Real Gila Monsters

This website would be lacking if it didn't include at least some general information about real Gila monsters.  Below, is a very brief description of Heloderma suspectum.  For more comprehensive information about Gila monsters and Beaded Lizards, I highly recommend the publications listed at the conclusion of this article.

Helodermatid lizards, Gila monsters, Heloderma suspectum and Mexican beaded lizards, Heloderma horridum, can be recognized by the presence of beadlike osteoderms on the surface of their bodies.  The genus, Heloderma, is derived from the Greek words helos for “nail stud” and derma “skin.”

Subspecies: Two Gila Monster subspecies are recognized...the Banded Gila monster, H. s. cinctum, and the Reticulate Gila monster, H. s. suspectum.  The Banded Gila monster retains most of the banded dorsal pattern of a hatchling to full maturity.  This subspecies occurs in northern and western Arizona, southwestern Utah and southeastern Nevada. Most of the individuals reported in California fall within the description of H. s. cinctum.

The adult Reticulate Gila monster, H. s. suspectum, is characterized by an irregular, or reticulated, pattern of mottles or blotches.  As juveniles, both Banded and Reticulate Gila monsters bear distinct “banded” dorsal patterns.  However, as H. s. suspectum matures, its dorsal pattern usually breaks up to form a more irregular or reticulated pattern.  This process is called an “ontogenetic change.” This is a good place to mention that individuals with dorsal patterns more suggestive of H. s. suspectum occasionally occur well within the established range of H. s. cinctum…and vice verse.

Gila monsters and Mexican beaded lizards are the only known venomous lizards in the western hemisphere. The Gila monster is the only venomous lizard native to the United States. Venom is stored in a gland in the lower jaw. The venom is guided to the wound by way of groves in the enlarged lower teeth. A chewing motion aids in the transference of venom. Bites inflicted on humans are rare...the majority of which are the result of careless handling. Note: The bite of a Heloderma lizard is potentially dangerous to humans (and extremely painful) and medical attention should be sought immediately.

Of the Helodermatids, only the Gila monster (Heloderma suspectum) occurs within the United States.  Its range extends southward to Sonora Mexico and with a small population occurring in northern Sinaloa.  Within the United States the predominant population is within Arizona.  Smaller (and spottier) populations occur in southeastern Nevada, southwestern Utah, southwestern New Mexico and southeastern California.

Gila monsters have been found in elevations exceeding 5,600 feet.  Gila monsters are associated with desert scrub, moist riparian and desert grassland environments. Gila monsters also seem to prefer rocky foothills as opposed to sandy open flats and agricultural areas.  It is believed that ample summer rainfall is also an important factor in habitat suitability.

Recommended reading (which also served as references for the above narrative):

Beck, Daniel, D. 2005. Biology of Gila Monsters and Beaded Lizards. University of California Press. Berkeley and Los Angeles, California.

Bogert, Charles M., and Martín del Campo. 1993. The Gila Monster And Its Allies. Society for the Study of Amphibians and Reptiles. Oxford, Ohio.

Brown, David E., and Neil B. Carmony. 1999. Gila Monster: Facts and Folklore of America’s Aztec Lizard. The University of Utah Press. Salt Lake City, Utah.






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