Behavior of the European brown bear at rub trees

Abstract: The rubbing of trees by bears is an example of scent-marking that has been studied only in a limited number of bear species in the world. Our study analyzes the marking behavior of the European brown bear (Ursus arctos), based on filming by remote cameras placed in front of 25 rub trees in the central Italian Alps during 2012 to 2014. We obtained 546 videos of bears from a sampling effort of 9,302 camera-days. The bears captured in the videos were classified according to age and sex, and type and duration of each behavior was recorded. The data allowed us to assess temporal patterns of rubbing behavior and differences within sex, age, and among individuals. Rubbing was performed significantly more by adult males, with a peak during the breeding season. Adult males also used a variety of positions to mark the trees as compared with the other sex-age classes. Rubbing also was observed during the nonbreeding season, but with lower frequency, whereas investigation of rub trees was performed by bears of all ages and sexes throughout the seasons. The only 3 female bears that rubbed the trees were recorded in autumn, outside the breeding season. The results showed that scent-marking triggered a response in individuals that subsequently passed by the same rub tree; in 62% of the cases, the second bear either rubbed or investigated the tree, regardless of the time since the passage of the first bear. Our results supported the hypothesis that tree-rubbing during the breeding season is a means of communication, as already documented for brown bears and American black bears (U. americanus) in North America, but the function of this display outside the breeding season remains unclear.