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Mark Hebblewhite 《The Journal of wildlife management》2011,75(8):1724-1730
Sommers et al. (2010) reported that recolonizing predators increased bovine calf mortality rates in the Upper Green River Cattle Allotment in western Wyoming. However, Sommers et al. (2010) failed to consider multiple competing hypotheses explaining calf loss rates, increasing the likelihood that their results are actually spurious. I reanalyzed their data using a multiple competing hypotheses framework that considered effects of livestock density, summer precipitation, bias in reporting rates, and whether mortality by different predator species was compensatory. I found support for a confounded web of factors influencing calf losses. Calf losses increased with livestock density (which increased during the study), but also during drier summers and with increasing rancher reporting rates. Although both wolves (Canis lupus) and grizzly bears (Ursus arctos) did increase calf losses, the presence of just grizzly bears alone did not significantly increase calf losses. Unconditional estimates of the effects of wolves and grizzly bears on calf losses were only 2.0% (95% CI 0.53–3.81), compared to 3.6% reported by Sommers et al. (2010). Most importantly, however, I report bias in favor of livestock producers in the authors' assumptions that cast further doubt on the rigor of their results. In conclusion, I recommend managers not consider the spurious predator compensation factors reported by Sommers et al. (2010) to be reliable. © 2011 The Wildlife Society. 相似文献
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Mark Hebblewhite Daniel R. Eacker Scott Eggeman Holger Bohm Evelyn H. Merrill 《Oikos》2018,127(9):1304-1318
Migration is expected to benefit individuals through exposure to higher quality forage and reducing predation rates more than non‐migratory conspecifics. Previous studies of partially migratory ungulates (with migrant and resident individuals) have focused on bottom–up factors regulating resident and migrant segments, yet differential predation between strategies could also be a density‐dependent regulatory mechanism. Our study tested for density‐dependence in mortality, as well as mechanisms of bottom–up or top–down regulation in the resident and migrant portions of the partially migratory Ya Ha Tinda elk population. We tested for density dependence in adult female and juvenile survival rates, and then discriminated between predator‐ and food‐regulation hypotheses by testing for density‐dependence amongst mortality causes for adult female elk. Notably, the population declined almost 70% from near previously published estimates of carrying capacity over 10 years, providing ideal conditions to test for density dependence. In contrast to predictions, we found only weak support for density dependence in adult survival and juvenile survival. We also found few differences between migrant and resident elk in adult or juvenile survival, though juvenile survival differences were biologically significant. Predation by humans and grizzly bears was density dependent, but similar between migratory strategies. Predation by wolves was the leading known cause of mortality, yet remained constant with declining elk density equally for both migrant and resident elk, indicating wolf predation was density‐independent. Instead of being strongly regulated by food or predation, we found adult female survival was driven by density‐independent predation and climatic factors. The few differences between migratory strategies suggest equivalent fitness payoffs for migrants and residents. This population is being limited by density‐independent predation leading to declines of both migratory strategies. Our results challenge classical predator–prey theory, and call for better integration between predator–prey and migration theory. 相似文献
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Thomas A. Rogers Bryan Bedrosian Jon Graham Kerry R. Foresman 《The Journal of wildlife management》2012,76(3):575-582
Ingestion of lead rifle bullet fragments found in discarded hunter-harvested ungulate gut piles negatively affects avian wildlife. Some large carnivores, such as grizzly bears, are also known to target these gut piles as a food source and are therefore potentially at risk of lead exposure. We investigated whether large carnivores in the greater Yellowstone ecosystem were exposed to lead, and if so, if ammunition ingested from gut piles was an apparent source of exposure. Grizzly bears (Ursus arctos, n = 82) exhibited higher blood lead levels (median = 4.4 µg/dL, range 1.1–18.6 µg/dL) than black bears (Ursus americanus, n = 35, median = 1.6, range 0.5–6.9 µg/dL), but blood lead levels did not increase during the autumn hunting season when potentially lead-tainted gut piles are available. Wolves (Canis lupus, n = 21) and cougars (Puma concolor, n = 8) showed lead concentrations near or below the minimum level of detection in both blood and tissue samples. Unlike findings in previous studies on avian scavengers, we did not find lead ammunition fragments to be a widespread source of lead exposure in large carnivores. Grizzly bears do, however, exhibit blood lead levels that are higher than what is considered safe in humans, but the source of this exposure remains unknown. © 2011 The Wildlife Society. 相似文献
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ROMAN GULA 《The Journal of wildlife management》2008,72(1):283-289
Abstract As wolves (Canis lupus) recover in Poland, their depredation on domestic animals is increasing, as have conflicts between wolves and farmers. From 1998 to 2004, I investigated spatial and temporal patterns of 591 verified incidents of wolf depredation in the eastern part of the Polish Carpathian Mountains. The wolf population I surveyed covered an estimated range of 4,993 km2. Depredation occurred over 1,595 km2 of that area. Sheep accounted for 84.8% of domestic animals killed by wolves. Depredation on sheep and number of sheep farms attacked by wolves increased between 1998 and 2004 (r2 = 0.61, P = 0.04 and r2 = 0.89, P = 0.02, respectively). The number of wolf attacks on sheep farms in a given year were negatively correlated to red deer (Cervus elaphus) population numbers (R2 = 0.69, P = 0.02). The amount of depredation caused by each of the 4 monitored packs was best explained by farm density in their territories (R2 = 0.59, P = 0.004). Number of attacks recorded on farms was positively correlated to distance from the farm to the pack's den and rendezvous sites (R2 = 0.16, P = 0.04). Of depredation recorded in the 4 pack's territories I surveyed, 77% occurred in 4 farms with no or inadequate protection. I concluded that wolf depredation in the studied area is opportunistic. Wolf predation intensity is a function of decreasing abundance of red deer, the density of sheep farms, and proximity of farms to the summer activity centers of wolf packs, and it is facilitated by poor husbandry practices. These results can aid in preventing wolf depredation and provide a foundation for a wolf management plan. 相似文献
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JASON E. HAWLEY THOMAS M. GEHRING RONALD N. SCHULTZ SHAWN T. ROSSLER ADRIAN P. WYDEVEN 《The Journal of wildlife management》2009,73(4):518-525
ABSTRACT Lethal control alone has not proven entirely effective in reducing gray wolf (Canis lupus) depredations in chronic problem areas. Opponents of lethal control argue that more emphasis should be placed on integrating nonlethal strategies into current management. However, few evaluations have tested the effectiveness of nonlethal options. We compared behavior patterns in terms of frequency and duration of bait station visits for 5 wolves fitted with shock collars to 5 control animals inhabiting wolf pack territories in northern Wisconsin during summers of 2003 and 2004. Shock collared wolves spent less time and made fewer visits to bait station zones than did control animals. During and after shocking, wolves shifted 0.7 km away from the bait station zone. Although active shocking did restrict wolf access, which could be useful in controlling wolf depredations during a limited time period, conditioning was not clearly demonstrated once shocking ceased. The effect of shock collar design and operation on long-term conditioning and shock-conditioned wolves on pack behavior needs further study. If long-term conditioning is possible, shock collars could be used by wildlife managers as a nonlethal wolf management method in chronic problem areas where lethal control has proven ineffective. 相似文献
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Could we live with reintroduced large carnivores in the UK? 总被引:2,自引:0,他引:2
CHARLES J. WILSON 《Mammal Review》2004,34(3):211-232
1. Literature on the wolf Canis lupus, brown bear Ursus arctos and lynx Lynx lynx is reviewed to determine if sufficient semi‐natural habitat exists in the UK for a viable population of any of these species and to assess the potential risks to human safety, livestock and economically valuable wildlife. Public attitudes to the recovery and reintroduction of some other mammals are also briefly reviewed. 2. The large home range sizes and low population densities of large carnivores mean that the Scottish Highlands is the only UK region with the potential to support a viable population. Human population density is also lower in the Highlands and the density of wild ungulate prey higher than in many parts of Europe where large carnivores survive. 3. Attacks on people have been recorded in Europe for healthy bears and for rabid bears and wolves but there are no reports of attacks by lynx. Bears are more carnivorous in the north of their range than in the south and although wild mammals seldom appear to be important prey serious predation of livestock can occur. Livestock predation is also reported for the wolf and the lynx but they appear to prefer wild prey if available. However, mass kills of up to 100 or more sheep are occasionally recorded for wolves. 4. Attitudes to reintroductions and carnivores generally tend to be favourable amongst the general public, but negative amongst those most likely to be adversely affected. Fears for human safety and significant livestock predation with bears and wolves, respectively, suggest that reintroduction of these species is unlikely to be acceptable in the foreseeable future. Reintroduction of the lynx may be feasible but habitat suitability and potential impact on vulnerable native wildlife need to be assessed. Socio‐economic and legal issues also need to be addressed before such a reintroduction is considered. 相似文献
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Wolf (Canis lupus) diets and potential effects on prey have been a prominent subject of interest to wildlife researchers and managers since reintroduction into Yellowstone National Park, Wyoming, USA, in 1995 and 1996. Post-reintroduction, wolves expanded south and recolonized areas in the southern Yellowstone ecosystem. Elk (Cervus elaphus) in this area are supplementally fed during winter (Dec–Mar) at state-managed feedgrounds, resulting in high-density congregations of elk. From December to March 2000–2007, we determined the winter predation patterns of wolves by examining the remains of 289 wolf kills on 3 state-managed feedgrounds and adjacent winter range near Jackson, Wyoming. During winters 2002–2005, we also monitored the movements of radio-collared elk on feedgrounds to describe the response of elk to the presence of wolf kills. Thirty-seven percent (n = 106) of kills were located on elk feedgrounds where elk composition included 49% calves, 42% adult females, 5% adult males, and 5% unknown. Sixty-three percent (n = 183) of kills were located on winter range adjacent to feedgrounds and prey species consisted of 90% elk (38% calves, 35% adult females, 24% adult males, 2% unknown), 9% moose (Alces alces; 13% calves, 69% adult females, 6% adult males, 1% unknown), 1% mule deer (Odocoileus hemionus; 1 fawn, 1 adult female), and 0.5% adult female bison (Bison bison). Mean age of elk killed on feedgrounds was 4.2 years (range = 0–20) and 4.6 years (range = 0–23) on winter range. Calves were selected more than available in most years with female elk killed less than expected. Adult males were killed more than expected in 2005–2007. Eighty-eight percent (n = 198) of the time elk remained on the feedground even when wolves made a kill. Less commonly, elk left the feedground, gathered in larger herds on adjacent feedgrounds absent of wolves, and returned within a few days (6%, n = 13) or left the feedground for another feedground and did not return for the rest of the winter (6%; n = 14). Elk were less likely to leave feedgrounds in the presence of a wolf kill when there were more elk on that feedground. Elk left feedgrounds with greater topography and tree cover (Alkali and Fish Creek) and gathered on the flat, open feedgrounds (Patrol Cabin) more frequently than they left flat, open feedgrounds for feedgrounds with greater topography and tree cover. Our results indicate wolves in our study area primarily preyed on elk and exhibited a strong preference for elk calves. High-density concentrations of elk on feedgrounds will continue to be an attractant for wolves. Although elk leave feedgrounds for reasons other than wolf presence, any displacement of elk from feedgrounds due to wolves will be temporary. State managers have the ability to alter management strategies (e.g., increasing wolf harvest, phasing out elk feeding, increasing the intensity of elk feeding) in an effort to affect predator-prey relationships. © 2019 The Wildlife Society. 相似文献
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Jeff Vance Martin 《Conservation Science and Practice》2021,3(3):e197
Threats posed by wild predators to livestock production have too often resulted in human–wildlife conflict, to the detriment of these keystone species and broader biodiversity conservation. Long-standard practices of lethal control are increasingly seen as costly, controversial, and ineffective, however, with nonlethal alternatives ever more prominent. In addition to assessing these tools' ecological effectiveness, there remains a key role for the social sciences, particularly qualitative research, in identifying obstacles to and opportunities for the long-term sustainability and scaling up of these coexistence interventions. The Wood River Wolf Project (WRWP), a collaboration among ranchers, environmental organizations, and government agencies in Blaine County, Idaho, has pursued coexistence between gray wolves and domestic sheep since 2008, demonstrating and developing nonlethal techniques and garnering regional and international attention as a model for collaborative coexistence. Yet the Project has also struggled with changing conditions and internal challenges. Investigation of this prominent effort—its history and practices as well as the broader socio-political and economic context—highlights the challenges of adaptive governance in the face of reduced capacity and hostile legal-political contexts, while providing important insights for practitioners and policymakers promoting wildlife coexistence in shared landscapes. 相似文献
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Nils J. Pedersen Todd J. Brinkman Richard T. Shideler Craig J. Perham 《Conservation Science and Practice》2020,2(7):e215
Industrial off-road activity in winter overlaps denning habitat of polar bear (Ursus maritimus) and grizzly bear (Ursus arctos) in the North Slope oilfields of Alaska (United States). To prevent disturbance of dens, managers have used forward-looking infrared (FLIR) cameras to detect dens, but the effectiveness of FLIR under different environmental conditions is unresolved. Our objective was to evaluate the effects of environmental variables on FLIR-based techniques for arctic bear den detection. Using a FLIR-equipped unmanned aircraft system (UAS), we conducted observations of artificial polar bear (APD) and grizzly bear (AGD) dens from horizontal and vertical perspectives between December 2016 and April 2017. We recorded physical characteristics of artificial dens and weather conditions present during each observation. We captured 291 images and classified each as detection or nondetection based on the number of pixels representative of a den “hot spot.” We used logistic regression to model the effects of four weather variables on the odds of detection (detection). We found that UAS-FLIR detects APDs two times better than AGDs, and that for both species detections are four times more likely from the vertical than horizontal perspective. Lower air temperature and wind speed, and the absence of precipitation and sunlight increased detection for APDs. A 1°C increase in air temperature lowered detection by 12% for APDs and by 8% for AGDs. We recommend that UAS-FLIR surveys be conducted early in the denning season, on cold, clear days, with calm winds, in the absence of sunlight (e.g., civil twilight). Our study further refines the application of FLIR techniques for arctic bear den detection and offers practical recommendations for optimizing detection. Putative den locations should be confirmed by a secondary method to minimize disturbance as anthropogenic activity continues in the Arctic. 相似文献
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The fossil record indicates that the brown bear (Ursus arctos) colonized North America from Asia over 50 000 years ago. The species historically occupied the western United States and northern Mexico but has been extirpated from over 99% of this range in the last two centuries. To evaluate colonization hypotheses, subspecific classifications, and historical patterns and levels of genetic diversity in this region, we sequenced 229 nucleotides of the mitochondrial DNA control region in 108 museum specimens. The work was set in a global context by synthesizing all previous brown bear control region sequences from around the world. In mid-latitude North America a single moderately diverse clade is observed, represented by 23 haplotypes with up to 3.5% divergence. Only eight of 23 haplotypes (35%) are observed in the extensively sampled extant populations suggesting a substantial loss of genetic variability. The restriction of all haplotypes from mid-latitude North America to a single clade suggests that this region was founded by bears with a similar maternal ancestry. However, the levels and distributions of diversity also suggest that the colonizing population was not a small founder event, and that expansion occurred long enough ago for local mutations to accrue. Our data are consistent with recent genetic evidence that brown bears were south of the ice prior to the last glacial maximum. There is no support for previous subspecies designations, although bears of the southwestern United States may have had a distinctive, but recent, pattern of ancestry. 相似文献
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Grizzly bears (Ursus arctos) cohabit landscapes with a diversity of ungulates, but the degree to which grizzly bears are carnivorous is unclear and likely varies across landscapes. We used stable isotopes of carbon and nitrogen to infer seasonal diets of grizzly bears in northern British Columbia while studying predator–prey dynamics in a largely undisturbed system. We found high seasonal variation in diets among individuals; males consumed more ungulate prey than did females throughout the year. In fall, both sexes increased their consumption of prey; large ungulates constituted 51% and 32% of the fall diets of males and females, respectively. This increase in carnivory appeared to be primarily associated with consumption of elk (Cervus elaphus). Estimates of prey proportions in the diets of grizzly bears were highly sensitive to the range of tissue to diet discrimination values that were incorporated in isotope models. Small changes in discrimination values resulted in estimated prey intakes that varied more than threefold as a percentage of the diet depending on sex and season. We caution against using standard discrimination values, and we recommend that diet reconstructions using stable isotopes be based on tissue-specific values that would be appropriate for the species of interest. © 2012 The Wildlife Society. 相似文献
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Michelle L. McLellan Bruce N. McLellan Rahel Sollmann Heiko U. Wittmer 《Ecology and evolution》2021,11(7):3422
Identifying mechanisms of population change is fundamental for conserving small and declining populations and determining effective management strategies. Few studies, however, have measured the demographic components of population change for small populations of mammals (<50 individuals). We estimated vital rates and trends in two adjacent but genetically distinct, threatened brown bear (Ursus arctos) populations in British Columbia, Canada, following the cessation of hunting. One population had approximately 45 resident bears but had some genetic and geographic connectivity to neighboring populations, while the other population had <25 individuals and was isolated. We estimated population‐specific vital rates by monitoring survival and reproduction of telemetered female bears and their dependent offspring from 2005 to 2018. In the larger, connected population, independent female survival was 1.00 (95% CI: 0.96–1.00) and the survival of cubs in their first year was 0.85 (95% CI: 0.62–0.95). In the smaller, isolated population, independent female survival was 0.81 (95% CI: 0.64–0.93) and first‐year cub survival was 0.33 (95% CI: 0.11–0.67). Reproductive rates did not differ between populations. The large differences in age‐specific survival estimates resulted in a projected population increase in the larger population (λ = 1.09; 95% CI: 1.04–1.13) and population decrease in the smaller population (λ = 0.84; 95% CI: 0.72–0.95). Low female survival in the smaller population was the result of both continued human‐caused mortality and an unusually high rate of natural mortality. Low cub survival may have been due to inbreeding and the loss of genetic diversity common in small populations, or to limited resources. In a systematic literature review, we compared our population trend estimates with those reported for other small populations (<300 individuals) of brown bears. Results suggest that once brown bear populations become small and isolated, populations rarely increase and, even with intensive management, recovery remains challenging. 相似文献
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JOHN D. C. LINNELL RONNY AANES JON E. SWENSON JOHN ODDEN MARTIN E. SMITH 《Biodiversity and Conservation》1997,6(9):1245-1257
Translocation of individual carnivores has been a standard management tool for decades in North America and southern Africa in response to livestock depredation and other conflict behaviours. As carnivore populations across Europe begin to increase it is expected that management problems will also increase. Before translocation becomes established as a management tool in Europe its success needs to be reviewed. In general, there has been very little follow-up of translocated animals. Almost no data exist on the subsequent levels of damage after translocation. Large carnivores have shown a consistent ability to return to the site of capture over distances of up to 400 km. Even those individuals that do not succeed in returning home roam over very large distances, best measured in units of hundreds of kilometres. Very few individuals remain at the release sites. Survival of translocated animals has occasionally been shown to be poor, often as a result of the large movements. In general, there needs to be a large area (hundreds or thousands of square kilometres) without conflict potential where the individuals can be released for the strategy to work. When such areas are not available, management efforts should concentrate on reducing conflict potential, or, where this is not practical, lethal control. This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献