Where Do Gila Monsters Live? Deserts of the US Southwest

Gila monster range by state and country

The Gila monster has one of the smallest ranges of any well-known North American reptile. It is found from near sea level up to about 1,500 m (4,900 ft).

The lizards are not found in Baja California or in Texas. The name comes from the Gila River basin of Arizona and New Mexico, where they were once common.

Sonoran and Mojave deserts

The Sonoran Desert, with its saguaro cactus, palo verde trees and summer monsoon rains, is the heart of Gila monster country. Its two rainy seasons, in winter and summer, support plenty of nesting birds, rodents and rabbits, the lizard’s main sources of eggs and young.

In the drier, cooler Mojave Desert to the northwest, Gila monsters are rarer and more scattered. Animals from this area often keep more of a banded juvenile pattern and are sometimes called banded Gila monsters, while those farther south are called reticulate Gila monsters.

What kind of habitat do Gila monsters need?

Within their range, Gila monsters are choosy about where they live. They prefer:

• Desert scrub with cactus, creosote bush, mesquite and other shrubs
• Rocky slopes, foothills and canyons, especially those with seasonal streams
• Desert grassland and the edges of oak woodland at higher elevations
• Washes and arroyos, dry streambeds that provide cover and food

They avoid wide, open flats and bare sandy areas. What matters most is shelter. Gila monsters depend on underground refuges with a stable temperature and enough humidity, such as burrows dug by other animals, gaps under boulders, rock crevices and dense thickets.

Life underground

Gila monsters spend around 90 percent of their lives in their shelters. Many use the same handful of refuges year after year, moving between them as the seasons change. In spring they may switch shelters every few days, while in winter they stay in one refuge, often a deep rocky crevice.

Underground they escape the extreme heat of summer days and the chill of winter nights. They spend winter in a sluggish state called brumation, the reptile equivalent of hibernation, from about November to February or March.

This hidden lifestyle, combined with a slow metabolism and few meals a year, explains why the lizards can survive in such a harsh place. It is also why so few people ever see one.

When are Gila monsters seen?

Most activity happens in spring, from about March to June, especially in the morning. This is when Gila monsters search for birds’ nests and burrows full of baby rabbits and rodents, and when they mate. Even then, a lizard may spend only a small fraction of days above ground.

During the hottest part of summer they become less active, but they may appear on warm evenings or after monsoon thunderstorms, sometimes drinking from fresh puddles. By autumn they withdraw underground again.

Hikers in Arizona are most likely to see one on a spring morning on a rocky trail or crossing a road near desert foothills. If you do, enjoy it from a distance and leave it alone. Gila monsters are protected by law in every state where they live, and handling one risks a painful bite. See Is the Gila monster venomous?

Threats to Gila monster habitat

The Gila monster’s range overlaps some of the fastest-growing urban areas in the United States, including Phoenix, Tucson and Las Vegas. New housing, roads and farms remove desert scrub and cut through the lizards’ home ranges. Road traffic kills many, and some are still killed by people who fear them.

Relocating lizards from building sites rarely works well. Studies have found that moved Gila monsters often try to return to their old home areas, crossing roads and open ground on the way. Protecting large areas of natural desert, such as national monuments, wildlife refuges and city preserves, is the best way to keep them.

The same desert habitats are home to other well-known animals, including the greater roadrunner and the Arizona bark scorpion.