Hibernation. Hibernation is a state of animal dormancy characterized by inactivity, slow breathing, and a lowered metabolic rate in response to lower temperatures (specifically during winter). During the rainy season finding the right food for many animals can be very challenging-- that's why they often have to enter a phase of inactivity which helps them save energy and survive the winter without eating much. Animals like the Polar bear store energy by eating extra food and storing it as body fat which they then use later on as energy while sleeping or during pregnancy. This period of inactivity is typical with endotherms which regulate heat by its internal bodily functions instead of relying on ambient heat. The animal decreases its metabolic rate, which then decreases body temperature and this may last several days, weeks, or months depending on the species, ambient temperature, time of year, and individual's body condition.