Hedgehogs are small, often spine-covered members of the insectivore family Erinaceidae. The spiny hedgehogs are 13 species in subfamily Erinaceidae. Most famed is the European hedgehog, Erinaceus europaeus, which is also a resident of New Zealand, where it was introduced. Not all members of the hedgehog family have tough spines. The moonrats, or gymnures, of Southeast Asia have coarse hair instead of spines.
The common European hedgehog looks rather like a large pine cone with eyes. Its rounded body is covered from nose to tail with inch-long spines, up to 5,000 of them. The animal's size is variable, from 5-12 in (12-36 cm) long. While the spines of a hedgehog are often sharp, they are not nearly so dangerous as those of a porcupine. They lack the barbs on the end that can catch in an animal's flesh, anchoring there. Instead, the spines just provide a tough covering that very few predators are willing to try to penetrate. Some animals have learned that hedgehogs have soft underbellies that can be attacked. In defense against this, hedgehogs can curl up into a ball, protecting their softer, more vulnerable parts. If attacked, a hedgehog will fight quite noisily, screaming in fury.
Both hedgehogs and moonrats are geared strictly for eating insects and other small invertebrates, especially earthworms. Their narrow pointed snouts and their strong claws are useful for digging insects out of the ground. However, the Daurian hedgehog (Hemiechinus dauuricus) of the Gobi Desert has taken to eating small rodents. This species has longer ears than other hedgehogs.
Some species live in deserts, where they normally breed only once a year. Inhabitants of moister areas, such as the European hedgehog, normally breed twice a year. Except when mating, hedgehogs are solitary animals. The female produces usually three or four young after a gestation period of about four or five weeks. When they are born, the blind babies' spines are white and soft. They harden as they grow during their first three weeks. By that time, they can see and they are beginning to explore beyond the burrow with the mother.
Hedgehogs, like all insectivores, are very active animals that require a lot of food to survive. When confronted by food scarcity or cold weather, many hedgehogs will enter a period of dormancy, or even genuine hibernation in order to conserve energy. They retreat into a protected section of the burrow in which they normally live. During a mild winter, however, they may not sleep at all. Residents of tropical areas do not hibernate. And even European hedgehogs, when transplanted to warmer countries, do not hibernate.
Hedgehogs are active at night, eating earthworms, various insects, and even snakes. This makes them popular in gardens, where they often eat insect pests. Perhaps one of the reasons they are called hedgehogs is that these animals snuffle and snort, pig-like, as they go after their food. During the day in warm weather, they rest in a small temporary nest of leaves at the base of the hedges they frequent. During colder weather, they burrow into the ground.
European hedgehogs burrow under hedges all over Europe, even in busy cities, and they have long been chosen as pets. However, the animals are so infested by fleas that only tiny babies raised in captivity can become flea-free pets.
Hedgehogs perform a curious activity that has been described as self-anointing. They find a fluid substance, such as sap, and then lick on it enough to develop saliva. Then, moving from one side to the other, they lick the surface of their spines. It has been suggested that somehow the use of any irritating substance to self-anoint might keep predators at bay.
If hedgehogs could shed their spines, they would look like the other members of the family: gymnures, also called moonrats and thought of as spineless hedgehogs. These small, little-known animals of Asia occur in five species.
The Philippine gymnure, or wood shrew ( Podogymnura truei), of the Philippine island of Mindanao lives at high altitudes. Less than 7 in (18 cm) long, it is regarded as threatened because its forest habitat is being destroyed. The females of the much larger moonrat of Malaysia (Echinosorex gymnurus) are larger than the males. This is the largest insectivore in the hedgehog family. It can be more than 2 ft (66 cm) long from head to tail. Unusually it is all white. The three species of lesser gymnures (Hylomys) are so small that they are easily mixed up with shrews, which live exactly the same kind of lifestyles.
Hedgehog. Racine, WI: Western Publishing, 1993. Kerrod, Robin. Mammals: Primates, Insect-Eaters and Baleen Whales. Encyclopedia of the Animal World series. New York: Facts on File, 1988.
Jean F. Blashfield