Northwestern Mexico and southwestern US



What’s in a name?

As the name might suggest, the Gila (pronounced HEE-la) monster has one of the worst reputations in the reptile world. This lizard is often feared and has been described as frightful and repulsive, especially in local folklore. It has been accused of many things, such as spitting venom, leaping several feet in the air to attack, stinging with its tongue, and killing people with gusts of poisonous breath. We’re glad you’re reading this fact sheet to learn the truth about these interesting lizards!

Monster habits

Gila monsters are heavy-bodied lizards covered with beadlike scales, called osteoderms, that are black and yellow or pink covering all but their belly. The lizards are solitary and live in desert and semi-desert areas with just enough moisture to support a few shrubs. Gila monster burrows are commonly found in rocky foothills, as they avoid open areas. The lizards can adjust their behavior according to the temperature. Gila monsters may be active at night if temperatures are extremely hot during the day or be crepuscular or diurnal if the temperature is optimal for them.

During cold winter months, Gila monsters stay in burrows dug with their stout claws or even burrows of desert tortoises and have fat stores in their tail to keep them alive during this time. When springtime comes, they begin to hunt again.

The Gila monster and its close cousin, the beaded lizard Heloderma horridum, are the only two venomous lizards in the world.
A drug for the management of Type 2 diabetes is based on a protein from the Gila monster’s saliva. The drug is sometimes referred to as lizard spit.
The Gila monster is named for the Gila River in Arizona.
It has been reported that the Gila monster may flip over while its jaws are still clamped onto prey. This move may help its venom flow into the wound.
The Gila monster is the largest lizard native to the US.
The Gila monster can eat a third of its body weight in one meal.
The Gila monster’s scientific name is “Heloderma suspectum,”which means studded skin.

One of the San Diego Zoo’s first Gila monsters was a male named Butch. He belonged to a local school’s biology department but would “vacation” at the Zoo each summer in the 1940s.

In 1963, the San Diego Zoo hatched reticulate Gila monsters, a first for any zoo in the world. We earned the prestigious Edward H. Bean Award in 1964 from the Association of Zoos and Aquariums for propagation of the species.

Today, several Gila monsters can be viewed in the Zoo’s popular Reptile House.

Much of the scrubland of the Gila monster's habitat has been cleared for agriculture, canals, roads and highways, and other human activities. Domestic cats and dogs often kill the lizards, and some Gila monsters are illegally collected for the pet trade. In 1952, the Gila monster became the first venomous animal in North America to be given legal protection.