Some mammals, like hedgehogs and dormice, hibernate in winter. This means that they spend the coldest months of the year resting somewhere safe and warm. Their heartbeat and their breathing both slow down whilst they hibernate. Hibernation is a bit like a really long sleep, where the animals only wake up occasionally, to go to the toilet or find food.
The clever part is that while they hibernate, they don’t need much food. Hedgehogs, for example, eat as much as they can in autumn, filling their tummies with worms and beetles. This gives them the energy they need to survive through the winter.
Animals hibernate in places where they won’t be disturbed, like compost heaps or log piles. Then, when spring arrives with its warmer weather, the animals appear again – and they’re usually ready for a nice big meal!