hedgehog, Old World insectivorous mammal of the family Erinaceidae.

The spiny hedgehogs are found in Africa and Eurasia, except SE Asia. They have rounded bodies up to 13 in. (33 cm) long, very short tails, and pointed snouts; their backs and sides are covered with stiff spines and their undersides with coarse hair. They are usually brown and yellow in color. When frightened, a hedgehog rolls itself into a tight ball with its spines pointing outward; when rolled up it is invulnerable to almost any predator.

The European hedgehog, Erinaceus europaeus, is about 9 in. (23 cm) long, with small ears. It is strictly nocturnal, spending the day in a burrow in the undergrowth; it hibernates in midwinter. The name hedgehog describes the tendency of these animals to make their burrows in the hedgerows that surround English fields.

Hedgehogs are not related to hogs, but they root in the ground for food in the manner of hogs. Their diet consists of small animals, including worms, insects, frogs, mice, and even poisonous snakes; they have a high level of immunity to viper venom. A hedgehog will bite a snake and then roll itself up as the snake strikes, repeating this procedure until the snake is dead.

E. europaeus is found throughout Europe and N Asia, as far north as the limits of the deciduous forest. Other spiny hedgehog species are found in Africa and Asia; many are desert dwellers. Some are wholly nocturnal and others only partially so; all either hibernate or aestivate and tend to hole up during dry weather. Some species have large pointed ears like those of dogs.

The hairy hedgehogs, or gymnures, are found instead of spiny hedgehogs in SE Asia. They resemble long-snouted rats and have coarse bristles but no spines. They give off a distinctive musky odor, produced by anal glands. The largest of the gymnures is the moon rat, Echinosorex gymnurus, with a 15-in. long (38-cm) body and an 8-in. (20-cm) tail.

There are no New World hedgehogs, although the North American porcupine, which is not an insectivore but a rodent, is sometimes erroneously called a hedgehog. The spines of hedgehogs differ from those of porcupines; they are not barbed and do not pull out of the animal's skin easily.

Both spiny and hairy hedgehogs are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Erinaceomorpha, family Erinaceidae.

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