ALAMOGORDO DAILY NEWS (New Mexico) 10 July 08 The Gila Monster and Beaded Lizard (Karl Anderson)
There are only two venomous lizards in the world the Gila monster (Heloderma suspectum) and the beaded lizard, or Mexican beaded lizard (Heloderma horridum).
The Gila monster, named for the Gila River Basin in Arizona where they were once very abundant, is native to southern California, Arizona, New Mexico and northern Mexico. In New Mexico, it can be found in the extreme southwest corner, near the Gila Wilderness area. It attains a length of up to 18 inches and a weight of 3 to 5 pounds.
The beaded lizard, or Mexican beaded lizard, is larger than the Gila and ranges from Guatemala north into Mexico, primarily along the western edges of mainland Mexico. Adults grow up to 30 inches and may weigh up to 7 or 8 pounds.
Unlike venomous snakes, which inject their venom through hollowed fangs, the Gila and beaded do not possess this ability. They apply their venom, which originates from glands in the lower jaw, by chewing on their victim.
Because they are mostly lethargic, they are truly of no danger to humans unless mishandled or provoked, and will then only react in defense.
Coloration of the Gila monster is a combination of black and orange or pinkish. There are two subspecies of Gila: the reticulated (Heloderma suspectum suspectum) and the banded (Heloderma suspectum cinctum). The reticulated lives in the southern portion of its range while the banded occurs to the north of its range, primarily in and around the Mojave Desert.
Coloration of the beaded lizard, ranges from a combination of black or dark brown and light yellow splotches, to solid black or dark brown with no yellow coloration whatsoever.
In the wild, both species prey on bird eggs, birds and baby rats or mice nothing that would require a venom to capture or subdue. Because of this, the reason for these lizards even possessing venom has always been somewhat of a mystery to biologists.
The scales on the upper body, which have the appearance of beads, are actually bony plates that form scales, called osteoderms. Scales on the belly are rectangular and flat. It was the beaded skin of the Gila monster that drew the attention of Native Americans hundreds or thousands of years ago. They used these intricate and colorful designs in their native art and basketry.
Many legends and misbeliefs have plagued the Gila monster for centuries.
It was once believed this lizard had no anal vent, that waste came out the same place where food was taken in through the mouth. The truth is the lizard, just like all lizards, does possess an anal vent but the cloaca is hidden by scales. But this myth, as most myths do, perpetuated ignorance of the animal that led to more beliefs. Because of this belief, for instance, it was also believed that its waste contaminated its mouth and teeth, which in turn produced venom and "nasty breath."
Yet another legend was that if a Gila monster bit someone, the lizard would not release its grip until the skies thundered.
The venom of both species, just like that of the Western diamondback rattlesnake, is a neurotoxin that affects the central nervous system. But unlike most venomous snakes, the quantity of venom in a bite from these lizards is relatively small in dosage.
Symptoms include an excruciating, localized pain, and weakness that is normally associated with a rapid drop in blood pressure.
There have been approximately 38 recorded bites to humans by Gila monsters since the 1930s. Of these, five were fatal. Of those five, three of the victims were known to have been under the influence of alcohol at the time they were bitten.
Four individual toxins, all potentially lethal, have been isolated and identified in the Gila monster's venom. One of these is horridum venom, which can cause hemorrhaging of internal organs and a bulging of the eyes. Another is helothermine, which causes lethargy, partial paralysis of the limbs and hypothermia in laboratory rats.
A smaller group, divided and categorized as bioactive peptides, includes helodermin, which has been shown to inhibit the growth of lung cancer.
In 2005, the FDA approved the drug exenatide for the treatment of Type 2 diabetes. Exenatide is a synthetic version of exendin-4, a protein derived from the Gila monster's saliva.
The Gila Monster has shared a mixed reputation among various Native American cultures. Both the Seri and Yaqui believed the skin of this lizard possessed healing properties, while the Apache held the belief that its breath could easily kill a person. And the Pima held the belief that it possessed spiritual powers that could cause illness.
I personally have had five Gila monsters and a pair of Mexican beaded lizards in my collection, which I used in educational programs on a regular basis. When left to themselves, the Gilas always seemed more active than the beaded lizards, but when it came to handling them, the beaded lizards were always more aggressive and required more caution on the part of the handler. Being larger, beadeds are also a great deal stronger than Gilas.
Both species have been very successfully bred in captivity, mostly in the past 20 years. Captive breeding programs have their advantages. To begin with, they take pressure off wild populations by collectors of the pet trade. Secondly, it is a sure bet that captive-born and raised specimens will have less stress and usually be free of disease.
The lifespan of both species is approximately 20 years in the wild and upwards of 30 years or more in captivity.
Despite the fact they are venomous, both species are very interesting to observe in the wild. If you ever have such an opportunity, consider yourself fortunate but don't touch!
The Gila Monster and Beaded Lizard

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