Factors affecting settling, survival, and viability of black bears reintroduced to Felsenthal National Wildlife Refuge, Arkansas

摘要

We used radiotelemetry and population modeling techniques to examine factors related to population establishment of black bears (Ursus americanus) reintroduced to Felsenthal National Wildlife Refuge (NWR), Arkansas. Our objectives were to determine whether settling (i.e., establishment of a home range at or near the release site), survival, recruitment, and population viability were related to age class of reintroduced bears, presence of cubs, time since release, or number of translocated animals. We removed 23 adult female black bears with 56 cubs from their winter dens at White River NWR and transported them 160 km to man-made den structures at Felsenthal NWR during spring 2000-2002. Total movement and average circuity of adult females decreased from 1 month, 6 months, and 1 year post-emergence (F sub(2, 14) =19.7, P <0.001 and F sub(2, 14) =5.76, P =0.015, respectively). Mean first-year post-release survival of adult female bears was 0.624 (SE=0.110, SE sub(interannual)= 0.144), and the survival rate of their cubs was 0.750 (SE=0.088, SE sub(interannual)=0.109). The homing rate (i.e., the proportion of bears that returned to White River NWR) was 13%. Annual survival for female bears that remained at the release site and survived >1-year post-release increased to 0.909 (SE=0.097, SE sub(interannual)=0.067; Z=3.5, P<0.001). Based on stochastic population growth simulations, the average annual growth rate ( lambda ) was 1.093 (SD=0.053) and the probability of extinction with no additional stockings ranged from 0.56-1.30%. The bear population at Felsenthal NWR is at or above the number after which extinction risk declines dramatically, although additional releases of bears could significantly decrease time to population reestablishment. Poaching accounted for at least 3 of the 8 adult mortalities that we documented; illegal kills could be a significant impediment to population re-establishment at Felsenthal NWR should poaching rates escalate.