Hedgehog Hibernation Fact Sheet

Why do hedgehogs hibernate?

Many animals that feed on invertebrate life rely on being able to find vast quantities of insects and other small creatures. As the hedgehog is larger with more bulk than most insectivores it sometimes finds itself in trouble if the food is not available. It is this lack of food, when the insects have either died out or have gone into hiding until Spring, that forces the hedgehog into the perilous business of hibernation.

What happens during hibernation?

The true miracle of hibernation brings about some very dramatic physiological changes which almost transforms the warm-blooded hedgehog into a cold blooded animal just for the coldest two or three months of the year.

Sleep is not an apt description of hibernation. In sleep all the bodily functions remain almost normal. A hedgehog, which is sleeping can be seen dreaming and moving just like any other sleeping mammal but in hibernation its metabolism almost reaches a stand still.

To all outward appearances it is dead; its feet, ears and skin feel cold to the touch but, as you touch it, unconscious reflexes make its spines stand up and tuck its head further into the impenetrable ball. Any sound will evoke the same response but the brain is virtually closed down.

Its heartbeat will have dropped from a frantic 190 a minute to a barely detectable 20 per minute. It hardly breathes at all, taking one breath every few minutes, and its body temperature, normally 35^oC, drops to 10^oC, a fall that would kill most other mammals. Deep within the hedgehog ball however, the temperature around the heart is normal.

All told a drop of around 25^oC in a hibernating hedgehog's temperature enables the rate of metabolism to slow allowing the fat reserves, that are the only source of sustenance to last much longer.

It is not normally until the coldest months of November January and February that hedgehogs finally settle down to hibernate. This is when they face the danger of floods, the cold and predators which can kill them whilst they are inactive. Huge numbers of hedgehogs do not survive hibernation, some that are sick or underweight will not have the strength or enough fat reserves to awaken them.

A hedgehog weighing less than 600grms should be kept indoors and fed throughout the winter.

Hedgehogs emerging from their nests after hibernation are usually very thirsty and water dishes left out will save lives.