Black bear habitat use and response to roads on Pisgah National Forest, North Carolina

Twenty black bears (Ursus americanus) were captured 22 times on Harmon Den, Pisgah National Forest, North Carolina, during 1986 and 1987. A total of 1956 telemetry locations were obtained on these animals.

Male home ranges (43 km²) were significantly larger (P<0.0004) than female ranges (13.3 km²) annually, but not in summer (P=0.25). Eight (35%) tagged bears died during the study; all mortality was human caused. Known mortality rates were 36% and 23% during 1986 and 1987, respectively. Modified mortality rate was 8%.

Habitat use was determined by plotting telemetry locations from ground and aerial tracking and transmitter drops on U.S. Forest Service Continuous Inventory of Stand Condition (CISC) maps. Bears preferred areas of nonforest and avoided yellow-poplar, chestnut oak, and scarlet oak stands during summer and selected for pine stands and avoided yellow-poplar stands in fall. Determining habitat use from transmitter drops was a more accurate method than ground or aerial tracking. Using this method, bears were found to avoid nonforest, pine, and yellow-poplar stands and select for chestnut oak stands. Selection for chestnut oak stands was likely a response to acorn abundance.

Bear responses to roads and their associated disturbances were measured by relating the number of road crosses by a bear to the road density in its home range, and to the traffic volume on these roads. Bears tended to avoid roads with mean traffic volumes of 15 vehicles per day as the density of these roads increased. However, bear movements were not inhibited by roads with traffic volumes of 100 vehicles per day. The reason for this is not clear but may result from poor telemetry accuracy. More road crossings occurred during daylight hours than at night. Interstate 40 acts as a barrier to bear movements as collared bears seldom crossed it (n=2).

The Harmon Den bear sanctuary appears to be serving its purpose by producing a stable and productive female population with many young males dispersing to less populated areas. Habitat management in this region is crucial to the bears's future. Better regeneration of oaks after clearcutting needs to be developed to ensure vital fall hard mast production. A reduction of the oak resource would detrimentally impact the black bear population of this region.