Gila Monster (Heloderma suspectum)


Class: Reptilia
Order: Squamata
Family:    Helodermatidae
Size:    Length: 1.5 to 2 feet (45 to 61 cm)
Weight: 3 to 5 pounds (6 to 11 kg)
Diet: Birds, mice, squirrels, frogs, eggs and lizards as well as carrion
Distribution: Southwest United States, Northwest Mexico
Young:  1  to 12 eggs, once per year
Animal Predators:  Unknown
IUCN Status: Vulnerable
Terms: No special terms
Lifespan: 20 years in captivity



·       Gila monsters are the only poisonous lizards found in the United States.

·       Mexican beaded lizards are the only other poisonous lizards in the world.

·       When they bite, Gila monsters hang on with a strong grip and chew.

·       Exendin-4, a component of Gila monster venom, is currently being tested as a new drug for treating type 2 diabetes.

·       They are named for the Gila Basin in Arizona.



Gila (pronounced heela) monsters are large lizards with a thick tail. Fat is stored in the tail in anticipation of lean times as well as hibernation in the winter months. Their scales are mostly black with bright yellow, pink, and white stripes, spots and bands. There are two subspecies—the Reticulated Gila Monster (Heloderma suspectum suspectum) in the south, and the Banded Gila Monster (Heloderma suspectum cinctum) to the north. 



Gila monsters live in the hot, dry areas from sea level to 1,640 yards (1,500 metres) in altitude. In the United States they are found mainly in the southwest, including Utah, Nevada, California, Arizona and New Mexico. They are also found in northwestern Mexico.


Feeding Habits

Gila monster can eat the equivalent of up to 35 percent of their body weight at one time. Their diets consist of birds, mice, squirrels, frogs, eggs and lizards as well as carrion, and they locate prey using the thick, forked tongue to sense the surroundings. 



Mating season occurs in May, when the males begin to seek out females. The male approaches the female, lying near her and rubbing his chin on her back. If the female is receptive, she lifts her tail; otherwise, she will try to bite him. Females lay their eggs in damp sand during July or August, then they cover them and leave. The eggs—large with leathery shells—do not hatch until the following May. From birth, the young are fully capable of fending for themselves. 



Because of their heavyset body size, Gila monsters appear slow and sluggish, but can turn and bite with amazing speed. The venom of Gila monsters is about as toxic as that of western diamondback rattlesnakes, but while snakes have hollow fangs through which their venom is injected, the venom of Gilas is introduced from glands in the lower jaw, flowing out through grooves on the teeth. When they bite, they hang on ferociously and grind their vicelike jaws into the victim. Although Gila monster bites are extremely painful, there are no substantiated cases of Gila monster bites having been fatal to humans. Gila monsters spend a good deal of time underground living in burrows—either self-dug or stolen from prey, coming out mainly during the spring mating season.



Gila monsters are legally protected in all the states in which they are found. 



Gila Monster Wildlife Fact File, IM Pub, US