Material & Methods


Two brown bear brothers sharing the same enclosure were observed between September and November 2023 at Kolmården Zoo in Sweden. The brothers, Bart and Bamse, were born 2002 in the Swedish wildrness of Hälsingland county. They were taken to Orsa Predator Park as cubs after their mother had died of a vehicle accident. They were transferred to Kolmården Zoo in 2005 and have been kept together since.
There were other brown bears at Kolmården Zoo though they had to be excluded from the study due to structural limitations, meaning that behavioural observations were not possible.


Bart is an intact male who has been reproducing successfully, though he was not active in breeding programs during the current study.


Bamse was castrated in 2008. His fur quality is in worse condition compared to Bart and the other bears in the park, especially in the spring.


The bears were offered a various diet of fruit, vegetables, animal protein and minerals

As the time for torpor approached, the amount of animal protein (fish and red meat) decreased until only fruit (apples and oranges) were provided. One week before torpor, no food was offered to the bears. Also, almost no dry pellets was provided to the bears during the observation period; occasionally the bears got it as dietary enrichment.