Geographical Range Southwestern United States and Northwestern Mexico
Habitat Desert areas with shrubs and small trees; mountain slopes
Scientific Name Heloderma suspectum cinctum
Conservation Status Threatened

This Lizard Bites!

The Gila monster is one of only two venomous lizard species in the world. The venom is generally used to thwart an attacker (rather than to subdue prey, as in snakes). When Gila monsters bite, venom flows from glands in the lower jaw to the bottom teeth, which have grooves to carry the liquid to the victim's body. Ouch!

Beaded Body

Gila monsters are a type of beaded lizard, so called because of the bead-like scales covering their head and back. Gila monsters come in two distinct color patterns. Banded Gila monsters (the kind we have at the Saint Louis Zoo) have alternating pink and black bands across their body. (The other color pattern, that of the Reticulated Gila monster, is more mottled.) The Gila monster's coloring may serve as camouflage, or it may be a warning to potential predators.

Gila monsters are fairly large lizards: adults can be more than 20 inches long, including the tail.

What's for Dinner?

These lizards aren't picky: they eat all kinds of things, including rodents, nestling rabbits, lizards, frogs, insects, and the eggs of birds and reptiles. Gila monsters stalk their prey by following their nose and tongue, using smell and taste to track their quarry. They hunt mostly on the ground, but they've been known to climb trees in search of a meal.

Gila monsters do most of their feeding in the late spring and early summer. During these times, fat is stored in their tails, which grow thicker and thicker. Their tails shrink again as the fat reserves are used up during the winter.

Making Monster Babies

Late spring is mating time for Gila monsters. In midsummer, females lay their eggs (usually three to 12) in shallow nests dug into the ground. These females are not stay-at-home moms, and leave their eggs after laying them. These eggs will be home alone for a long time: it will be up to 10 months before they hatch.

At birth, the young are just over six inches long. These babies have bite! They come fully equipped with venom, and are able to defend themselves if attacked.

Not Too Hot, Not Too Cold

Gila monsters spend much of their time in underground dens -- usually rocky crevices in the ground or abandoned mammal burrows. In their dens they can avoid extremely high and low temperatures. They emerge when temperatures above ground are more moderate -- daytime in the spring, and nighttime in the summer. (They may also come out on overcast summer days, or warm winter days.) These are the times they're most active. They're least active during the coldest part of winter, when they come out of their burrows only to bask in the sun.

Though two or more adults may share a burrow, Gila monsters spend most of their active time alone.

Even Monsters Need Help

Gila monsters are threatened, meaning they face a high risk of extinction in the wild.

Though state and local laws protect these lizards, the animals still face two big problems -- habitat loss due to urban development and agriculture, and illegal collection for use as pets. You can help by not buying a Gila monster, and by spreading the word about these threatened animals.

Fun Facts

  • Gila monsters are immune to their own venom. So when two males decide to fight over a female (which sometimes happens), the venom from their bites will not kill their opponent.
  • Gila monsters can live for 20 years or longer.
  • The Gila monster is named after the Gila Basin in Arizona.

Class: Reptilia
Order: Squamata
Family: Helodermatidae