Description: This species is the largest of the lizards found in the United States. Contrary to the usual sleek forms of most lizards, the Gila monster is a stoutly built, plump animal with a thick tail, short but sturdy legs, and wide feet that end in five toes tipped with short, sharp, curved claws. Its head is large and roughly oval in shape and ends in a blunt nose.

The upper part of the body is covered with sturdy, bead-like scales that fit side by side rather than being overlapped like the scales of most lizards. The scales toward the belly transition to more plate-like structures. The basic background color is black with varied patterns of pink to orange to yellow. The nose, jaws, and eyes are dark in color.

Habitat: Gila monsters are most commonly found in desert lowlands and rocky mountain foothills, but on occasion may be found at altitudes of up to 5,000 feet. They prefer areas that are moist enough to support desert scrub shrubs, palos verde trees, and some cactus species, but will also frequent more arid sandy areas. They generally avoids cleared or open areas such as agricultural lands.

Range: Sonoran, Mojave, and Chihuahuan deserts including southwest Utah, southwest New Mexico, southern Nevada, the southeastern tip of California, and northern Mexico.

Found in these States: AZ | NM

Venom: The venom of a Gila monster is normally not fatal to healthy adult humans. No reports of fatalities have been confirmed after 1930, and the rare fatalities recorded before that time occurred in adults who were intoxicated by alcohol or had mismanaged the treatment of the bite. The Gila monster can bite quickly, and may not release the victim without intervention. If bitten, the victim may attempt to fully submerge the lizard in water, pry the jaws open with a knife or stick, or physically yank the lizard free. While pulling the lizard directly increases risk of severe lacerations from the lizard's sharp teeth, it may also mitigate envenomation. Symptoms of the bite include excruciating pain, edema, and weakness associated with a rapid drop in blood pressure.

Diet: The Gila monster's diet consists of a variety of objects: small mammals (young rabbits, mice and squirrels), birds, lizards, and eggs (of birds, lizards, snakes, turtles, and tortoises). The Gila monster has the capability to consume large amounts of food at one time (young can consume 50% of their body weight at a single feeding, adults can consume 35%). This is advantageous in an envirnoment in which finding prey at regular intervals may be difficult. Prey are rarely envenomated, which indicates that venom is used mainly for defense. Prey are detected by olfaction (the sense of smell). The Gila monster, like most snakes, uses its tongue for olfaction.

Reproduction: Mating, which is usually in May, begins with the male tongue-flicking to seek a females's scent, while rubbing his cloaca on the ground. When a male locates a female, he lies by her and rubs his chin on her back and neck while holding her with his hindlegs. If a female objects to the male, she will try to bite him while crawling out from underneath. If receptive, she raises her tail. The male then moves his tail under hers, bringing their vents into contact. Copulation lasts from 30 minutes to an hour. The female lays her eggs (1 to 12) in an underground cavity, normally in July or August. Incubation lasts on average about ten months, and the young to hatch and emerge the following May. The process (fertilization through emergence) lasts about a year.

Status: There are no federal regulations protecting Gila monsters; however, Mexico and all states where they occur naturally (Arizona, New Mexico, Nevada, Utah, and California) protect these animals, requiring permits for their possession. California lists the banded Gila monster subspecies, H. suspectum cinctum, which is native to California, as a species of special concern. Private individuals are not given permits to keep the lizard. The are illegally captured for pets.

Probably the greatest danger to these animals is human encroachment and the loss of habitat due to the clearing of land for agricultural and residential purposes and the construction of roads.

The Gila monster is designated as Near Threatened in the IUCN Red List (2007). It is also listed in CITES – Appendix II, which regulates trade of certain species and animal products.

Taxonomy: