In the winter, animals that do not store food in the fall for winter must survive on the food left over from summer. Some animals also survive winter by growing warm coats of fur that they will lose in the spring. Many birds fly south to warmer areas for the winter and return in the spring.
Some animals hibernate or go into a deep sleep in the winter (this is to save energy).
Hibernation is a state that some animals enter in the winter in order to survive a season when food is not easily available. Animals that hibernate enter a temporary sleep-like condition in which their body temperatures drop significantly and their heart rate and breathing slow drastically.
Hibernating animals do not need to eat or drink because their metabolism slows and their bodies can live off of stored fat. Before going into hibernation, animals must store up fat.
When temperatures increase at the beginning of spring, the animals wake up.
Hibernation is a way for animals to survive the changing seasons and environment.