Why do animals hibernate?

From a young age, we’re taught that some animals go to sleep for the winter and wake up again in the spring – but do you know why? The answer might be more surprising than you think.

What is hibernation?

Hibernation isn’t just a long sleep. In technical terms, hibernation is the process during which an animal’s body temperature and metabolic rate drops in order to conserve energy during the time of year when resources are most scarce. In the case of a bat, it could slow down so much it only takes one breath an hour, with its heartbeat going from 1000 beats per minute to just 25.

Hibernating snails retreat into their shells and close up the opening, so they use virtually no energy. If they’re in a particularly dry area, some snails have been known to hibernate for years!

Hibernation can also happen in warmer climates in order to avoid the hottest parts of the year, or to avoid food shortages. Echidnas in Australia have been known to go into hibernation after wildfires, emerging once there is enough food around again.

While there is a single definition of hibernation, it can happen in many different forms, with animals hibernating in big groups or alone, above ground or below, one long, solid dormancy or short ones with gaps to eat, drink and move about.

Which animals hibernate?

There aren’t any hard and fast rules to determine which animals will hibernate, each species has evolved differently and may hibernate in different ways.

Some smaller, warm-blooded animals go into such a deep hibernation, they’re virtually impossible to wake. Bears go into a lighter hibernation so that they’re able to react to any nearby danger. Some insects and amphibians produce a kind of natural anti-freeze to prevent them from freezing in cold weather.

Meanwhile, other animals (like humans) have evolved without the need to hibernate. We have biological and technological means to stay warm and safe all year around. Many species of birds migrate to warmer climates in winter months, avoiding the dangers of freezing temperatures and less food.

In the UK, some hibernating animals have varying levels of legal protection. These include:

  • Badgers
  • Bats
  • Dormice
  • Frogs
  • Hedgehogs
  • Newts
  • Red squirrels
  • Toads

How can we look after hibernating animals?

Hibernating animals should be left alone. As spring comes and things warm up, animals emerging from hibernation will be starving – some lose as much as a quarter of their body weight throughout the hibernation period – so making sure there’s plenty of food to go around will help them make a quick recovery.

Some hibernating animals react so strongly to a change in environment that waking them from hibernation early could shock their system so much that they can’t survive – so if you’re planning any work over the winter months, it’s important to be sure that the habitat isn’t a haven for hibernating animals and that you’re not disturbing a habitat that hibernating animals will be looking to return to.

Even those animals in the deepest hibernation appear to ‘wake’ occasionally. Scientists are not sure why, but it could be that they leave their state of slowed metabolism and lowered temperature to catch up on their sleep! Some creatures are more active than others during this time, and climate change is posing a threat to them. The warmer the outside temperature is, the longer creatures tend to be awake and active before going back into full hibernation mode. This uses up their valuable energy stores and reduces the chance of their survival. With climate change causing milder winters and warmer temperatures, there’s a greater chance of animals expending too much energy during what’s supposed to be a low activity period.

The best way to protect all habitats is to take a considerate approach, both in terms of the immediate environment and potential homes of wildlife (hibernating or otherwise), and in terms of reducing rates of pollution to avoid contributing further to climate change and the negative impact it has on habitats everywhere.

If you need advice about the wildlife around your project and want to make sure you won’t be disturbing a habitat perfect for hibernating animals, get in touch with us on 01225 459564 or email

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