Denning behaviour of Scandinavian brown bears Ursus arctos

During 1986-2001, denning behaviour of brown bears Ursus arctos was documented for 55 dennings of 33 radio-marked males in central Sweden, and 12 and 29 dennings of nine males and 19 females, respectively, in northern Sweden. Male brown bears spent on average 161 days (27 October - 4 April) in dens in the southern area. The duration of their denning decreased with increasing age and body mass. Comparing these data with those obtained for females in the same study area by Friebe et al. (2001), males emerged from dens earlier than females, spending significantly less time in their dens. The denning period of females was influenced by their reproductive status; pregnant females spent the longest time in their dens. Denning dates correlated clearly with timing of autumn snowfall. Males in the north denned earlier, emerged later and spent on average 45 days more in their dens than males in central Sweden. Similarly, females in the north spent on average 37 days more in their dens than females in the south. Daily movements of males tracked to their dens in 2001 showed a general trend towards lower rates of movement in the last two weeks before denning, as found in females. Mean distance between dens used in successive years varied with age and sex; it was significantly greater for subadult males than for females and adult males as a result of dispersal behaviour. Adult bears showed a high degree of fidelity to a general denning area within their annual ranges.