Winter sleep with room service: denning behaviour of brown bears with access to anthropogenic food

Abstract

Large quantities of food subsidies provided by humans to animal communities have the potential to change a variety of animal life traits, including denning behaviour of facultative hibernators like bears. Brown bears Ursus arctos regularly use anthropogenic food, but it has remained unclear if human food subsidies affect their hibernation and denning behaviour, despite the consequences this could have for bear interactions with humans and other species. We studied denning behaviour of European brown bears in Slovenia, where intensive supplemental feeding with corn is practiced throughout the year, including winter. We used GPS telemetry data to locate den sites and to monitor bear denning chronology. We conducted a meta-analysis to compare our results with other bear populations across Europe, Asia and North America. A consistent relationship between latitude and time spent denning was observed for male and female brown bears across the species’ range (for each degree of latitude northwards, denning period increased for 3.1 days), and males on average denned 10.3 days longer than females throughout the latitudinal gradient. However, our study area deviated strongly from regions where supplemental feeding was not practiced. In Slovenia, denning period averaged 82 days for females and 57 days for males, which was 45 and 56% shorter compared to the time predicted for this latitude, respectively. We also observed regular den abandonments (61% of bears abandoned dens, on average 1.9 times per winter). During the winter period bears increased use of supplemental feeding sites for 61% compared to the non-denning period. We conclude that the availability of anthropogenic food is an important driver of denning behaviour in brown bears. Reduction in the denning period increases the potential for bear interactions with other species, including humans, and we highlight possible management and ecological implications of this human-caused perturbation to denning behaviour of wild ursids.