I’m writing this sat cosily in front of a fire, but feeling sorry for myself as I have a cold. It’s been a hectic few weeks, out every evening for one thing or another, and lots happening at work. Right now, I can’t help envying the hedgehog who is hibernating in our hogitat. I wish I could hibernate.
Hibernation is a very clever strategy for getting through the winter, when there’s not much food around for some animals. Comparing it to a long, deep sleep fails to do justice to it. The body temperature of hibernating animals drops to match its surroundings (but always kept above 1 degree C so it does not freeze). Their heart rate slows, and they can go almost an hour between short bursts of breathing. This reduces their energy consumption by around 90%.
Hibernating animals rely of fat supplies built up during summer and autumn. By now nearly all hedgehogs and dormice will be hibernating. Those who aren’t are likely to be underweight individuals looking for more food before they hibernate. While hibernation uses much less energy than being active, they still need enough fat to keep their bodies ticking over, and also to help them wake up.
On warmer winter days hibernating animals might wake from hibernation, and may even stir to find food or drink. But each time the animal wakes it uses up some of its precious fat reserves, so mild or variable winters are not good for hibernating creatures.
Hibernation is not without its risks. It can take hibernating animals several hours to wake, so they cannot respond quickly to threats like predators or floods. A considerable proportion of hibernating animals do not make it through the winter, not having enough fat reserves. But then winter does kill off a lot of more active animals as well.
Of UK mammals, only bats, dormice and hedgehogs properly hibernate. Other mammals, such as badgers, will reduce their activity, and stay snuggled down sleeping in their setts, but not shut down so much. Given the risks of hibernation, maybe I’d be better off imitating the badger instead… If you don’t see me for a while, you’ll know what I’m up to!