Winter is coming! How wildlife survives the cold.

As winter settles over the British countryside, wildlife is faced with a big challenge: how to survive freezing temperatures and food shortages. Some species embrace one of nature’s most fascinating survival tactics - hibernation - while others use unique strategies to stay active and alive during the harshest months.

In this post, we’ll explore the ins and outs of hibernation in British wildlife, explain how it works, and take a closer look at why some animals don’t hibernate at all. From hedgehogs to bats, and even non-hibernating species like foxes and deer, you’ll discover how these animals manage to make it through the winter.

Which Animals Hibernate in the UK?

Several British species rely on hibernation to get through the winter. This process allows them to conserve energy and survive when food becomes scarce, and temperatures drop dangerously low. The most well-known hibernators in the UK include:

Hedgehogs: These charming creatures hibernate from November to April, nestling in piles of leaves, under sheds, or in hedgerows. They rely on stored fat to keep them alive through the long, cold months.

Dormice: Hazel dormice are perhaps one of the more elusive hibernators in the UK. They hibernate close to the ground, under leaf litter or dense vegetation, from October to May.

Bats: British bat species, such as the common Pipistrelle, hibernate in caves, lofts, and tree hollows. Since their food, flying insects, disappears in winter, they enter hibernation to conserve energy.

Reptiles and Amphibians: Common lizards, adders, frogs, and newts enter a state of dormancy in sheltered locations like burrows, under rocks, or in mud.

Butterflies: Species like the peacock butterfly and brimstone enter a hibernation-like state known as diapause, hiding in tree hollows, sheds, or dense foliage.How Does Hibernation Work?

Hibernation is an incredible biological process that allows animals to survive extreme conditions by slowing down their bodily functions. It consists of three key phases: preparing for hibernation, sustaining it, and waking up as spring approaches.

1. Preparing for Hibernation

As autumn gives way to colder days, animals begin preparing for the long sleep ahead. One of the most critical steps is building up fat reserves. Hedgehogs, for example, enter a phase known as hyperphagia, where they consume large amounts of food to bulk up for winter. This fat will fuel their bodies during hibernation when they won't be eating.

Shelter is another important factor. Hedgehogs find safe spots in hedgerows or under piles of leaves, while bats choose stable environments like caves or attics. Their metabolic processes also begin to slow as their bodies prepare for the energy-conserving state of hibernation.

2. Sustaining Hibernation

Once in hibernation, animals enter a deep state of torpor, where their metabolism, heart rate, and body temperature drop dramatically. Hedgehogs’ heart rates decrease from around 190 beats per minute to as low as 20, and their body temperature can fall close to the surrounding environment.

During hibernation, these animals don’t eat or drink, instead relying on their fat reserves. Amphibians like frogs may hibernate underwater, absorbing oxygen through their skin. Bats and hedgehogs may go through torpor cycles, where they briefly wake up to regulate body functions before returning to their deep sleep.

3. Waking Up from Hibernation

As the days grow longer and temperatures rise, environmental cues signal the end of hibernation. Hedgehogs, bats, and dormice wake up gradually as their metabolism ramps back up. Many animals rely on brown fat, specialised tissue that generates heat, to rewarm their bodies and help them become active again.

Once awake, these animals are often very hungry! Hedgehogs immediately begin searching for insects, worms, and other food to restore the energy lost during hibernation.

So Why Don’t All Animals Hibernate?

While many animals hibernate to survive winter, others have evolved different strategies to deal with the cold and lack of food. These adaptations allow them to remain active and thrive during the winter months without needing to hibernate.

1. Physical Adaptations for Cold Weather

Some animals are naturally equipped to handle the chill. Species like foxes, deer, and many birds grow thicker fur or feathers in winter, providing better insulation. This helps them maintain body heat even in freezing temperatures.

Squirrels, for example, don’t hibernate but rely on fat reserves they build up in autumn. They may also store food in hidden caches to eat when food is scarce.

2. Migration to Warmer Climates

Many birds, such as swallows and geese, avoid the challenges of winter by migrating to warmer climates where food is more readily available. Migrating allows them to continue feeding and living actively without entering hibernation.

3. Diet Flexibility

Some animals don’t need to hibernate because they can adapt their diets to the available food. Foxes and badgers, for instance, are omnivores and scavengers. They switch between hunting, scavenging, and foraging depending on what’s available, ensuring they find food even in winter.

Herbivores like deer feed on whatever plant material they can find, such as twigs, bark, and evergreen leaves, sustaining themselves through the winter months.

4. Short-Term Dormancy: Torpor

Instead of full hibernation, some animals enter a lighter form of dormancy known as torpor. Birds like hummingbirds may enter torpor overnight to conserve energy when temperatures drop, only to wake up when the sun rises and warms the air.

Whilst not native to the UK, even large animals like bears enter a state called “winter sleep” or “denning,” which is not as deep as hibernation but helps them conserve energy while remaining able to wake and move if necessary.

5. Behavioural Adaptations

Many animals change their behaviour during winter. Squirrels, for instance, reduce their activity levels and spend more time in nests to conserve energy. Some animals, like starlings, huddle together to conserve body heat, helping them stay warm and avoid the need for hibernation.

The Science Behind Hibernation (simplified)

Hibernation is a finely tuned biological process. During hibernation, animals undergo controlled hypothermia, lowering their body temperature to match their surroundings and saving energy in the process. Brown fat plays a crucial role in helping them wake up, providing the heat necessary to raise body temperature after months of dormancy.

Additionally, hormones like leptin and insulin help regulate fat storage and metabolism during hibernation, ensuring that animals use their energy reserves efficiently.

Conclusion: The Survival Strategies of British Wildlife

Hibernation is a life-saving strategy that helps many British animals survive the cold, dark months of winter. From hedgehogs to bats and dormice, these animals have evolved to endure months without food, conserving energy and waiting for the warmer weather to return.

But hibernation isn’t the only way to survive winter. Animals like foxes, squirrels, and birds employ a range of physical and behavioural adaptations to stay active throughout the season. Whether through migration, dietary flexibility, or growing thicker coats, these species have their own fascinating ways of making it through the winter months.

As spring approaches, we can look forward to seeing our wildlife reawakened, refreshed and ready for the new season ahead.