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Estimating reproductive rate is an important element in understanding the demographic status of any bear population. These rates have been traditionally estimated by marking a sample of individuals with radiocollars and tracking them for the life of the transmitter. Rates of reproduction have been estimated in various ways, but all essentially calculate a ratio of female cubs produced by the number of females in the sample. Inherent in these calculations is the assumption that the sample is representative of the female population at large. We compare methods used to estimate reproductive rate, comparing the proportion of females in various reproductive states estimated from capture data with a method that estimates transition probabilities and stable state conditions. The latter is unaffected by capture heterogeneity among reproductive states. We use examples from 2 study areas (Greater Yellowstone Ecosystem [Wyoming, Montana, Idaho] and Kenai Peninsula, Alaska), with grizzly (Ursus arctos) and black (Ursus americanus) bears. We discuss the effect of capture heterogeneity and concluded that reproductive rates are more accurately estimated using transition probabilities and stable state conditions if studies are short in duration, capture heterogeneity is evident, or individual bears in the sample are not recollared during the study.
Accurate and precise population estimates are necessary to answer many management questions, but these estimates are generally unavailable for large carnivores because of their extensive movements, low densities, and secretive natures. These traits also often prevent the bounding of occupied areas necessary to estimate densities. We used a modified Petersen mark–recapture methodology to estimate black bear density in 1998 at 2 study sites on the Hoopa Valley Reservation, California, from mark–resight data. We used culvert traps to capture, radiocollar, and eartag bears, radio telemetry to establish closure, and remote cameras to collect resighting data. We calculated bear densities (90% confidence intervals) of 0.18 (0.09–0.32) and 1.33 (0.54–3.29) bears/km2 on the 2 sites. Knowledge of bear densities can now be incorporated into forest management actions and associated bear control measures on the Hoopa Valley Reservation.
Because of its biological characteristics, its important place in the minds of humans, and the considerable international interest for its conservation, management of the brown bear (Ursus arctos) in Europe is challenging. The Brown Bear Management Plan for Croatia (BMPC) was approved in 2004 and addressed interests such as ecology, aesthetics, and economics, as well as concern for the safety of people and property. It attempts to ensure conditions for the long-term survival of the brown bear, a species listed as endangered by some international regulations but as a game species (subject to regulated hunting) in others, including Croatia. Careful evaluation of actions affecting population size represents the most critical part of this plan. Those actions should sustain long-term viability of the bear population while maintaining densities at a level that minimize human–bear conflict. To achieve this goal, a series of actions and measures have to be regulated that are related to (1) bear habitat, (2) human activities in the habitat (e.g., highway construction, feeding of bears by humans), (3) prevention of problematic bear occurrences, and (4) the scientific monitoring of population changes. Although the plan's development and implementation is the responsibility of bear management experts, various interests groups were considered. In large carnivore management, and especially in bear management, there are no final and universal solutions. Changes in the number of bears, areas of their presence, or behavior require new decisions. This plan offers guidelines for the decision-making process, and, because it includes a revision process, can be adapted to address new circumstances that arise. Citizens interested in conservation, not only in Croatia but also in neighboring countries, expect Croatia to work toward maintaining the long-term existence of as many bears as possible in appropriate habitats, with as few negative effects as possible. This plan is an important step in fulfilling those expectations.
American black bear (Ursus americanus) population dynamics are most sensitive to survival of adult females. To ensure that harvest is sustainable, harvest should be skewed to males. In addition, in jurisdictions with a spring harvest, lactating females should not be harvested. Hunting over bait provides hunters the opportunity to observe bears, yet many hunters have difficulty identifying the sex of bears at bait sites. We evaluated the use of suspended baits to determine whether this technique could help hunters correctly distinguish male from female black bears. We also evaluated hunter knowledge of black bears and hunter familiarity with hunting regulations to determine whether these influenced harvest. The proportion of female black bears harvested at suspended or traditional ground bait sites was similar; however, hunters did not always give bears the opportunity to stand at suspended baits. The suspended bait technique shows promise and should be explored further in a larger study. Using the provincial harvest as the control group (33% females on average), power analysis indicated that a sample size of 1,325 harvested animals would be required in the treatment group to detect a small effect size (10%; i.e., reduction of female harvest from 33% to 29.7%) with β = 0.1. A 20% effect size (i.e., reduction of harvest from 33% females to 26.4%) would require a sample size of 247 harvested bears in the treatment group, and a 30% effect size (i.e., reduction of harvest from 33% females to 23%) would require a sample size of 101 harvested animals in the treatment group.
A variety of approaches have been used by wildlife agencies to educate people about encounters with American black bears (Ursus americanus), but little evaluation of their effectiveness has occurred. We distributed brochures, posters, and adhesive signs with messages about how to be safe around black bears in 2 areas of New Mexico where this information had not been widely disseminated and where encounters between people and black bears were common. To evaluate the effectiveness of our efforts, we used identical survey instruments to poll residents and campers in the 2 areas where safety information was widely distributed (treatment areas) and residents and campers in 3 other areas where information was not distributed (reference areas). Knowledge levels of respondents in treatment areas were higher than those of respondents in reference areas for residents and to a lesser extent for campers. Residents in treatment areas had the highest knowledge levels of all sample groups. Respondents generally understood the critical role anthropogenic food plays in creating nuisance behavior. We discuss recommendations for further research.
Throughout North America, when American black bears (Ursus americanus) enter backcountry campsites to obtain human food, undesirable and potentially dangerous incidents occur. This problem is minimized if overnight users of the backcountry (‘backpackers’) carry their food in bear-resistant canisters or use metal storage lockers. I surveyed 242 backpacking groups in Sequoia and Kings Canyon National Parks (SEKI), during the summer of 2003. Voluntary use of canisters or storage lockers was high (91%). Users' most frequent explanations for canister use were: to protect food, to protect themselves, to keep bears wild, and convenience. Survey results suggest that losing food to a bear also encouraged the subsequent use of a canister. Availability of rental canisters at the trailhead facilitated this storage option. A minority of backpacking parties (9%) persisted in using food hanging (a method easily overcome by SEKI bears), explaining that they had always stored food that way or that canisters were too small and heavy. This user group is sufficiently large that bears continued to obtain human food, and nuisance behaviors persisted. To ensure that backpackers universally store food in a way that it is unavailable to bears (canisters or lockers), regulations may be desirable.
Fatty acids (FA) ingested in the diet are incorporated into the adipose stores of predators in predictable ways. Consequently, the FA composition of the diet influences the FA composition of a consumer's adipose tissue. Over the last decade, this basic premise has been used to examine the foraging habits and trophic relationships of a variety of predators, including seals, whales, seabirds, and bears. By examining differences in the relative proportions of multiple FA (i.e., a FA signature), patterns of foraging can be detected across regions, over time, or among intraspecific groups. Development of FA signature analysis has reached the point where FA data from predators and prey can be incorporated into a statistical model that generates a quantitative estimate of predator diet. Here, I review how FA signature analysis has been applied to both qualitative and quantitative examinations of bear foraging. I discuss the techniques used to analyze and interpret FA data as well as some of the limitations of this approach. Finally, I suggest how this cost-effective technique can be further developed to provide an accurate picture of the ecological role of bears in a variety of habitats.
We report on 3 cases of mixed-aged litters (young born in different years) in brown bears (Ursus arctos); in 1 instance the cub-of-the-year (hereafter called cubs) died in the den. Two cases occurred in Sweden after mothers were separated from their young during the breeding season. In one, the mother was separated from the accompanying cub for at least 12.5 hours and possibly up to 3.3 days, and later possibly separated for 4 days. In the other, the mother was separated from her yearling at least 3 times for 1–14, 1–6 and 1–6 days. She was with a male during the first separation. Specific events that produced the mixed-aged litter observed in Greater Yellowstone Ecosystem were unknown and our interpretation is based on estimates of ages of accompanying young from photographs. The observation of only 2 mixed-aged litters, after den emergence, from a sample of 406 observed cub litters accompanying radiomarked females confirms the rarity of this phenomenon. The mechanism apparently includes a short separation of mother and young, and, in the case of cubs, the mother must mate while lactating. Better understanding of the physiological mechanisms that allow mixed-age litters would help us in the debate about the occurrence of sexually selected infanticide in bears.
We investigated the denning ecology of 19 (12 males and 7 females) radiocollared Asiatic black bears (Ursus thibetanus) from 2001 to 2004 in the Misaka Mountains, central Japan. We approached 14 dens of 5 females on foot. Thirteen dens were located in cavities that formed between the roots of trees growing on the upper edges of landslides or steep inclines, and 1 den was located in a cavity under a rocky ledge. We were unable to access 39 more dens for which we had approximate locations due to a combination of distance from roads, steep terrain, and high shrub densities. All 53 dens we approached or approximately located were on steep slopes. There were few large trees with large cavities in the study area, which may explain why we failed to find any dens in such cavities.