How do animals hibernate through winter?

When food becomes scarce and temperatures drop, some animals enter hibernation, a state of dramatically reduced metabolic activity. Before hibernating, animals like bears, groundhogs, and bats build up fat reserves by eating heavily in autumn. Once they enter hibernation, their body temperature drops significantly, their heart rate slows from dozens of beats per minute to just a few, and their breathing nearly stops. This drastically reduces energy consumption, allowing them to survive on stored fat for months. True hibernators like groundhogs become nearly impossible to rouse, while bears experience a lighter version sometimes called torpor. Animals typically find sheltered dens, burrows, or caves to protect themselves from the cold, and they emerge in spring when temperatures rise and food becomes available again.