Mexican Beaded Lizard Fact File


The name of the Mexican beaded lizard comes from the bead like scales which cover the head and back. On the underside the scales are softer. Their colour is variable across their range. They may be entirely black in some areas while in others this is patterned with paler yellow blotches.

Their limbs are short but powerful. They have a thick, fleshy tail that make up over 50% of their total length. This tail is used for storing excess fat. Their head is wide and flat.

A Mexican beaded lizard will measure between 70 and 100cm (28 and 39in) long and weigh up to 4kg (8.81lbs). The males are larger than the females.


The Mexican beaded lizard is carnivorous. They feed on eggs, snakes, insects, lizards, small mammals and birds. Food is swallowed whole.

When food is plentiful they will store excess fat in the tail. During periods of food scarcity they will use this fat storage to survive and as they do this the tail thins.

Their thick tongue is used to locate food. Food can be found on the ground and they may also climb to find food.

To assist in catching their food they have venom. Unlike snakes they do not have fangs and the venom is instead delivered by chewing the prey item.

Scientific Name

Heloderma horridum

Conservation Status

Least Concern


4kg (8.81lbs)


70-100cm (28-39in)


30 years



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North America is the native home of the Mexican beaded lizard. Here they can be found throughout Mexico and Guatemala. They stick to the Pacific ocean side of Mexico.


They make their home in semi-arid rocky areas, tropical scrubland and open forests.

Most of their time is spent underground or on rock ledges.

Mexican beaded lizard


Breeding takes place during September and October. Males will defend their rights to mate with a female through aggressive fights that can run over several hours.

By December the female lays her clutch of eggs. Clutch size is highly variable ranging from 2-22 eggs. They are buried in to a hole dug underground.

The eggs incubate underground for 6 months. Following hatching the young dig their way to the surface. One there they are on their own and will receive no support from the parents.

At hatching the young average 20cm (7.9in) long.

Sexual maturity is achieved between 2 and 3 years old.

mexican beaded lizard


Mexican beaded lizards are primarily active by night and spend most of their day tucked away in a burrow. They may spend as much as 95% of their time in the burrow.

Predators and Threats

Mexican beaded lizards face predation from the coyote and raptors.

When faced with a predator they may used their venom to defend themselves. They will also hiss and open their mouth to prey.

Humans reduce the population of the Mexican beaded lizard through deforestation, deliberate killings, urban sprawl and forest fires.

They are also captured in small amounts for the illegal wildlife trade.

Quick facts

The Mexican beaded lizard is one of only two venomous lizards on Earth. It is fatal for small animals though the effects in human are not as severe in most people. The other venomous species is the gila monster.

Enzymes found in their venom have been used in the treatment of diabetes and research is ongoing to see if they would be useful for other diseases.

Photo Credits

All Images

Public Domain


Burnie, D., 2011. Animal. 3rd ed. London: DK

Stout, N. 2003. "Heloderma horridum" (On-line), Animal Diversity Web. Accessed July 15, 2020 at

Ariano-Sánchez, D., Muñoz-Alons, A., Marquez, L.C. & Acevedo, M. 2014. Heloderma horridum. The IUCN Red

List of Threatened Species 2014: e.T9864A3152367. Downloaded on 16 July 2020. 2020. The Zoo | Beaded Lizard. [online] Available at: <> [Accessed 16 July 2020]. 2020. Mexican Beaded Lizard. [online] Available at: <> [Accessed 16 July 2020]. 2020. Mexican Beaded Lizard | Saint Louis Zoo. [online] Available at:

<> [Accessed 16 July 2020].

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