Hibernation is a state of inactivity and metabolic depression in endotherms. Hibernation refers to a season of heterothermy that is characterized by low body temperature, slow breathing and heart rate, and low metabolic rate. Hibernation cuts down on the energy needed to stay alive. It lets them sleep the whole winter through when there's nothing to eat. If they'd stayed awake and burnt energy they would have starved before spring came around.
This hedgehog is getting ready for hibernation.
This squirrel is cuddling another squirrel, getting ready for hibernation.
This mama bear is cuddling her baby bears, getting ready for hibernation.
Migration is the movement from one part of something to another. Most migration is seasonal. Sometimes not all members of a migratory population leave an area. This is called partial migration.