Fewer animals hibernate than you might think in the UK, but all animals have ways to adapt to the colder weather of winter.
In fact only three mammals hibernate. They are bats, dormice and hedgehogs. They spend the autumn building up body fat and then they find their winter hiding places when the weather turns cold. Here, they enter a state of almost complete shutdown, lowering their heart rate and body temperature.
How do mammals that don’t hibernate survive winter?
The mammals that don’t hibernate have different ways of surviving the winter. Some grow their coats as a protection against the cold or change their diet to what’s available in the winter. Foxes are a great example of both of these strategies. Other mammals enter a state of dormancy, like a mild form of hibernation. They conserve energy but, unlike hibernating mammals, they are easily roused and they don’t lower their heart rate and body temperature. Badgers are a good example. Squirrels are mistakenly believed to hibernate by many, in fact, they just slow down and spend a lot more time sleeping in the winter. Their busy autumn of collecting nuts is simply to store them for the barren months of winter. Quite intelligent planning ahead when you think about it.
Do snakes, frogs and toads hibernate?
Reptiles and amphibians, such as snakes and frogs do sort of hibernate, but it’s different to mammals. They enter a state of torpor and inactivity which is called brumation. Snakes will find burrows, dens and logs to hide under. Likewise, most frogs in Britain brumate on land, preferring places such as animal burrows. Some frogs will nestle down in the mud at the bottom of ponds, ensuring they are not covered. Their bodies can diffuse the oxygen they need for survival. As these creatures are cold blooded, they don’t lower their body temperature like hibernating mammals do.
Why don’t we see so many insects in winter?
Insects are different again. Many of them effectively hibernate but for insects the term is not hibernation, it is diapause. This is a state of suspended animation, hidden in trees, under leaves and logs and even in homes. To keep the cold temperatures at bay, some insects produce chemicals which act like antifreeze to keep from icing up. Insects that enter diapause include bumble bees, some butterflies, and queen bees and queen wasps. Other insects simply die away, with their life cycle not seeing the four seasons through.
Birds don’t hibernate do they?
No. Birds don’t hibernate. Many, such as blackbirds, crows and robins see the winter through, enjoying slim pickings – which is why it is important to fill up your bird feeders in winter. The smart ones head back to the warm sunshine of Africa, where there is plenty of food for them, for an extended winter holiday.
Three fun facts about hibernation:
- The shelter a hibernating animal uses is called a hibernaculum
- In warm countries some creatures have a form of hibernation called aestivation, which they go into when it’s too hot, or there is a drought or shortage of food.
- Dormice are the longest hibernators in Britain, staying put for six months or more. Their name comes from the French dormir – to sleep!