Arizona is a major North American biodiversity hotspot for reptiles, boasting a concentration of lizard species that thrive across its varied terrain. The state’s diverse biomes, ranging from the arid Sonoran Desert lowlands to high-elevation grasslands and woodlands, support nearly 50 unique types of lizards. These reptiles have evolved physical characteristics and behaviors to survive the extremes of heat and cold found in the Southwest. Understanding the lizards of Arizona begins with recognizing the most common backyard visitors and extends to appreciating the highly specialized creatures of the deepest desert.
The Most Frequently Encountered Species
The lizards most commonly observed by residents and hikers in Arizona are typically species with wide distributions that tolerate human-altered environments. These include the Desert Spiny Lizard, the Western Fence Lizard, and several species of Whiptails.
The Desert Spiny Lizard is a stout reptile, growing up to 5.6 inches in body length, and is characterized by rough, overlapping scales that give it a spiky appearance. Males often display bright blue or violet patches on their throats and bellies, which they use in territorial displays like “push-ups” on rocks or tree trunks. This species is an adept climber, frequently seen basking on logs, rock piles, or in the branches of trees like cottonwood and mesquite.
The Western Fence Lizard, sometimes called the “blue-belly,” is another widespread species, characterized by its granular scales and the conspicuous blue patches on the underside of adult males. They are often found on vertical surfaces, such as fences, wood piles, and rock outcroppings, utilizing their sharp claws for climbing. Their diet consists largely of insects and spiders, which they actively hunt throughout the day.
Whiptail lizards, such as the Arizona Striped Whiptail, are recognized by their long, slender bodies, pointed snouts, and exceptionally long, whip-like tails. These are fast-moving ground-dwellers that actively forage for insects and other invertebrates. Many whiptail species in Arizona are entirely female and reproduce asexually through parthenogenesis, essentially cloning themselves.
Specialized Desert Dwellers
Some Arizona lizards display unique physical and behavioral adaptations that allow them to inhabit the state’s most challenging, arid environments.
The Flat-tailed Horned Lizard, for example, is found only in the extreme southwestern corner of Arizona, preferring low dunes and flatlands with fine, hard-packed sand. This small lizard is exceptionally flat and wide, with a fringe of scales along its sides that help eliminate its shadow, allowing it to blend seamlessly into the sandy substrate. The Flat-tailed Horned Lizard relies on this camouflage and its ability to burrow under the sand to avoid detection and seek refuge from extreme midday heat.
The Zebra-tailed Lizard is a master of speed, known for its ability to run bipedally on its hind legs across open, sandy desert flats and washes. The lizard’s namesake feature is the distinct black and white striping on the underside of its tail, which it curls over its back and wags when running. This tail-wagging serves as a distraction display, potentially drawing a predator’s attention away from the lizard’s body during a quick escape. Another specialist, the Fringe-toed Lizard, is restricted to areas with windblown sand, such as dune fields. This species has evolved elongated, pointed scales on its hind toes, which act like snowshoes to provide traction on the loose sand, enabling it to “swim” just beneath the surface to evade predators and the hottest temperatures.
Arizona’s Largest and Most Distinctive Lizards
Two species stand out for their size and unique biological characteristics. The Gila Monster is the largest native lizard in the United States, reaching up to 22 inches in length, and is one of only two known venomous lizard species in the world.
Its thick, heavy body is covered in bead-like scales and patterned with black and contrasting colors like pink, orange, or yellow. The Gila Monster is a slow-moving, reclusive creature, spending up to 98% of its time below ground in burrows, and its venom is primarily a defensive mechanism. Its venom is delivered through grooved teeth in the lower jaw, which requires the lizard to hold onto its victim and “chew” the venom into the wound, making bites rare and usually the result of harassment.
The Common Chuckwalla is the state’s second-largest lizard, characterized by a robust, flattened body and loose folds of skin on its neck. This lizard is predominantly herbivorous, feeding on leaves, flowers, and fruit, and prefers rocky habitats like boulder piles and lava flows. When threatened, the Chuckwalla retreats into a rock crevice and gulps air, inflating its body to wedge itself firmly into the space. This defense mechanism makes it nearly impossible for a predator to dislodge.
Identification Tips and Safe Observation
Observing Arizona’s diverse lizard population requires attention to specific details and respect for their natural behavior. Identifying common lizards often relies on examining the texture of their scales and the presence of distinct markings, such as bright throat or belly patches which indicate an adult male in many species. When observing lizards in the wild, they should never be approached or handled as they are highly susceptible to disturbance. Lizards often perform “push-up” displays, which are territorial signals or a way to regulate body temperature, and should be viewed from a distance. The Gila Monster is protected by state law, making it illegal to harass, harm, or collect the animal, and this rule of non-interference applies to all reptiles. Respecting their space ensures safety and allows these reptiles to continue their roles in the desert ecosystem.