THE PILOT (Southern Pines, N Carolina) 13 December 05 Zoo Tales: Gila Monster Reptile of Myth (Tom Gillespie works for the public relations office of the N.C. Zoo)
Few North American animals have been the source of more myths and misconceptions than the often-misunderstood Gila monster. It’s the largest lizard found in the United States and one of only two species of venomous lizards in the world.
In the wild, the Gila monster (Heloderma suspectum) is generally found in western and southern Arizona, into Sonora in Mexico, although they have also been located in areas of California, Nevada, Utah and New Mexico. They are usually found in the dry desert scrub and rocky mountain foothills — up to an elevation of about 1,500 feet above sea level — and seem to avoid open flats and agricultural areas.
Gila monsters have a “beadwork” appearance made up of rounded raised scales with a striking bright pink and black coloration. Embedded within the scales covering the body are osteoderms, or small boney plates. Such boney scales and plates were common among the dinosaurs but are unusual in lizards today.
Their scientific name, Heloderma, means “sun-skinned reptile. Some naturalists call the Gila monster a hybrid, a cross between snakes and lizards. It’s easy to see why that idea started, since its body resembles that of a lizard and its head, that of a snake.
Although the Gila monster is venomous, it is unlike venomous snakes that inject their victims through hypodermic-like fangs. The Gila monster envenomates its victims by chewing on them with grooved teeth containing sharp cutting edges that allow the venom to flow into the wound. In its smaller victims, the venom causes severe pain and a rapid drop in blood pressure that can induce shock and death. Although their venom contains anticoagulants and digestive enzymes (such as in snake venoms) that can cause skin damage and sickness, they do not produce enough venom to be a serious threat to a healthy adult. There are no recent accounts of human deaths from Gila monster bites.
Over the centuries, Gila monsters have inspired myriad myths and superstitions. A long-held belief is that if a Gila monster bites, it will not let go until it thunders or until sundown. This is false, but they do have a powerful bite and are capable of hanging on tenaciously.
Another is that their breath is nauseating and poisonous. Again untrue. Since their diet often consists of rotting flesh, the offensive nature of their breath is understandable. Their breath is indeed often fetid and can sometimes be detected at some distance. But it has been suggested that this is a way in which they catch insects and small animals, “the foul gas overcoming them,” as one naturalist puts it.
Gila monsters eat their prey intact. Besides providing them with food, it also supplies them with water, a necessary requirement in their desert habitats where water is often scarce.
Like most reptiles, Gila monsters are egg-layers. Females lay their clutch (up to 12 eggs) in late June or August in depressions dug into the soil, where they remain incubating underground throughout the winter and hatch the following spring.
Today, Gila monsters are a protected species. They first received protection in 1952 in Arizona — the first venomous reptiles to receive such legislation. Like so many other species today, the Gila monster’s habitat is daily being destroyed. Agricultural clearing, urban development and roads have been the major encroachments. Additionally, domestic cats and dogs kill many of them. Although their collection is illegal, many are still gathered for the pet trade.
Visitors to the North Carolina Zoo can see the park’s four Gila monsters, usually exhibited in pairs at the Sonora Desert habitat.
Zoo Tales: Gila Monster Reptile of Myth