The ecology of winter den sites of Brown bears (Ursus arctos) in Kouhkhom region, Fars province

Winter denning is a major event in the life cycle of brown bears, making den sites important components of bear habitat. In the present study, we investigated the structural characteristics of brown bear dens in Kouhkhom region, located north of Bakhtegan National Park. Structural characteristics, including entrance height, entrance width, chamber width, chamber height, tunnel length, tunnel width, den length, and bed dimensions, were measured for 20 dens (presence locations) and 20 caves where signs of bear were not found (absence locations). For each location, landscape variables including elevation, slope, aspect, distance to roads, distance to human settlements, and distance to water were also determined. Our results indicate that brown bears in this region occupy natural caves, rock crevices, and excavated holes under boulders as winter dens. We recorded eight active dens with bedding made with plant material, with an average dimension of 7×70×78 cm3. The profiles of winter dens in the region were outlined. A comparison of presence and absence locations using two independent samples t test showed significant differences in entrance height and entrance width at the micro scale, and distance to roads, distance to human settlements, distance to water, slope, and elevation at the landscape level. It is very likely that these variables are important determinants of den site selection by brown bears.