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Gila Monster, a poisonous desert lizard of the southwestern United States and northern Mexico. It is named for the Gila River, Arizona, near which it is found.

The adult Gila monster ranges in length from 18 to 21 inches (46 to 53 cm). Its broad, stocky body has an orange or pinkish beadworklike covering with black patches. Fat stored in the large, heavy tail enables the Gila monster to survive for long periods without food.

Although usually clumsy and sluggish, the Gila monster strikes suddenly when aroused, hanging onto its victim in bulldog fashion. The poison is conducted through grooved teeth. The bite is painful, but seldom fatal, to humans.

The Gila monster usually stays hidden under rocks or in burrows during the day, emerging after sunset to feed on eggs, insects, and small animals. The female lays from four to seven soft-shelled eggs in the sand in July or August. They are hatched by the sun's heat. The brightly colored young, about four inches (10 cm) long, shift for themselves from birth.

The Gila monster is Heloderma suspectum of the family Helodermatidae.