Hibernation is when an animal goes into a state of extended inactivity. Often hiding itself away from the elements and predators, the animal's metabolism will slow to less than a quarter of its normal rate. This cools the creature's body and slows its heartbeat to just a few times per minute, for up to months at a time. "They turn down the pilot light really," says Kelly Drew, a neuropharmacologist at the University of Alaska Fairbanks who studies the brains of hibernating Arctic ground squirrels. Hibernation is often stimulated by harsh conditions, shorter days or colder temperatures, which drive an animal to begin putting on fat and otherwise preparing to hibernate.
The creature will then stay in this period of inactivity until it gets the right signal—light or temperature—to stir from its torpor. Yet many misconceptions surround this powerful adaptation.
For one, although hibernation resembles a deep sleep, it is not thought to be related to sleep at all. Read more