Why do some animals sleep all winter?

Imagine sleeping from the first snow until the flowers come back. Some animals really do that! It is called hibernation, and it is a clever way to get through the cold winter.

Why a winter nap?

In winter, the ground freezes and many plants stop growing. Berries, bugs and seeds become very hard to find. If a little animal kept running about looking for food, it might use up all its energy and find almost nothing to eat.

So instead of searching, some animals do something amazing: they fall into a deep, deep sleep and wait for spring.

A body in slow motion

During hibernation, the animal’s body slows right down. Its heart beats slower, its breathing gets gentle, and its body goes cool. It uses hardly any energy at all, like a toy with the power switched almost off.

So what keeps it alive? In autumn the animal eats and eats to build up a thick layer of fat. All winter long, its sleeping body slowly burns that stored fat for fuel.

Who hibernates?

Dormice, hedgehogs, bats and ground squirrels are famous winter sleepers. When the warm air and fresh food return in spring, they wake up, stretch, and are hungry for breakfast!

Wonder fact: A hibernating ground squirrel’s heart can drop from over 200 beats a minute to just a few — so slow you might think it had stopped!