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Gila Monster

Heloderma suspectum

Photo: A Gila monster crawls across rocks

Photo: A Gila monster crawls across rocks (View larger version)

Photograph by James P. Blair

Published

At a length of up to two feet (0.6 meters) and a maximum weight exceeding five pounds (2.3 kilograms), the venomous Gila monster (pronounced HEE-luh) is the largest lizard native to the United States.

Easily identified by their black bodies marked with dramatic patterns of pink, orange, or yellow, Gilas are found in the Mojave, Sonoran, and Chihuahuan deserts of the southwestern U.S. and northwestern Mexico. They take their name from Arizona's Gila River basin, where they were first discovered.

The Gila monster is one of only a handful of venomous lizards in the world. Others include the similar-looking Mexican beaded lizards, as well as iguanas and monitor lizards. Its venom is a fairly mild neurotoxin. And though a Gila bite is extremely painful, none has resulted in a reported human death. Unlike snakes, which inject venom, Gilas latch onto victims and chew to allow neurotoxins to move through grooves in their teeth and into the open wound.

Gilas are lethargic creatures that feed primarily on eggs raided from nests and newborn mammals. They may spend more than 95 percent of their lives in underground burrows, emerging only to feed and occasionally to bask in the desert sun. They can store fat in their oversized tails and are able to go months between meals.

Gila populations are shrinking due primarily to human encroachment, and they are considered a threatened species.