San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
Western chuckwalla, photographed in San Diego County, by Dick Schwenkmeyer

Sauromalus ater
Common Chuckwalla

IGUANIDAE

Sauromalus is derived from Greek sauros, meaning lizard and omalus, homalus, meaning flat, in reference to the chuckwalla's flattened body shape. It lacks a mid-dorsal crest, and when compared to its closest relatives (the other iguanas), the low profile is obvious. The name ater means black. A previous scientific name used for the chuckwalla is Sauromalus obesus.

The name chuckwalla (or chuckawalla) is derived from the Shoshone word "tcaxxwal" or "caxwal," the form used by the Cahuilla Indians of southeastern California and originally written in Spanish as "chacahuala."

Description

Size: The stout-bodied chuckwalla is the second largest lizard in the United States, next in size only to the gila monster. A male individual can measure up to 18 inches in total length, while the female is somewhat smaller.

Coloration: The coloration of these lizards is geographically variable and also varies between juveniles and adults, in addition to males and females. In adult males, the head, shoulder, and pelvic regions are melanistic, while the mid-body is light beige or tan and occassionally speckled with brown flecks. The tail is off-white. Adult females are brownish in color with a scattering of dark brown and red spots. Young chuckwallas have four or five broad bands across the body, and three or four on the tail. These bands are usually lost in adulthood. Uniformly small scales cover the body, with larger scales protecting the ear openings.

Range and Habitat

"Often we see them waddling along, then suddenly leaping from rock to rock. in spite of their ungainly appearance, they move about with great speed -- in contrast to their profound patience while lying still. One that I found eating flowers in an encelia bush suddenly dropped down and took refuge in a rock crevice. It was more than an hour before it came forth and began feeding again."
Edmund C. Jaeger
-- Desert Wildlife

The chuckwalla is distributed throughout the deserts of southern California, southern Nevada, southwestern Utah, western Arizona, Sonora, and Baja California. Its distribution closely mirrors the combined Mojave and Sonoran Deserts.

The chuckwalla's preferred habitat is boulder-covered slopes, at elevations up to 4500 feet, although they are more common at lower elevations. They sun themselves on prominent rocks during warm weather, and it's not unusual to see several chuckwallas at the same time from a single vantage point.

Natural History

In the wild, chuckwallas are shy, and, if approached, will hide in the cracks and crevices of nearby boulders. If the threat persists, they can wedge themselves tightly in the crevice by inflating their lungs which causes their body to press against the rock faces. This makes extraction nearly impossible for a predator.

Chuckwallas are strictly herbivores in the wild. They're particularly fond of yellow flowers, such as those found on the brittle-bush (Encelia farinosa), and, on occasion, will climb into this plant to get to the yellow feast.

Mating occurs between April and July, with a clutch of as many as 16 eggs laid between June and August. The eggs hatch in the late warm season.

Conservation Status

The chuckwalla is currently a Federal Special Concern species (FSC). In desert communities with active development, the preferred habitat of the chuckwalla is under attack. In areas without disturbance, chuckwallas appear healthy and stable.


Text and photo by Dick Schwenkmeyer.

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