BY TOM GILLESPIE

Special to The Pilot

The desert iguana (Dipsosaurus dorsalis) is not only one of seven lizard species exhibited at the North Carolina Zoo, but it's also one of the most common lizards of the Sonoran and Mojave deserts in the southwestern United States and northwestern Mexico. They can also be found on several of the Gulf of California islands.

Desert iguanas were first discovered and named by Europeans in 1853, but were reclassified two years later, when differing species were found. Their generic name comes from a combination of two Greek words: dipsa (thirsty) and sauros (lizard). The specific name, dorsalis, comes from the Latin word dorsum, meaning "back," and refers to the row of scales running down its back almost to the tip of its tail.

In the wild, they live in sandy, open desert areas dominated by creosote bushes, and occupy burrows and rock crevices. They can also be found in rocky streambeds at elevations of as much as 4,000 feet. Creosote bushes provide both the lizard's diet - from its flowers - and a place for the lizards to burrow under the plant's roots for protection from thermal extremes and predators.

Extensive burrowers, they create their own or use the ready-made burrows of small mammals, kangaroo rats and tortoises. They plug the entrance of their burrows at night to conserve heat and to deter nocturnal snake predators.

They emerge later in the year and later in the day than other lizards and remain active longer into the hottest part of the day than other lizards. Body temperatures of 45 degrees C (113 F) have been recorded, well above lethal levels for most other species. In fact, they are thought to be more heat-tolerant than any other North American reptile, thanks in part to a black lining of the abdominal cavity that protects them from ultraviolet sun rays.

Just as desert iguanas in the wild hibernate during the winter, emerging in mid-March, they're also taken off exhibit at the N.C. Zoo from September through March. Little is known about their habitat requirements for reproduction. When breeding begins in April and May, they typically lay only one clutch of eggs each year, usually 3-8 eggs, but can lay two clutches under the right conditions. Hatchlings emerge in late July through August and sometimes on into September.

For protection, they can inflate their bodies with air when disturbed, making them appear larger than normal to predators. Thick, powerful legs make them fast runners. When they need to move quickly, they often do so on two legs, folding their front legs near their body and using their powerful hind legs to propel themselves forward. Described as "blunt-headed," desert iguanas have a light brown ground color, marked with irregular bars and spots and gray spots on the trunk and neck. Their pale or white sides and belly give the effect of an all-white lizard, allowing it to blend in with its native sandy, rocky habitats. During the breeding season, their sides become pinkish in both sexes.

They're medium-sized in relation to other lizards but small in comparison to their rain-forest cousins. They can swim but rarely have the opportunity in their desert environments. Adults can reach a length of 15-16 inches, including a tail that is about 1.5 times as long as the body. They're vegetarians, but they'll eat insects when vegetation is scarce.

In the wild, the primary predators of both iguanas and their eggs are large birds and rodents, foxes, weasels, coyotes and some snakes. Many are killed by automobiles while crossing desert roads. Because of the role humans play in the habitat alteration and pet-trade gathering of these iguanas, man is also considered a primary predator. Desert iguanas aren't considered endangered.

N.C. Zoo visitors can view desert iguanas daily, April through August, in the Sonora Desert exhibit in the North America region.