Which Animals Hibernate – and How to Help Them

While we’re busy going about our lives in winter, wildlife is slowing down. Right down. Tucked into piles of leaves in the woodland, or hiding under garden sheds, animals are hibernating. Others are brumating, or diapausing (keep reading to find out what those terms mean!). Here’s the lowdown on which animals hibernate – and how you can help them this winter.

WHAT IS HIBERNATION?

You might think hibernation means animals having a big, long, wintry sleep, but there’s a bit more to it than that.

Hibernating animals are in a state called torpor: their heart rate and metabolism slow right down, their breathing becomes very shallow and slow and their body temperature drops. The only energy they use is to sustain their body heat and to keep their blood flowing. A hedgehog’s heart rate will drop from 190 beats per minute to around just 20 faint beats per minute during hibernation, and a dormouse’s heart rate will slow down by up to 90%. During this barely-conscious state, creatures’ brain patterns are very different to when they’re sleeping.

Animals prepare for hibernation in autumn, by eating lots to keep their fat reserves high. Some species use leaves, bracken and other plant matter to build an impressive, insulated and waterproof nest to curl up in, called a hibernaculum. Hedgehog hibernacula can measure up to 60cm diameter and have walls of up to 10cm thick!

Watch the video below to learn more about the endangered hazel dormouse – and see one hibernating.

WHY DO ANIMALS HIBERNATE?

Animals hibernate to conserve energy so that they can survive the cold winter months, when the food they normally eat is in very short supply.

DO ANIMALS HIBERNATE ALL THE WAY THROUGH WINTER?

Usually not. A common misconception is that hibernating animals tuck themselves up in autumn and don’t re-emerge until spring. But there are various reasons why they might sometimes wake up. In an extremely cold snap, hibernating creatures sometimes emerge and move around a to avoid freezing. They might also wake if the weather’s unseasonably warm, to search for snacks and top up those fat reserves. And they might move and find a new place to settle down if they are disturbed. You should never deliberately disturb or try to wake a hibernating animal as this could be fatal to them.

WHICH ANIMALS HIBERNATE IN THE UK?

Technically, the word ‘hibernate’ only really applies to mammals – and just three mammals in the UK hibernate. They are hedgehogs, hazel dormice and bats.

Hedgehogs and dormice build their own hibernacula, whilst bats seek out a cool, dark place like a hollow tree, abandoned building or cave.

Other types of UK wildlife do enter a period of dormancy over winter, but it has a different name (more on that below).

DO BADGERS HIBERNATE?

Nope. Badgers don’t hibernate. But they do build up their fat reserves in autumn and spend most of their time underground during winter. And along with squirrels, they can enter temporary torpor when the weather gets very cold. This is like a mini hibernation; it’s a deep sleep in which an animal’s heart rate slows right down, to help conserve energy. It can last anything from a few hours to a few weeks.

DO FROGS AND TOADS HIBERNATE?

Reptiles and amphibians need the sun to regulate their body temperature, so in winter, they enter a state of dormancy called brumation. It’s very similar to hibernation, with them occasionally waking to move, eat and drink – but generally, these cold-blooded creatures hide away for much of winter. Snakes and lizards crawl between rocks, toads bury themselves in mud and newts and some types of frogs brumate at the bottom of ponds.

DO BEES HIBERNATE?

It depends on the bee! Honeybees stay in their hive, huddled together to generate heat and keep warm – with the queen at the centre, of course. They rely on the stores of honey they made earlier for energy, but on a mild day they'll leave the hive to expel waste and forage for nectar and pollen on winter flowers, like mahonia.

At the end of the summer, bumblebee colonies die off, all except for the queen. Similar to a hedgehog or dormouse, she gorges on food in autumn, then retreats to a nook or cranny or under loose soil. There, she enters a state of dormancy similar to hibernation, ready to emerge and lay her eggs in spring.

For solitary bees it’s a different story: their larvae mature into bees in autumn but stay tucked up in their cocoons until spring. This suspension of development is called diapause, and it happens to many insects, including ladybirds (who huddle together over winter) and certain butterflies. Some bees can remain in diapause in for up to ten years – and the desert-dwelling yucca moth larvae can survive in this stasis for up to 30 years!

HOW TO HELP HIBERNATING ANIMALS 

It's important to leave animals that are hibernating (or brumating!) well alone, but that doesn't mean we can't help them. Here are some things we can do to help them survive the winter...

• If you already feed hedgehogs in your garden, keep leaving supplementary dog or cat food (but not fish) and water at your usual feeding station over winter. Read more in our blog about how to welcome hedgehogs into your garden.
• Create places for animals to hibernate in: bug hotels, piles of leaves, log piles etc.
• Garden thoughtfully, being careful not to disturb any hibernating creatures. Leave compost heaps and piles of leaves untouched .
• Plant winter flowering plants to feed hungry honeybees. Hellebores, mahonia, snowdrops and crocuses will all be appreciated by our pollinating pals.
• If you have a pond, leave a ball floating on top to stop it from freezing. If it does freeze, make a hole in the ice. Decaying leaves trapped under ice can be dangerous to brumating frogs and newts.
• If you accidentally disturb a hibernating hedgehog, cover it with leaf matter, stay quiet and move away. Leave food and water nearby in case it wakes. If you’re concerned, contact your local hedgehog rescue.