Chuckwalla

The common chuckwalla is a large, flat-bodied lizard of the Sonoran and Mojave Deserts in the south-western United States and north-western Mexico, ranging from eastern California, Utah and Nevada south to Baja California and Sonora. It reaches a total length of 20 in (51 cm) and a weight of 2.0 lb (0.9 kg), with a large rounded belly and a blunt-tipped tail. Adult males are black on the head, shoulders and pelvis with a light tan, brown-speckled midbody, while females are brownish with dark red spots. Mainly herbivorous, it eats creosote bush flowers, leaves and fruit, and occasionally insects. When threatened, it wedges itself into a rock crevice by inflating its lungs.

About the chuckwalla

The common chuckwalla, also called the northern chuckwalla, is a large, flat-bodied lizard in the family Iguanidae. It has a rounded belly and a wide-based, blunt-tipped tail, and reaches a total length of up to 20 inches (51 centimeters) and a weight of up to 0.9 kilograms (2.0 pounds). Small scales cover most of the body, with larger scales protecting the ear openings.

Coloration varies by location, age, and sex. Adult males have black heads, shoulders, and pelvic regions with a light tan midbody speckled in brown, while adult females are brownish with scattered dark red spots. Juveniles carry four or five broad bands across the body and three or four on the tail, patterns that fade in adult males but persist to some degree in females.

The species inhabits the Sonoran and Mojave Deserts of the southwestern United States and northwestern Mexico, ranging from eastern California, Utah, and Nevada south to Baja California and Sonora. Taxonomically, the species has a tangled history: U.S. populations were long called Sauromalus obesus, a name still common in field guides, but a 1998 review concluded the U.S. and Mexican forms belonged to a single species, and in 2004 the International Commission on Zoological Nomenclature ruled that Sauromalus ater — first described in 1856, two years before S. obesus — took priority. Five subspecies are currently recognized: S. a. ater, S. a. shawi, S. a. multiforaminatus, S. a. townsendi, and S. a. tumidus.

The generic name Sauromalus combines Greek words meaning "lizard" and, roughly, "flat," describing the animal's flattened build, while the specific name ater is Latin for "black" or "dark." The common name itself comes from the Shoshone word tcaxxwal, or the related Cahuilla form caxwal, used by Indigenous peoples of southeastern California long before English-speaking naturalists adopted it.

Behavior and diet

Chuckwallas are harmless to humans and typically flee from threats. When cornered, a chuckwalla wedges itself into a rock crevice and inflates its lungs using a gular pump, distending its body until it is jammed tightly in place and difficult to extract. Males are seasonally and conditionally territorial: where resources are abundant, a size-based hierarchy forms with one large male dominating smaller rivals, and chuckwallas use color, push-ups, head-bobbing, and mouth-gaping to communicate and defend territory.

The species is diurnal and ectothermic, spending much of the morning basking, with different postures by season — lying flattened against sun-warmed rock in spring, sitting or "stilting" in summer heat. Chuckwallas are active at temperatures up to 102°F (39°C) and brumate during cooler months, emerging in February.

Primarily herbivorous, chuckwallas eat creosote bush flowers, leaves, and fruit, preferring annual forbs and grasses but turning to the leaves of perennial shrubs when needed; they occasionally eat insects. Individuals in areas with greater plant diversity tend to grow larger. Mating occurs from April to July, with females laying 5 to 16 eggs between June and August; the eggs hatch in late September.

Range and habitat

The chuckwalla's range spans the Sonoran and Mojave Deserts of the southwestern United States and northwestern Mexico, from eastern California, Utah, and Nevada south through Baja California and Sonora. It favors rocky desert habitat where crevices offer shelter from predators and extreme heat, a feature central to its main defense strategy of wedging itself in place when threatened.

Conservation status

The chuckwalla is classified as Least Concern by the IUCN. Historically, the species was a food source for Native Americans in the Death Valley region, who hunted chuckwallas hiding in rock crevices by puncturing their lungs with a bone-barbed hook to deflate them and make extraction possible.