Many animals snuggle up in caves, burrows (holes in the ground), or hollow tree trunks and sleep during the cold winter months when food is harder to find and cold weather makes it harder for their bodies to work. This is called hibernating. When an animal hibernates, its heart beats very slowly and it also breathes less. The animal’s body temperature goes way down also – to just a few degrees above freezing! The animal’s brain also goes into a form of sleep. It takes a long time for a hibernating animal to wake up. Hibernating is great for animals because they do not have to try to find food and they don’t have to even go outside in the cold at all!
Because its body slows down and stops working the way it normally does and because the animal is not moving around and using up energy, its body is able to survive off of the fat that it stored up by eating a lot in the fall. Besides being protected from the cold while they hibernate, the sleeping animals are also usually well protected from any other animals who might bother them. They make sure their den, cave, or burrow is only big enough for them and their babies and that it is someplace that is hard for other animals to find. Some animals that hibernate are reptiles and amphibians like frogs and snakes, insects like ladybugs and bees, some fish, and some mammals like bats, hedghogs, and prairie dogs.
Other animals, like foxes and rabbits, do not hibernate at all – they stay active throughout winter. Their speed helps them find and catch food (or escape from predators) and their fur usually changes to white so that they blend in with the snow and are protected from other larger animals.