Den structure and selection of denning habitat by brown bears in the Romanian Carpathians

Abstract: The Romanian Carpathian Mountains provide one of the largest areas suitable for brown bear (Ursus arctos) in Europe, but the long history of logging has reduced old-growth forest to fragments. Continuous timber extraction, along with new recreation opportunities from motorized vehicles, may affect brown bear denning habitat through disturbance. As such, understanding den site selection at the landscape and local levels is important for the conservation and sustainable management of the Romanian brown bear population. We used data on 86 den sites collected between 2010 and 2013 in Southeastern Carpathians and developed Resource Selection Functions for second-order (landscape-level) and third-order (local level) den habitat selection, using habitat structure and topographic attributes of den locations. The altitude of dens ranged between 440 and 1,320 m, with a mean slope of 19.7 ± 0.8%. Aspect was evenly distributed between southwest (22.9% of the dens), east (20.5%), south (18.1%), and southeast (15.7%). Dens stabilized by boulders were dominant (68%), and had maximum mean length = 149.2 ± 5.6 cm, width = 109.1 ± 4.8 cm, and height = 113.8 ± 10.5 cm. At both local and the landscape scales, bears selected for steeper slope and higher percent coverage of mixed (beech–fir–spruce [Fagus sylvatica–Abies alba–Picea abies]) forest. At the landscape scale, bears also selected dens at higher altitude, and with greater coverage of old forest, and away from urban areas and recent clear-cuts. Our spatial predictions have the potential to inform forest management by identifying areas where disturbance of brown bear denning habitat should be avoided or limited, thus contributing to brown bear management and conservation planning in the Romanian Carpathians.