Chuckwalla & Western Fence Lizard

Part of the Lizards and Snakes: Alive! exhibition.

Chuckwalla Lizard
© AMNH / Denis Finnin

These lizards like wide-open spaces. The big one basks on large boulders, and the small one scurries underfoot all over the Southwest.


When Chuckwallas are threatened, they wedge themselves in rock crevices to avoid being eaten. They also expand like balloons. Many lizards inflate themselves to look bigger and more menacing--in the Chuckwalla's case, it also makes the fit tighter.


These fine scales help the Chuckwalla slip into cracks and crevices of desert boulders. Once there, the pressure of its inflated body against the rock makes it hard to dislodge.


Sharp claws help anchor the Chuckwalla in its rocky hideaway and tighten its grip on rocky surfaces.

Western Fence Lizard
© AMNH / Denis Finnin


The color of this lizard has earned it the nickname "blue belly." Bright body colors are one way lizards communicate.


The Fence Lizard's scales are always keeled, or ridged; ridges may provide stiffness and strength. Lizards with keeled scales look rough; lizards with flat scales look shiny.


You can't see it, but something about these lizards helps prevent a serious human illness called Lyme disease. When the ticks that transmit the disease feed on fence lizards, a protein in the lizard's blood kills the Lyme bacteria. If that tick then bites a human, the human won't get sick.

Meet the Families

A Fence Lizard or a relative--Phrynosomatidae, including about 130 species in all--can be found in nearly every habitat in North and Central America: from cliff faces to cloud forest to sand dunes. Chuckwallas and their close relatives-Iguanidae, including around 40 species in all--also occupy a wide range of habitats.

Mexican horned lizard
© Wendy Hodges/University of Texas Permian Basin

Mexican Horned Lizard

Phrynosoma asio

When threatened, these lizards squirt blood from vessels in the corners of their eyes. Some predators are repulsed by the blood--perhaps more by its smell than its appearance.



Mesquite lizard
© Jonathan Campbell/University of Texas Arlington

Mesquite Lizard

Sceloporus grammicus

Freezing temperatures are common where this lizard lives, high on mountains in Mexico. Amazingly, the animals can tolerate freezing and thawing without ill effects.



Mojave Fringe-toed Lizard
© Tom Brennan/Arizona State University

Mojave Fringe-toed Lizard

Uma scoparia

This animal lives on-and in-windblown dunes, diving beneath the sand for cover. Special valves on its nose keep the sand grains out. In some areas its habitat is threatened by humans in off-road vehicles.

Fast Facts

Name: Chuckwalla; Sauromalus ater
Size: 28 to 46 centimeters (11 to 18 inches)
Range: Southwestern U.S. and Mexico
Diet: Fruits, leaves, buds and flowers

Fast Facts

Name: Western Fence Lizard; Sceloporus occidentalis
Size: 13-15 centimeters (5-6 inches)
Range: Western U.S.
Diet: Insects