In the period between 2005 and 2010 a study on the activity of the brown bear (Ursus arctos) in the winter time was carried out in the area of the Dinaric Alps. Eighteen specimens were equipped with telemetry collars - five males, four pregnant females, six leading females, a female without offspring and two females with unknown reproductive status. The study showed that the average denning period for the monitored male bears was 61 days, 110 for pregnant females and 85 for the leading females, but due to the large individual variability the differences between genders and the reproductive status of females were not statistically significant. On average monitored bears began their denning period on December 3rd and ended it on March 2nd. In summer and early autumn we examined and measured 23 dens of 19 different specimens. 17 of these dens were karst caves, five were rock shelters and one outdoor den in a dense pine forest. We confirmed the hypothesis that the duration of denning depends on the type of burrow. In contrast, we observed no obvious correlation between the dimensions of selected caves and the length of hibernation. In the northern Dinarides the duration of denning did not depend on winter temperatures or the thickness of the snow. The start of hibernation was also not conditioned with the first snow. During winter and when they are not denning, brown bears spend more time at the feeding stations than in the active part of the year. There they can find alternative food source.
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