Chuckwalla

**Chuckwallas** are large lizards found primarily in arid regions of the southwestern United States and northern Mexico. Some are found on coastal islands. The six species of chuckwallas are all placed within the genus ***Sauromalus***; they are part of the iguanid family, Iguanidae.

## Description

There is only one species of chuckwalla that inhabits the Southwestern deserts: the common chuckwalla *(Sauromalus ater).* The San Esteban Island (or piebald) chuckwalla *(Sauromalus varius),* the largest of all the chuckwallas, inhabits only San Esteban Island and Isla Roca Lobos in the Sea of Cortez (Gulf of California). The piebald chuckwalla has a gray-to-black face, with same-colored splotches over its entire body, which is tan to yellow. There has been a study going on for years at the Arizona Sonora Desert Museum involving San Esteban Island chuckwallas, where there is a large breeding colony. Among other things, the behavior and reproductive biology of these impressive lizards is being studied there.

There is another Baja Island form which is quite distinctive, *Sauromalus hispidus,* the spiny chuckwalla. This species lives on Isla Angel de la Guarda and several smaller islands near Bahía de Los Angeles. What makes this animal very different is its spiny tail. All other chuckwallas have a much smoother tail. These large, plump lizards have loose folds of skin around the neck and shoulders. They have a thick blunt tail and grow 11 to 18 inches long. These diurnal lizards emerge in the morning and, before seeking food, bask in the sun until their optimum body temperature of 100 - 105 degrees F. is reached.

## Diet

Strictly herbivorous, the chuckwalla eats fruit, leaves, buds and flowers. When the chuckwalla senses danger, it scurries between rocks and lodges itself tightly in crevices by inflating itself. In the common chuckwalla, depending upon the population, male coloration may include black head, forelegs and upper trunk, and reddish-yellow toward the rear or a showy bright red body. Females are usually a much less showy gray or brown with little pattern. The young, however, are usually quite striking with a dark background color and yellow bands around the body and down onto the tail.

## Range and Habitat

Mojave and Sonoran deserts of southeastern California, southern Nevada and Utah, western Arizona and south to Sonora, Mexico and the mainland and islands of Baja. The other species are island-dwelling, so have much more restricted distributions. The Angel Island chuckwalla (*S. hispidus*) is found on Isla Ángel de la Guarda and surrounding islands off the coast of the Baja California Peninsula. Two rare and endangered species are the Montserrat chuckwalla (*S. slevini*) found on Islas Carmen, Coronados, and Montserrat in the southern Gulf of California and the San Esteban chuckwalla or painted chuckwalla (*S. varius*) found on San Esteban Island, Lobos, and Pelicanos.

Chuckwallas prefer lava flows and rocky areas typically vegetated by creosote bush and other such drought-tolerant scrub. The lizards may be found at elevations up to 4,500 ft (1,370 m). Primarily herbivorous, chuckwallas feed on leaves, fruit, and flowers of annuals and perennial plants; insects represent a supplementary prey. The lizards are said to prefer yellow flowers, such as those of the brittlebush (*Encelia farinosa*). Harmless to humans, these lizards are known to run from potential threats. When disturbed, a chuckwalla wedges itself into a tight rock crevice and inflates its lungs to entrench itself.

Males are seasonally and conditionally territorial; an abundance of resources tends to create a hierarchy based on size, with one large male dominating the area's smaller males. Chuckwallas use a combination of color and physical displays, namely "push-ups", head-hobbing, and gaping of the mouth, to communicate and defend their territory. Chuckwallas are diurnal animals and as they are ectothermic, spend much of their mornings and winter days basking. These lizards are well adapted to desert conditions; they are active at temperatures up to (39 °C). Juveniles emerge first, then adults, as temperatures reach around 90 °F.[4] Chuckwallas hibernate during cooler months and emerge in February. Mating occurs from April to July, with five to 16 eggs laid between June and August. The eggs hatch in late September. Chuckwallas may live for 25 years or more.