The common chuckwalla is a large, flat-bodied lizard with a large, rounded belly, and a wide-based, blunt-tipped tail. They are able to reach a total length of 20 inches and a weight of 2.0 lb. Small scales cover its body, with larger scales protecting the ear openings. The coloration of these lizards varies by location and between juveniles and adults, as well as between males and females. In adult males, the head, shoulder, and pelvic regions are black, while the mid-body is light tan speckled with brown. Adult females are brownish in color with a scattering of dark red spots. Young chuckwallas have four or five broad bands across their bodies, and three or four on the tail which are lost in adulthood by males, but retained somewhat by females.
Chuckwallas are diurnal animals, and as they are ectothermic, spend much of their mornings and cooler days basking. These lizards are well adapted to desert conditions; they are active at temperatures up to 102 °F. Chuckwallas brumate during cooler months and emerge in February.
It inhabits the Sonoran and Mojave Deserts of the Southwestern United States and northwestern Mexico. Its range extends from eastern California, Utah, and Nevada south to Baja California and Sonora.
Common chuckwallas are found in deserts, where the air is hot and dry. They are found in deserts with rocks and crevices for hiding, such as areas of past lava flows, rocky hillsides, and outcrops. They use underground burrows and crevices for hibernation in the winter. They inhabit island and coastal environments. These lizards require a moderate amount of vegetation and foliage in the habitat in order to sustain themselves.
Common chuckwalla courtship is comprised of males enticing females by size or persistence. Usually males have multiple females living in their territory and he mates with them. Male chuckwallas use head-bobbing, licking, circling, nudging, jaw-rubbing, and other methods to persuade females to mate. Males compete for females by biting and head-knocking.
Common chuckwallas breed between April and August when food is most abundant. When females are receptive, their ovaries become enlarged. Males produce sperm each year while females produce eggs every other year, on average. Males reach sexual maturity at about 2 years old. Females may take 2 to 3 years to reach maturity. Average clutch size per breeding season varies from 5 to 16 eggs and the annual reproductive frequency of each female varies greatly from year to year depending on food availability and rainfall. Some females produce 2 separate broods, others produce none. Females incubate the eggs until they hatch. The incubation period lasts about 35 days. The birth mass range of the eggs is 6.0 to 9.6 grams. Larger females produce clutches more frequently than smaller females.
In the wild: 15 years
In human care: 15-30 years
Common chuckwallas are herbivores, feeding on perennial and annual plants. Their diets are generally high in fiber and low in fat and protein. Annuals comprise 60% of their diet in the summer months, while perennials comprise 40%. When annuals die in the winter, perennials become their main source of plant food. They have been reported eating leaves and the fruit of creosote bushes in the summer months, as well as some insects that reside on the vegetation they eat. Browneyes and desert ragweed are the main plants in the chuckwalla diet.