Grizzly Bear Dens - GB427

During hibernation, grizzly bears inside Yellowstone National Park (and the Greater Yellowstone Ecosystem) are tasked with finding suitable areas to construct their winter dens. Typically, grizzlies in Yellowstone dig their dens on 30-60 degree slopes with northern exposures between the range of 6500-10000 ft (Judd et al. 1986). Grizzlies typically will select den locations at the base of trees on northern face. The orientation of the den can insure that significant snowfall will insulate the den during extreme temperatures (Craighead and Craighead 1972). Den construction typically takes 3-7 days, where the bear may move up to, or more than one ton of dirt and debris material (referred to as a tailings pile)(Craighead and Craighead 1972).

The den constructed consists of several parts: the entrance, tunnel, and chamber. Grizzlies will typically bring bedding material into their dens, including but not limited to spruce and pine boughs; sometimes even duff. Den entrances are typically small and grizzlies "bearly" fit through them. This is to minimize heat loss during the winter; additionally, a smaller entrance will cover with snow quicker than a larger one.
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The den I explored today, belongs to male GB427. Males and females with cubs typically have the largest dens. The entrance of the den was just large enough for me to be able to fit my shoulders comfortable through. The chamber was so large , I could have curled up and taken a nap!