DISTRIBUTION: The Gila Monster can be found across most of western and southern Arizona. Its range extends from the far northwestern corner of the state, down through our western deserts to Yuma, and eastward across nearly all of sub-Mogollon Rim southern Arizona. In our state it has been found at elevations ranging from just above sea level near Yuma to over 5,500′.

HABITAT: Biotic communities ranging from Arizona’s desertscrubs into the lower reaches of Great Basin Conifer Woodland and Madrean Evergreen Woodland are home to this lizard. It is most commonly found above the flats in rocky drainages and on rugged bajadas, hillsides, and mountain slopes.

BEHAVIOR: The relatively slow moving and lethargic Gila Monster spends most of its time in underground burrows. When surface active it tromps with an awkward, lumbering gait. Its total surface activity may add up to just 3 weeks per year. It is diurnal in spring and fall and nocturnal during the hot summer months. During the cold months of winter and late fall it hibernates in an underground shelter. It is not aggressive unless it is harassed or captured.

DIET: The Gila Monster is a carnivore that feeds on nestling mammals, nestling birds, the eggs of birds and reptiles, lizards, and carrion. It stores fat in its tail. Four or 5 meals may be enough to sustain the lizard for an entire year.

REPRODUCTION: Males combat for access to receptive females. Mating takes place in spring and summer and eggs are laid in summer. Clutch size ranges from 2 to 12 eggs. Hatchlings emerge from the nest the following spring. Females usually lay a clutch of eggs every other year.

REMARKS: This lizard is a member of Helodermatidae, the only family of venomous lizards in the world. Venom secreted from glands in the lower jaw is delivered through grooves in the teeth. Bites are reported to be painful, but are rarely fatal to humans who get medical attention. Captive specimens have lived to over 25 years of age. Protected in Arizona.
It is against Arizona State law to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect the Gila Monster or to attempt to engage in any such conduct.

By Thomas C. Brennan

Beck, Daniel, D. 2005. Biology of Gila Monsters and Beaded Lizards. University of California Press. Berkeley and Los Angeles, California.

Stebbins. 1985. Western Reptiles and Amphibians. Houghton Mifflin. New York, NY

Stebbins, R.C. 2003. A Field Guide to Western Reptiles and Amphibians, Third Edition. Houghton Mifflin Company, Boston, MA.