Servheen, C.W. and R.W. Klaver. 1983. Grizzly bear dens and denning ecology in the Mission and Rattlesnake mountains, Montana. International Conference on Bear Research Management 5:201-207
Abstract
Forty-one grizzly bear (Ursus arctos horribilis) dens were found in the Mission and Rattlesnake Mountains, Montana, from 1976 through 1979. Ten of these dens were used by transmitter-equipped grizzly bears. Thirty-nine dens were excavated in open, side-hill park habitat and 2 were under forest canopy. Two dens occurred at 1250 m while 39 were between 2050 and 2500 m. Slope angle of sites averaged 30 degrees for 15 measured dens. Dens occurred on all aspects except northwest. Movement to the den site in the fall was independent of low-elevation weather conditions and occurred between 10 October and 20 November. Two adult females moved to their dens prior to any snow and may have displayed a period of pre-hibernation lethargy prior to final den entry. Final den entry was closely associated with severe snowstorms at the den site that apparently sealed the den entrance with snow. Final den entry dates varied from 2 November until after 21 November. Dates of emergence varied from prior to 31 March to 26 April. Adult females accompanied by young remained at the den site after emergence for 7 to 12 days. All other grizzly bears left the den and moved to lower elevations immediately after emergence. One transmitter equipped grizzly bear used its winter den during August as a bedding site. This is the first verification of summer use of a den by a grizzly bear. Two adult male black bears (Ursus americanus)w ere radio-instrumented to determine their denning habits. Both denned below 1800 m under forest canopy. Significant differences (P < 0.001) between den entrance height of excavated black bear and grizzly bear dens indicate that this measurement may be a useful indicator of species.