) were reintroduced in 1995–1996 and rapidly increased in abundance (λ = 1.23) and distribution. Estimated wolf kill of elk now exceeds hunter harvest, but has a smaller effect on population dynamics because wolves concentrate on calves and older females (>14 yr) with low reproductive value. During 1995–2004, estimated abundance decreased from 23,000 to 12,000 elk. The recent ratio of wolves to elk is relatively low compared to the estimated equilibrium ratio, suggesting that the wolf population may yet increase in the future. Thus, reduction of harvests of prime-aged female elk to decrease removals of animals with high reproductive value and increase adult female survival appears essential. We analyzed the relative impact of removals by hunters and by wolves using Fishers (1930) reproductive value and found that the impact of hunters is far more important than that by wolves, a finding of broad significance.