10 Gripping Gila Monster Facts

Close-up shot of a gila monster under the cactus

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Gila monsters are the only venomous lizard native to the United States and the largest lizard north of the Mexican border. Though they have quite a reputation, much of what you've heard about these animals is likely untrue, or at least exaggerated.

Discover 10 unexpected facts about Gila monsters, the amazing animals that have a scary bite but may also help save human lives.

1. Gila Monsters Require a Very Specific Environment

Gila monster and eggs in the desert

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While they may look tough and intimidating to some, Gila monsters, like many animals, are quite vulnerable and need a specific microclimate. They prefer semi-arid conditions, but they don't just live in any desert-like area. They can be found throughout the Southwestern United States and northwestern Mexico, primarily in Arizona and Sonora, their core geographic range.

2. Their Tails Are Important for Their Health

Bright orange and black Gila Monster venomous lizard in the road in Arizona.

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While Gila monsters can reach lengths of almost 2 feet, 20% of that is just their tail, which they use to store fat and for balance as they walk. In fact, these large lizards can live for several years on the fat they keep in their tails. Because they serve such an important purpose, their tails can't detach and regrow, like other lizard tails.

3. Gila Monsters Are Actually Pretty Mellow

Though they have a reputation as vicious, venomous attackers, Gila monsters are actually quite mellow. They are "shy and retiring reptiles, not prone to attacking humans unless they are significantly agitated," according to the University of Arizona's Poison and Drug Information Center.

Gila monsters tend to avoid humans and other large animals. They will give warning to potential predators by opening up their mouths and hissing.

4. They Have an Impressive Set of Teeth

Gila Monster Skeleton on display

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Gila monster teeth on both their upper and lower jaws are thin and pointy, since their primary purpose isn't chewing, but to grab—and hold onto—prey.

The teeth on their lower jaw are larger and grooved, which helps their venom flow into their victim when they bite.

5. They Have a Serious Bite

Although rare, getting bitten by a Gila monster is serious and does require medical attention. The bite is reported to be quite painful, and the animal may even grind its jaw to drive venom deeper into the area.

If you're bitten by a Gila monster, try to detach the lizard by prying open its mouth with a stick. You should then use plenty of water to irrigate the wound, immobilize the affected limb at heart level, and seek immediate medical attention.

Gila monster venom contains a fairly mild neurotoxin that is not fatal to humans. However, it's important that a medical professional check the bite for broken teeth, signs of infection, and to ensure that tetanus immunization is current.

6. Gila Monster Venom Is Used in Diabetes Medications

Gila monsters are medically important because their venom is used to create a drug for type 2 diabetes. Exendin-4, a peptide in their venom that helps slow the lizard's digestion, is similar to a human peptide that stimulates insulin production and lowers blood sugar. The anti-diabetic agent Byetta was introduced to the pharmaceutical market in 2005.

7. They Hibernate in Winter

 An adult gila monster (Heloderma suspectum) sleeping on a sandy ground.

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Gila monsters are most active during April and May, when it's easiest for them to find food. That's also when they mate and females lay their eggs, which take four months to hatch. They hibernate from November to March.

8. Gila Monsters Only Need to Eat a Few Times per Year

These large lizards raid nests to eat eggs and small birds, and can also catch frogs and small mammals with their powerful bite, killing them with their strong jaw and sharp teeth. They also eat insects and already-dead animals they might come across.

They can eat pretty huge meals, consuming up to one-third of their weight in one session. Since they store fat well and have a low metabolic rate (that's part of the reason they're pretty non-aggressive), they don't need to eat all that much to stay healthy.

9. They Are Good Tree Climbers

Gila monsters can easily make their way up trees or large cacti of various kinds, even those with slippery bark. It is not their standard behavior, though. Their long claws are mostly used for digging, but they can also use them to climb out of harm's way if they feel threatened or to escape a predator.

10. They Live for Decades

Gila monsters can live up to 20 years in the wild, a rather long lifespan for a lizard. In captivity, one specimen was recorded to have lived to age 36. Still, Gila monsters are considered Near Threatened by the IUCN due to commercial exploitation and habitat destruction for urban and agricultural development.

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