Brief Description

Gila Monsters are thick-bodied lizards that grow 18 to 24 inches in length. They are black with either orange, pink or yellow broken blotches, bars and spots, with bands extending onto their thick, blunt tail. They have black faces and quite often black feet, their scales are small, bead-like. They are named after the Gila River Basin of the south-western United States.

The Gila Monster is one of only two species of venomous lizards; both are of the family Helodermatidae and both are similar in appearance and habits. Its venomous cousin, the Mexican Beaded Lizard (Heloderma horridum), is larger and darker, with a much thinner tail.

Most of the Gila Monster's teeth have two grooves that conduct the venom, a nerve toxin, from glands in the lower jaw. The toxin is not injected like that of the snake, but flows into the wound as the lizard chews on its victim. While the bite can overpower predators and prey, it is rarely fatal to humans.

There are 2 subspecies of Gila Monsters in the deserts of the Southwest:

H.s. suspectum (Reticulated) resides primarily in the Sonoran and Chihuahuan deserts. Adults are mottled and blotched.


H.s. cinctum (Banded) resides primarily in the Mojave Desert. Adults have a broad double cross bands.

Distribution

Gilas occur in the Sonoran, Mojave and Chihuahuan deserts of extreme south-western Utah, southern Nevada, south-eastern California, western Arizona and south-western New Mexico into Mexico. 

Habitat

Desert and semiarid regions of gravelly and sandy soils with shrubs. Found under rocks, in burrows of other animals and in holes it digs itself.

Behavior / Diet

During warm weather the Gila Monster feeds at night on small mammals, birds and eggs. Fat stored in the tail and abdomen during this period is utilized during the winter months. Both species of Heloderma are sluggish in habit, but they have a strong, fast, tenacious bite. They often perform a 'crocodile roll' when biting onto something too big.