When Do Hedgehogs Hibernate? Hedgehog Hibernation Explained

When does hedgehog hibernation start and end?

The European hedgehog is one of the few true hibernators in Europe. The timing depends mainly on temperature and food supply rather than a fixed date. As nights get colder and insects and worms become scarce, hedgehogs build a winter nest and settle in.

Adult males, which do not raise young, often begin hibernating first in autumn and tend to emerge earlier in spring. Females that have had late litters, and young hedgehogs born in late summer, are usually the last to settle down because they are still feeding to gain weight.

What happens to a hedgehog’s body during hibernation?

Hibernation is not ordinary sleep. It is a controlled state of very low activity called torpor, in which the hedgehog lets its body cool to save energy.

• Body temperature: falls from about 35 °C (95 °F) to just a few degrees above the temperature of the nest, often around 2–5 °C (36–41 °F).
• Heart rate: drops from well over a hundred beats a minute when active to only a small fraction of that.
• Breathing: becomes very slow, with long pauses between breaths.
• Energy use: falls to a tiny fraction of normal, so stored fat can last for months.

A hibernating hedgehog is cold to the touch and rolled into a loose ball. It cannot move quickly or defend itself, which is why its choice of nest is so important.

Why do hedgehogs wake up in winter?

Hibernation is not one long, unbroken sleep. Hedgehogs warm up for short periods roughly every week or two. During these arousals they may stay in the nest, but many also move to a new nest: studies of tagged hedgehogs show that most change nest sites at least once during the winter.

Rewarming is costly. To raise its body temperature back to normal, a hedgehog burns a special tissue called brown fat, which produces heat quickly. Each arousal uses a large share of the energy spent over the whole winter, so frequent disturbance can drain a hedgehog’s reserves.

On mild winter nights, hedgehogs are sometimes seen out foraging briefly. This is normal behavior for a healthy animal that has woken naturally, although a very small, thin hedgehog out in freezing weather is likely to be in trouble.

Where do hedgehogs hibernate?

Hedgehogs build a winter nest called a hibernaculum. It is made of dead leaves, especially large, flat leaves such as oak, beech and sycamore, packed in layers around the animal. Well-built nests can be 50 cm (20 in) or more across and keep the inside temperature much steadier than the air outside.

Typical sites include:

• Bramble thickets and dense hedges
• Log and brush piles
• Spaces under tree roots, garden sheds and decking
• Compost heaps and piles of leaves

In Finland, hedgehogs often use the spaces among pine roots. Hedgehogs are scarce in marshes and moorland partly because these habitats lack the right leaves and shelter for winter nests.

How much fat does a hedgehog need to survive?

A hedgehog lives off the fat it built up in late summer and autumn, and it loses a considerable part of its body weight over the winter. That is why autumn is such a busy feeding season, and why the supply of beetles, caterpillars and worms matters so much; see what do hedgehogs eat?

Young hedgehogs from late litters are most at risk, because they have little time to grow before the weather turns cold. Starvation during hibernation is one of the most common causes of death in European hedgehogs, especially in their first winter. Older, heavier adults have a much better chance of surviving until spring.

Do other hedgehogs hibernate?

There are about 17 hedgehog species across Europe, Africa and Asia, and all of them can enter some form of dormancy. How long they stay inactive depends on climate:

• Northern white-breasted hedgehog of eastern Europe: hibernates much like the European hedgehog.
• Amur and Daurian hedgehogs of northeast Asia: face very cold winters and hibernate for long periods.
• Desert and long-eared hedgehogs of dry regions: may become dormant for shorter spells when food runs short, in hot or cold seasons.
• African hedgehogs in warm climates: often stay active through the year, entering torpor only when it is cool or food is scarce.

Hedgehogs are one of many animals that sleep through the lean season; see animals that hibernate for others, from bats to dormice.

Myths about hedgehog hibernation

• Hedgehogs sleep through the whole winter without waking. They wake regularly and often change nests.
• Hedgehogs hibernate because of the date. It is temperature and food, not the calendar, that sets the timing, which is why hibernation varies from year to year.
• Any hedgehog seen in winter is sick. A healthy adult may be briefly out on a mild night; size, condition and weather matter more than the season alone.