HIBERNATION and other confusing stuff

Consciousness: that annoying time between naps.

Author Unknown

Why do hedgehogs hibernate?

Good question. You tell me. I always used to believe what is written everywhere such as:

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.

That makes perfect sense until you start looking after them and you have dozens of them around all through the winter. That's when you start to notice they all do different things.

Take winter 2009/10. 24 hedgehogs all in the same room. 9 in and out of hibernation. 1 in permanent hibernation, the rest causing mayhem. They all have the same conditions, food and water available at all times. So why the difference?

I'm hoping that more research will be done, not least so that overwintering carers have a better idea of how to treat recovered animals that can't yet be released but I have my own theories.

I may be well wide of the mark but I believe that in addition to food and temperatures, lack of cover plays a big part. Hedgehogs normally charge around in undergrowth, sheltered from predators by shrubs and bushes. During the winter, all that cover is gone so they find somewhere they can hide until it grows again.

What is hibernation?

Heart slows from 190 beats per minute to a barely detectable 20. Temperature normally 35oC, drops to 10oC

Before going into hibernation a hedgehog will spend weeks building up its fat reserves. It's those fat reserves, plus the slower metabolism, that allow it to survive the long winter.

Hibernation turns a warm-blooded hedgehog into what is, for all intents and purposes, a cold blooded animal. Hibernation is not sleep. A sleeping hedgehog can be seen dreaming and moving just like any other mammal but once in hibernation, the metabolism almost completely stops.

The hedgehog seems to be dead; its feet, ears and skin feel extremely cold but a touch triggers unconscious reflexes that make the spines slowly rise, it may also tuck its head further into the impenetrable ball. Sounds will evoke the same response but the brain is almost completely dormant.

The heartbeat drops, it takes one breath every few minutes and its body temperature plummets to a level that would kill most other mammals, but research shows that the temperature of the heart stays normal.

If you find what you think is a dead hedgehog, especially during the winter or early spring, please do not assume that it's dead and bury it. Unless there are obvious signs that it is deceased, such as decomposition, please take it to a vet and ask them to check for vital signs. Give them the hibernation details above as they may not be used to dealing with hibernating hogs.

If the hog is injured but still alive then it will need to be woken up. This is a job for the experts and you should call for advice before doing anything

When is hibernation?

It is not normally until the coldest months of November January and February that hedgehogs finally settle down to hibernate

Author Unknown

Again, this isn't an exact science. It seems to depend upon many things, weather, location, availability of food, availability of good shelter. They face the danger of floods, cold and predators all of 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.

Any hedgehog weighing less than 600g should be kept indoors and fed throughout the winter for release in the Spring.

Waking up

Water is life's mater and matrix, mother and medium. There is no life without water.

Albert Szent-Gyorgyi

Hedgehogs emerging from their nests after hibernation are usually very thirsty and water dishes left out will save lives. Our rescue animals will often sleep for several days then come out and demolish a dish of water before going back to bed. Food is left untouched.