Description: The common chuckwalla is a large, flat-bodied lizard with a large, rounded belly, and a wide-based, blunt-tipped tail. Reaching a total length of 20 inches and a weight of 2.0 lbs.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 midbody 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.

Habitat: Common chuckwallas are found in deserts, where the air is hot and dry (9 to 45 degrees Celsius). 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 chuckwallas can be found between sea level and 1400 m elevation.

Range: Sauromalus ater, the common chuckwalla, inhabits deserts in the western United States and Mexico and 30 known islands in the Gulf of Mexico. Specifically, the Mojave and Sonoran deserts are known to have thriving populations of chuckwallas. They can be found as far west as southeastern California and Nevada, and are abundant in Arizona, New Mexico, Texas, Utah, and parts of Colorado.

Found in these States: AZ | CA | NV | UT

Diet: 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 (Larrea tridentata) in the summer months, as well as some insects that reside on the vegetation they eat. Browneyes (Oenothera clavaeformis) and desert ragweed (Franseria dumosa) are the main plants in the chuckwalla diet. In captivity they are fed various greens, vegetables, fruits, and flowers. They obtain water from the plants they eat and produce it metabolically.

Reproduction: 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. Females allow copulation if they determine the male is desired, males may assert themselves if they are large and forceful. During copulation, males use their jaws to grasp females by the loose skin on their nape. Mating usually takes place in the early spring after hibernation. Both sexes have multiple partners year to year. Males compete for females by biting and head-knocking. Mating occurs from April to July, with five to 16 eggs laid between June and August. The eggs hatch in late September.

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 when they reach a 125 mm snout-vent length, or at about 2 years old. Females reach sexual maturity at the same length, but may take 2 to 3 years to reach that length. 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 (range 33 to 50 days). The birth mass range of the eggs is 6.0 to 9.6 grams. Larger females produce clutches more frequently than smaller females. However, smaller females may reproduce in consecutive years.

Status: Common chuckwalla populations are protected by national parks and naturally protected due to their remote habitat (rugged terrain and harsh climate). Trends towards developing desert areas of of the United States and parts of Mexico are affecting common chuckwalla habitat; however the population status as a whole has been reported as large, and stable.

Commercial sales of the chuckwalla have not shown any major impact on the species as a whole, but some subspecies are locally threatened by excessive collecting and habitat degradation. The South Mountain subpopulation, near Phoenix, Arizona is targeted because they have a unique color pattern that isv desirable for pet trade. The Colorado River dam has greatly reduced common chuckwalla populations in the Glen Canyon area of Utah, and grazing activities of goats, sheep, and burros have shown a small negative impact. Overall, the IUCN categorizes common chuckwallas as “Least Concern” due to large population distribution and no immediate threats. Although total population size is not known, the estimated total adult population size could be 100,000 or greater.

Taxonomy: