Bear-hybrids: behaviour and phenotype

The behaviour of a female and a male bear hybrid (brown bear Ursus arctos x polar bear Ursus maritimus) was studied. Behavioural and morphological comparisons between the hybrids and the two parent-species were made.The observation period covered July to November 2007. Different objects were offered to the bears to evoke new patterns of behaviour. While manipulating the offered objects, both bears showed elements of behaviour also found in polar bears, though the male performed those to a larger extend. Not only in the way of manipulating objects but also in the male's type of stereotype parallels to polar bears can be drawn. Phenotypically both bears possess features of both species, brown bear and polar bear. Concerning it lighter colour of fur and the structure of hair the female hybrid resembles more a polar bear than the male. Summarising, the female appears phenotypically more like a polar bear, the male with respect to the behaviour.     

25‐OH‐D3, calcium,phosphorus, and alkaline phosphatase content in sera from captive polar bear (Ursus maritimus) cubs at the Denver Zoological Foundation

After the development of rickets in two hand‐reared polar bear (Ursus maritimus) cubs at the Denver Zoological Foundation we initiated a project opportunistically evaluating sera 25‐OH‐D₃, calcium, phosphorus, and alkaline phosphatase levels in seven mother‐reared polar bear cubs. From one to three serum samples were obtained while the cub was still in the den with no access to natural sunlight and one after the cub exited the den. The sera 25‐OH‐D₃ increased as the cubs grew (108±37 nmol/L [n=7] while in den, 184.6±48.3 nmol/L [n=7] out of the den) but were substantially lower then captive adults (348±215 nmol/L [n=36]) or free‐ranging adults (360±135 nmol/L [n=56]). We found that age was correlated significantly with 25‐OH‐D₃ levels but den status (in or out) was not significant. Sera calcium and phosphorus values were highest in denned cubs (calcium, 2.9±0.4 mmol/L [n=13]; phosphorus, 3.1±0.5 mmol/L [n=13]) and then declined as the cubs matured and left the den (calcium, 2.5±0.1 mmol/L [n=7]; phosphorus, 2.4±0.4 mmol/L [n=7]). The enzyme alkaline phosphatase (presumably the bone isoenzyme) was high in denned growing cubs (831±426 IU/L [n=13]) and then declined gradually as the cubs aged and exited the den (96±83 IU/L [n=7]). Zoo Biol 0:1–7, 2007. © 2007 Wiley‐Liss, Inc.     

Detailed model of shelter areas for the Cantabrian brown bear

We propose a methodology to determine critical areas for brown bear (Ursus arctos) in the Cantabrian Mountains (Spain), considered as shelter areas in which there are concentrations of winter dens and groups of resting sites. We assessed a function which enabled a precise spatial distribution model to be constructed. This function helps to explain the present division of the range of the bears into two isolated populations and to identify areas for protection with the aim of increasing their probabilities of survival or connection.

This has been done using a multivariate analysis and by applying the results to variables modelled on a geographic information system. We took a location containing 161 bear dens and resting sites. These positions have been characterised by modelling variables in a grid of 50-m cells derived from the topography (digital model of elevations, orientations, slopes, altitude variability in an area around each location). The variables include those that quantify distance weighting according to difficulties associated with access to different disturbance elements (infrastructures or buildings), variables that quantify distances to refuges (forests, scrubs, and rocky areas) and their shape (perimeter, thickness, eccentricity or shape of the forest and type of rocky areas). We constructed a logistic regression model with this data that locates and highlights shelter areas with an 86% average rate of precision. This result reveals that the eastern population has shelter areas around the present range, indicating a possible expansion area; however, there is a gap measuring close to 30 km between both populations that is almost entirely lacking in shelters and that contains important infrastructures. Increasing refuge conditions in the gap to connect shelter areas will make it possible to recover the area as a corridor.     

卧龙自然保护区黑熊种群生存力初步分析

依据黑熊种群的相关参数,借助旋涡软件（Vortex 8.21),对卧龙自然保护区内黑熊的种群动态进行了模拟分析,结果表明：在没有近亲繁殖和食物歉收,人类诱捕等灾害影响的情况下,卧龙黑熊种群数量100年间稳步增长;而在加入近亲繁殖和灾害等因素时,种群数据下降,据此,提出了相应的保护措施和建议。     

Resource Selection by Recolonizing American Black Bears

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.     

Brown Bear Density and Estimated Harvest Rates in Northwestern Alaska

Human-caused mortality in general, and unregulated hunting in particular, have been implicated in reductions in brown bear (Ursus arctos) populations throughout much of their range. In northwestern Alaska, USA, bear densities have not been assessed in 20 years while harvest regulations have been liberalized, raising concerns that broad undetected population declines might occur. We used a modified mark-resight approach to estimate brown bear density during 2005–2018 in 4 subareas throughout the region. We also summarized harvest information for each subarea and used our survey results to estimate harvest rates. We estimated densities for independent bears assuming constant or heterogeneous probabilities of detection and occurrence. We present the results of the constant model for more direct comparison with past work and the heterogeneity model results to provide estimates of density that are less likely to be negatively biased. Using the constant model, we estimated the density of independent bears was 17.0, 49.2, 24.9, and 19.4/1,000 km² on portions of the Seward Peninsula, the lower Noatak River, the upper Noatak River, and Gates of the Arctic National Park and Preserve, respectively. These estimates are broadly similar to those from past work in interior and northwestern Alaska, with the exception of the lower Noatak River subarea where our estimates are the highest reported for a bear population in northern Alaska. We estimated that the harvest rate on the Seward Peninsula was approximately 5.2% or 7.7% on average, depending upon the model used. In the remaining areas, we estimated annual harvest rates were <2.5%, well within sustainability guidelines from past work. Overall, our results suggest that brown bear densities are similar or somewhat higher than in the past in much of northwestern Alaska and that current harvest rates are sustainable in most areas, except perhaps the Seward Peninsula. Ongoing survey work will be useful for further evaluating the assumptions of the modified mark-resight survey approach, assessing population trajectory, and determining the effect of harvest on brown bear populations. © 2021 The Wildlife Society.     

Estimates of Abundance and Harvest Rates of Female Black Bears Across a Large Spatial Extent

American black bears (Ursus americanus) are an iconic wildlife species in the southern Appalachian highlands of the eastern United States and have increased in number and range since the early 1980s. Given an increasing number of human-bear conflicts in the region, many management agencies have liberalized harvest regulations to reduce bear populations to socially acceptable levels. Wildlife managers need reliable population data for assessing the effects of management actions for this high-profile species. Our goal was to use DNA extracted from hair collected at barbed-wire enclosures (i.e., hair traps) to identify individual bears and then use spatially explicit capture-recapture methods to estimate female black bear density, abundance, and harvest rate. We established 888 hair traps across 66,678 km² of the southern Appalachian highlands in Georgia, North Carolina, South Carolina, and Tennessee, USA, in 2017 and 2018, arranged in 174 clusters of 2–9 traps/cluster. We collected 9,113 hair samples from those sites over 6 weeks of sampling, of which 1,954 were successfully genotyped to 462 individual female bears. Our spatially explicit estimator included a percent forest covariate to explain inhomogeneous bear density across the region. Densities ranged up to 0.410 female bears/km² and regional abundance was 5,950 (95% CI = 4,988–7,098) female bears. Based on hunter kill data from 2016 to 2018, mean annual harvest rates for females were 12.7% in Georgia, 17.6% in North Carolina, 17.6% in South Carolina, and 22.8% in Tennessee. Our estimated harvest rates for most states approached or exceeded theoretical maximum sustainable levels, and population trend data (i.e., bait-station indices) indicated decreasing growth rates since about 2009. These data suggest that the increased harvest goals and poor hard mast production over a series of prior years reduced bear population abundance in many states. We were able to obtain reasonable population abundance and density estimates because of spatially explicit capture-recapture methods, cluster sampling, and a large spatial extent. Continued monitoring of bear populations (e.g., annual bait-station surveys and periodic population estimation using spatially explicit methods) by state jurisdictions would help to ensure that population trajectories are consistent with management goals. © 2021 The Wildlife Society.     

Black Bears Select Large Woody Structures for Dens in Southeast Alaska

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.     

Evaluation of Connectivity Among American Black Bear Populations in Georgia

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.     

Multisource noninvasive genetics of brown bears (Ursus arctos) in Greece reveals a highly structured population and a new matrilineal contact zone in southern Europe

In human‐dominated landscapes, connectivity is crucial for maintaining demographically stable mammalian populations. Here, we provide a comprehensive noninvasive genetic study for the brown bear population in the Hellenic Peninsula. We analyze its population structuring and connectivity, estimate its population size throughout its distribution, and describe its phylogeography in detail for the first time. Our results, based on 150 multilocus genotypes and on 244‐bp sequences of the mtDNA control region, show the population is comprised by three highly differentiated genetic clusters, consistent with geographical populations of Pindos, Peristeri, and Rhodope. By detecting two male bears with Rhodopean ancestry in the western demes, we provide strong evidence for the ongoing genetic connectivity of the geographically fragmented eastern and western distributions, which suggests connectivity of the larger East Balkan and Pindos‐Dinara populations. Total effective population size (N _e) was estimated to be 199 individuals, and total combined population size (N _C) was 499, with each cluster showing a relatively high level of genetic variability, suggesting that migration has been sufficient to counteract genetic erosion. The mtNDA results were congruent with the microsatellite data, and the three genetic clusters were matched predominantly with an equal number of mtDNA haplotypes that belong to the brown bear Western mitochondrial lineage (Clade 1), with two haplotypes being globally new and endemic. The detection of a fourth haplotype that belongs to the Eastern lineage (Clade 3a1) in three bears from the western distribution places the southernmost secondary contact zone between the Eastern and Western lineages in Greece and generates new hypotheses about postglacial maxima migration routes. This work indicates that the genetic composition and diversity of Europe''s low‐latitude fringe population are the outcome of ancient and historical events and highlight its importance for the connectivity and long‐term persistence of the species in the Balkans.