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Along with its relative the Mexican bearded lizard, the Gila monster is one of only two venomous lizards in the world. Its venom is produced by modified salivary glands in the lower jaw and is drawn into grooves in the teeth, where it is injected into the prey. The venom causes cardiac and respiratory failure in prey, but is generally not fatal to healthy adult humans, although the rare bites that do occur are quite painful. Not all of the lizard’s prey are subdued with venom. Aside from small mammals, lizards and birds, it also preys on insects, reptile and bird eggs, earthworms and carrion.
Adult Gila monsters range from 12 to 24 inches in length. Their short tails store fat to metabolize in periods of food shortage and vary in thickness accordingly. Native to arid and semiarid regions of the southwestern United States and western Mexico, the Gila monster is primarily nocturnal, sheltering from the sun under rocks or in burrows during the day.
The Gila monster currently faces increasing habitat loss to urban development, road building, and agricultural expansion. Individuals are also gathered from the wild for sale as pets, presumably to customers willing to risk the rare painful, though nonfatal, bite.
Nature picture credits (left to right): Photo © Bob Kupbens (Sleeping Gila monster); Photo © Bob Kupbens (closeup).
