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Hedgehogs have no really close relatives among other mammals, however, it is thought that they may belong to the same family as the mole and vole. But most experts believe that they are a family all on their own.
In Britain the hedgehog is our only spiny animal. The spines are just modified hairs about 2-3cms long and taper to a very sharp point. Rolling up into a defensive ball is one of the hedgehog’s main characteristics. No other mammal does it so completely or so efficiently. It has two pairs of muscles, one pair that pulls the skin up over the top of the head and the other pair that pulls the skin down the lower back. Then a large circular muscle which runs round the animal’s body at the edge of the spiny part of the skin contracts, rather like the drawstring of a duffel bag, and as it closes it forces the head, legs and tail inside. The spines are made to bristle and point rigidly in all directions like a mass of barbed wire. In this state the hedgehog is so well protected that it probably has fewer natural enemies than any other mammal of similar size.
By the time a baby hedgehog leaves the nest it has about 3,000 spines on its back. As it grows older and bigger more spines appear and an average adult weighing about 600gms has a total of 5,000 or so spines. A very large hedgehog over twice that size may have 7,500 spines.
The hedgehog is not spiny on the underside (if it was it couldn’t roll up!) but has long and rather coarse grey-brown hair.
Its little tail is about 2cms long and is bare of spines and hair. The hedgehog has quite long legs about 10cms from hip to toe. Their back feet are long and narrow and their front feet are shorter and broader (this is because they use their front feet to forage for food). They have sharp claws.
Hedgehogs have very poor eyesight (although they are believed to be colour sighted). They rely on their acute hearing and sense of smell to locate and catch their prey (it can pick up human scent many yards away, if the wind is in the right direction!) It can hear and smell a worm 3cms below the ground. As well as earthworms, hedgehogs eat beetles, caterpillars, earwigs, slugs, snails, spiders and flies and a host of other small creatures.
Hedgehogs are nocturnal animals and, unless ill, are rarely seen out in the day. Most of the night is spent foraging for food and taking short naps. A hedgehog can travel between 1 and 3 miles in a night and can actually run quite fast. They can reach average speeds of 30-40 metres per minute (nearly 2mph) including short sprints of 2 metres per second (6mph). This is about the maximum speed we can walk without breaking into a run!
Hedgehogs are surprisingly good climbers. They can easily scale a 6ft brick wall and wire fences are a doddle!
They can also swim fairly well and are capable of squeezing through extraordinarily small holes. While they look to be podgy animals, much of the hedgehog’s apparent bulk is in its loose fitting skin. This is like a chunky sweater ~ very mobile and covering a comparatively slight occupant!
Most baby hedgehogs are born in May, June and July, but a female can also have a second litter born around September/October. These little late hedgehogs are known as ‘autumn babies’ and stand little chance of surviving.
Baby hedgehogs are born blind and deaf and are pale pink in colour. Within an hour after birth the first spines begin to appear, about 100 of them and they are pure white. Later brown spines grow, and when the baby reaches approx. 2 weeks old, the white ones (although still there) are barely visible. This is also the age when their eyes and ears open and their skin becomes darker. They have milk teeth, just like human babies, and these begin to be replaced in the third week of life. When they are 4 - 5 weeks old the babies are now big enough to go on foraging trips with the mother. The babies soon learn what to eat but return to the nest to take their mother’s milk as well. At 6-8 weeks old the babies leave the nest. At this stage they weigh about 250gms, ten times their weight at birth.
Once the family has dispersed, brothers and sisters are unlikely to meet again as hedgehogs live solitary lives. Hedgehogs meet and pass each other like ships in the night!
A hedgehog starts to prepare for hibernation around the end of November. In order to survive hibernation he must weigh in excess of 600gms. ~ This is why autumn babies rarely survive.
During hibernation the animal’s metabolic rate, cardiovascular system and respiratory rate all slow down to the minimum level to preserve life.
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