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Heloderma suspectumGila Monster

By Matthew D. Stewart

Ge­o­graphic Range

The Gila mon­ster ranges from the ex­treme south­west­ern Utah, south­ern Nevada, and ad­ja­cent San Bernadino County, Cal­i­for­nia, south­eas­tr­ward through west and south Ari­zona and south­west­ern New Mex­ico. It ranges south into Mex­ico through Sonora to north­west­ern Sinaloa. It ranges from sea level to 1,500 me­ters in al­ti­tude. (Ernst, 1992)

Habi­tat

The Gila mon­ster can be found in arid areas. These areas usu­ally con­tain scat­tered cacti, shrubs, mesquite, and grasses. Rocky slopes, ar­royos, and canyon bot­toms (mainly those with streams) sup­port pop­u­la­tions in Ari­zona. (Ernst, 1992)

Phys­i­cal De­scrip­tion

This is one of only two ven­omous lizard species in the world (the other is the Mex­i­can beaded lizard, Helo­derma hor­ridum). Gila mon­sters are large and stout lizards with a short fat tail (max­i­mum length of 56 cen­time­ters). Their scales are beaded yel­low, pink, and black. The broad head, chin, and neck are black, as well as the legs and feet. The black eyes have a round pupil. The ear open­ing is a nar­row oblique or ovoid slit. The limbs of the lizard are stout and have heavy claws. (Ernst, 1992)

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 (1-12) 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. (Ernst, 1992)

Lifes­pan/Longevity

Be­hav­ior

Few data are avail­able on the pop­u­la­tion struc­ture and dy­nam­ics of the Gila mon­ster be­cause the or­gan­isms are ex­tremely dif­fi­cult to sex. The Gila mon­ster is a di­ur­nal for­ager. It is re­ferred to as being a "docile rep­tile." (Ernst, 1992) ( http://​www.​Pharmacy.​Arizona.​EDU/​centers/​poison_​center/​critters/​reptiles/​gila mon­ster.|)

Food Habits

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. (Ernst, 1992) (Bogert, 1956)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

The Gila mon­ster has lit­tle eco­nomic im­por­tance to hu­mans. There is a small mar­ket for the hemipe­nis, which is used as an aphro­disiac. A small "pet" mar­ket for the species has also arisen. It is il­le­gal, how­ever, for the Gila mon­ster to be cap­tured or held in the states where it ex­ists. The rep­tiles can be found in many zoos. (Bogert, 1956) ( http://​www.​Pharmacy.​Arizona.​EDU/​centers/​poison_​center/​critters/​reptiles/​gila mon­ster)

Con­ser­va­tion Sta­tus

The lizard is often killed be­cause it is poi­so­nous. The Gila mon­ster is legally pro­tected in all states in which they are found. (Ernst, 1992) (Bogert, 1956)

Other Com­ments

The Gila mon­ster lacks the abil­ity to jump, con­trary to pop­u­lar myth (Ernst, 1992)

Con­trib­u­tors

Matthew D. Stew­art (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

native range

the area in which the animal is naturally found, the region in which it is endemic.

Ref­er­ences

Ernst, C.H. 1992. Ven­omous Rep­tiles of North Amer­ica. Smith­son­ian In­sti­tu­tion Press, Wash­ing­ton.

Bogert, C.M. 1956. The Gila mon­ster and its Al­lies. Vol­ume 109. Amer­i­can Mu­seum of Nat­ural His­tory, New York.

http://​www.​Pharmacy.​Arizona.​EDU/​centers/​apdic/​gilamonster.​shtml

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Classification

  • Kingdom Animalia animals
  • Phylum Chordata chordates
  • Subphylum Vertebrata vertebrates
  • Class Reptilia turtles, snakes, lizards, and relatives
  • Order Squamata
  • Family Helodermatidae
  • Genus Heloderma
  • Species Heloderma suspectum Gila Monster