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1.
    
ABSTRACT Studies of reintroduced animals are beneficial to evaluate the success of reintroduction programs and to understand factors influencing fitness of reintroduced individuals. The geographic distribution of the federally threatened Louisiana black bear (Ursus americanus luteolus) has been reduced to 3 isolated populations due to habitat loss and excessive harvest. We reintroduced 23 adult female Louisiana black bears and their cubs to east-central Louisiana, USA, and documented postrelease space use, survival, movements, and reproduction. Individual females used larger home ranges after reintroduction than they had in the source population (P = 0.037). Spring ranges of reintroduced females were smaller than summer, autumn, and annual ranges (all P < 0.09), which did not differ from each other (all P > 0.60). Survival of reintroduced females did not differ between their first (S = 0.933) and second (S = 1.00) year after release or from annual survival of females in the source population (S = 0.964–1.00). Mean straight-line distance traveled by females from their release sites to the center of established home ranges or last recorded locations was 22.7 km. Six females reproduced after reintroduction and produced 15 cubs. Mean postrelease litter size of parturient reintroduced females (2.5) was similar to reported mean litter size of females in the source population (2.4). Our results suggest that the Louisiana reintroduction program is proceeding favorably; however, future studies should continue to monitor survival and reproduction of reintroduced females in Louisiana. Additional demographic parameters (i.e., cub survival) should be estimated to allow for population viability analysis to determine if the new population is self-sustaining.  相似文献   

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ABSTRACT Understanding den selection for the federally threatened Louisiana black bear (Ursus americanus luteolus) will assist managers in effectively managing bear populations and the landscapes they inhabit. We assessed den selection of 72 female Louisiana black bears at multiple spatial scales in northern and central Louisiana, USA. We used 230 den-years to examine den type preference, microhabitat characteristics of dens, and effects of landscape characteristics on den selection. We also evaluated reuse of tree dens and their availability across several study areas. Bears selected tree dens more frequently (65%) than ground dens. Most (55%) ground dens were associated with standing or downed trees, and most tree dens were in baldcypress (Taxodium distichum; 86%) or surrounded by water (80%). Selection of ground dens was positively associated with landscape metrics related to presence of water, whereas selection of tree dens was positively associated with proximity to edge and greater proportions of swamp and areas containing water. Reuse of tree dens averaged 15% (range = 0–20%) across study areas and our estimates of tree-den availability indicated that tree dens were not a limiting resource for Louisiana black bears in the northern or central portions of Louisiana. Although Louisiana black bears demonstrated plasticity in den selection, we recommend managers use forest management practices that conserve appropriate tree dens and create ground-denning opportunities, because both would promote the recovery of Louisiana black bear populations.  相似文献   

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The Wallow Fire, the largest wildfire in Arizona history, encompassed 2,170 km2 and provided a rare opportunity to examine habitat selection and home ranges of American black bears (Ursus americanus) before and after a wildfire. We had fitted global positioning system (GPS) collars on 47 bears from 2005 to April 2011, and 10 of these were still collared when the fire started in May 2011. We captured and collared an additional 7 black bears within the fire perimeter post-fire (Jul–Sep 2011 and Jun 2012). To evaluate how black bears were affected by the fire, we fit a step selection function using a conditional mixed effects Poisson regression model to estimate the relative strength of black bear habitat selection in response to burn severity. Additionally, we estimated home range sizes using an autocorrelated kernel density estimator by means of a continuous-time movement model. We then used a generalized linear model with a negative binomial error distribution and mixed effects to estimate the effect of the burn severity on black bear home range size, while controlling for sex and drought. In spring and summer in years prior to the fire, bears selected areas that later burned in the fire. After the fire, bears used all burn severities, but their selection for high-severity burns decreased significantly in summer 2011 and fall 2012. Home range sizes were 3.06 times larger pre-fire than post-fire. Our study demonstrates that black bears continued to use all burn severities after a major wildfire, and that post-fire conditions did not result in expanded black bear home ranges.  相似文献   

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Abstract: We compared historic (1985–1992) and contemporary (2003–2006) black bear (Ursus americanus) den locations in Rocky Mountain National Park (RMNP), Colorado, USA, for habitat and physiographic attributes of den sites and used maximum entropy modeling to determine which factors were most influential in predicting den-site locations. We observed variability in the relationship between den locations and distance to trails and elevation over time. Locations of historic den sites were most associated with slope, elevation, and covertype, whereas contemporary sites were associated with slope, distance to roads, aspect, and canopy height. Although relationships to covariates differed between historic and contemporary periods, preferred den-site characteristics consistently included steep slopes and factors associated with greater snow depth. Distribution of den locations shifted toward areas closer to human developments, indicating little negative influence of this factor on den-site selection by black bears in RMNP.  相似文献   

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Abstract: Regional wildlife-habitat models are commonly developed but rarely tested with truly independent data. We tested a published habitat model for black bears (Ursus americanus) with new data collected in a different site in the same ecological region (i.e., Ouachita Mountains of Arkansas and Oklahoma, USA). We used a Mahalanobis distance model developed from relocations of black bears in Arkansas to produce a map layer of Mahalanobis distances on a study area in neighboring Oklahoma. We tested this modeled map layer with relocations of black bears on the Oklahoma area. The distributions of relocations of female black bears were consistent with model predictions. We conclude that this modeling approach can be used to predict regional suitability for a species of interest.  相似文献   

8.
At least 63 people were killed in 59 incidents by non-captive black bear (Ursus americanus) during 1900–2009. Fatal black bear attacks occurred in Canada and Alaska (n = 49) and in the lower 48 states (n = 14). There were 3.5 times as many fatal attacks in Canada and Alaska but only 1.75 times as many black bears, and much less human contact for black bears in Canada and Alaska. There was a weak positive correlation (rs = 0.56, P ≤ 0.000) between the estimated size of a bear population within a given jurisdiction and the number of fatal black bear attacks. Some jurisdictions had no fatal black bear attacks but had large estimated black bear populations. Of fatal attacks, 86% (54 of 63, 1.08/yr) occurred between 1960 and 2009. There was positive linear relationship between the number of fatal black bear attacks per decade and human population size in the United States and Canada per decade (r2 = 0.92, β = 0.000, P ≤ 0.001). Of fatal attacks, 91% (49 of 54) occurred on parties of 1 or 2 persons. In 38% (15 of 40) of incidents, peoples' food or garbage probably influenced the bear being in the attack location. We judged that the bear involved acted as a predator in 88% (49 of 56) of fatal incidents. Adult (n = 23) or subadult (n = 10) male bears were involved in 92% (33 of 36) of fatal predatory incidents, reflecting biological and behavioral differences between male and female bears. That most fatal black bear attacks were predatory and were carried out by 1 bear shows that females with young are not the most dangerous black bears. As a result of our research agencies managing black bear can more accurately understand the risk of being killed by a black bear, and can communicate this to the public. With training, people can learn to recognize the behaviors of a bear considering them as prey and can act to deter predation. © 2011 The Wildlife Society.  相似文献   

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ABSTRACT Understanding landscape structure and the role of habitat linkages is important to managing wildlife populations in fragmented landscapes. We present a data-based method for identifying local- and regional-scale habitat linkages for American black bears (Ursus americanus) on the Albemarle-Pamlico Peninsula of North Carolina, USA. We used weights-of-evidence, a discrete multivariate technique for combining spatial data, to make predictions about bear habitat use from 1,771 telemetry locations on 2 study areas (n = 35 bears). The model included 3 variables measured at a 0.2-km2 scale: forest cohesion, forest diversity, and forest-agriculture edge density, adequately describing important habitat characteristics for bears on our study area. We used 2 categories of unique habitat conditions to delineate favorable bear habitat, which correctly classified 79.5% of the bear locations in a 10-fold model validation. Forest cohesion and forest-agriculture edge density were the most powerful predictors of black bear habitat use. We used predicted probabilities of bear occurrence from the model to delineate habitat linkages among local and regional areas where bear densities were relatively high. Our models clearly identified 2 of the 3 sites previously recommended for wildlife underpasses on a new, 4-lane highway in the study area. Our approach yielded insights into how landscape metrics can be integrated to identify linkages suitable as habitat and dispersal routes.  相似文献   

10.
Human–wildlife interactions are often associated with a myriad of stakeholder groups, intense political scrutiny, and limited biological data, creating complex decision-making situations for wildlife management agencies. Limited research exists on the development and testing of tools (e.g., models to predict the spatial distribution of interactions) to reduce human–black bear (Ursus americanus) interactions (HBI). Available models predicting spatial distribution of HBI are usually developed at scales too large to predict across urban areas, are rarely tested against independent data sets, and usually do not incorporate both landscape and anthropogenic variables. Our objective was to develop a predictive modeling tool that could identify areas of high conflict potential across urban landscapes. We compared locations of HBI in Missoula, MT, recorded by Montana Fish, Wildlife & Parks from 2003 to 2008, to random locations using logistic regression. The final model discriminated the relative spatial probability of HBI within Missoula well, and a second study area moderately. The probability of HBI in Missoula increased when residents lived close to forested patches and major rivers and streams and in intermediate housing densities (approx. 6.59 houses/ha). Our results provide a wildlife management tool and a repeatable statistical framework that predicts spatial distribution of HBI using only a small set of variables. © 2011 The Wildlife Society.  相似文献   

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We defined patterns of habitat use and selection by female grizzly bears (Ursus arctos) in the Besa-Prophet watershed of northern British Columbia. We fitted 13 adult females with Geographic Positioning System (GPS) radio-collars and monitored them between 2001 and 2004. We examined patterns of habitat selection by grizzly bears relative to topographical attributes and 3 potential surrogates of food availability: land-cover class, vegetation biomass or quality (as measured by the Normalized Difference Vegetation Index), and selection value for prey species themselves (moose [Alces alces], elk [Cervus elaphus], woodland caribou [Rangifer tarandus], Stone's sheep [Ovis dalli stonei]). Although vegetation biomass and quality, and selection values for prey were important in seasonal selection by some individual bears, land-cover class, elevation, aspect, and vegetation diversity most influenced patterns of habitat selection across grizzly bears, which rely on availability of plant foods and encounters with ungulate prey. Grizzly bears as a group avoided conifer stands and areas of low vegetation diversity, and selected for burned land-cover classes and high vegetation diversity across seasons. They also selected mid elevations from what was available within seasonal ranges. Quantifying relative use of different attributes helped place selection patterns within the context of the landscape. Grizzly bears used higher elevations (1,595 ± 31 m SE) in spring and lower elevations (1,436 ± 27 m) in fall; the range of average elevations used among individuals was highest (500 m) during the summer. During all seasons, grizzly bears most frequented aspects with high solar gain. Use was distributed across 10 land-cover classes and depended on season. Management and conservation actions must maintain a diverse habitat matrix distributed across a large elevational gradient to ensure persistence of grizzly bears as levels of human access increase in the northern Rocky Mountains. © 2011 The Wildlife Society.  相似文献   

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Habitat fragmentation and loss contribute to isolation of wildlife populations and increased extinction risks for various species, including many large carnivores. We studied a small and isolated population of American black bears (Ursus americanus) that is of conservation concern in central Georgia, USA (i.e., central Georgia bear population [CGBP]). Our goal was to evaluate the potential for demographic and genetic interchange from neighboring bear populations to the CGBP. To evaluate resource selection and movement potential, we used 35,487 global positioning system locations collected every 20 minutes from 2012 to 2014 from 33 male bears in the CGBP. We then developed a step selection function model based on conditional logistic regression. Male bears chose steps that avoided crops, roads, and human developments and were closer to forests and woody wetlands than expected based on availability. We used a geographic information system to simulate 300 bear movement paths from nearby bear populations in northern Florida, northern Georgia, and southern Georgia to estimate the potential for immigration to the CGBP. Only 4 simulated movement paths from the nearby populations intersected the CGBP. The creation of a hypothetical 1-km-wide corridor between the southern Georgia population and the CGBP produced only minor improvements in interchange. Our findings suggest that demographic connectivity between the CGBP and surrounding bear populations may be limited, and coupled with previous works showing genetic isolation in the CGBP, that creation of corridors may have only marginal effects on restoring gene flow, at least in the near term. Management actions such as translocation and the establishment of stepping stone populations may be needed to increase the genetic diversity and demographic stability of bears in the CGBP. © 2021 The Wildlife Society.  相似文献   

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Understanding space-use patterns by elk (Cervus canadensis) is essential to alleviating human-elk conflicts, particularly when crop depredation by elk can make it harder to justify to the public the need to restore elk populations to regions with agricultural landscapes. In 2016–2017, we used global positioning system data from 20 female elk to investigate their selection for agricultural cover during the agricultural season (1 May–31 Oct) in northwestern Minnesota, USA. We estimated resource selection functions with resource availability defined at the home range scale. Elk space use was primarily determined by distance to forest cover in areas proximate to agricultural fields. During diurnal periods, elk selected areas with forest cover near agricultural fields planted with legumes and cereal. During nocturnal periods, elk selected for agricultural fields with little to no canopy and that were planted with legumes. We suggest that management of elk in northwestern Minnesota will require practices that discourage the use of agriculture by elk while improving natural habitats within areas managed for elk restoration. We suggest that forestry practices (i.e., thinning and burning) could improve cover and forage openings for elk in restoration areas. Furthermore, managers could work with agricultural producers where elk occur to plant crops favored by elk (i.e., legumes) outside known home ranges and plant fields within home ranges with crops that elk avoided (i.e., hay). Collectively, these practices may shift the ranges of elk herds into restoration areas and lower conflict between the public and elk restoration efforts. © 2020 The Wildlife Society.  相似文献   

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American black bears (Ursus americanus) were extirpated from Oklahoma, USA, in the early twentieth century but have since recolonized eastern portions of the state after immigrating from Arkansas, where they were successfully translocated. Within the last 2 decades, a population of black bears was detected in the Oklahoma Ozark region, prompting studies to determine population size, growth rate, and genetic makeup. To understand how black bears were recolonizing the human-dominated landscape, we investigated resource selection at 2 scales. Between 2011 and 2016, we collected global positioning system collar spatial data for 10 males and 13 females. We calculated average kernel density home ranges on a seasonal scale for all collared bears. We used generalized linear mixed models to calculate resource selection functions at the study area, defined by locations of all radio-collared black bears (second order) and the scale of individual black bear home ranges (third order). Resource selection did not differ significantly by sex. Black bears across seasons and scales selected riparian forest and moist oak (Quercus spp.) forest land cover types and mostly selected against indicators of human activity (e.g., pasture-prairie, anthropogenic land cover types, roads, and areas of high human population density). Black bears also selected areas with rugged terrain at high elevations, although not consistently across seasons and scales. Black bear recolonization appeared to be negatively affected by areas and features characterized as human-altered. Further expansion of the range of black bears may be limited by anthropogenic disturbance in the region. © 2021 The Wildlife Society.  相似文献   

15.
We describe primers and polymerase chain reaction conditions to amplify 21 tetranucleotide microsatellite DNA loci in black bears (Ursus americanus). We tested primers using individuals from two populations, one each in Georgia and Florida. Among individuals from Georgia (n = 29), primer pairs yielded an average of 2.9 alleles (range, one to four) and an average observed heterozygosity (HO) of 0.50 (range, 0.00 to 0.79). Among individuals from Florida (n = 19), primer pairs yielded an average of 5.7 alleles (range, one to 14) and an HO of 0.55 (range, 0.00 to 1.00). A comparison of previously developed markers with individuals from Georgia suggests that bear populations in Georgia and Florida have reduced allelic diversity relative to other populations.  相似文献   

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Grizzly bears (Ursus arctos) and American black bears (U. americanus) are sympatric in much of Yellowstone National Park. Three primary bear foods, cutthroat trout (Oncorhynchus clarki), whitebark pine (Pinus albicaulis) nuts, and elk (Cervus elaphus), have declined in recent years. Because park managers and the public are concerned about the impact created by reductions in these foods, we quantified bear diets to determine how bears living near Yellowstone Lake are adjusting. We estimated diets using: 1) stable isotope and mercury analyses of hair samples collected from captured bears and from hair collection sites established along cutthroat trout spawning streams and 2) visits to recent locations occupied by bears wearing Global Positioning System collars to identify signs of feeding behavior and to collect scats for macroscopic identification of residues. Approximately 45 ± 22% ( ± SD) of the assimilated nitrogen consumed by male grizzly bears, 38 ± 20% by female grizzly bears, and 23 ± 7% by male and female black bears came from animal matter. These assimilated dietary proportions for female grizzly bears were the same as 10 years earlier in the Lake area and 30 years earlier in the Greater Yellowstone Ecosystem. However, the proportion of meat in the assimilated diet of male grizzly bears decreased over both time frames. The estimated biomass of cutthroat trout consumed by grizzly bears and black bears declined 70% and 95%, respectively, in the decade between 1997–2000 and 2007–2009. Grizzly bears killed an elk calf every 4.3 ± 2.7 days and black bears every 8.0 ± 4.0 days during June. Elk accounted for 84% of all ungulates consumed by both bear species. Whitebark pine nuts continue to be a primary food source for both grizzly bears and black bears when abundant, but are replaced by false-truffles (Rhizopogon spp.) in the diets of female grizzly bears and black bears when nut crops are minimal. Thus, both grizzly bears and black bears continue to adjust to changing resources, with larger grizzly bears continuing to occupy a more carnivorous niche than the smaller, more herbivorous black bear. © 2012 The Wildlife Society.  相似文献   

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Abstract: We present a comprehensive look at a sample of bear spray incidents that occurred in Alaska, USA, from 1985 to 2006. We analyzed 83 bear spray incidents involving brown bears (Ursus arctos; 61 cases, 74%), black bears (Ursus americanus; 20 cases, 24%), and polar bears (Ursus maritimus; 2 cases, 2%). Of the 72 cases where persons sprayed bears to defend themselves, 50 (69%) involved brown bears, 20 (28%) black bears, and 2 (3%) polar bears. Red pepper spray stopped bears' undesirable behavior 92% of the time when used on brown bears, 90% for black bears, and 100% for polar bears. Of all persons carrying sprays, 98% were uninjured by bears in close-range encounters. All bear—inflicted injuries (n = 3) associated with defensive spraying involved brown bears and were relatively minor (i.e., no hospitalization required). In 7% (5 of 71) of bear spray incidents, wind was reported to have interfered with spray accuracy, although it reached the bear in all cases. In 14% (10 of 71) of bear spray incidents, users reported the spray having had negative side effects upon themselves, ranging from minor irritation (11%, 8 of 71) to near incapacitation (3%, 2 of 71). Bear spray represents an effective alternative to lethal force and should be considered as an option for personal safety for those recreating and working in bear country. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):640–645; 2008)  相似文献   

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Variation in life history and demography across a species' range informs researchers about regional adaptations and affects whether managers can borrow information from other populations in decision-making. The American black bear (Ursus americanus) is a long-lived game species whose continued persistence depends on management of harvest and removal of habituated bears that come into conflict with humans. Understanding the demography of black bears guides efforts at management and conservation, yet detailed knowledge of many populations is typically lacking. I performed a hierarchical Bayesian meta-analysis of black bear demographic studies across the geographic range of the species to explore how vital rates vary across the range, what information they give us about population growth, and whether managers can justify borrowing information from other studies to inform management decisions. Cub, yearling, and adult survival and fecundity varied between eastern and western North America, whereas subadult survival did not show geographic structuring. Adult survival and fecundity appeared to trade off, with higher survival in the western portions of bears' range and higher fecundity in the east. Although adult survival had the highest elasticity, differences in reproduction drove differences in population growth rate. Mean population growth rate was higher in the east (0.99; 95% credible interval [CrI]: 0.96, 1.03) than the west (0.97; 95%CrI: 0.93, 1.01). Despite declining trends in the west, 34% of the distribution of population growth rate was >1, compared to 55% in the east. Further work needs to be done to address the cause of the apparent trade-off between adult survival and fecundity and explore how the estimated growth rates are likely to affect population status of black bears. Because population growth rates are close to 1 and small deviations could impact whether a population is considered increasing or decreasing, managers need to employ caution in borrowing vital rates from other populations. © 2011 The Wildlife Society.  相似文献   

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ABSTRACT Knowledge of the distribution and pathology of West Nile virus (WNV) in black bears is a necessary tool that allows wildlife managers to implement a management plan, set harvest quotas, and relocate nuisance bears. We studied the presence and significance of WNV titers in free-roaming black bears (Ursus americanus) in northeastern Wisconsin between February 2003 and March 2005. Serum neutralizing antibodies to WNV, with confirmation by plaque-reduction neutralization test to both WNV and Saint Louis encephalitis, identified exposure in 13 of 74 (17.6%) bears. This compares with a 6% infection rate in black bears in Virginia and 22% in European brown bears (Ursus arctos). Pathologic effects from exposure to WNV were not seen in any of the black bears studied.  相似文献   

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Timber interests target coastal temperate rainforests, and within them stands composed of large trees potentially selected by American black bears (Ursus americanus) for denning. We identified the location of 75 black bear dens (used ≥14 days) in an intensively logged area on Prince of Wales Island, Alaska, USA. We ground-visited a subset (n = 43) of these sites to measure the diameter of living trees and woody structures used by black bears for denning. We contrasted dens with random trees available in the study area in a series of models to characterize black bear den selection. All but 1 of 43 ground-visited dens were located within woody structures, and all but 2 of these structures were >1 m diameter at breast height (dbh). We built resource selection functions (RSFs) to investigate black bear den selection across a range of spatial scales, though estimated selection was generally scale invariant. Black bears strongly selected large-diameter woody structures (dead or alive) as dens at the home-range scale, with the estimated relative strength of selection (RSS) for a 2-m-diameter tree approximately 166 times that of a 1-m-diameter tree. The estimated RSS of logged forest was unexpectedly greater (2.75 times) than that of the remaining commercially valuable old-growth forest. Selection for den structures within stumps in previously logged stands suggests features of the woody structure may be of greater importance to black bears selecting dens than attributes of the surrounding forest. There was no observed correlation between bear den selection and second-growth age, indicating that stumps may persist as suitable dens well after logging. Because denning is an important part of their life history and the denning structures used by black bears on Prince of Wales Island will eventually decay, retaining habitat value for bears in areas intensively managed for timber harvest requires strategies to recruit very large, old trees throughout the landscape. © 2021 The Wildlife Society.  相似文献   

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