Genus Sauromalus - Chuckwallas

Family IGUANIDAE [IGUANINAE]

Introduction

These dark chunky herbivores are inhabitants of the hot south-west USA and Mexico. The classification of the genus is in a state of flux at the moment, so the names given below may change in the next few years.

Although less well-known than the other large iguanas of this family, chuckwallas still have their followers. They are not impossible to keep provided that they are provided with a suitably high temperature, herbivorous diet, enough space (these are large lizards) and very low humidity: however, both the Bartletts and Manfred Rogner appear to discourage this species as a captive for all but the most dedicated or specialist keepers. By nature they are rather secretive, so keeper interaction similar to that of the other large iguanas should not be expected. In the wild they are one of the few lizard groups that have been hunted regularly for food.

Generically the species are all fairly similar. In shape they are plump and dorsoventrally flattenened, having the appearance of bulging out at the sides. The tail is about the same length as the snout-vent length. Sizes vary, but the maximum is about 40cm/16". Chuckwallas prefer lava flows and areas of rock, so despite their location in desert areas they are not sand-dwellers as such. Although insects may occasionally be taken, the overwhelming part of the diet is vegetarian. Like the Desert Iguana Dipsosaurus dorsalis (similar in some ways in its ecology), chuckwallas have a preference for the leaves of the creosote bush: they also like the yellow flowers of certain plants. If feeling threatened they will immediately seek refuge in a crevice or similar place where they can inflate their bodies by an impressive amount, thus wedging themselves firmly.

Further details and suggestions of captive keeping can be found in Bartlett and Bartlett and Rogner.

	Sauromalus
S. ater, Northern Chuckwalla	S. australis	S. hispidus, Spiny Chuckwalla
S. obesus, Chuckwalla	S. slevini, Monserrat Chuckwalla	S. varius

Scientific Name	Common Name	Distribution	Size	Notes
Sauromalus
S. ater	Northern Chuckwalla	Mexico (California)
S. a. ater
S. a. klauberi	Spotted Chuckwalla			Considered a full species by some authorities.
S. australis	Peninsular Chuckwalla	Mexico (S Baja California)		May also be considered a subspecies of S. ater or of S. obesus.
S. hispidus	Spiny Chuckwalla	Mexico (Isla Angel de la Guarda and surrounding islands in Gulf of California)		Scalation: enlarged and tuberculate scales on head and nape. Coloration: mainly overall black.
S. obesus	Chuckwalla	USA (California, Colorado, Nevada, Utah)	Max 21cm/8¼"	Smith describes the species as being late to emerge from hibernation, about a month after Uta stansburiana. Apart from human hunters, birds of prey are also predatory on S. obesus. Smith noted that in captivity the species would talke grass, cantaloupes, watermelon, bananas, lettuce and radish tops among other items. He also wrote that the tail skin did not shed easily for some reason. Scalation: mostly flat and lacking sharp points, but some on the sides of the neck and body are somewhat enlarged and pointed. Gular fold is distinguished by its tiny scales smaller than those on either side of the fold. Femoral pores 11-24. Ear opening is large and oval and protected by 2-3 enlarged thickened scales on the anterior border. Coloration: young are born with 4-5 broad brown transverse bands on the body and 3-4 on the tail, the bands being about twice as wide as the spaces between. With age those bands on the body begin to break up through light areas appearing within them, until in adults they are restricted to vague areas near the rump and across the shoulders. The light areas turn red. The tail bands remain relatively static but their distinctiveness varies between individuals. Smith describes the adults as "rather brightly marked, but extremely variable". Another complication is that the species changes colour according to light, temperature and movement.
S. o. obesus	Great Basin Chuckwalla	USA (SE California, S Nevada, S Utah, N Arizona), Mexico (N Baja California)		Scalation: scales finer and less spinose, especially on tail; scales around middle of upper arm 50-61. Coloration: similar to S. o. tumidus but the red is paler and in places yields to black. The phase near Phoenix is distinguished by being overall jet black apart from the tail, which is brilliant orange (this phase is now protected).
S. o. multiforminatus	Glen Canyon Chuckwalla			Small range: found in narrow area along Colorado River from Utah to Arizona. Coloration: juveniles are often brick red colour and may retain bands (females especially) of this colour throughout life.
S. o. townsendi	Sonoran Chuckwalla	Mexico (W Sonora and Guaymas)		Marginally smaller than S. o. tumidus. Coloration: dull and mostly lacking red pigment.
S. o. tumidus	Gila Chuckwalla	USA (C & SW Arizona), Mexico (N Sonora)		Scalation: scales larger and less spinose: 39-49 scales around mid forelimb. Coloration: head, shoulders and forelimbs are black; torso brick red; rear limbs dark (although the feet may be light); tail is cream, becoming lighter towards the tip.
S. slevini	Monserrat Chuckwalla	Mexico (Islas Carmen, Coronados and Monserrat in the Gulf of California)
S. varius	Variable Chuckwalla	Mexico (Islas San Esteban, Lobos and Pelicanos in the Gulf of California)		Coloration: overall straw-tan colour, overlain with random patches of dark pigment; most specimens are light, but some are dark.

Bibliography

Handbook of Lizards: Lizards of the United States and Canada, Hobart M Smith, Cornell University, 1946 (1995 reprint).

Lizard Care from A to Z, R D and Patricia Bartlett, Barron's, New York 1997.

Echsen [Lizards] 1, Manfred Rogner, Eugen Ulmer, Stuttgart 1992.

"Chuckwallas, the genus Sauromalus, with notes on keeping and breeding Sauromalus ater", Harry Wölfel, Reptilia 48.

Amphibians and Reptiles of Baja California, Lee Grismer, University of California Press, 2002. Impressive guide to the herpetofauna of the region.

Links

Wikipedia entry on Sauromalus

Back to Iguanids | Back to Lizards | Back to Reptiles | Back to Homepage