Search

Sea otters were extirpated throughout much of their range by the maritime fur trade in the 18th and 19th centuries, including the coast of Katmai National Park and Preserve in southcentral Alaska. Brown bears are an important component of the Katmai ecosystem where they are the focus of a thriving ecotourism bear-viewing industry as they forage in sedge meadows and dig clams in the extensive tidal flats that exist there. Sea otters began reoccupying Katmai in the 1970s where their use of intertidal clam resources overlapped that of brown bears. By 2008, the Katmai sea otter population had grown to an estimated 7,000 animals and was likely near carrying capacity; however, in 2006–2015, the age-at-death distribution (AADD) of sea otter carcasses collected at Katmai included a higher-than-expected proportion of prime-age animals compared to most other sea otter populations in Alaska. The unusual AADD warranted scientific investigation, particularly because the Katmai population is part of the Threatened southwest sea otter stock. Brown bears in Katmai are known to prey on marine mammals and sea otters, but depredation rates are unknown; thus, we investigated carnivore predation, especially by brown bears, as a potential explanation for abnormally high prime-age otter mortality. We installed camera traps at two island-based marine mammal haulout sites within Katmai to gather direct evidence that brown bears prey on seals and sea otters. Over a period of two summers, we gathered photo evidence of brown bears making 22 attempts to prey on sea otters of which nine (41%) were successful and 12 attempts to prey on harbor seals of which one (8%) was successful. We also developed a population model based on the AADD to determine if the living population is declining, as suggested by the high proportion of prime-age animals in the AADD. We found that the population trend predicted by the modeled AADDs was contradictory to aerial population surveys that indicated the population was not in steep decline but was consistent with otter predation. Future work should focus on the direct and indirect effects these top-level predators have on each other and the coastal community that connects them.

Contamination with arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) is a global concern impairing resilience of organisms and ecosystems. Proximity to emission sources increases exposure risk but remoteness does not alleviate it. These toxic elements are transported in atmospheric and oceanic pathways and accumulate in organisms. Mercury accumulates in higher trophic levels. Brown bears (Ursus arctos), which often live in remote areas, are long-lived omnivores, feeding on salmon (Oncorhynchus spp.) and berries (Vaccinium spp.), resources also consumed by humans. We measured blood concentrations of As, Cd, Hg and Pb in bears (n = 72) four years and older in Scandinavia and three national parks in Alaska, USA (Lake Clark, Katmai and Gates of the Arctic) using high-resolution, inductively-coupled plasma sector field mass spectrometry. Age and sex of the bears, as well as the typical population level diet was associated with blood element concentrations using generalized linear regression models. Alaskan bears consuming salmon had higher Hg blood concentrations compared to Scandinavian bears feeding on berries, ants (Formica spp.) and moose (Alces). Cadmium and Pb blood concentrations were higher in Scandinavian bears than in Alaskan bears. Bears using marine food sources, in addition to salmon in Katmai, had higher As blood concentrations than bears in Scandinavia. Blood concentrations of Cd and Pb, as well as for As in female bears increased with age. Arsenic in males and Hg concentrations decreased with age. We detected elevated levels of toxic elements in bears from landscapes that are among the most pristine on the planet. Sources are unknown but anthropogenic emissions are most likely involved. All study areas face upcoming change: Increasing tourism and mining in Alaska and more intensive forestry in Scandinavia, combined with global climate change in both regions. Baseline contaminant concentrations as presented here are important knowledge in our changing world. Validerad;2023;Nivå 2;2023-05-10 (joosat);Funder: Research Council of Norway; Inland Norway University of Applied Sciences; Norwegian Environment Agency (grant number 19047048); National Park ServiceLicens fulltext: CC BY License

Gut microbiomes (GMBs), complex communities of microorganisms inhabiting the gastrointestinal tracts of their hosts, perform countless micro-ecosystem services such as facilitating energy uptake and modulating immune responses. While scientists increasingly recognize the role GMBs play in host health, the role of GMBs in wildlife ecology and conservation has yet to be realized fully. Here, we use brown bears (Ursus arctos) as an ecological model to (1) characterize GMB community composition associated with location, season, and reproductive condition of a large omnivore; (2) investigate how both extrinsic and intrinsic factors influence GMB community membership and structure; and (3) quantify differences in GMB communities among different locations, seasons, sex, and reproductive conditions. To achieve these aims, we subsampled brown bear fecal samples collected during United States National Park Service research activities at three National Parks and Preserves (Katmai, Lake Clark, and Gates of the Arctic) and extracted microbial DNA for 16S rRNA amplicon sequencing and microbial taxonomic classification. We analyzed GMB communities using alpha and beta diversity indices, subsequently using linear mixed models to examine relationships between alpha diversity and extrinsic and intrinsic factors. Katmai brown bears hosted the greatest alpha diversity, whereas Gates brown bears hosted the least alpha diversity. Our results indicate that location and diet drive GMB variation, with bears hosting less phylogenetic diversity as park distance inland increases. Monitoring brown bear GMBs could enable managers to quickly detect and assess the impact of environmental perturbations on brown bear health. By integrating macro and micro-ecological perspectives we aim to inform local and landscape-level management decisions to promote long-term brown bear conservation and management.

The Arctic is generally warming with lengthening growing seasons that can influence individuals, populations, and communities. However, temperature data indicate that the changes are largely local and variable. We compared body size, body condition, and productivity among four Arctic brown bear (Ursus arctos) studies separated in time and space from 1977 to 2016. As body size, condition, and productivity varied among populations, local conditions, both biotic and abiotic, appear to influence the size, condition, and productivity of individual bears and, thus, bear populations. We conclude that current local studies are critical in informing management decisions, because extrapolations from concurrent adjacent studies or reliance on past local studies may not represent the present condition of an Arctic brown bear population.

Body size reflects realized physiological niche width at the population level and provides insights into the potential resiliency of a species to natural and anthropogenic perturbations to ecosystems. We analyzed patterns of American black and brown bear body size through a meta‐analysis of data from 18 studies conducted across North America, to evaluate the effects of species, sex, latitude, sympatry, and harvest. We used a bootstrap model selection procedure, which accounted for differences in sample size and population variation between studies, to investigate patterns in body mass. As expected, we found that brown bears were generally larger than black bears and both species were sexually dimorphic (i.e., males were generally larger than females). Black bear body size was not related to latitude, whereas brown bear body size was greatest at intermediate latitudes, possibly due to the presence of salmon. Neither sympatry nor harvest was associated with body size for either species at the geographic scale of our meta‐analyses, but both may warrant consideration at the local scale. Body size, as an index of population health, reflects phenotypic plasticity within species and populations and may serve as a useful indicator of niche utilization. Indeed, understanding large‐scale physiological patterns such as these can assist in understanding past, present, and future changes to realized niches and subsequent resiliency of species and populations.

Stable isotope data from durable, sequentially grown tissues (e.g. hair, claw, and baleen) is commonly used for modelling dietary niche breadth. The use of tissues grown over multiple months to years, however, has the potential to complicate isotopic niche breadth modelling, as time-averaged stable isotope signals from whole tissues may obscure information available from chronologically resolved stable isotope signals in serially sectioned tissues. We determined if whole samples of brown bear guard hair produced different isotopic niche breadth estimates than those produced from subsampled, serially sectioned samples of the same tissue from the same set of individuals. We sampled guard hair from brown bears (

Variation in life history strategies facilitates the near global distribution of mammals by expanding realized niche width. We investigated physiological plasticity in the spring body composition of adult female brown bears (Ursus arctos) across 4 diverse Alaskan ecosystems. Brown bears are a highly intelligent omnivore with a historic range spanning much of North America, Europe, and Asia. We hypothesized that body mass, fat mass, lean mass, and total caloric content would increase across populations with increasing food resource availability. Throughout their range, brown bears enter a period of torpor during winter months, decreasing their metabolic rate as an adaptation to this period of reduced food availability. They also give birth to and nourish offspring during this time. Due to this specific life history strategy, we further hypothesized that proportional body fat and the proportion of total calories derived from fat would be consistent across populations. Our results supported our first hypothesis: body, fat, and lean masses, and caloric content of bears across populations increased with the quality and abundance of available food. However, the proportional body fat content and proportion of calories from fat differed across populations indicating population-specific strategies to meet the demands of reduced seasonal food availability, offspring production and rearing, and climate as well as some plasticity to respond to environmental change or ecosystem perturbations. Investigations of body condition and energetics benefit from combined assessments of absolute, proportional, and caloric metrics to understand the nuances of brown bear physiological dynamics across and within populations.

Animal space use is influenced by many factors and can affect individual survival and fitness. Under optimal foraging theory, individuals use landscapes to optimize high-quality resources while minimizing the amount of energy used to acquire them. The spatial resource variability hypothesis states that as patchiness of resources increases, individuals use larger areas to obtain the resources necessary to meet energetic requirements. Additionally, under the temporal resource variability hypothesis, seasonal variation in available resources can reduce distances moved while providing a variety of food sources. Our objective was to determine if seasonal home ranges of brown bears (Ursus arctos) were influenced by temporal availability and spatial distribution of resources and whether individual reproductive status, sex, or size (i.e., body mass) mediated space use. To test our hypotheses, we radio collared brown bears (n = 32 [9 male, 23 female]) in 2014–2016 and used 18 a priori selected linear models to evaluate seasonal utilization distributions (UD) in relation to our hypotheses. Our top-ranked model by AICc, supported the spatial resource variability hypothesis and included percentage of like adjacency (PLADJ) of all cover types (P 0.17 for males, solitary females, and females with dependent young), and body mass (kg; P = 0.66). Based on this model, for every percentage increase in PLADJ, UD area was predicted to increase 1.16 times for all sex and reproductive classes. Our results suggest that landscape heterogeneity influences brown bear space use; however, we found that bears used larger areas when landscape homogeneity increased, presumably to gain a diversity of food resources. Our results did not support the temporal resource variability hypothesis, suggesting that the spatial distribution of food was more important than seasonal availability in relation to brown bear home range size.

Behavioral differences within a population can allow use of a greater range of resources among individuals. The brown bear (Ursus arctos) is a generalist omnivore that occupies diverse habitats and displays considerable plasticity in food use. We evaluated whether brown bear foraging that resulted in deviations from a proposed optimal diet influenced body condition and, in turn, denning duration in Lake Clark National Park and Preserve, Alaska. To assess assimilated diet, we used sectioned guard hair samples (n = 23) collected in autumn to determine stable carbon and nitrogen isotope ratios. To index proportional contributions of meat and vegetation to assimilated diets, we compared the carbon (δ13C) and nitrogen (δ15N) values of hair samples with the values identified for major food categories. We then compared percentage body fat and body mass in relation to the proportion of assimilated meat in the diet using linear models. We also examined the influence of autumn percentage body fat and mass on denning duration. Percentage body fat was not influenced by the proportion of assimilated meat in the diet. Additionally, percentage body fat and body mass did not influence denning duration. However, body mass of bears assimilating proportionately more meat was greater than bears assimilating less meat. Our results provide support for previous findings that larger bears consume higher amounts of protein to maintain their body size and therefore forage further from the proposed optimal diet. Additionally, our results demonstrate that individuals can achieve similar biological outcomes (e.g., percentage body fat) despite variable foraging strategies, suggesting that individuals within generalist populations may confer an adaptive advantage through behavioral plasticity.

Despite frequent observations of gray wolves (Canis lupus L., 1758) using nonungulate prey, the seasonal and interannual variation in the use and relative importance of alternative prey sources to gray wolf diets have not been studied at the individual scale. We used stable isotope analysis (δ13C and δ15N) of guard hair and blood components (clot and serum) collected over 4 years to examine the occurrence, extent, and temporal variation of Pacific salmon (genus Oncorhynchus Suckley, 1861) as a food resource by both individual wolves and social groups in Lake Clark National Park and Preserve in southwestern Alaska, USA. Our results demonstrate substantial variability in the use of salmon over time. During summer, diets of five wolves consisted of at least 50% salmon, while the diets of 17 wolves consisted of primarily terrestrial prey. Over 3 years, one group of wolves consistently consumed salmon in summer and switched to terrestrial prey in winter. Prey choices were generally similar within social groups; however, the degree to which individuals consumed salmon was highly variable. The use of salmon as exhibited by wolves in Lake Clark is likely widespread where salmon are abundant and this finding should be taken into consideration in the conservation and management of wolves and their prey.

We collected blood and serum from 155 brown bears (

Increasingly, population- and ecosystem-level health assessments are performed using sophisticated molecular tools. Advances in molecular technology enable the identification of synergistic effects of multiple stressors on the individual physiology of different species. Brown bears (Ursus arctos) are an apex predator; thus, they are ideal candidates for detecting potentially ecosystem-level systemic perturbations using molecular-based tools. We used gene transcription to analyze 130 brown bear samples from three National Parks and Preserves in Alaska. Although the populations we studied are apparently stable in abundance and exist within protected and intact environments, differences in transcript profiles were noted. The most prevalent differences were among locations. The transcript patterns among groups reflect the influence of environmental factors, such as nutritional status, disease, and xenobiotic exposure. However, these profiles also likely represent baselines for each unique environment by which future measures can be made to identify early indication of population-level changes due to, for example, increasing Arctic temperatures. Some of those environmental changes are predicted to be potentially positive for brown bears, but other effects such as the manifestation of disease or indirect effects of oceanic acidification may produce negative impacts.

We quantified the amount, spatial distribution, and importance of salmon (Oncorhynchus spp.)-derived nitrogen (N) by brown bears (Ursus arctos) on the Kenai Peninsula, Alaska. We tested and confirmed the hypothesis that the stable isotope signature (δ15N) of N in foliage of white spruce (Picea glauca) was inversely proportional to the distance from salmon-spawning streams (r=–0.99 and P

We collected blood and serum from 155 brown bears (Ursus arctos) inhabiting five locations in Alaska, US during 2013–16 and tested samples for evidence of prior exposure to a suite of bac...

Recruitment of brown bear (Ursus arctos) offspring into a population is the product of initial cub production and subsequent survival and is a critical component of overall population status and trend. We investigated the relationship between maternal body size, body condition, and age (as a surrogate for gained experience) and recruitment of dependent offspring (≥1 yr old) in 4 Alaska, USA (2014–2017), brown bear populations using logistic regression. Body size alone was our top predictor of the presence of offspring and appeared in all top models. Our data suggest that bear size is the primary driver of productivity across all 4 study populations, with larger bears having a greater chance of being observed with offspring. The effect of body condition was likely confounded by the increased energetic costs of supporting cubs through time and had a negative relationship with recruitment. Age (experience) was positively related to recruitment. Understanding the relative importance of body size, body condition, and age on the recruitment of offspring provides insights into life-history trade-offs female bears must manage as they strive to meet the nutritional costs of cub production and rearing, while minimizing risks to themselves and their offspring. Further assessment of long-term longitudinal studies of brown bears that assess the lifetime reproductive output of individuals would be highly informative to further assess the effect of experience on recruitment and to support the management of brown bear populations for recovery, conservation, sustained yield, and ecosystem function.

We assessed American black bear (Ursus americanus) harvest trends, generally, and black bear harvest over bait, specifically, in Alaska from 1992 to 2010 at 3 spatial scales: statewide, on drainages adjacent to and including National Park Service (NPS) units, and on NPS lands. Statewide, black bear reported harvest increased by an average of 93 bears/year, and harvest over bait increased by an average of 21 bears/year over this period. Harvest over bait increased by 4.3% (SE = 4.3) annually, and harvest by other methods increased by 3.9%/year (SE = 3.1). The proportion of females harvested over bait was 30.9% compared to 26.4% by other methods. Harvest increased around Lake Clark National Park and Preserve, while other units and adjacent lands had stable or decreasing harvest rates. Few bears were harvested using bait on NPS units (≤37 bears

We used deuterium water dilution to estimate body composition of free-ranging wolves (Canis lupus L., 1758) in the Nelchina Basin, Alaska. Body mass differed between sexes throughout the year but did not vary within sex. Mean fat mass and mean energy content were highest in both sexes in the spring. Mean lean mass was lowest in both sexes in the spring. Body mass and lean body mass were positively related to animal age in both males and females up to age 6–8 years. There was no relationship between body fat content and animal age in either sex except in older animals. Thus, growth beyond age 2 consists primarily of lean mass. Body mass of reproductively active females was greater than nonreproductively active females in the spring but not in summer or fall. Deuterium should be allowed to circulate in the wolf for at least 120 min to ensure complete equilibration regardless of season, sex, age, or reproductive status.

Previous studies have demonstrated the potential of carbon and nitrogen stable isotope analysis (SIA) of feces for use in understanding dietary components and sources. These studies suggest that SIA is useful because it is noninvasive and provides more recent dietary information integrated over a shorter time period than SIA of tissues. We sought to determine whether SIA could be employed in the analysis of feces of American black bears (Ursus americanus) in Utah. Using archived feces, we compared SIA with gross fecal analyses (GFA) to determine if a relationship existed. The percent volume of grass and pine nuts were the only significant indicators of the δ13C of feces. The amount of animal matter was the sole significant indicator of the δ15N value of feces. Although these measures were only weakly indicative (R2 ≤ 0.21), it is interesting that even in an environment that is isotopically homogenous, δ15N and δ13C provided information on the contribution of dietary components. The comparatively ...

We describe landscape use of female brown bears (Ursus arctos) on the Kenai Peninsula, Alaska, USA. Radiocollars, fitted to 43 adult female brown bears, provided radio relocations, which we used to describe habitat use patterns by season and reproductive class at the landscape scale. Brown bears were associated with areas with low densities of human developments and roads, as well as riparian areas that were close to cover. Presence of streams and lakes that supported spawning salmon (Oncorhynchus spp.) positively influenced summertime distribution of bears. Female brown bears with cubs avoided concentrations of other bears. Resource managers may use this information to respond to brown bear conservation issues associated with increasing human populations and associated development in the establishment of road density standards, seasonal road closures, management of recreation sites, and vegetation management on the Kenai Peninsula.

Salmon (Oncorhynchus spp.) are an important resource for terrestrial wildlife. However, the salmon requirements of wildlife populations and the role wildlife play in nutrient transport across ecosystems are largely ignored in salmon and habitat management. Any activity that reduces the availability of or access to salmon by wildlife may adversely affect wildlife populations and, potentially, ecosystem-level processes. Thus, when the conservation of specific wildlife populations or healthy ecosystems is the management objective, allocation of salmon to wildlife should be considered. We provide an example of how such allocations could be calculated for a hypothetical bear population. Ultimately, salmon allocation for wildlife calls for integrated management of natural resources across agencies, across species, and across ecosystems. We summarize the current state of knowledge relative to the interaction between Pacific salmon and the terrestrial ecosystem, with special emphasis on the import of salmon to terrestrial wildlife and the import of wildlife to terrestrial and aquatic ecosystems.

Phillips and Koch (2002) suggested that the standard, linear mixing model used to estimate assimilated diets may produce inaccurate results when animals consume foods that vary markedly in their C:N ratios and elemental concentrations. They presented a concentration-dependent model and used published values on captive and freeranging bears to illustrate theoretical shortcomings of earlier, concentration-independent models. The assimilated diet estimates for Alaskan bears on the Kenai Peninsula using their concentration-dependent model differed markedly from previously published results (Jacoby et al. 1999). For example, the importance of salmon to brown bears (Ursus arctos) decreased from 50% to 26% of the assimilated diet and for black bears (Ursus americanus) allopatric to brown bears from 53% to zero. Estimating the importance of salmon to bears has profound conservation implications as salmon stocks become increasingly depleted by human activities. Brown bear populations with significant access to salmon are up to 50 times denser, adult females are twice as heavy, and litter sizes are 25% larger than in salmon-deprived populations (Hilderbrand et al. 1999c). Recently, brown bears have been identified as major conveyors of the marinederived nutrients in salmon to Alaskan riparian forests (Hilderbrand et al. 1999a; Helfield and Naiman 2001). Thus, the validity of the Phillips and Koch (2002) estimates must be evaluated as they note that incorrect assumptions in mixing models "may produce misleading results with major ramifications on assessments of feeding ecology and management strategies". The original dietary estimates of the importance of salmon by Jacoby et al. (1999) and Hilderbrand et al. (1999b, c) used a bear-specific, carbon-enrichment, linear mixing model (Hilderbrand et al. 1996) to separate marine (salmon) from terrestrial carbon sources. This approach is the most direct of all the models, has the fewest assumptions as fractionation effects related to digestion and substrate routing are part of the feeding trial results used to generate the original regression, and has been used previously to estimate the importance of salmon to earlier humans (Chisholm et al. 1982; Taylor et al. 1998). Phillips and Koch (2002) also used a concentration-independent mixing model to simultaneously estimate assimilated dietary salmon, terrestrial meat, and terrestrial plant content and "reached roughly the same conclusions" as Jacoby et al. (1999) and Hilderbrand et al. (1999b, c). Even though the above two estimates are in agreement and are derived from markedly different models and assumptions, Phillips and Koch (2002) insisted that the very different values generated by their concentration-dependent model that requires more inputs and assumptions are the correct values. The estimates from the Phillips and Koch (2002) concentration-dependent model are driven by the composition and C:N concentrations of the hypothesized assimilated diet, particularly the plant portion of the diet that was composed of equal parts apples (Malus sylvestris), blackberries (Rubus sp.), domestic cranberries (Vaccinium macrocarpon) and raspberries (Rubus sp.), and rhubarb stems (Rheum rhabarbarum). Despite extensive literature on the diets of bears, Phillips and Koch (2002) clearly made no effort to mimic a realistic plant diet in their modeling efforts as no Alaskan bear consumes their hypothetical diet. Although the actual plant names are irrelevant in illustrating their model, outputs of the model, comparisons to previous estimates, and management implications do depend on the diet chosen. The lack of realistic diet inputs in their example poses serious scientific and conservation concerns. The plant component of their hypothetical diet has a gross C:N ratio of 44:1 as compared to 4.6:1 and 3.7:1 for salmon and terrestrial meat (Table 1 in Phillips and Koch C.T. Robbins (X) School of Biological Sciences and Department of Natural Resource Sciences, Washington State University, Pullman, WA 99164-4236, USA e-mail: ctrobbins@wsu.edu Tel.: +1-509-3351119, Fax: +1-509-3353184

The influence of seasonal dietary meat intake on changes in body mass and composition in wild and captive brown bears (Ursus arctos) was investigated because the importance and availability of meat to brown bear populations is currently an important management consideration in several North American ecosystems. Adult female brown bears on the Kenai Peninsula, Alaska, utilized meat heavily in both spring and fall. Meat accounted for 76.2 ± 26.0% (mean ± 1 SD; primarily moose carrion and calves) of assimilated carbon and nitrogen in the spring and 80.4 ± 22.2% (primarily salmon) in the fall. Mass increases in the spring (71.8 ± 28.2%) were mostly lean body mass, but increases in the fall (81.0 ± 19.5%) were primarily fat. Daily intake by captive brown bears fed meat ad libitum during 12-day trials was positively related to body mass. Mass change was positively related to intake in both seasons, but the composition of the gain varied by season, with spring gains primarily lean body mass (64.2 ± 9.4%), while fall gains were 78.8 ± 19.6% lipid. Absolute rates of gain by wild bears occasionally equaled, but were usually much less than, those of captive bears. This was likely due to a combination of factors, which included the time required to locate and handle meat resources, the limited availability of or access to meat resources, and (or) the duration of meat resource availability. Estimated intake by bears not feeding selectively on high-energy components of moose and salmon were 8.5 ± 1.5 kg/day and 541 ± 156 kg/year and 10.8 ± 4.6 kg/day and 1003 ± 489 kg/year, respectively. Intake would drop by as much as 58% for bears feeding exclusively on salmon roe. Management strategies for areas with brown bears that consume significant amounts of meat should address the perpetuation and availability of these meat resources.

We hypothesized that the relative availability of meat, indicated by contribution to the diet, would be positively related to body size and population productivity of North American brown, or grizzly, bears (Ursus arctos). Dietary contributions of plant matter and meat derived from both terrestrial and marine sources were quantified by stable-isotope analysis (δ13C and δ15N) of hair samples from 13 brown bear populations. Estimates of adult female body mass, mean litter size, and population density were obtained from two field studies of ours and from other published reports. The populations ranged from largely vegetarian to largely carnivorous, and food resources ranged from mostly terrestrial to mostly marine (salmon, Oncorhynchus spp.). The proportion of meat in the diet was significantly correlated with mean adult female body mass (r = 0.87, P < 0.01), mean litter size (r = 0.72, P < 0.01), and mean population density (r = 0.91, P < 0.01). Salmon was the most important source of meat for the largest, most carnivorous bears and most productive populations. We conclude that availability of meat, particularly salmon, greatly influences habitat quality for brown bears at both the individual level and the population level.

Safe and effective immobilization of grizzly bears (Ursus arctos) is essential for research and management. Fast induction of anesthesia, maintenance of healthy vital rates, and predictable recoveries are priorities. From September 2010 to May 2012, we investigated these attributes in captive and wild grizzly bears anesthetized with a combination of a reversible α2 agonist (dexmedetomidine [dexM], the dextrorotatory enantiomer of medetomidine) and a nonreversible N-methyl-d-aspartate (NMDA) agonist and tranquilizer (tiletamine and zolazepam [TZ], respectively). A smaller-than-expected dose of the combination (1.23 mg tiletamine, 1.23 mg zolazepam, and 6.04 µg dexmedetomidine per kg bear) produced reliable, fast ataxia (3.7 ± 0.5 min, x̄±SE) and workable anesthesia (8.1 ± 0.6 min) in captive adult grizzly bears. For wild bears darted from a helicopter, a dose of 2.06 mg tiletamine, 2.06 mg zolazepam, and 10.1 µg dexmedetomidine/kg produced ataxia in 2.5 ± 0.3 min and anesthesia in 5.5 ± 1.0 min. Contrary to published accounts of bear anesthesia with medetomidine, tiletamine, and zolazepam, this combination did not cause hypoxemia or hypoventilation, although mild bradycardia (50 beats per min) occurred in most bears during the active season. With captive bears, effective dose rates during hibernation were approximately half those during the active season. The time to first signs of recovery after the initial injection of dexMTZ was influenced by heart rate (P0.001) and drug dose (P0.001). Intravenous (IV) injection of the reversal agent, atipamezole, significantly decreased recovery time (i.e., standing on all four feet and reacting to the surrounding environment) relative to intramuscular injection. Recovery times (25 ± 8 min) following IV injections of the recommended dose of atipamezole (10 µg/µg of dexmedetomidine) and half that dose (5 µg/µg) did not differ. However, we recommend use of the full dose based on the appearance of a more complete recovery. Field trials confirmed that the dexMTZ + atipamezole protocol is safe, reliable, and predictable when administered to wild grizzly bears, especially during helicopter capture operations.

The potential use of stable-isotope analyses (δ13C and δ15N) to estimate bear diets was assessed in 40-day feeding trials using American black bears (Ursus americanus). Bear plasma and red blood cells have half-lives of ~4 days and ~28 days, respectively. The isotopic signature of bear plasma is linearly related to that of the diet, and with the exception of adipose tissue, there is no isotopic fractionation across bear tissues. Isotopic analyses were used to estimate the diets of three bear populations: Pleistocene cave bears (U. speleaus) in Europe, grizzly bears (Ursus arctos horribilis) inhabiting the Columbia River drainage prior to 1931, and brown bears (U. arctos) of Chichagof and Admiralty islands, Alaska. Cave bears were omnivores with terrestrially produced meat contributing from 41 to 78% (58 ± 14%) of their metabolized carbon and nitrogen. Salmon contributed from 33 to 90% (58 ± 23%) of the metabolized carbon and nitrogen in grizzly bears from the Columbia River drainage. Finally, most brown bears on Chichagof and Admiralty islands feed upon salmon during the late summer and fall; however, a subpopulation of bears exists that does not utilize salmon.

Increased popularity of recreational activities in natural areas has led to the need to better understand their impacts on wildlife. The majority of research conducted to date has focused on behavioral effects from individual recreations, thus there is a limited understanding of the potential for population-level or cumulative effects. Brown bears (Ursus arctos) are the focus of a growing wildlife viewing industry and are found in habitats frequented by recreationists. Managers face difficult decisions in balancing recreational opportunities with habitat protection for wildlife. Here, we integrate results from empirical studies with expert knowledge to better understand the potential population-level effects of recreational activities on brown bears. We conducted a literature review and Delphi survey of brown bear experts to better understand the frequencies and types of recreations occurring in bear habitats and their potential effects, and to identify management solutions and research needs. We then developed a Bayesian network model that allows managers to estimate the potential effects of recreational management decisions in bear habitats. A higher proportion of individual brown bears in coastal habitats were exposed to recreation, including photography and bear-viewing than bears in interior habitats where camping and hiking were more common. Our results suggest that the primary mechanism by which recreation may impact brown bears is through temporal and spatial displacement with associated increases in energetic costs and declines in nutritional intake. Killings in defense of life and property were found to be minimally associated with recreation in Alaska, but are important considerations in population management. Regulating recreation to occur predictably in space and time and limiting recreation in habitats with concentrated food resources reduces impacts on food intake and may thereby, reduce impacts on reproduction and survival. Our results suggest that decisions managers make about regulating recreational activities in time and space have important consequences for bear populations. The Bayesian network model developed here provides a new tool for managers to balance demands of multiple recreational activities while supporting healthy bear populations.

Notes 2303 Isotopic analyses of bone collagen of European cave bears (Ursus speleaus) have provided additional insight into their nutritional ecology, but these analyses are a tool that must be used in conjunction with other methods of investigation. While Bocherens’ comments focused purely on the methodology of isotope analyses to argue that cave bears were vegetarians, we base our conclusion of omnivory in this comment on ursid morphology, isotopic analyses, digestive physiology, and foraging dynamics. However, we do wish to (i) correct an error identified by Bocherens and (ii) propose an alternative view of cave bear diets that bridges the relatively narrow conclusions reached by other recent investigators. All Pleistocene samples analyzed by Hilderbrand et al. (1996) were bone collagen extracted from adult specimens. Thus, the influence of a cub’s milk diet and the resulting increased δ15N signatures of dentine collagen are irrelevant to the conclusions of Hilderbrand et al. (1996). However, the error that we made was in assuming that the collagen values in Bocherens et al. (1994, Table 5) were for bone. Because they are actually tooth collagen values, they are not comparable to the bone collagen values measured by Hilderbrand et al. (1996). While geographic variation in isotopic signatures can occur, the degree of variation seen is not enough to refute the conclusions reached by Hilderbrand et al. (1996). The north to south δ15N gradient suggested by Bocherens is not a simple, straightforward process (Cormie and Schwarcz 1994). While grazing bovids would generally increase their consumption of C4 grasses in more southerly latitudes and thereby have an increased δ15N signature, cave bears are characteristic of “a food chain based on C3 plants” (Nelson 1998). North American cervids, ranging from latitude 36 to 60N, preferentially feed on C3 plants and display similar δ15N signatures (3.9 ± 0.6‰ in Alaska, 4.0 ± 1.0‰ in Yellowstone National Park, and 4.3 ± 1.0‰ in Colorado and New Mexico (Jacoby et al. 1999)). Cave bear remains have been found across a similar latitudinal range (38–52N) in Europe (Kurten 1976). Hilderbrand et al. (1996) recognized that cave bears ranged across Europe and likely consumed varied diets, therefore adult cave bear specimens were selected from widely diverse geographic locations. Thus, rather than infer characteristics of the entire species from samples collected at a few sites in France (Bocherens et al. 1994), Hilderbrand et al. (1996) assesed the dietary ecology of the species from samples collected across the cave bear’s range. Yield, %C, and %N of extracted collagen were assessed for all samples by Hilderbrand et al. (1996). However, these values were not reported because (i) no isotope values would have been reported if it was not certain that bone collagen was indeed being used, as yield of extraction and purity are basic to all such studies (Chisholm et al. 1983, cited by Hilderbrand et al. 1996), and (ii) assessment of the European cave bear diet was a small part of a much larger study in which more than 1000 samples were analyzed for their isotope content, and the reporting of all such data seemed superfluous. The δ15N values reported for bone collagen of modern and historic mammals by Bocherens et al. (1994) and Hilderbrand et al. (1996), with the exception of the cave bear, are very similar and within expected ranges. However, the cave bear bone collagen values are very different, 2.9 ± 1.3‰ (n = 9) (Table 1 in Bocherens et al. 1994) versus 8.4 ± 0.5‰ (n = 10) (Hilderbrand et al. 1996). Either a mistake was made by one group, as suggested by Bocherens, or both values are correct and require a biological explanation. The traditional view of European cave bears as herbivores originated from studies of morphology, specifically jaw structure, dentition, and tooth wear (Kurten 1972), prior to detailed studies of bear nutritional ecology. Kurten (1972) argued that “vegetarianism [had] gone to a veritable culmination in the cave bear” in which the “lengthened and expanded molars” were necessary to degrade the “tough cellulose which encased the plant cell wall.” Recent studies of cave bear diets using morphology and (or) isotopic analyses have led to varying conclusions, including that they were (i) a strictly vegetarian (Bocherens et al. 1994), (ii) highly omnivorous, specializing on plant parts (e.g., “particularly tough nuts and fibrous tubers”) and invertebrates (e.g., grubs) (Stiner et al. 1998), (iii) highly specialized “root grubbers” that could not have been vegetarian in the sense of consuming only leaves and stems but may have supplemented their diet with rodents encountered during root digging (Mattson 1997), and (iv) omnivores that consumed vertebrate flesh in addition to the wide range of other plant and animal foods consumed by north-temperate-zone bears (Hilderbrand et al. 1996). While tooth wear and dentition indicate that plant matter, tubers, and associated abrasive material were components of

We investigated the effect of hibernation and reproductive status on changes in body mass and composition of adult female brown bears (Ursus arctos) on the Kenai Peninsula, Alaska, This information is fundamental to understanding nutritional ecology of wild brown bear populations. Six adult females haudled in the fall and following spring (paired samples) lost 73 ± 22 kg (x ± SD; 32 ± 10%) of fall body mass over 208 ± 19) days. Of this mass loss, 56 ± 22% (55 ± 22 kg) was lipid and 44 ± 22% (43 ± 21 kg) was lean body mass. Catabolism of lipid stores accounted for 88.4 ± 8.1% of the body energy used to meet maintenance demands. Overwinter differences in body composition of adult females assessed only once in either the fall ± 21) or spring n ± 32) were similar to those of paired samples. Relative fatness of bears entering the den was positively related to the contruibution of fal (%) to body mass (P < 0.01) and body energy (P < 0.01) losses during hibernation. Thus relative fatness at the onset of lasting influences the relative proportion of lipid store and lean body mass catabolized to meet protein and energy demands during hibernation. In the spring lone females had greater body and lean masses than females with culis of the year or yearlings. Lipid content was greatest in lone females in the fall. Studies using body mass and composition as indices of population health should consider season or reproductive class.

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.

Bioelectrical impedance analysis (BIA) and isotopic water dilution have been proposed as methods suitable for determining the body composition of wild bears. We investigated the accuracy of these 2 techniques in a single-blind study. Water dilution was a more precise predictor of the body fat content of black bears (Ursus americanus) and brown bears (U. arctos) than was BIA, as indicated by comparison of the standard error of the estimate (SEE; 2.31% vs. 3.27%). The mean of the estimates from both methods predicted bear body fat content with the least error (SEE = 1.67%). The magnitude of the error for either method was not significantly related to body mass, lipid content, or animal age. Accurate, repeatable BIA estimates require extensive training and experience to standardize measurement conditions. Isotopic water dilution has fewer error sources but requires laboratory analyses.