One of the only two species (both in the family Helodermatidae) of venomous lizards , named for the Gila River basin and found in the southwestern U.S. and northern Mexico.
The Gila monster ( Heloderma suspectum ) grows to about 20 in. (50 cm) long, is stout-bodied with black and pink blotches or bands, and has beadlike scales. During warm weather, it feeds at night on small mammals, birds, and eggs and stores fat in the tail and abdomen for the winter. It is sluggish but has a strong bite. The venom (a neurotoxin) is conducted along grooves in the teeth from glands in the lower jaw. Bites are rarely fatal to humans. The other venomous species is the Mexican beaded lizard ( H. horridum ).