|Common chuckwalla (Sauromalus ater) male|
|Common chuckwalla (Sauromalus ater) f|
Chuckwallas are large lizards found primarily in arid regions of the southwestern United States and northern Mexico. Some are found on coastal islands. There are five species of chuckwallas, all within the genus Sauromalus; they are part of the iguanid family, Iguanidae.
Taxonomy and etymology 
The generic name, Sauromalus, is a combination of two Ancient Greek words:σαῦρος (sauros) meaning "lizard". and ομαλυς (omalus) meaning "flat". The common name chuckwalla derives from the Shoshone word "tcaxxwal" or Cahuilla "caxwal", transcribed by Spaniards as "chacahuala".
Physical description 
Chuckwallas are a stocky wide-bodied lizard with a flattened midsection and prominent belly. Their tails are thick, tapering to a blunt tip. Loose folds of skin characterize the neck and sides of the body, which is covered in small, coarsely granular scales. The common chuckwalla (Sauromalus ater) measures 15 3/4 inches in length whereas insular species such as the giant chuckwalla of San Esteban Island (Sauromalus varius) can measure as much as 30 inches in total length.
They are sexually dimorphic with males having reddish-pink to orange, yellow or light gray bodies and black heads, shoulders and limbs; females and the immature have bodies with scattered spots or contrasting bands of light and dark in shades of gray or yellow. Males are generally larger than females and possess well-developed femoral pores located on the inner sides of their thighs; these pores produce secretions believed to play a role in marking territory.
Range, habitat and diet 
The genus Sauromalus has a wide distribution in biomes of the Sonoran and Mojave Deserts. The common chuckwalla (Sauromalus ater) is the species with the greatest range, found from southern California east to southern Nevada and Utah, western Arizona and south to Baja California and northwestern Mexico. The peninsular chuckwalla (Sauromalus australis) is found on the eastern portion of the southern half of the Baja California peninsula.
The other species are island-dwelling and therefore have much more restricted distributions. The Angel Island chuckwalla (Sauromalus 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 (Sauromalus slevini) found on Islas Carmen, Coronados and Montserrat in the southern Gulf of California and the San Esteban chuckwalla or painted chuckwalla (Sauromalus varius) found on San Esteban Island, Lobos and Pelicanos.
Chuckwallas prefer lava flows and rocky areas. These areas are typically vegetated by creosote bush and other such drought-tolerant scrub. The lizards may be found at elevations of up to 4,500 feet (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).
Behavior and reproduction 
Harmless to humans, these lizards are known to run from potential threats. When disturbed, a chuckwalla will wedge itself into a tight rock crevice and inflate its lungs in order 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 colour and physical displays, namely "push-ups", head-hobbing, and gaping of the mouth, to communicate and defend their territory (see animal communication).
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 of up to 102 °F (39 °C). Juveniles emerge first, then adults, as temperatures reach around 90 °F. Chuckwallas hibernate during cooler months and emerge in February.
Mating occurs from April to July, with 5–16 eggs laid between June and August. The eggs hatch in late September. Chuckwallas may live for 25 years or more.
Human use 
The Comca’ac (Seri) considered the Angel Island species of chuckwalla an important food item. It is believed they translocated the lizards to most of the islands in Bahia de los Angeles for use as a food source in times of need.
- "Sauromalus". Integrated Taxonomic Information System. Retrieved 15 September 2008.
- Schwenkmeyer, Dick. "Sauromalus ater Common Chuckwalla". Field Guide. San Diego Natural History Museum. Retrieved 2008-09-17.
- Stebbins, Robert C., (2003) A Field Guide to Western Reptiles and Amphibians, 3rd Edition. Houghton Mifflin Company, ISBN 0-395-98272-3
- Hollingsworth, Bradford D. (1998). "The Systematics of Chuckwallas (Sauromalus) with a Phylogenetic Analysis of Other IguanidLizards". Herpetological Monographs (Herpetologists' League) 12: 38–191. JSTOR 1467020.
- Case, T. J. (1982). "Ecology and evolution of insular gigantic chuckwallas, Sauromalus hispidus and Sauromalus varius". Iguanas of the World (Park Ridge, New Jersey: Noyes Publications). pp. 184–212. ISBN 0-8155-0917-0.
- Deban, S.M., J.C. O’Reilly, and T.C. Theimer 1994. Mechanism of defensive inflation in the chuckwalla, Sauromalus obesus. Journal of Experimental Zoology 270: 451-459
- Richard Felger and Mary B. Moser (1985) People of the desert and sea: ethnobotany of the Seri Indians Tucson: University of Arizona Press.
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