Culture is widely accepted as an important social factor present across a wide range of species. Bears have a culture as defined as behavioral traditions inherited through social learning usually ...from mothers to offspring. Successful bear cultures can enhance fitness and resource exploitation benefits. In contrast, some bear cultures related to response to humans and human‐related foods can be maladaptive and result in reduced fitness and direct mortality. In environments with minimal human influence most bear culture has evolved over generations to be beneficial and well adapted to enhance fitness. However, most bears across the world do not live in areas with minimal human influence and in these areas, bear culture is often changed by bear interactions with humans, usually to the detriment of bear survival. We highlight the importance of identifying unique bear cultural traits that allow efficient use of local resources and the value of careful management to preserve these adaptive cultural behaviors. It is also important to select against maladaptive cultural behaviors that are usually related to humans in order to reduce human–bear conflicts and high bear mortality. We use examples from Yellowstone National Park to demonstrate how long‐term management to reduce maladaptive bear cultures related to humans has resulted in healthy bear populations and a low level of human–bear conflict in spite of a high number of Yellowstone National Park visitors in close association with bears.
Bears have a culture as defined as behavioral traditions inherited through social learning usually from mothers to offspring. Successful bear cultures can enhance fitness and resource exploitation benefits. We highlight the importance of identifying unique bear cultural traits that allow efficient use of local resources and the value of careful management to preserve these adaptive cultural behaviors.
Avoiding humans will be more difficult and energetically costly for animals as outdoor recreation increases and people venture farther into wildland areas that provide high‐quality habitat for ...wildlife. Restricting human access can be an attractive management tool to mitigate effects of human recreation activities on wildlife; however, the efficacy of such measures is rarely assessed. In 1982, Yellowstone National Park identified areas important to grizzly bears (Ursus arctos) to help protect critical grizzly bear habitat and reduce the likelihood of human injuries by bears. Referred to as bear management areas (BMAs), human access is restricted in these areas for 2–8 months each year, with timing and type of restrictions varying by area. We examined 2 datasets to evaluate grizzly bear selection of BMAs and differences of bear density in BMAs and non‐BMAs. First, we used 17 years of recent global positioning system telemetry data for grizzly bears to assess their selection of BMAs during periods when human access was allowed, and when access was restricted. We used step‐selection functions to test the hypothesis that bears spend time in places that allow them to avoid people and select quality food sources. There was support that grizzly bears differentially select for BMAs regardless of whether human access was restricted at the time, compared with areas outside BMAs, and that selection changed with sex and season. Only males during the summer and hyperphagic seasons changed their selection of BMAs based on whether access restrictions were in place, and overall, male bears preferred unrestricted BMAs (BMAs without restrictions in place). Females preferentially selected BMAs regardless of whether the area had access restrictions in place only during the mating season. Individuals varied widely in their preference for BMAs and access restrictions. Bears likely choose to spend time in BMAs based on available food resources rather than restrictions to human access. Supporting this interpretation, our analyses indicated that a greater proportion of BMA in an area was associated with higher densities of grizzly bear. Thus, restrictions to human access likely help reduce the potential for human–bear interactions, accomplishing one of the original objectives for establishing the BMAs.
In 1982, Yellowstone National Park instituted seasonal (from 2 to 8 months) restrictions to human access in areas thought to be important to grizzly bears (Bear Management Areas, BMAs), to help protect critical habitat for grizzly bears and reduce the likelihood of human injuries by bears. We evaluated selection of these areas by grizzly bears and found support that they selected BMAs, but that bears likely chose to spend time in these areas for the resources available rather than the restrictions to human access. We also found higher densities of grizzly bears inside BMAs, compared with outside these areas, suggesting that restrictions of human access likely helped to reduce the potential for human‐bear interactions.
The quality and availability of resources are known to influence spatial patterns of animal density. In Yellowstone National Park, relationships between the availability of resources and the ...distribution of grizzly bears (Ursus arctos) have been explored but have yet to be examined in American black bears (Ursus americanus). We conducted non‐invasive genetic sampling during 2017–2018 (mid‐May to mid‐July) and applied spatially explicit capture‐recapture models to estimate density of black bears and examine associations with landscape features. In both years, density estimates were higher in forested vegetation communities, which provide food resources and thermal and security cover preferred by black bears, compared with non‐forested areas. In 2017, density also varied by sex, with female densities being higher than males. Based on our estimates, the northern range of Yellowstone National Park supports one of the highest densities of black bears (20 black bears/100 km2) in the northern Rocky Mountains (6–12 black bears/100 km2 in other regions). Given these high densities, black bears could influence other wildlife populations more than previously thought, such as through displacement of sympatric predators from kills. Our study provides the first spatially explicit estimates of density for black bears within an ecosystem that contains the majority of North America's large mammal species. Our density estimates provide a baseline that can be used for future research and management decisions of black bears, including efforts to reduce human–bear conflicts.
A spatially explicit density estimate of American black bears was generated for the northern range of Yellowstone National Park. Density estimates were higher than expected and provide baseline information to use in future management decisions and track trends in the population over time.
Understanding the density‐dependent processes that drive population demography in a changing world is critical in ecology, yet measuring performance–density relationships in long‐lived mammalian ...species demands long‐term data, limiting scientists' ability to observe such mechanisms. We tested performance–density relationships for an opportunistic omnivore, grizzly bears (Ursus arctos, Linnaeus, 1758) in the Greater Yellowstone Ecosystem, with estimates of body composition (lean body mass and percent body fat) serving as indicators of individual performance over two decades (2000–2020) during which time pronounced environmental changes have occurred. Several high‐calorie foods for grizzly bears have mostly declined in recent decades (e.g., whitebark pine Pinus albicaulis, Engelm, 1863), while increasing human impacts from recreation, development, and long‐term shifts in temperatures and precipitation are altering the ecosystem. We hypothesized that individual lean body mass declines as population density increases (H1), and that this effect would be more pronounced among growing individuals (H2). We also hypothesized that omnivory helps grizzly bears buffer energy intake from changing foods, with body fat levels being independent from population density and environmental changes (H3). Our analyses showed that individual lean body mass was negatively related to population density, particularly among growing‐age females, supporting H1 and partially H2. In contrast, population density or sex had little effect on body fat levels and rate of accumulation, indicating that sufficient food resources were available on the landscape to accommodate successful use of shifting food sources, supporting H3. Our results offer important insights into ecological feedback mechanisms driving individual performances within a population undergoing demographic and ecosystem‐level changes. However, synergistic effects of continued climate change and increased human impacts could lead to more extreme changes in food availability and affect observed population resilience mechanisms. Our findings underscore the importance of long‐term studies in protected areas when investigating complex ecological relationships in an increasingly anthropogenic world.
Revealing mechanisms underlying demography of long‐lived omnivores is of critical in a changing world. Using long‐term data on grizzly bears from the Greater Yellowstone Ecosystem, we show that variation in individual performance (measured as lean body mass) is primarily a density‐dependent process, particularly among younger females. Conversely, large omnivores exhibit plastic tactics in the face of current landscape‐level perturbations maintaining seasonal threshold of body fat required for hibernation and reproduction. However, synergistic effects of continued climate change and other forms of human impact could in the future affect food availability, and consequently, the observed population resilience mechanisms.
In 2011, 2 hikers were killed by grizzly bears (Ursus arctos) in separate incidents on backcountry trails in Hayden Valley, Yellowstone National Park, USA (YNP). Hayden Valley provides prime habitat ...for grizzly bears and is known to have high densities of bears. During 1970–2017, 23% (10 of 44) of all backcountry grizzly bear–inflicted human injuries and fatalities in YNP occurred in the valley even though it comprises only 1% of the park. In addition, 3 of the last 5 fatal bear attacks in the park occurred in the valley. We evaluated retrospectively whether restrictions and closures on visitor recreational activity would have prevented many of these injuries. We considered prohibitions on recreational activity during seasons when bears forage for specific high-quality foods; potential closures that coincided with the times of day and year bears were most active in the valley; and visitor use restrictions that would have prevented the most common human behaviors associated with grizzly bear–caused human injuries. The food-based closure that may have prevented the most human injuries occurred during middle to late summer when bears scavenge bison (Bison bison) carcasses that result from annual rutting behavior of bison in the valley. However, safety precautions such as hiking in groups of ≥3, remaining on maintained trails, and carrying bear spray would likely reduce the frequency of bear-inflicted human injuries more than most food-based seasonal closures. Our analyses provide broadly applicable findings regarding use of visitor behavior restrictions and seasonal closures to reduce the risk of bear-inflicted human injuries.
Responses of American black bears to spring resources Bowersock, Nathaniel R.; Litt, Andrea R.; Merkle, Jerod A. ...
Ecosphere,
November 2021, 2021-11-00, 20211101, 2021-11-01, Letnik:
12, Številka:
11
Journal Article
Recenzirano
Odprti dostop
In temperate regions of the world, food resources are seasonally limited, which causes some wildlife species to seek out nutrient‐rich resources to better meet their caloric needs. Animals that ...utilize high‐quality resources may reap fitness benefits as they prepare for mating, migration, or hibernation. American black bears (Ursus americanus) are omnivores that consume both plant and animal food resources to meet macronutrient needs. Black bears capitalize on high‐quality food resources, such as soft mast in summer and hard mast during autumn, but we know less about the importance of resource quality during spring. Therefore, we sought to understand the relationship between the spatiotemporal variation in the availability of food and resource selection of black bears during spring. We also aimed to infer potential changes in foraging tactics, from opportunistic foraging to more active selection. Although black bears are described as opportunistic omnivores, we hypothesized they select areas with high‐quality forage when available. We instrumented 7 black bears with GPS collars in 2017 and 2018 and estimated fine‐scale resource selection with integrated step‐selection functions. We found evidence that black bear movements were influenced by forage quality of vegetative food resources. However, we failed to find evidence that black bears actively alter their movements to take advantage of seasonal neonate elk. Although black bears represent a substantial cause of mortality for neonate elk, we found that black bears likely feed on neonates encountered opportunistically while traveling between patches of high‐quality forage. Few studies have shown evidence of an omnivorous species capitalizing on spatiotemporal variation in forage quality, yet our data suggest this may be an important strategy for species with diverse diets, particularly where resources are seasonally limited.
Wildlife managers often rely on permanent or temporary area closures to reduce the impact of human presence on sensitive species. In 1982, Yellowstone National Park created a program to protect ...threatened grizzly bears (Ursus arctos) from human disturbance. The bear management area (BMA) program created areas of the park where human access was restricted. The program was designed to allow unhindered foraging opportunities for bears, decrease the risk of habituation, and provide safety for backcountry users. The objective of our study was to evaluate human-bear interaction in BMAs and determine if they were effective. We used human and grizzly bear global positioning system location data to study 6 of 16 BMAs from 2007 to 2009. We contrasted data when BMAs were unrestricted (open human access) and restricted (limited human access). We used location data collected when BMAs were unrestricted to delineate a human recreation area (HRA) and determined a daily human active and inactive period. We applied the HRA and daily activity times to bear location data and evaluated how bear movement behavior changed when people were present and absent. We found that grizzly bears were twice as likely to be within the HRA when BMAs were restricted. We also found that grizzly bears were more than twice as likely to be within the HRA when BMAs were unrestricted, but people were inactive. Our results suggest that human presence can displace grizzly bears if people are allowed unrestricted access to the 6 BMAs in our study. Our study provides evidence for the utility of management closures designed to protect a threatened species in a well-visited park. Our approach can be reapplied by managers interested in balancing wildlife conservation and human recreation.
Global positioning system (GPS) wildlife collars have revolutionized wildlife research. Studies of predation by free-ranging carnivores have particularly benefited from the application of location ...clustering algorithms to determine when and where predation events occur. These studies have changed our understanding of large carnivore behavior, but the gains have concentrated on obligate carnivores. Facultative carnivores, such as grizzly/brown bears (Ursus arctos), exhibit a variety of behaviors that can lead to the formation of GPS clusters. We combined clustering techniques with field site investigations of grizzly bear GPS locations (n = 732 site investigations; 2004â2011) to produce 174 GPS clusters where documented behavior was partitioned into five classes (large-biomass carcass, small-biomass carcass, old carcass, non-carcass activity, and resting). We used multinomial logistic regression to predict the probability of clusters belonging to each class. Two cross-validation methodsâleaving out individual clusters, or leaving out individual bearsâshowed that correct prediction of bear visitation to large-biomass carcasses was 78â88 %, whereas the false-positive rate was 18â24 %. As a case study, we applied our predictive model to a GPS data set of 266 bear-years in the Greater Yellowstone Ecosystem (2002â2011) and examined trends in carcass visitation during fall hyperphagia (SeptemberâOctober). We identified 1997 spatial GPS clusters, of which 347 were predicted to be large-biomass carcasses. We used the clustered data to develop a carcass visitation index, which varied annually, but more than doubled during the study period. Our study demonstrates the effectiveness and utility of identifying GPS clusters associated with carcass visitation by a facultative carnivore.
Diversionary feeding uses food to lure animals away from areas where they are unwanted or could cause conflicts with people. With bears (Ursidae) increasingly attracted to human food sources ...worldwide, diversionary feeding represents a seemingly logical and publicly acceptable means of alleviating conflicts. Feeding wildlife is widely practiced in Europe to enhance hunting and reduce conflicts, but feeding of bears is discouraged across North America. The efficacy and potential side-effects of bear feeding remain an open question because of a lack of rigorous studies. Here we examine 5 case studies from which we attempt to draw inferences about feeding as a conflict-mitigation strategy. Studies included U.S. national parks, where after bear feeding was banned conflicts were reduced; Aspen, Colorado, where lucrative dumpsters in town did not divert bears from using human-related foods at other sources; rural Minnesota, where results of intentional feeding of a small sample of bears were confounded with other variables; the Tahoe Basin of California–Nevada, where an emergency feeding effort during a drought-caused food failure seemed to reduce conflicts within approximately 1 km of the feeding site; and Slovenia, where a high density of feeders at established locations seemed to divert bears from using settlements during autumn hyperphagia. Although none of these studies were true experiments with treatments and controls, the range of circumstances yielded insights into when feeding could be effective: when food demands are not readily met by natural foods; when the provisioned food is easily found outside the potential conflict area; when the food is attractive; and when bears do not associate the feeding with people. However, long-term feeding may increase bear population size, which may increase conflicts overall, or trigger a demand for population control. Diversionary feeding, if used, should be conducted as an adaptive management strategy by professionals so as to learn more about factors influencing its effectiveness.
Predatory fish introduction can cause cascading changes within recipient freshwater ecosystems. Linkages to avian and terrestrial food webs may occur, but effects are thought to attenuate across ...ecosystem boundaries. Using data spanning more than four decades (1972-2017), we demonstrate that lake trout invasion of Yellowstone Lake added a novel, piscivorous trophic level resulting in a precipitous decline of prey fish, including Yellowstone cutthroat trout. Plankton assemblages within the lake were altered, and nutrient transport to tributary streams was reduced. Effects across the aquatic-terrestrial ecosystem boundary remained strong (log response ratio ≤ 1.07) as grizzly bears and black bears necessarily sought alternative foods. Nest density and success of ospreys greatly declined. Bald eagles shifted their diet to compensate for the cutthroat trout loss. These interactions across multiple trophic levels both within and outside of the invaded lake highlight the potential substantial influence of an introduced predatory fish on otherwise pristine ecosystems.
PDF
