Hibernation
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Hibernation is a time of inactivity. Some animals hibernate, usually during the winter, when food is short. They fall into a sleep-like state. They can regulate their metabolism to consume less energy. They lower their body temperature, slow their breathing, and slow other vital functions. During hibernation, the body uses fat for energy, which the animal has typically gathered in summer and autumn.
Typical animals that hibernate are bats, ground squirrels (like marmots), hedgehogs, and marsupials.