Patterns in the use of rub trees by the Eurasian Brown Bear

Abstract

The behaviour of marking trees by the brown bear occurs throughout the range of presence of the species. It has recently been recognised as a mean of intra-specific chemical communication, besides the likely function of ecto-parasite removal, and evidence from grizzlies showed that scent marking of trees is mainly performed by adult males during the breeding season. However, detailed studies on this behaviour in the Euroasian brown bear are lacking. We conducted a three year study on a wild bear population of 50 individuals in the Eastern Italian Alps, using camera traps. We aimed to assess the use of trees by bears’ age and sex classes, its temporal variation, and to determine key habitat and human disturbance drivers of the intensity of use of rub trees. Camera trapping yielded more than 500 videos of bears from more than 9000 camera trapping days, age and sex classes were identified in 59% of the videos. Results showed that rubbing was mainly performed by adult males, with females and sub-adults that only occasionally rubbed. Rubbing was performed more during the breeding season, confirming that the main function of this behaviour is associated to males' breeding strategy. Olfactory investigation was performed by bears of all ages and sexes, indicating the importance of scent marking at rub trees for intra-specific communication. We used the camera trapping event rate as a raw index of intensity of usage of rub trees and found it to be affected by aspect, type of roads and passage of motor vehicles at the sites, while the passage of people did not affect it. We also estimated bear occupancy and detectability and found that the latter was influenced by trail type and distance from roads and buildings. Our study provides a first contribution to the use of rub trees by brown bears in the Alps. Download the complete issue.