What is the state of dormancy that animals experience in winter called?

Hibernation is a type of deep sleep some animals (like bears) go into during winter. It is a sleep-like state during which their metabolism slows, and they conserve energy. Animals that hibernate do nothing: hibernation is a time of rest and inactivity, almost like a coma. People also use this word for other types of inactivity. For example, you could talk about the hibernation of an athlete who has taken a year off from competition.

Source: Vocabulary.com