The grey wolves live in swamps, beaver dams, mountains, green lands, and forests. The grey wolf also lives in Canada, portions of the great lakes regions, and some western states, such as Wyoming, Idaho, and Montana. Wolves will use a den right before they have pups. A pregnant female will seek out a den before she delivers her pups.
Dens may be a deep riverbank, a cleft between rocks, hollow logs, spaces under an overturned tree, or a space under a rock over hang. Dens are marked by a pile of dirt. Each den has two entrances and each entrance is fifteen to twenty inches wide and twenty to twenty-three inches high.
Wolves only use dens when they are going to give birth. A pregnant female gives birth to pups in late April. They sleep outside when they are not using dens and they curl up and stretch out.