hibernaculum
The place where a hibernating animal shelters for the winter.
Aeolus Cave, which is set into a wooded hillside in Dorset, Vermont, is believed to be the largest bat hibernaculum in New England; it is estimated that before white-nose hit, nearly three hundred thousand bats—some from as far away as Ontario and Rhode Island—came there to spend the winter.
Where it comes from
Borrowed from Latin hībernāculum (“winter quarters”).
Adapted from the Wiktionary entry hibernaculum (CC BY-SA 4.0).