The Gila monster is the biggest lizard native to the United States. It is one of only two dangerously venomous lizards in the world. Gila monsters are found in deserts and dry scrubby grasslands with rocky outcrops in the southwestern United States and northwestern Mexico.
Gila (pronounced “hee-luh”) monsters grow from 12 to 22 inches (30-56 cm) long and weigh as much as 5 pounds (2.3 kg). Gila monsters have bulky bodies and broad heads, strong legs, and shiny beadlike scales. Gila monsters are marked with orange, pink, or yellow patches, contrasting with bands of black. Gila monsters have large, swollen tails. Their tails store food as fat. When food is scarce, the Gila monster can shrink to four-fifths its usual size.
Gila monsters eat insects, worms, lizards, young rodents, baby birds, and eggs. They have a sharp sense of smell; they can also “taste” their surrounding with their tongue. A Gila monster can eat up to a third of its weight in one meal. Gila monsters don’t eat often; they can survive on less than a dozen big meals in one year. Gila monsters hunt by day during the spring, but at dusk or after dark when temperatures grow hot in summer. Gila monsters are not fast; they walk with a slow, lumbering gait.
Gila monsters are venomous. They have venom glands in their lower jaw. The venom flows out through grooves in the teeth. Gila monsters must bite and hold on to make the venom ooze into its victim’s bloodstream. The Gila monster uses its venomous bite only as a defense against predators.
Gila monsters spend 90 percent of their time resting in earthen burrows or under rocks. They hibernate during cold winter weather. Female Gila monsters lay 5 to 10 eggs in late summer. The eggs hatch the following spring. The young are about 6 inches (15 cm) long.
Gila monsters have a lifespan of about 20 years. The scientific name of the Gila monster is Heloderma suspectum.