In the winter, many animals, including bears, bats, and hedgehogs, hibernate to conserve energy as food becomes scarce. Hibernation is a deep sleep that helps them to save energy and survive the winter without eating much. They slow down their metabolism, heart rate, and body temperature to expend less energy. It's essentially a survival strategy to get through the cold months when food is hard to come by. Each animal's hibernation pattern is unique and can last for a few days, weeks, or even months.