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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.
The capability to understand the nutritional ecology of free-ranging bears has increased dramatically in the last 20 years. Advancements have occurred because (1) managers and biologists recognized the need to link habitat quality, productivity, and variability with bear movements, home ranges, and demographic parameters like reproductive output, survival, and population growth, and (2) several research teams are using new methods to build on the results of earlier field studies. Our ability to couple new field methods and empirical field research with controlled experiments using captive bears has been central to our increased understanding of bear nutrition. Newer methods include the use of stable isotopes to quantify assimilated diet and nutrient flows within ecosystems, bioelectrical impedance to measure body composition, and naturally occurring mercury to estimate fish intake. Controlled experiments using captive bears have been integral to developing methods, isolating specific variables by controlling the environment, and providing additional nutritional understanding necessary to interpret field observations. We review new methods and apply our increased understanding of bear nutritional ecology to 3 management issues: (1) the importance of salmon (Oncorhynchus spp.) to brown bears (Ursus arctos) in the Pacific Northwest, (2) the consequences of the closure of the Yellowstone garbage dumps to grizzly bears, and (3) the relocation of problem bears.
Implanting radiotransmitters in wild animals to monitor physiological processes and survival rates is an accepted practice, but the degree of success for subcutaneous implants rarely has been reported, making it difficult to improve the practice of and equipment for subcutaneously implanting transmitters. We implanted radiotransmitters subcutaneously in 42 (21M:21F) wild American black bear (Ursus americanus) cubs from 2 study areas in Virginia during 1996–1999. We monitored the cubs from the date of implantation until the implants fell out, the cubs died, the transmitters failed or became undetectable, or until the cubs denned as yearlings the following den season. We removed 3 animals from our analysis because we judged that their fates were unrelated to the implants. Over 64% (25 of 39) of implants fell out or were rejected prematurely (2–198 days), 23% (9 of 39) presumably failed for unknown reasons, 5% (2 of 39, part of the previous 9) failed and were worn to the following den season, and 1 of 39 bears died less than 1 month after implant surgery. Only 10% (4 of 39) of implanted black bear cubs wore working transmitters to the following den season. We estimated an overall implant survival estimate of 6.5% for the implants. Our success was very limited using subcutaneous implants, but this can be improved through improvements in the surgical procedures, further miniaturization of transmitters and batteries, impermeable transmitter packages, and better understanding interactions among family members following implant surgery.
Knowledge of and atittudes toward brown bear (Ursus arctos), lynx (Lynx lynx), and wolf (Canis lupus) in Latvia were assessed through surveys. Brown bears are rare and protected, whereas lynx and wolf are game species. Questionnaires were distributed in public schools and to a self-selected sample of readers of a national hunter's magazine. The Latvian public generally supported large carnivore conservation. Among the 3 species considered, the most positive attitudes were toward brown bears. Negative attitudes were a result of real or perceived effects large carnivores have on livestock husbandry and game management. Nearly 70% of respondents thought protection of bears should be continued, whereas 24% of respondents supported control of bear populations. A majority of respondents believed that wolf and lynx populations should be controlled, but very few respondents supported total eradication of large carnivores in Latvia. A greater proportion of rural inhabitants favored control of carnivore populations than residents in other locales. In contrast, hunters (n = 157, almost entirely male, mostly rural, and somewhat older) favored unlimited harvesting of large carnivores. Most respondents expressed interest in obtaining more information on large carnivores, suggesting a role for an expanded education campaign.
Some bear hunters in Virginia, primarily houndsmen, feed American black bears (Ursus americanus) to attract them to hunting sites, but also because some hunters believe that supplemental food improves bear reproduction and survival. However, a regulation prohibiting unauthorized feeding of bears, deer (Odocoileus virginianus), and turkey (Meleagris gallopavo) on national forest and state-owned lands in Virginia became effective 1 July 1999. We sent a survey to all members of the Virginia Bear Hunters Association (VBHA) (n = 459) to determine the amount of food provided to bears by hunters between 1 July 1998 and 30 June 1999. Survey response rate was 52%. One hundred thirteen of 238 (48%) survey respondents spent $18,378 on supplemental food during that time. One hundred twenty-eight respondents provided 2,942,394 kilograms of food to bears between 1 July 1998 and 30 June 1999. Whole-shelled corn, pastries, and rendered animal fat (grease) accounted for 58% of the total mass; however, whole-shelled corn, pastries, and bread were the 3 most common foods offered. July, August, and September were the months during which most respondents fed bears. Food supply can affect reproduction, survival, harvest rates, nuisance occurrences, population size, and distribution of bears. If supplemental feeding has an effect on bear population dynamics, changes in regulations regarding feeding may negatively impact black bear populations, as well as public relations and future cooperation between wildlife agencies and hunters.
Over 1,000 Asiatic black bears (Ursus thibetanus) are killed each year in Japan to control depredation activity. Our objective was to determine if killing bears reduces depredation costs. We focused our study on Nagano Prefecture, where 2,562 nuisance bears were reported killed and where reported depredation cost exceeded ¥1,430 million between 1979 and 1999. We used mixed models with repeated measures to determine if annual depredation costs were associated with the number of bears killed. Our data set included 15 years (1985–99) of kill and cost data for 122 municipal jurisdictions within 10 regions. We performed analyses at the regional level based on combined harvest and nuisance kill data, and at the municipal level based only on nuisance kill data. We classified the number of kills into 3 classes (low, medium, high). Analyses were repeated using prior-year kills to examine whether a possible time-lag existed. Annual depredation costs were positively associated with the kill data at the regional level (F = 5.51; 2, 72.3 df; P = 0.006) during the same year. However, we observed no association based on prior-year kill data (F = 0.96; 2, 65.1 df; P = 0.390), suggesting that depredation costs and bear kills are a function of nuisance bear numbers rather than reflecting a causal relationship between the 2 measures. Nuisance bear numbers may in turn be affected either by the availability of natural foods or by general population trends. At the municipal level, depredation costs were not associated with the number of nuisance bears killed during the same year (F = 1.36; 2, 466 df; P = 0.258) or the prior year (F = 0.42; 2, 459 df; P = 0.656). Our results suggest that systematically killing Asiatic bears may not be an effective tool for mitigating nuisance costs. In municipalities where nuisance costs remain high, we recommend that alternative methods be tested for their efficacy in mitigating costs. Such methods may include public education, changing or removing financial incentives to kill bears, changing crop rotations to crops that are not attractive to bears in risk areas, promoting natural food production, using electric fences, and applying aversive conditioning techniques.
In the North Bilaspur Forest Division in Madhya Pradesh, India, the sloth bear (Melursus ursinus) population is ecologically isolated, and some bears have developed aggressive behavior. Available bear habitat is highly fragmented and degraded and is interspersed with human habitation. In this study we assessed habitat use patterns of sloth bears with the goal of establishing management guidelines to reduce human–bear conflicts. Goodness-of-fit comparisons showed that expected use of each habitat category differed from habitat availability. Bear sign was most frequent in sal forest followed by land near water, sal mixed forest, and mixed forest. However, bear use of terrain categories was not different from expected use. A large number of bear dens were near water and human settlements. Bears regularly used more than 50% of observed den sites. Because of nearness to human settlement and degraded habitat, bears largely depended on villages for food, resulting in frequent human–bear encounters, some of which led to maulings and fatalities. One management priority is to protect highly preferred habitats of sloth bears. Bear population control and translocation of bears from isolated habitat patches to more suitable areas may be carried out simultaneously with education and awareness programs to conserve this species and to mitigate human–bear conflicts on a long-term basis.
In Central India, the North Bilaspur Forest Division (NBFD) harbors a large number of sloth bears (Melursus ursinus). The managed forests of the division are mostly patchy, fragmented, degraded, and interspersed with crop fields and villages with high human and cattle population. The feeding ecology of sloth bears was studied by analyzing 568 scats; 21 species of plants, termites, ants, and bees, as well as unidentified animal matter (bone, hairs and tissue) were found in bear scats. Year-round frequencies of occurrence of animal and plant matter were similar. Animal matter constituted 87% of scats during monsoon and 82% during winter seasons, but dropped to 65% during summer. On percent dry-weight basis, plant matter was greater than animal matter in scats in all seasons. Frequency of occurrence of insects was high during monsoon (87%) and winter (82%), whereas Ficus species were more common (68%) during summer season. Ficus species were high in percent weight in all seasons. Ficus species appear to be important to bears, especially when fields lack crops, few other species are fruiting, and soil is hard, making it difficult to dig for ants and termites. The presence of groundnut and corn (maize) in diets during the monsoon suggests crop damage by bears, thereby increasing chances of human–bear conflict.
Previously published observations of bears consuming murid rodents have been limited to short anecdotes. Only 2 studies reported bears consuming rodent food caches. I investigated the consumption of voles (Microtus spp.) and vole food caches by grizzly bears (Ursus arctos) in the Yellowstone region, 1977–92, using data collected during a study of 140 radiomarked bears. Study bears excavated vole nests, burrows, or food caches at 45 different sites. Excavations of nests (n = 37) were more common than excavations of food caches (n = 15). The remains of voles were found in 62 bear feces. Occurrences of voles in bear feces and excavations by bears for vole nests or food caches were essentially uncorrelated over time, suggesting that total consumption of voles and pursuit of voles or vole food caches by excavation were affected by different factors. Excavations by bears were largest in size and peaked in number during the driest months of the study period and were most likely to occur on gently sloping sites with abundant grasses, especially of the genus Phleum, and sedges (Carex). Bear excavations were more common during drought, probably because voles increased their burrowing in response to drying of wet soils, decreased above-ground security, and decreased abundance of above-ground foods. Food caching by voles has been documented in Canada and at high latitudes in the U.S., but prior to this study, only once in the U.S. Rocky Mountains. Bears consumed vole food caches primarily during September and were most successful finding caches at sites where yampah (Perideridia gairdneri) was abundant. Study bears excavated vole nests most often during spring and fall. Although voles were not a major source of energy for Yellowstone's grizzly bears, some individuals frequently foraged for voles during certain years.