Gila Monster

Part of the Lizards and Snakes: Alive! exhibition.

Gila Monster
© AMNH / Denis Finnin

Shy and beautiful, the Gila Monster is also highly venomous.


Gila (HEE-luh) Monster scales are rounded and pebblelike, and they don't overlap. The scales--especially those on the Gila Monster's head--are supported beneath the skin by bony elements called osteoderms. Osteoderms are visible on this CT scan.


The Gila Monster flicks its forked tongue to pick up scent particles that can lead the animal to food, including eggs, baby birds and small mammals. It can find eggs buried 15 centimeters (six inches) deep. Sharp claws help dig up the meal.

Gila Monster display case
© AMNH / Roderick Mickens


Glands in the lower jaws secrete venom. The venom funnels through special grooves in the Gila Monster's teeth and mixes with saliva--and with the blood of prey animals--killing or disabling them.


Powerful muscles control the jaws and give the Gila Monster a bite like a bulldog--it just won't let go. This gives the venom a chance to work, weakening or disabling the lizard's prey.


The Gila Monster, like a number of lizards, stores fat in its bulky tail, allowing it to go a long time between meals. It spends much of its life inactive, underground, waiting for rain.

Gila Monsters can go a long time without eating. That's partly because lizards don't use up energy keeping their bodies warm. When the Gila Monster does eat, a substance in the saliva helps its system adjust to the sudden rush of sugars and nutrients. Drug researchers have copied that protein to help treat diabetes in humans.

Meet the Family

There are only two living species in the family Helodermatidae-the Gila Monster and the Beaded Lizard. These are the only limbed squamates that produce highly toxic venom, which they do with their salivary glands. Both species have pebblelike skin and very sharp, curved teeth that are grooved to conduct venom into the blood of a prey animal. The earliest known relative of Gila Monsters lived nearly 100 million years ago.

Beaded Lizard
© David Northcott / DRK Photo

Beaded Lizard

Heloderma horridum

This lizard species ranges from western Mexico to Guatemala. A ground-dweller in the northern part of its range, it climbs trees farther south.

Beaded lizards are different colors, depending on where they live. In the north they are yellow and black; in the south, they are all dark.

Gila Monster eating quail eggs
Gila Monster (Heloderma suspectum) eating quail eggs
© C. Allan Morgan/DRK Photo

Gila Monster

Heloderma suspectum

Gila Monsters roam widely in search of food, and the eggs of ground-nesting birds are among their favorite meals. Here, a Gila Monster eats quail eggs.

Fast Facts

NAME: Gila Monster; Heloderma suspectum
SIZE: 30 to 50 centimeters (12 to 20 inches)
RANGE: Southwestern U.S. and northwestern Mexico
DIET: Eggs, young birds, small mammals