Piebald Chuckwalla

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.

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.

The generic name, Sauromalus, is said to be a combination of two ancient Greek words: sauros meaning "lizard" and omalus meaning "flat". The proper ancient Greek word for "flat" is however homalos (ὁμαλός) or homalēs (ὁμαλής). Its specific name varius is Latin for "speckled" in reference to the chuckwalla's mottled coloration. It was first described by American herpetologist Mary C. Dickerson in 1919. The common name chuckwalla derives from the Shoshone word tcaxxwal or Cahuilla caxwal, transcribed by Spaniards as chacahuala. The Seri people named originally the island for this species: Coftécöl lifa or the Peninsula of the Giant Chuckwalla.