Migration
Acclimation
Hibernation
When an animal such as a bear goes into a deep sleep over the course of the winter. During this time, the rate of his heart, as well as the rate at which the animal uses fat for energy declines considerably.
When an animal adapts to new temperatures, altitudes, climate, or environment (some animals grow a thick coat of fur in preparation for winter).
When an animal travels from one region or climate to another (i.e. birds)