Density and distribution of a colonizing front of the American black bear Ursus americanus

Abstract

AbstractEffective management of small expanding populations is aided by the availability of reliable estimates of distribution, as well as by demographic characteristics such as population density, genetic diversity and sex ratio. The range of the black bear Ursus americanus in the southeastern United States is expanding to include areas from which it has been extirpated for more than a century. Lack of baseline demographic data in recently reoccupied areas leaves little information on which to base emerging management needs. We estimated the current extent of expansion at the colonizing front of a black bear population in the central Appalachian Mountains and identified landscape‐scale habitat characteristics affecting the expansion. In 2007, we genotyped hair samples collected throughout a 8,205‐km2 area at six microsatellite loci to identify individual black bears and estimate genetic diversity. We used capture‐recapture and occupancy analyses to estimate density and distribution of black bears in our study area. Our results suggest that black bears were not uniformly distributed, but were localized to high elevations and protected public conservation lands. Limited availability of high elevations to the west, north and northeast of our study area may limit further expansion. Despite a limited distribution and low estimated population density (7.51 bears/100 km2), genetic diversity at genotyped loci was high (mean Ho = 0.81). Until the population grows further, the small number of individuals in the region may be sensitive to management practices that result in mortalities, especially to females. Our research exemplifies the utility of remote genetic sampling to estimate population demographics of wide‐ranging mammals throughout a large study area, particularly where private land ownership hinders intensive study.