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Gila monster

Scientific name: Heloderma suspectum

Country: USA, Mexico

Continent: North America

Diet: Small mammals, birds, lizards, eggs

Food & feeding: Carnivore

Habitats: Scrub forest, desert and semi-desert

Conservation status: Near threatened

Relatives: Blue-tongued skink, Komodo dragon

Description: The Gila monster is a large ground-dwelling lizard, named after the Gila River Basin of south-western United States. It is heavily built with a large blunt head, short thick tail and grows to about 60 cm in length - the largest lizard in the United States. It has black, orange, pink or yellow blotches, bars and spots with bands extending across its tail and raised knobbly scales across its back.

Lifestyle:.The Gila monster has a keen sense of smell to help locate food, but it is slow moving and therefore tends to hunt slow moving prey. It feeds on nesting birds or rodents and the eggs of birds and reptiles. It uses its twitching tongue and Jacobson's organ (a double pit in the roof of the mouth which picks up scent particles enabling it to know what it is tasting and smelling) to locate prey, which it then seizes and bites. It can eat a third of its body weight in one meal. The Gila monster is one of only two species of venomous lizard, both belonging to the family Helodermatidae, that are similar in appearance and habitat. Its venomous cousin, the Mexican beaded lizard (Heloderma horridum) is slightly larger and darker. Most of the Gila monster's teeth have two grooves which conduct the venom from the lower jaw. The toxin is not injected like snake venom but instead flows into the wound as the lizard chews its victim. Small animals die very quickly from the venom, which attacks the nervous system and causes paralysis of the respiratory muscles. The effectiveness of the venom varies in humans but it is rarely fatal. The poison may be used more for defence than attack.

During the hottest months, the Gila monster is most active at night, staying in its burrow during the day. Fat stored in its abdomen and tail is used during the winter months when it hibernates and may need to survive for long periods without food or water.

Family & friends: The Gila monster is generally a solitary animal, coming together only to breed.

Growing up: Gila monsters mate throughout the summer and leave their 3-5 large eggs during the autumn or winter (this is unusual). They are left to incubate in a hole in the sand for about three months after which the young, about 20 cm in length, hatch out. In captivity, they can live for over 20 years.

Conservation news: The main threats to the Gila monster are human development of the arid scrub areas where it lives and attack by feral or domestic cats and dogs.

Bristol Zoo’s Gila monsters are part of a European breeding programme (EEP).