Many animals live in dens, including foxes, bears, bobcats and raccoons. Animals that are found in woodlands are likely to live in dens. Some animals use dens only for nesting and rearing young, while others make dens more permanent homes.
Black bears give birth and sleep in their dens. Although they sleep in the dens during the winter months, they are not considered true hibernators and may wake occasionally. A black bear's den can be anything from a cave to a hollow tree or large pile of brush. An example of an animal that uses a more permanent den is the beaver. The well-recognized lodges made in streams out of pieces of wood and mud are dens with underwater entrances.