Why do some animals hibernate during the winter?

Animals hibernate during the winter to survive the cold months when food is scarce. By entering a state of dormancy, their metabolic rate slows down, allowing them to conserve energy. During hibernation, many animals, like bears, bats, and ground squirrels, rely on fat reserves stored in their bodies to survive. Some animals, like amphibians and reptiles, may enter a deeper form of hibernation called brumation, where their bodily functions nearly stop, and they rely entirely on stored energy until the warmer months return.