Gila monster
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| Heloderma suspectum Cope, 1869 |
The Gila monster (pronounced HEE-la, IPA pronunciation: [hilə]) (Heloderma suspectum) is a species of venomous lizard that lives from southwest Utah to the southern Sonora and northern Sinaloa; extreme southwest New Mexico to southern Nevada and just into eastern California. Heloderma suspectum also occurs up to an elevation of 4,800 feet. The Gila monster is more common in the wetter, rockier paloverde-saguaro desert scrub association than the drier, sandier creosote bush-bersage association. Heloderma suspectum also seem to prefer rocky foothills and avoid open areas and agricultural regions. Gila monsters live in burrows dug by other animals or may construct their own. They are known to stay underground in their borrows for 95% of their time.
It is a heavy, slow moving lizard, up to 60 cm (24 inches) (2 feet) long, and is the largest lizard native to the USA. Its skin has the appearance of beads in the colors black, pink, orange, and yellow, laid down in intricate patterns. These beads are actually small bony plates that form scales, and are known as osteoderms. It is closely related to the Mexican beaded lizard, Heloderma horridum.
The name "Gila monster" refers to the Gila River Basin in Arizona. The generic name for Heloderma is from the Greek words Helos coming from the head of a nail or stud, and derma for skin, therefore Heloderma means studded skin. Suspectum comes from the notion that Cope had, that this lizard might be venomous due to the grooves in the teeth.
Unlike snakes which use hollow teeth (fangs), the Gila monster injects venom into its victim through grooves in the teeth of its lower jaw. Each of the teeth is loosely anchored to allow them to be broken off and is easily replaced throughout their lives. The Gila monster produces only small quantities of its neurotoxic venom, which is secreted into the lizard's saliva. By chewing its prey, however, it tries to put as much of the poison into the bloodstream of its victim as possible. The Gila monster's bite is normally not fatal to humans (there are no reliable reports of fatalities), but it can bite quickly and holds on tenaciously.
The Gila monster's diet generally consists of small rodents, juvenile birds as well as eggs of both birds and reptiles. The Gila monster eats large meals infrequently and can consume a meal of one third of its body weight. Reduced feeding is due to low metabolism and relatively cool body temperature. Young Gila monsters are known to be able to consume up to 50% of their body weight in food. An adult Gila monster can consume its entire yearly energy budget in three or four meals. In order to find nests and young juvenile prey, the Gila monster has a keen sense of smell and hearing; using these senses, it can use ground vibrations to find food in burrows, on the ground, or in vegetation. They can store food in their tails as well. The tail, which contributes nearly 40% of total body length, is alternately marked with four or five black or brown bands, which serve as a type of fingerprint – no two Gila monsters are alike.
There is no apparent sexual dimorphism within this species, but it is noted that males are larger, have a wider head, and also have a squarer frame than females. Female Heloderma suspectum tend to have an oval shaped body. Heloderma suspectum are relatively social creatures. Studies have shown that they recognize and interact with many individuals throughout their home range and have been seen in burrows together in separate years. In late April through late May, six or more individuals may occupy burrows at a time.
Gila monsters are oviparous, meaning that they lay eggs. Five eggs is the average clutch size, but can reach up to twelve eggs at a time. In southern Arizona, Gila monsters breed in May and June and lay their eggs in June and August of the following year. These eggs then incubate in burrows and develop from fall to the early spring, and young appear in April and June. Interestingly, no other egg-laying lizard in North America over-winters their eggs and hatches them the following year, like Heloderma suspectum does. When captively bred, the gestation period of a Gila monster is 42-55 days.
It is against Arizona State law to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect this animal or any attempt to engage in such conduct. Humans are the number one predator of the Gila monster. Habitat destruction and pollution are the major threats to the well being of the lizard. Other predators include dogs, the Harris hawk, and the red-tailed hawk.
In 2005 the Food and Drug Administration of the United States approved a drug for the management of type 2 diabetes, Byetta (exenatide), a synthetic version of a protein derived from the Gila monster's saliva. The drug is sometimes referred to humorously as 'lizard spit'.
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[edit] Conservation status
Gila monsters are a protected species under Arizona state law in the United States, and may not be collected, killed, or kept in captivity without a license in that state. They are listed as a threatened species under the United States Federal Endangered Species Act, as well as in Mexico. They also appear in Appendix II of CITES, which puts restrictions on their export. The main threat to the species is human encroachment and habitat destruction.[1]
[edit] Media
The low budget Hollywood movie called "The Giant Gila Monster" was filmed using a live beaded lizard on scaled down scenery.
[edit] References
- Beaman (1996). Heloderma suspectum. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Listed as Vulnerable (VU A2cd v2.3)
