The San Esteban chuckwalla (Sauromalus varius ), also known as the piebald chuckwalla or pinto chuckwalla, is a species of chuckwalla belonging to the family Iguanidae endemic to San Esteban Island in the Gulf of California. It is the largest of the five species of chuckwallas, and the most threatened.
The San Esteban chuckwalla is the largest species of chuckwalla, reaching 61 cm (24 in) in body length and 76 cm (30 in) overall length, and weighing up to 1.4 kg (3.1 lb). It is considered a textbook example of island gigantism, as it is three to four times the size of its mainland counterparts. The male's skin is gray with tan to yellow patches over its entire body, and its face is gray to black. The female is duller in appearance with fewer patches. The colorations provide almost perfect camouflage against some of their predators.
The San Esteban chuckwalla is endemic to San Esteban Island in the Gulf of California. While it is abundant on this small island, it occurs naturally nowhere else and is protected under the Endangered Species Act. At one time, the Seri translocated populations of this lizard to other islands in the Sea of Cortés as a food item, but none of these populations has survived beyond the original population found on San Esteban.
Chuckwallas prefer dwelling in lava flows and rocky areas with nooks and crannies available for a retreat when threatened. These areas are typically vegetated by creosote bush and cholla cacti which form the staple of their diet, as the chuckwalla is primarily herbivorous. Chuckwallas also feed on leaves, fruit, and flowers of annuals, perennial plants, and even weeds; insects represent a supplementary prey if eaten at all.
Harmless to humans, these large lizards are known to run from potential threats. When disturbed, the chuckwalla wedges itself into a tight rock crevice, gulps air, and inflates its body 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 in the sun. These lizards are well adapted to desert conditions; they are active at temperatures up to 102 °F (39 °C).
Mating occurs from April to July, with 5 to 16 eggs laid between June and August. The eggs hatch in late September. San Esteban chuckwallas may live for 25 years or more.
