Why do some animal species hibernate during cold seasons?

Animals hibernate to save energy when their food disappears and it gets too cold.

Imagine your house has a huge fridge full of snacks, but you have to pay for every meal by walking around the kitchen. If you stay awake all night, you get hungry and tired. Animals in winter face a similar problem because plants die down, bugs hide deep underground, or water freezes shut. Since they cannot find enough breakfast, lunch, and dinner to keep their bodies running at full speed, they go into a long sleep mode called hibernation.

Think of a smartphone battery. If you turn the screen off and close all the apps, it lasts much longer even if you leave it on. An animal doing this uses its stored fat like a battery pack instead of eating new food. Their body temperature drops a bit, their heart beats slower, and they breathe very slowly. This is called torpor.

They tuck themselves into safe spots like cozy dens or hollow logs. They do not dream as much and wake up rarely if at all. When spring comes and the sun warms the ground again, they wake up feeling like they just had a very long nap. Their bodies remember how to start working again, and they go out to find fresh food that is now easier to catch.