The Four Sub-Species of
The Mexican Beaded Lizard is one of only two venomous lizards in the
world, the other being the Gila Monster (Heloderma suspectum). It’s
latin name consists of the two words Heloderma horridum. Heloderma,
meaning studed skin, and horridum, meaning horrible (horrible studded
lizard). This seems quite a fitting name for this unique animal, although
I don't think they're horrible at all. Heloderm lizard's skin consists
of several tiny beads called ostioderms. Each bead contains a tiny
piece of bone that gives them almost an armor plated skin.
The lifespan of these lizards is said to be around thirty years, although
in my opinion it’s more like fifty. For females, average adult
size is 30in and three and a half to five pounds. For males, average
adult size is 36in and five to six pounds. Exceptionally large males
can reach 40in and close to ten pounds.
Most Beaded Lizards reach sexual maturity at two and a half to
three years old. Once oviposition occurs, the incubation period
is around 165 to 215 days. At about that time the hatchlings will
pip their head out of the egg. It usually takes two or three days
for them to come all the way out, absorbing their yolk sack and
ingesting the liquid content of their egg. Newly hatched neonates
are usually five to six inches and weigh around 40 grams. Until
the animals are substantial in size, sexing is nearly impossible.
Males generally have much broader heads and longer necks, with females
having narrower heads and shorter necks, although there’s
always exeptions to every rule.
|A picture of a Heloderma horridum
alvarezi. Photograph credit: Dennis Sheridan
of Beaded Lizards
Class: Reptilia Order: Squamata Family: Helodermatidae
Heloderma horridum horridum
• Heloderma horridum charlesbogerti
• Heloderma horridum alvarezi
• Heloderma horridum
Only the horrdium and exasperatum types are bred in the United States
by private individuals. The charlesbogerti type has been bred by the
San Diego Zoo.
|From top to bottom: An adult,
a two year and a yearling
||Size Comparison: Male on the
left, Female on the right
The animals originate in the Pacific Drainages from Southern Sonora,
Mexico to Southwestern Guatemala and two Atlantic drainages, from
Central Chiapas, Mexico to Southeastern Guatemala. Habitat is primarily
tropicial deciduous forest and thorn scrub forest, also found in
pine-oak forest, with elevations from sea level to 1500 meters.
In the wild, the animals are only active from April to mid-November.
They spend only about an hour per day above the ground, and their
natural diet is consistent of reptile and bird eggs and occasionally
small mammals. The lizard uses its venom primarily as a defensive
weapon. (Johnson, J. P. and C. Ivanyi, 2001. North American Regional
Beaded Lizard Studbook. 3rd Edition. Arizona-Sonora Desert Museum.)
|H.h. exasperatum habitat - Southern Sonora,
Photography by C.M. Gienger
|A Rio Fuerte beaded lizard in climbing a tree.
Photography by C.M. Gienger
The venom glands are located in the lower jaw. At the base of each
tooth is a grooved pit for venom delivery. The venom is delivered
by the lizard by a chewing motion, a rather crude delivering device.
The bite from an animal is extremely painful and can be potentially
fatal, but this is only in extremely rare cases. See Bob
Applegate's website for an actual bite account.
|A pair of Heloderma horridum exasperatums mating.
||Heloderma horridum Eggs with hatchlings starting
To the left: A tooth of a Heloderma horridum,
notice the pit in the tooth.
To the right: The Jaw of a Gila Monster (Similar to a Beaded Lizard)
Both drawings come from Bogart and Del Campo's The Gila Monster
and Its Allies and were drawn by S.B. McDowell ©1956
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