The Gila Monster is a species of venomous LIZARD native to the southwestern United States and northwestern Mexico. It is the only species in the genus Heloderma and is one of the two species of venomous lizards in North America, the other being the Mexican beaded LIZARD. The Gila Monster is a large LIZARD, growing up to 24 inches in length and weighing up to 5 pounds. It is characterized by its bright orange or yellow coloration with black markings, and its thick, leathery skin. It is an ambush predator, feeding on small mammals, birds, and eggs.