Some animals sleep in winter because the weather can be very cold and it is difficult for them to find food. Then can sleep for a long time. This kind of winter sleep is called “hibernation”If an animal moves about a lot, it needs food. Hibernating animals do not need to eat much because they are not moving about. Their hearts beat very slowly and they also breathe slowly. They find a place out of danger to sleep in. their body fat keeps them alive and warm while they are sleeping.Some animals, such as bears, may wake up from their hibernation on warm winter days and then quickly go back to sleep again when they see the snow is still thick on the ground, when the weather becomes warmer in spring, the animals start to wake up and look for food.