San Esteban Island Chuckwalla

Sauromalus varius

Description

The San Esteban Island chuckwalla is an isolated population of the more widespread piebald chuckwalla (also Sauromalus varius ). Chuckwallas are medium-sized, plump lizards, with a blunt tail. The San Esteban Island chuckwalla is the largest of the chuckwallas, reaching a length of up to 2 ft (60 cm). Other chuckwalla populations are generally less than 18 in (46 cm) long. The body color is tan to yellow, with gray splotches and a gray face.

Behavior

The San Esteban Island chuckwalla is a herbivore, feeding on the foliage, flowers, and fruit of selected plants. When it feels threatened, it runs into a rocky crevice where it inflates itself by swallowing air, making it extremely difficult for a predator to extricate the lizard.

Habitat

Like other chuckwallas, the San Esteban Island chuckwalla inhabits rocky areas with interspersed, open flats in semi-desert areas.

Distribution

The San Esteban Island chuckwalla only occurs on San Esteban, Lobos, and Pelicano Islands, in the Gulf of California off Baja California, Mexico. The piebald chuckwalla has a much more widespread distribution, occurring in the Mojave and Sonoran Deserts of southeastern California, southern Nevada, and Utah, western Arizona, and nearby Mexico (including the Baja islands).

Threats

The small, isolated populations of the San Esteban Island chuckwalla are threatened by habitat degradation caused by introduced species of plants and mammalian herbivores. Introduced mammalian predators are also a threat.

Conservation and Recovery

The San Esteban Island chuckwalla is listed as an endangered species by the Mexican and U. S. governments, and its international trade is prohibited by the Convention on International Trade in Endangered Species (CITES). Some of the introduced herbivores have been controlled on the Baja islands, but others remain there, as do the invasive non-native plants. A captive colony of the San Esteban Island chuckwalla has been studied at the Arizona Sonora Desert Museum since 1977, yielding useful insight into the biology and ecology of the species. The captive animals have bred, and if necessary this colony could be a source of animals to release into the natural habitat of the species to supplement the wild population.

Contact

Instituto Nacional de Ecología
Av. Revolución, 1425
Col. Campestre, C.P. 01040, Mexico, D.F.
http://www.ine.gob.mx/

Reference

Burghardt, G. M., and A. S. Rand, editors. 1982."Ecology and Evolution of the Insular Gigantic Chuckwallas, Sauromalus hispidus and Sauromalus varius." in Iguanas of the world—Their Behavior, Ecology, and Conservation. Noyes, Park Ridge. pp. 184-211.