Some animals, like dormice, go into hibernation over the colder months, whilst others, like badgers, enter a state of torpor.
The hazel dormouse is one of just three species that truly hibernate in winter.
Why do animals hibernate?
Animals hibernate to survive long periods of cold weather, when food sources are scarce. Only three wildlife species in the UK truly hibernate; the rest go into torpor.
What’s the difference between hibernation and torpor?
Hibernation involves an animal dropping their body temperature and significantly reducing their heart rate in order to conserve energy. They also lower their metabolism so they can go for long stretches of time without needing to eat or drink. They rarely leave their hibernation spot all winter, although may briefly rouse on milder days to look for extra food or go to the toilet.
Meanwhile, those in a state of torpor (or dormancy) dial back their day-to-day activities, and sleep only for a number of days or weeks. Unlike hibernation, torpor is involuntary, and this survival mechanism is triggered when environmental conditions are too harsh to handle. Torpid animals still experience a drop in body temperature and metabolic rate, but they are not in a constant state of deep sleep, so are more likely to wake up periodically.
Between October and November, dormice begin to hibernate and remain in their nests until April or May.
Ahead of their hibernation period, hazel dormice will bulk up by consuming as much food as possible, and can become twice their normal size. In order to prolong their hibernation period, they build their tiny woven nests in grassy areas surrounded by moss and leaves on the ground. This helps create a warmer, more humid environment and prevents them from becoming dehydrated.
Bat
Around November, all native bat species search for cool, dark places to roost for the winter. These can be anything from hollows in trees to man-made structures like pillboxes. Underground roosting options, like caves, are also a big hit.
The length of their hibernation period varies from species to species. Greater Horseshoe Bats are believed to spend six months or longer hibernating, whilst pipistrelles may only require around five.
During hibernation, a hedgehog is able to reduce its heart rate from 190 beats per minute to around 20. Like other fellow hibernating creatures, they prepare themselves by eating as much as possible during October and November, before taking refuge in sheltered nests made from leaves, grass and other plant material.
Hazel dormice hibernate in warm, woven nests
Which animals enter torpor in the UK?
Badger
Badgers enter a state of torpor for a number of days or possibly weeks. During harsh periods of weather, they hunker down in their setts, rousing every so often to forage.
Amphibians
Frogs, toads and newts conserve energy during extreme weathers. They'll often seek out damp areas least likely to be hit by frost, such as log piles or compost heaps. They may also opt for shallow, muddy waters or sheltered canal banks.
Badgers spent winter in torpor in their underground setts
Can I wake an animal in hibernation?
No, if you come across an animal in hibernation or torpor, it is important to leave it undisturbed. Causing it to wake puts its survival and welfare at risk by interfering with its energy reserves.
