Home ranges of related females often overlap, and a male's home range generally overlaps with those of several females. During the cooler months of the year, grizzly bears go into a deep sleep, which many physiologists classify as a highly specialized hibernation. They will use an existing den or cave or will dig a new den. Bears enter their dens as early as the end of October and as late as December. They emerge from their dens between mid March and early April.
Black bear are generally smaller than grizzlies.