Gila monster

Facts

IUCN NEAR THREATENED (NT)

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.

Factsheet
Class	REPTILIA
Order	SQUAMATA
Suborder	SAURIA (AUTARCHOGLOSSA)
Family	HELODERMATIDAE
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

Distribution

Distribution
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

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.

How this animal should be kept

Gila monsters are rather large animals, and need large enclosures. The minimum dimensions for an individual gila monster enclosure should be 1.5 x 0.7 x 0.7 m), bigger is always better. The substrates can include playground sand, bark chips, or naturalistic substrate. Gila monsters do like to dig; a mixture of playground sand, peat moss, and bark chips, which allows these animals to construct hiding areas, may therefore be a good substrate choice.

They do well with a thermal gradient of 24-27 degrees C on the cool end and a warm spot of (29-32 degrees C).

They should also be provided with a humidity site. Humidity sites can be constructed out of plastic containers large enough to hold one gila monster. An access hole should be cut into one end of the container and moist peat moss or sphagnum moss placed inside to fill up about half the volume of the box. Gilas will often utilize such areas for a significant portion of the day. Other hiding areas should also be provided, so the animals can choose their preferred environmental conditions. At night, the temperature may be allowed to drop to 21-24 degrees C.

Gila monsters should be hibernated (from app. November to March) to encourage successful reproduction. Two weeks before cooling down, they should not be fed anymore, allowing their digestive tracts to clear. After the clearing period, the ambient temperature should be lowered over the period of two weeks until the hibernation temperature of 10-12.7 degrees C is reached. Hibernating gilas should be provided with access to water at all times to prevent dehydration. Unlike the situation in nature, gestation in captivity runs only from 35-55 days. When the female is close to oviposition, she will often shed. This is a signal to move the female into her own quarters and provide an egg-laying chamber. The eggs should be incubated in slightly moist vermiculite (1:3 ratio water to vermiculite by weight). Gila monster eggs do not tolerate very high humidity, and are prone to fungal attacks. The humidity in the incubator should be 50-60%. Incubation temperatures should range from 25.5-27.7 degrees C. The eggs generally hatch in 120-150 days.