Understanding Hedgehog Hibernation

As the temperatures drop and food becomes scarce, many of us begin to think about hedgehogs snuggling down for their long winter sleep. But hibernation isn’t as simple as curling up in a nest and snoozing until spring. For hedgehogs, hibernation is a complex process, driven by environmental and hormonal cues, and their survival depends heavily on the preparation they make in the autumn – and the support we can offer from our gardens.

Here’s a closer look at what happens to hedgehogs during hibernation, why food and shelter are so important, and how you can give them the best chance of making it safely through the colder months.

What Triggers Hibernation?

Hibernation is not essential for hedgehogs. In fact, hedgehogs in warmer climates, such as parts of New Zealand, may not hibernate at all, while those in severe climates hibernate for long periods. In the UK, the cold combined with a lack of natural food supply are the key triggers. Hedgehogs in captivity, kept warm with food available, may never hibernate.

This is why it’s always recommended to keep leaving food and fresh water out in your garden through the winter months. Dried specialist hedgehog food lasts longer than wet food if it isn’t eaten straight away, making it a practical option.

Building the Right Fat Reserves

By the time hedgehogs are ready to hibernate, around 30% of their body weight will be fat. Both brown and white fat play important roles:

White fat (under the skin and around the stomach and intestines) makes up about a third of body weight before hibernation. It provides a steady energy supply during long periods of torpor.

Brown fat (around the shoulders, chest, neck, and under the front legs) is used for generating heat. This becomes vital during arousals, when hedgehogs briefly wake to normal body temperature before returning to hibernation.

If fat stores are insufficient, a hedgehog may still attempt to hibernate but will not survive. Even healthy hedgehogs lose 25-40% of their body weight over winter as these fat reserves are consumed. Males usually enter hibernation first, as they’ve had more time after the summer’s mating season to bulk up.

The Science of Torpor

During hibernation, hedgehogs enter a state of torpor where many bodily functions slow dramatically:

Heart rate and respiration are reduced.

Kidney and liver activity decreases to conserve energy.

Body temperature drops from around 35°C to as low as 2–5°C, close to the surrounding environment.

The “optimum” hibernation temperature is about 4–5°C. At this point, metabolism is at its lowest, and fat reserves last longest. However, extremes of temperature can be dangerous:

If the environment is too cold (<1°C), hedgehogs risk frostbite or even freezing.

If it is too warm, metabolism speeds up, burning fat reserves too quickly.

Both situations can cause hedgehogs to wake too often, which rapidly depletes their brown fat.

Arousal During Winter

Hibernation isn’t one continuous sleep. Hedgehogs experience periodic arousals, where they warm up to normal temperature and may stay in the nest or venture out briefly. These arousals may prevent freezing in extreme cold, but they are energy intensive and burn through fat supplies.

That’s why leaving food and water available throughout the winter is so important. A hedgehog that wakes up unexpectedly needs to replenish its reserves quickly, or it may not survive the rest of hibernation.

Emerging in Spring

Arousal from hibernation in spring is triggered by longer daylight hours and rising temperatures. Males usually wake first, possibly to get ahead with feeding before females emerge, or to be ready for mating. Hormonal changes – such as decreased melatonin and rising testosterone – also play a role in reactivating the reproductive system.

When hedgehogs first wake, they are extremely weak and underweight, making immediate access to food and water critical for survival. Gardens that provide this support become vital lifelines.

How You Can Help

You can make a real difference to hedgehogs during their winter hibernation by:

Leaving food and water out all winter. Use specialist hedgehog food, dried kibble, or meaty cat/dog food (no fish flavours, gravy, milk, or bread).

Providing safe nesting areas. Leaf piles, log piles, or purpose-built hedgehog houses in quiet, sheltered spots are ideal.

Avoiding disturbance. Check piles of leaves, compost heaps, and log stacks before moving or burning them. Always inspect grassy borders before strimming.

Keeping access routes open. A small 13cm gap at the base of a fence allows hedgehogs to roam and find food.

Every Garden Counts

Hibernation is a delicate balance of biology and environment, and many hedgehogs won’t make it through the winter without enough fat reserves or safe shelter. By making small adjustments to your garden and ensuring food and water are always available, you can give these incredible little animals the best possible chance of survival.

So, this winter, while hedgehogs curl up in their nests and the natural world slows down, you can rest assured knowing your garden is doing its part to help them wake healthy and strong in the spring.