Ursus

I/nteragency Grizzly Bear Study Team, US Geological Survey, Biological Resources Division, Montana State University, Bozeman, Montana 59717, USA 2U.S. Geological Survey, Biological Resources Division, Northern Rocky Mountain Science Center, ...

The total number of brown bears (Ursus arctos) in Europe is presently about 50,000 (about 14,000 outside Russia), within an area of more than 2.5 million km2 (800,000 km2 outside Russia). About 37,500 bears are found in the northeastern European population; 8,100 in the Carpathian Mountains; 2,800 in the Alps-Dinaric-Pindos; 1,000 in Scandinavia; 520 in the Rila-Rhodope Mountains; 200 in

Background: Hibernation has been a key area of research for several decades, essentially in small mammals in the laboratory, yet we know very little about what triggers or ends it in the wild. Do climatic factors, an internal biological clock, or physiological processes dominate? Using state-of-the-art tracking and monitoring technology on fourteen free-ranging brown bears over three winters, we recorded movement, heart rate (HR), heart rate variability (HRV), body temperature (T b), physical activity, ambient temperature (T A), and snow depth to identify the drivers of the start and end of hibernation. We used behavioral change point analyses to estimate the start and end of hibernation and convergent cross mapping to identify the causal interactions between the ecological and physiological variables over time. Results: To our knowledge, we have built the first chronology of both ecological and physiological events from before the start to the end of hibernation in the field. Activity, HR, and T b started to drop slowly several weeks before den entry. Bears entered the den when snow arrived and when ambient temperature reached 0 °C. HRV, taken as a proxy of sympathetic nervous system activity, dropped dramatically once the bear entered the den. This indirectly suggests that denning is tightly coupled to metabolic suppression. During arousal, the unexpected early rise in T b (two months before den exit) was driven by T A , but was independent of HRV. The difference between T b and T A decreased gradually suggesting that bears were not thermoconforming. HRV increased only three weeks before exit, indicating that late activation of the sympathetic nervous system likely finalized restoration of euthermic metabolism. Interestingly, it was not until T A reached the presumed lower critical temperature, likely indicating that the bears were seeking thermoneutrality, that they exited the den.

Abstract: We used resource selection functions (RSF) to estimate relative probability of grizzly bear (Ursus arctos) use for habitats, landscape features, and areas of varying human access density across a 5,342-km2 study area in west-central Alberta, Canada. Models were ...