Gila monster

The Gila monster is a slow, heavy, venomous lizard of the southwestern United States and the Mexican state of Sonora. It is the only venomous lizard native to the United States and the largest lizard native to the United States and Canada. It grows to about 56 centimetres long and weighs 550 to 800 grams. The name comes from the Gila River basin in Arizona and New Mexico.

Its skin looks like beads of orange and black. The scientific name Heloderma means 'studded skin'. The lizard has a fearsome reputation, but it is sluggish and rarely a real danger to humans, although a bite is painful. It is protected by state law in Arizona, and our card says it spends most of its time in burrows and stores fat in its tail to go without food for months.

How does the venom work?

The lower teeth have grooves that carry venom into the wound. The venom contains several peptides, small protein pieces. One of them, exendin-4, became the basis for a type of medicine called GLP-1 receptor agonists, used to treat type 2 diabetes and obesity. So a lizard that people feared has helped people with illness. The Gila monster is heavy, strong and slow, and it is sluggish by nature, so it is not generally dangerous. Its bite is painful, though.

Ancient family

Its relatives are beaded lizards in Mexico and Guatemala. The family Helodermatidae goes back to the Cretaceous period, and the animals have changed so little that they are sometimes called living fossils. Pieces of Gila monster bone armour from the Late Pleistocene, 10,000 to 8,000 years ago, have been found near Las Vegas, Nevada. The paleontologist Edward Drinker Cope, who described the species, suspected from the grooves in its teeth that the lizard was venomous.

On the globe

The toy model of the Gila monster is in the Sonoran Desert of Arizona. Look for the orange-and-black beaded pattern.