Christopher Servheen

Trophic relations of brown and black bears in several western North American Ecosystems

We examined the historical and current diets of brown bears (Ursus arctos) and black bears (U. americanus) in the Greater Yellowstone Ecosystem, Glacier National Park and immediately adjacent areas of national forests, Cabinet-Yaak mountains of northwestern Montana and northern Idaho, Blackfeet and Flathead Indian reservations east and south of Glacier National Park, the Kenai Peninsula of Alaska, and the southwestern states of Colorado, New Mexico, and Arizona. Dietary estimates are an essential first step in understanding variation in productivity and density of current populations and, therefore, predicting success of reintroduced populations. Hair or bone samples from 14 federal or state agencies, museums, and universities were examined via stable isotope analyses to quantify the importance of animal and plant resources to sympatric brown and black bears. Stable isotope analyses have numerous advantages over fecal analyses or direct observation because diets of (1) individuals and thereby specific age and sex classes within a population can be compared, and (2) long-dead bears can be compared to living bears to evaluate historical changes in ecosystems. Meat content of current brown bear diets, which varied extensively between individuals and age and sex classes in all populations, averaged 51 ± 19% (x ± SD) for subadult and adult males and females in the Greater Yellowstone Ecosystem and 11 ± 14% in Glacier National Park and Cabinet-Yaak mountains. Within these ecosystems, adult male brown bears were more carnivorous than any other age or sex class. Brown bears that used easily obtained, abundant meat sources had dietary meat contents generally ≥70%. The meat:plant ratios in the diets of historical Greater Yellowstone Ecosystem bears (1,000 YBP) and Glacier National Park bears (1908-18) were similar to ratios in current diets. Sympatric black bears in the Wyoming, Montana, and Idaho ecosystems had dietary meat:plant ratios that were not different from all brown bear age and sex classes, except adult males. Alaskan black bears made extensive use of salmon (Oncorhynchus spp.) when brown bears were rare (53 ± 28% of the diet), but did not use salmon when sympatric with abundant brown bears.

Temporal, Spatial, and Environmental Influences on the Demographics of Grizzly Bears in the Greater Yellowstone Ecosystem

Abstract ABSTRACT During the past 2 decades, the grizzly bear (Ursus arctos) population in the Greater Yellowstone Ecosystem (GYE) has increased in numbers and expanded in range. Understanding temporal, environmental, and spatial variables responsible for this change is useful in evaluating what likely influenced grizzly bear demographics in the GYE and where future management efforts might benefit conservation and management. We used recent data from radio-marked bears to estimate reproduction (1983–2002) and survival (1983–2001); these we combined into models to evaluate demographic vigor (lambda [λ]). We explored the influence of an array of individual, temporal, and spatial covariates on demographic vigor. We identified an important relationship between λ and where a bear resides within the GYE. This potential for a source–sink dynamic in the GYE, coupled with concerns for managing sustainable mortality, reshaped our thinking about how management agencies might approach long-term conservation of the species. Consequently, we assessed the current spatial dynamic of the GYE grizzly bear population. Throughout, we followed the information-theoretic approach. We developed suites of a priori models that included individual, temporal, and spatial covariates that potentially affected reproduction and survival. We selected our best approximating models using Akaikes information criterion (AIC) adjusted for small sample sizes and overdispersion (AICc or QAICc, respectively). We provide recent estimates for reproductive parameters of grizzly bears based on 108 adult (>3 years old) females observed for 329 bear-years. We documented production of 104 litters with cub counts for 102 litters. Mean age of females producing their first litter was 5.81 years and ranged from 4 to 7 years. Proportion of nulliparous females that produced cubs at age 4–7 years was 9.8, 29.4, 56.4, and 100%, respectively. Mean (±SE) litter size (n = 102) was 2.0 ± 0.1. The proportion of litters of 1, 2, and 3 cubs was 0.18, 0.61, and 0.22, respectively. Mean yearling litter size (n = 57) was 2.0 ± 0.1. The proportion of litters containing 1, 2, 3, and 4 yearlings was 0.26, 0.51, 0.21, and 0.02, respectively. The proportion of radio-marked females accompanied by cubs varied among years from 0.05 to 0.60; the mean was 0.316 ± 0.03. Reproductive rate was estimated as 0.318 female cubs/female/year. We evaluated the probability of producing a litter of 0–3 cubs relative to a suite of individual and temporal covariates using multinomial logistic regression. Our best models indicated that reproductive output, measured as cubs per litter, was most strongly influenced by indices of population size and whitebark pine (Pinus albicaulis) cone production. Our data suggest a possible density-dependent response in reproductive output, although perinatal mortality could have accounted for the correlation. We analyzed survival of cubs and yearlings using radiotelemetry of 49 unique female bears observed with 65 litters containing 137 dependent young. We documented 42 deaths: 32 cubs, 5 yearlings, and 5 that could have died as a cub or yearling. Using a nest survival estimator coded in Program MARK, our best model indicated that cub and yearling survival were most affected by residency in the GYE. Survival was highest for cubs and yearlings living outside Yellowstone National Park (YNP) but within the U.S. Fish and Wildlife Service (USFWS) Grizzly Bear Recovery Zone (RZ). Cubs and yearlings living inside YNP had lower survival rates, and those living outside the RZ had the lowest survival rates. Survival rates were negatively related to a population index, suggesting density dependence. Survival improved with higher whitebark pine seed production, greater winter severity, larger litter size, and higher female (mothers) age. We tested theories of sexually selective infanticide, but results were equivocal. We investigated factors influencing survival of subadult and adult grizzly bears using data from 323 radio-marked bears monitored for 5,989 months. Telemetry records were converted into monthly encounter histories, and survival was estimated using known fate data type in Program MARK. Bears were grouped into a study sample and conflict (bears specifically trapped because of conflict with humans) sample according to circumstance of capture and monitoring, with data from both contributing to survival estimates. A censored (C) data set included 69 documented mortalities but censored 22 bears with unknown fate. A second, assumed dead (AD), data set considered these 22 bears as mortalities. Most known mortalities (85.5%) were human caused, with 26 and 43 from the study and conflict samples, respectively. Mean annual survival, C F, for study sample female bears using C and AD data sets were C F = 0.950 (95% CI = 0.898–0.976) and AD F = 0.922 (95% CI = 0.857–0.995). Process standard deviation (SD) for study sample female bears was estimated at SDC = 0.013 and SDAD = 0.034. Our best models indicated that study sample bears survived better than conflict sample bears, females survived better than males, survival was lowest during autumn, and survival increased during years with good whitebark pinecone production. Bears with a higher proportion of annual locations outside the RZ exhibited poorer survival than individuals located more frequently inside YNP, the RZ, or both. Indices of winter severity, ungulate biomass, and population size, plus individual covariates, including presence of dependent young, prior conflicts with humans, and age class, were not important predictors of survival in our models. We documented a trend of increased survival through the study that was offset in recent years by lower survival of bears located more frequently outside the RZ. This result suggests that efforts to reduce female mortality initiated in 1983 were successful, and similar measures outside the RZ would improve the prospect for continued growth and expansion of the GYE grizzly bear population. To estimate sustainable mortality of the population, we produced trajectories of the GYE grizzly bear population under a range of survival rates of independent females (>2 years old) using an individual-based, stochastic simulation program and demographic data from radio-marked bears. We incorporated yearly (process) variation in survival rates as estimated from data after removing sampling variation. We summarized trajectories by mean λ and by probability of λ < 1, both within a 10-year period, and examined sensitivity of results by altering our initial assumptions to reflect uncertainty. Because process variation of female survival was low, λ decreased stochastically only slightly from that expected under a completely deterministic model. Uncertainty about mean cub and yearling survival rates was considerable, but because λ was relatively insensitive to these parameters, incorporating this uncertainty also lowered resulting trajectories only slightly. Uncertainty about independent female survival had a much larger effect on probability of population decline despite having little effect on expected λ. Under our current understanding of the GYE grizzly bear population dynamics, λ was independent of male survival rate; variation in male mortality produced only short-term effects on abundance and long-term effects on sex ratio. The appropriate mortality target for independent female bears depends on the risk of a population decline (i.e., λ < 1) that managers and the public are willing to accept. For the chance of a population decline to be ≤5% under conditions applying during 1983–2002, annual mortality of independent females would have to be ≤10%. Projections are useful only if viewed over a relatively short time frame because they were based solely on mean 1983–2002 conditions and because small samples make it difficult for managers to know the true mortality rate. To further explore the implications of geographic structure in female survival, we built an array of deterministic models using estimates of reproduction and survival from our best models. We calculated deterministic estimates of λ incorporating our residency covariate plus changes in whitebark pinecone production and winter severity. A source–sink dynamic is suggested for the GYE, with λ ≥ 1 inside YNP and the RZ but λ ≤ 1 outside the RZ. Such a source–sink dynamic requires new discussions about population management, mortality thresholds, and elimination of anthropogenic foods on the edge of the ecosystem. To enhance future management, we present food and population monitoring guidelines that should be considered in light of our findings. RESUMEN Durante las dos últimás décadas, la población del oso pardo (Ursus arctos) ha aumentado en números y se ha extendido geograficamente. Es útil entender los variables temporales, ambientales y espaciales que provocan este cambio, primero para evaluar las probables influencias sobre los demográficos del oso pardo en The Greater Yellowstone Ecosystem (el ecosistema mayor de Yellowstone) (GYE), y segundo para saber dónde dedicar los futuros esfuerzos que puedan beneficiar la conservación y el manejo de la población. Hemos utilizado datos de osos radiomarcados para medir y evaluar la reproducción (1983–2002) y la supervivencia (1983–2001). Hemos combinado estos datos y los hemos puesto en modelos para evaluar el vigor demográfico (lambda [λ]). Hemos explorado la influencia de una serie de covariables individuales, temporales, y espaciales sobre el vigor demográfico. Hemos identificado una relación importante entre λ y el lugar donde reside el oso dentro del GYE. La existencia potencial de una dinámica fuente-sumidero junto a la necesidad de manejar una tasa sostenible de mortalidad, nos llevaron a replantear la cuestión acerca de que cómo las agencias administrativas pueden abordar la conservación a largo plazo de la especie. Por consiguiente, hemos evaluado al actual dinámica espacial d

EFFECTS OF TRANSPORTATION INFRASTRUCTURE ON GRIZZLY BEARS IN NORTHWESTERN MONTANA

Abstract Highways and railroads have come under increasing scrutiny as potential agents of population and habitat fragmentation for many mammalian species, including grizzly bears (Ursus arctos). Using Global Positioning System (GPS) technology and aerial Very High Frequency (VHF) telemetry, we evaluated the nature and extent of trans-highway movements of 42 grizzly bears along the U.S. Highway 2 (US-2) corridor in northwest Montana, USA, 1998–2001, and we related them to highway and railroad traffic volumes and other corridor attributes. We employed highway and railroad traffic counters to continuously monitor traffic volumes. We found that 52% of the sampled population crossed highways at least once during the study but that crossing frequency was negatively exponentially related to highway traffic volume. We found that grizzly bears strongly avoided areas within 500 m of the highway and that highway crossing locations were clustered at a spatial scale of 1.5 km. Most highway crossings occurred at night when highway traffic volume was lowest but when railroad traffic was highest. Highway crossing locations were flatter, closer to cover in open habitat types, and within grassland or deciduous forest vegetation types. Nighttime traffic volumes were low, averaging about 10 vehicles/hr, allowing bears to cross. However, we project that US-2 may become a significant barrier to bear movement in ∼30 years if the observed trend of increasing traffic volume continues.

Black bear resource selection in the northeast Cascades, Washington

We examined resource selection of black bears in the northeast Cascades of Washington at two spatial scales. Specifically, we compared habitats selected for within home ranges to those available in the study area, and habitats selected for versus those available within home ranges. Compositional analysis showed selection of similar habitats at each spatial scale, with some differences. In the dry climate of the eastern Cascades, black bears appeared to locate home ranges within habitats that would provide abundant food resources, such as riparian and deciduous forests, meadows and shrubfields. Once established in a home range, black bears selected for a mosaic of habitat types that provided security cover in proximity to food resources, such as riparian and deciduous forests, other forest types and meadows.

Factors associated with fecal glucocorticoids in Alaskan brown bears (Ursus arctos horribilis).

The aims of this study were to validate a radioimmunoassay (RIA) for quantifying glucocorticoid metabolite concentrations in the feces of Alaskan brown bears (Ursus arctos horribilis) and to investigate whether any of the following factors are associated with those concentrations: the presence of humans or other bears, fishing difficulty, sex‐age class, diet, and season. We tested an established corticosterone RIA for assay sensitivity, similarity, precision, and sample matrix effects of brown bear feces, and it proved satisfactory. We collected fecal samples from brown bears along salmon‐spawning streams and assessed fecal glucocorticoid (FG) concentrations. We observed that the factors explaining the most variation in measured concentrations were date and diet type and that there was a significant interaction between the two. We did not observe a significant effect of human and bear activities or sex‐age class on FG concentrations. This study demonstrates that although FG concentrations may be assessed in brown bears, complex dietary patterns and seasonal variations must be taken into consideration in the study design in order to make inferences regarding stress.

Impacts of fruit production cycles on Malayan sun bears and bearded pigs in lowland tropical forest of Sabah, Malaysian Borneo

We observed a period of famine in the lowland tropical rain forest of Sabah, Malaysia from August 1999 to September 2000. All six Malayan sun bears ( Helarctos malayanus ) that were captured and radio-collared were in poor physical condition, and two were later found dead. The physical condition of bearded pigs ( Sus barbatus ) that were captured, observed or photographed by camera traps also revealed that the pigs were in various stages of emaciation and starvation. We surmise that the famine resulted from prolonged scarcity of fruit during an intermast interval in the study area. These phenomena of emaciated animals and fruit scarcity have also been reported from other areas of Borneo. Lowland tropical rain-forest trees of Borneo display supra-annual synchronized general fruiting. We believe that the starvation we observed and the generally low density of large animals in Borneo forests is a consequence of a history of prolonged food scarcity during non-general-fruiting years, but may be accentuated by anthropogenic factors such as forest fragmentation, selective logging, and reduced density of fig trees in logged forests.

Transplanting grizzly bears Ursus arctos horribilis as a management tool: results from the Cabinet Mountains, Montana, USA

Abstract A study of grizzly bears Ursus arctos horribilis in the Cabinet Mountains, Montana indicated that the future of the population was in jeopardy, and population augmentation was recommended. The US Fish and Wildlife Service (USFWS) issued an augmentation plan in 1987. The first of four projected transplants was completed in July 1990. The first transplanted grizzly bear was a 5-year-old female that weighed 71 kg. The first bear remained in the Cabinet Mountains following release and was monitored for 13 months before the radio collar was lost. This bear was visually located in the target area on 15 May 1992 approximately 19 km from the release site. Her home range from July 1990 through May 1992 encompassed 555 km 2 . Data regarding movements and habitat use were analysed and compared with native grizzly bears in the Cabinet Mountains. Trapping efforts in southeast British Columbia for additional bears to transplant were again conducted in 1991 and 1992. The effort resulted in the capture of eight different grizzly bears in 1991, but none met the sex and age criteria of 2-6-year-old females. Efforts in 1992 resulted in the capture of a second 71 kg 6-year-old female (bear 258) which was released at the same location as the first bear exactly 2 years later on 22 July 1992. Movements of bear 258 from July through November 1992 encompassed 388 km 2 in the target release area. This second bear emerged with a single cub in May 1993 and was radio-monitored until July 1993 when it was found dead in the target release area. No trace of the cub was found although it had been seen with its mother in late June. The cause of death is as yet unknown pending completion of toxicology reports. A third subadult female bear (286) was captured in July 1993 and released in the target area where she has remained through October 1993. Transplanting of bears can be a valuable tool in the conservation of small bear populations worldwide.

Bet-hedging applications for conservation

One of the early tenets of conservation biology is that population viability is enhanced by maintaining multiple populations of a species. The strength of this tenet is justified by principles of bet-hedging. Management strategies that reduce variance in population size will also reduce risk of extinction. Asynchrony in population fluctuations in independent populations reduces variance in the aggregate of populations whereas environmental correlation among areas increases the risk that all populations will go extinct. We review the theoretical rationale of bet-hedging and suggest applications for conservation management of least terns in Nebraska and grizzly bears in the northern Rocky Mountains of the United States. The risk of extinction for least terns will be reduced if we can sustain the small central Platte River population in addition to the larger population on the lower Platte. Similarly, by restoring grizzly bears to the Bitterroot wilderness of Idaho and Montana can reduce the probability of extinction for grizzly bears in the Rocky Mountains of the United States by as much as 69–93%.

Success of Grizzly Bear Population Augmentation in Northwest Montana

Abstract Augmentation of large carnivore populations can be a valuable management and recovery tool, but success of many programs has not been well documented. The Cabinet–Yaak grizzly bear (Ursus arctos) population was located in northwestern Montana and northern Idaho, USA, and was estimated at 30–40 individuals. The Cabinet Mountains portion of this area may be isolated from the remainder of the zone and was the site of a test of grizzly bear population augmentation. Experimental objectives included evaluating site fidelity, reproduction, and long-term survival of the translocated bears. Four subadult females (2–6 yr old) were translocated from southeastern British Columbia, Canada, from 1990 to 1994. Three of 4 transplanted bears remained in the target area for ≥1 year and satisfied the short-term goal for site fidelity. Recent genetic evidence gathered through hair-snagging efforts has determined that at least one of the original transplanted animals has reproduced, thereby providing evidence of success for the long-term goals of survival and reproduction.

A comparative analysis of management options for grizzly bear conservation in the U.S.–Canada trans-border area

Abstract Grizzly bear (Ursus arctos) populations spanning the U.S.–Canada border in the south Selkirk, Purcell–Yaak, and Cabinet Mountains are small, vulnerable, and at the front lines of any further range contraction in North America. Recent genetics work demonstrated that the south Selkirk grizzlies are an isolated population (no male or female connectivity) of fewer than 100 individuals with a 15–20% reduction in genetic diversity and that the Purcell–Yaak population is declining and demographically isolated (no female connectivity) with fewer than 50 individuals. The <25 animals living in the Cabinet Mountains population are likely isolated from both the south Selkirk Mountain and the Purcell–Yaak populations. We recognize these populations need enhanced management. To guide the development of a comprehensive management plan, we explored the effects of 3 actions (population augmentation, enhanced population interchange, and reduced mortality through management actions). We simulated 2 populations of 50 and 100 individuals using population viability analysis (PVA) software (VORTEX). We examined these management actions and combinations of them on population growth rate and extinction probabilities. Our simulations suggest that augmentation had the largest demographic effect on population growth rate over the short-term, mortality reductions had the largest effect in the long-term, and establishing population interchange and reducing mortality had the greatest effect on extinction probability. Enhanced cooperative U.S. and Canadian efforts are required to address the issues facing these small grizzly populations and to build connectivity to existing larger populations and areas of vacant habitat. Our findings apply to recovery and conservation efforts for small populations of all species of bears.