A small cavern or hollow place in the side of a hill, or among rocks; esp., a cave used by a wild beast for shelter or concealment; as, a lion's den; a den of robbers.

a cave where a bear goes for shelter and to give birth to its young

place where animals gather together to sleep and give birth to their young.

the habitation of wild animals

A shelter, often a small cave or hole dug out of the ground, to protect the breeding female and her young pups from weather and other animals.

an animal's shelter.

A shelter, natural or constructed, used for sleeping, for giving birth and raising young, and/or for providing shelter during winter.

an enclosure in which wolf pups are born and where they spend the first four weeks of their lives.