Beaded Lizard

Beaded Lizard


Southwestern United States; northern and southwestern Mexico to northern Guatemala


This lizard inhabits desert scrub and tropical thorn woodlands; spending as much as 98 percent of its life underground to avoid the desert heat.


It is recognized by the stripes and spots that vary from white to yellow on its black bumpy skin, called ostioderms. These unique bumps are what gave it the name, beaded lizard. The Mexican beaded lizard and its cousin, the Gila monster, are the only two lizard species that have this beady appearance.

This lizard also has a thick, fleshy tail that is slightly shorter than the rest of the body, and short powerful limbs.

Beaded Lizard

These lizards are most often found in burrows during the heat of the day and become active at night when it is cooler outside. They will hibernate when temperatures remain consistently cool throughout the day.  When food is scarce, the Mexican Beaded Lizard lives off fat reserves in the tail. Fat is stored in the tail of the lizard making it appear swollen. After the fat reserves are used up the tail appears thin again.

Although beaded lizards appear sluggish, they are able to move rapidly when threatened. They can also produce a hissing sound to warn off intruders. If that doesn’t work they may bite the predator, delivering a painful venomous bite.


Mexican beaded lizards reach sexual maturity between two to three years of age. Courtship and mating occur in September and October (springtime where they live). Males engage in ritual combat that may last several hours; the winner has the privilege of mating with the female. The female lays between two and 22 eggs between October and December and buries them. She then leaves and the young hatch the following June or July. It usually takes two or three days for them to completely hatch. They measure about six to eight inches in length.

Interesting Facts:

Mexican beaded lizards and their close relative, the Gila monster, were once thought to be the only two venomous lizards found in the world. However, new research indicates that as many as 100 other species of lizards may also be venomous including the famous Komodo dragon.

Beaded lizards possess venom glands in their lower jaws. These are modified salivary glands. Each gland has a separate duct leading to the base of its grooved teeth. To deliver the toxin, the lizards chew the venom into their prey. The bite is very strong and painful, especially since they may not loosen their grip for several seconds. The venom is a weak hemotoxin and although human deaths are rare, it can cause respiratory failure and often makes people very ill. If bitten, a person should quickly seek medical treatment. There is no anti-venom for their bite.

Unlike people, in the wild if food is scarce, this lizard can go without eating for long periods. It stores fat in its tail so that it can survive when not eating. Wondering why the lizard was able to maintain and control its insulin and glucose levels between meals, scientists studied it. What they discovered was a new protein in the lizard’s saliva and venom that have helped to develop new drugs to treat diabetes. You could say a beaded lizard has super spit!


In the wild, this lizard helps keep rodent populations in check. It is threatened by habitat loss from development, human recreational activities and illegal collection for the pet trade.

Did YOU Know?    
Unlike venomous snakes, beaded lizards can't forcefully eject the toxin from their venom glands; instead, they have to chew the venom into their victim.
Beaded Lizard
Class: reptiles
Order: Squamata
Family: Helodermatidae
Genus: Heloderma
Species: horridum
Length: 3-36 inches including tail
Weight: 3-6 lbs
Average Lifespan: In excess of 30 years
Wild Diet: Feed primarily on eggs, young birds, mammals, other reptiles and dead animals.
Predators: Preyed upon by coyotes and birds of prey.
CITES Status: This lizard species is protected under the Convention on International Trade in Endangered Species of Wild Flora and Fauna (Appendix II)
Where at the Zoo? Small Animal Building

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