Abstract:Understanding metapopulation dynamics in large carnivores with naturally fragmented populations is difficult because of the large temporal and spatial context of such dynamics. We coupled a long-term database of visitor sighting records with an intensive 3-year telemetry study to km for females (n = 7) and 92 km for males (n = 4), and 3 animals conducted migrations of at least 154, 178, and 214 km, respectively. Our observations exemplify the importance of stochastic events on demographics of small populations and highlight the potential scale of bear movement among montane islands of southwestern North America. They also provide insight into the use of dispersal data in parameterizing metapopulation models for large carnivores.

American black bears (Ursus americanus (Pallas, 1780)) are characterized by female philopatry and malebiased dispersal, with predictable consequences for genetic structure of populations. We studied a recolonizing population of black bears on a desert montane island to test genetic-based predictions of bear social behavior. We assessed genetic paternity and relatedness among bears within Big Bend National Park, Texas, from 1998 to 2001 via maternally and biparentally inherited markers and field observations. Data from seven microsatellite loci permitted us to assign paternity for 7 of 12 cubs, and multiple paternity was revealed in one litter. Levels of relatedness in the Park were comparable to those found in a nearby large population in Coahuila, Mexico. Adult female bears in the Park were more closely related to each other than males were to each other. Microsatellite data were consistent with previous analyses of mtDNA sequences that indicated bears in the Mexico-Texas metapopulation exhibit male-biased dispersal. Demographic and genetic data provided a pedigree for 23 of 31 sampled bears and depicted the matriarchal structure of this recently recolonized population. Although females in this insular population are closely related to each other, as predicted by characteristics of ursine social ecology, incoming dispersal by unrelated males results in periodic supplementation of genetic variation.Résumé : Les ours noirs américains, Ursus americanus (Pallas, 1780), se caractérisent par une philopatrie des femelles et une dispersion faite surtout par les mâles, ce qui a des conséquences prévisibles sur la structure génétique des populations. Nous avons étudié une population d'ours noirs qui est en train de se rétablir sur une montagne isolée en région désertique afin de vérifier des prédictions sur leur comportement social basées sur la génétique. Nous avons évalué la paternité génétique et le degré de parenté des ours du parc national de Big Bend, Texas, de 1998 à 2001, au moyen de marqueurs hérités de la mère ou des deux parents et par des observations de terrain. Les données sur sept locus microsatellites nous ont permis d'attribuer la paternité de 7 de 12 oursons et d'identifier une paternité multiple dans une portée. Le degré de parenté dans le parc est semblable à celui que l'on trouve dans la grande population voisine de Coahuila, Mexique. Les ourses adultes sont plus proches parentes les unes des autres que ne le sont les mâles. Les données sur les locus microsatellites sont en accord avec des analyses antérieures des séquences d'ADNmt qui indiquent que les ours de la métapopulation Mexique-Texas ont une dispersion qui est surtout l'apanage des mâles. Des données démographiques et génétiques ont permis de dresser le pedigree de 23 des 31 ours échantillonnés et la description de la structure matriarcale de cette population colonisatrice récente. Bien que les femelles de cette population isolée soient fortement apparentées les unes aux autres, tel que le prédisent les caractéristiques de l'écolog...

American black bears (Ursus americanus)have recolonized parts of their former range in the Trans-Pecos region of western Texas after a >40-year absence. Assessment of genetic variation, structuring, gene flow, and dispersal among bear populations along the borderlands of Mexico and Texas is important to gain a better understanding of recolonization by large carnivores. We evaluated aspects of genetic diversity and gene flow for 6 sampling areas of black bears in southwestern North America using genotypic data from 7 microsatellite loci. Our results indicated that genetic diversity generally was high in the metapopulation of black bears in northern Mexico and western Texas. The episodic gene flow occurring via desert corridors between populations in northern Mexico and those in western Texas has permitted the establishment of only moderate levels of genetic structuring. Bayesian clustering analyses and assignment testing depicted the presence of 3 subpopulations among our 6 sampling areas and attested to the generally panmictic nature of bear populations in the borderlands region. The potentially ephemeral nature of the small populations in western Texas and genotypic characteristics of bears recolonizing these habitats attest to the importance of linkages along this portion of the borderlands of the United States and Mexico to effectively conserve and manage the species in this part of its range.

American black bears (Ursus americanus) have recolonized western Texas following extirpation in the mid‐1900s. Knowledge of winter ecology of black bears is important for conservation and management because denning, parturition, and early cub development occur during this period. We monitored 13 radiocollared black bears for 22 den‐years in Big Bend National Park (BBNP) during 1998–2003. All pregnant females (n = 6), 2 females with yearlings, 7 subadults, and 1 adult male denned. Three females with yearlings remained active during winter 1998–1999. We located 4 cave dens, 5 ground dens, and 6 rock‐pile dens. Volume and elevation of den sites averaged 2.00 m3 (SD = 1.51) and 1,800 m (SD = 346), respectively. Mean (±SD) dates of den entrance and emergence for 5 pregnant females were 30 December±17 days and 27 April±21 days, respectively, producing a mean denning period of 118±29 days. Pregnant females exited dens later (P= 0.003) and denned longer (P=0.02) than solitary females and males. Black bears in western Texas used den sites located in higher elevations that were remote and highly defensible. A den‐habitat model described less than 56 km2 of suitable denning habitat within and bordering BBNP. Resource managers should reduce visitor and management activities in and around potential denning areas during winter.