Gila monster

(Heloderma suspectum)




Facts about this animal

It is a heavy, slow moving lizard, up to 60 cm long. The skin has the appearance of black, pink, orange, and yellow beads, laid down in intricate patterns. These beads are small bony plates that form scales, and are known as osteoderms. The broad head, chin, and neck are black, as well as the legs and feet. The Gila monster, like most snakes, uses its – forked - tongue for olfaction. Gila monsters are mainly diurnal and terrestrial but infrequently climb into vegetation. Refuges include spaces under rock, dense shrubs, burrows, or woodrat nests. Sub-surface shelters are also important components of the habitat. Gila monsters spend more than 95 % under cover and can be seen basking near shelters only occasionally. They are oviparous (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. No other egg-laying lizard in North America over-winters their eggs and hatches them the following year, like Heloderma suspectum. Gila monsters are the most venomous lizard native to the USA However they produce only small quantities of their neurotoxic venom, which is secreted into the saliva. By chewing their prey, they put venom into the bloodstream of their victims. Prey is however rarely envenomated, which indicates that venom is used mainly for defense. Their diet generally consists of small rodents, juvenile birds as well as eggs of both birds and reptiles and now and then another reptile.

Did you know?
that 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 Cope's notion that the lizard might be venomous due to the grooves in the teeth The Gila monster eats large meals infrequently and can consume a meal of one third of its body weight. Young Gila monsters are known to be able to consume up to 50% of their body weight. An adult Gila monster can consume its entire yearly energy budget in three or four meals. A fat reserve can be stored in the tail. Their food requirements are reduced by a low metabolic rate, as well as the relatively cool body temperatures they maintain for most of the year. 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 shelters together in separate years. In late April through late May, six or more individuals may occupy burrows at a time.


Name (Scientific) Heloderma suspectum
Name (English) Gila monster
Name (French) Lézard perlé, Monstre de Gila
Name (German) Gila Krustenechse
Name (Spanish) Monstruo de Gila
CITES Status Appendix II
CMS Status Not listed



Photo Copyright by
U.S. Fish and Wildlife Service



Range Mexico, USA (southwest)
Habitat Desert grassland, Mohave and Sonoran desert scrub, and thorn scrub; less often oak or pine-oak woodland. Canyon bottoms, arroyos (dry creeks), and rocky slopes may support relatively dense populations. It occurs also in wetter and rockier palo verde-sahuaro desert but rarely in agricultural areas. Its elevational range extends from near sea level to 1,950 m.
Wild population The species is fairly common in at least some parts of the range, but never very abundant. The total adult population size is unknown but is probably at least several thousand. Nevertheless the populations are declining over most of the United States range due to illegal exploitation by commercial and private collectors as well as habitat destruction due to urbanization and agricultural development. The Gila monster is legally protected in all states in which it is found however it is killed quite often, because it is poisonous. The population trend is to decrease (Red List IUCN 2011).
Zoo population 365 reported to ISIS (2007)

In the Zoo

Gila monster


How this animal should be transported

For air transport, Container Note 41 of the IATA Live Animals Regulations should be followed.


Find this animal on ZooLex


Photo Copyright by
Micha L. Rieser

Why do zoos keep this animal

Heloderma suspectum is a vulnerable species. In 1990, an International Studbook was initiated, but this was discontinued in 1998 and coordinated ex- situ breeding efforts are since taking place at the regional level.

As Heloderma is the best-known venomous lizard genus, keeping Gila monsters is also of educational interest.