How well do you know your hedgehog?

Where did the hedgehog come from?
The hedgehog comes from an ancient family and fossils suggest that hedgehog-like creatures have been on the earth for about 15 million years.

Has it any relations?
The modern hedgehog has no close relatives amongst other mammals although it may have distant links with moles and shrews. It belongs to a family all on its own and has developed along a separate evolutionary line for millions of years. The family has a dozen or so species, five in S.E. Asia, three in Africa and two in China but no indigenous ones in the Americas or in Australasia. Our British Hedgehog is the same species that occurs in most of the continent of Europe and is called Erinaceus europaeus. It has also been introduced into New Zealand.

What does a hedgehog look like? 
Who doesn’t know?

What’s on the outside?
Of course the hedgehog is characterised by its spines. These are modified hairs, about 2-3cms (1”) long, which cover the back of its head and body. As a hedgehog grows the number of its spines increases until an adult has between 5000 and 7000. By this time it will be somewhere between 20-30cms (8”-12”) in length but its tail will be less than 2-3cms long.

Whole spine

And what about the inside?
Under the prickles the hedgehog has a remarkable system of muscles that are designed to raise and lower its spines. When it is frightened it will tighten the muscles around its flanks and curl up. Its soft parts are thus completely guarded by a defensive cover of prickles that few enemies can penetrate. But what about its bones? Have a look at the diagram of a hedgehog’s skeleton below -

Skeleton

Scientists have discovered very little unusual about the hedgehog's skeleton except the shortness of the neck. This probably helps it to roll up into a compact ball more easily. The hedgehog's peculiar ability to roll itself into a ball, and to stay in this position for a long time (especially during hibernation) however, is made possible by the powerful muscle that covers its back like a cape. A look at the X-ray picture of a rolled up hedgehog below will make it clear why this self-defence mechanism means that it has fewer enemies than any other mammal of similar proportions.

X-ray view of rolled up hedgehog.

Our thanks to Guy Troughton for the drawings.

More facts about hedgehogs:

• They have relatively long legs - about 10cms (4") - and these enable them to run as fast as we can walk.

• Their front feet are shorter and broader than their back ones.

• The claws on their powerful front feet are particularly useful for digging.

• Each night (when not hibernating) hedgehogs will probably make a slow and apparently haphazard search for food and will travel between 2-3kms (1-2 miles).

• They have small bright eyes but cannot see very well. At night they will use their excellent sense of smell and hearing to guide them.

• Their weight will be largely determined by the food they get, but most one-year olds will weigh between 450-680gms (1-1½1bs).

• Self-anointing is an activity only hedgehogs do. It seems to be connected with strange smells or tastes that cause them to produce large quantities of frothy saliva. They then spread the foam over their spines by flicking it with their tongue.

• If a young hedgehog survives its early life in the nest and then its first hibernation, it can expect to live for 4 or 5 years longer. By this time it will be getting old but might live to the age of ten.

• Generally they lead solitary lives and tend to go out of their way to avoid other hedgehogs, except during the mating season.

• Like most mammals the hedgehog has a characteristic smell and this will usually warn other hedgehogs to keep out of the way.

• In the mating season the male may be attracted by the different smell of the female and commence a rather prolonged and noisy courtship with her.

• Hedgehogs do not pair bond - the female raises her young unaided by the male.

• Litters of young, called hoglets, are born from May onwards to as late as September and average about 2 to 6 in number. At about 4 weeks of age they venture out of their nest with their mothers and at about 6-8 weeks old they leave the nest and wander off on their own - they weigh around 250gms (8oz) at this stage.