Longevity and reuse of black bear dens in managed forests of coastal British Columbia

Abstract

AbstractWe evaluated longevity and reuse of denning structures by American black bears (Ursus americanus) in coastal temperate rainforests of British Columbia from 1992 to 2010 to assess potential impacts of forest management on these critical habitat features over time. We identified 67 dens during a 4‐yr intensive radio‐telemetry study (1992–1995): 40 dens of 21 radio‐collared black bears and 27 dens found incidentally. Dens occurred in or beneath large diameter trees or wooden structures derived from trees (i.e., logs, root boles, and stumps; ${\bar {x}}$ = 143 cm diameter, SD = 49 cm). Longevity of dens varied by type, tree species that formed the den, and forest management that occurred at or near the den. Twenty‐four of 28 dens of radio‐collared bears that were monitored were still usable in 2010, whereas only 5 of 14 dens found incidentally were still usable in 2010. We assessed reuse of bear dens 3 times following initial identification: during the radio‐telemetry study, again in 2000, and finally in 2010. Radio‐collared bears reused dens from previous years on 7 of 25 potential occasions during the course of the radio‐telemetry study. Upon assessment in 2000 and 2010, 17 of 24 (71%) available dens first used by radio‐collared bears were reused at least once between 1993 and 2010. The high rate of reuse may indicate low availability of den structures in our study area. Because black bears in coastal British Columbia only used trees or structures derived from trees for winter dens and forest harvesting reduces the supply of these necessary structures, conservation and recruitment of suitable den trees is necessary if maintaining black bear populations is a management goal in these areas. © 2011 The Wildlife Society.