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Gila Monster

Heloderma suspectum

About the Gila Monster

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Geographic Range:

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Class: Reptilia  
Order: Squamata  
Family: Helodermatidae
Genus: Heloderma  
Species: suspectum 

The Gila monster is the largest lizard native to the United States. They're stout with an elongated body, short limbs, and sharp claws. Their thick, blunt tails are specially adapted to allow the lizards to store fat for future needs. A well-nourished Gila will have a thick, robust tail. Their skin is unique, with individual, round, raised scales that give these lizards a beaded appearance and texture. Small, bony plates are embedded in their scales. Although such protective "bony skin" appears to have been fairly common in dinosaurs, the Gila is one of the few living reptiles with these types of scales.

Gila Monster Facts

Appearance:
The Gila monster is the largest lizard native to the United States. They're stout with an elongated body, short limbs, and sharp claws. These claws are suited to digging burrows and to dig out other animals' eggs for food. Their thick, blunt tails are specially adapted to allow the lizards to store fat for future needs. A well-nourished Gila will have a thick, robust tail.

Their skin is unique, with individual, round, raised scales that give these lizards a beaded appearance and texture. Small, bony plates are embedded in their scales. Although such protective "bony skin" appears to have been fairly common in dinosaurs, the Gila is one of the few living reptiles with these types of scales.

These lizards have evolved to fit in well with their surroundings. Their colorful, beadlike skin camouflages them in the desert. There are extensive color and pattern variations among Gila monsters throughout their range. Generally, they're pink, yellow or orange with black reticulated and/or banded patterns.

Size:
Length: 20-24 inches
Weight: 3-5 pounds

Reproduction: Glia monster mating takes place in the early summer and begins with the male flicking his tongue to search for the female's scent. If a female objects to a male, she'll bite him and crawl away. The breeding season is usually in July or August, after which females will lay one to 13 (five is the average) eggs in damp soil and incubate them for 10-12 months.

Median Life Expectancy:
Gila monsters live for 10-25 years on average, and sometimes up to 30.

Habitat/Range:
Gila monsters live at elevations to 1,500 meters and seem to prefer rocky desert scrub and foothills, avoiding open flats and agricultural areas. Gila monsters are found in the southwestern United States, specifically Arizona, California, Nevada, New Mexico and Utah. They're also found in northwestern Mexico.

Diet:
The Gila monster diet consists of small mammals, lizards, frogs, insects, carrion, birds and eggs. They've adapted to eating large meals infrequently. This allows them to consume most of their food during their limited Spring activity period. Gila monsters are able to consume large quantities of food (up to 1/3 of their body weight) and their resting metabolic rate is so low that the energy expenditure for foraging is offset by their long periods of inactivity.

Behavior:
Adult Gilas are predominately diurnal (active during the day). To avoid the extreme heat of the desert, most of their activity occurs in the morning and the late afternoon. Sometimes, during the summer, they're seen out after dark, especially in the southern part of their range. Gilas have relatively “leaky” skin, and they avoid dehydration by spending most of their lives in moist and humid shelters. They spend most of their lives underground, hibernating throughout the year and emerging for three months in the spring to feed and mate. They can be seen throughout the year basking at the entrance of their shelters on unseasonably warm, winter days.

A Gila's nerve venom is designed for protection-- not for collecting food. Biting is a last resort. The venom is delivered any time the Gila bites because it's instantaneously injected from the grooves in the teeth of the lower jaw. Often, the lizard will continue to grip and chew additional venom into its victim. The venom contains substances that may cause pain, edema, bleeding, nausea and vomiting in humans, but is seldom fatal.

Predators:
Humans are the Gila monster’s primary predator. Adult Gilas are a food source for hawks, primarily the Harris hawk, owls, including the Great Horned owl, and coyotes. Snakes take juveniles.

Conservation:
Human encroachment, agriculture and habitat destruction coupled with being taken from the wild for the pet trade in large numbers pose threats to the existence of Gila monsters in the wild.