They live primarily underground in self dug burrows, burrows left by other animals, or under rocks. Gila monsters measure 16 to 24 inches and may weigh up to 3.5 pounds with a large heavy body, massive head, and sausage shaped tail. Their body is covered with small, round, closely set scales and patterned with contrasting markings of orange, yellow, or pink and black. Their limbs are short with strong powerful claws. Their tail serves as a fat storage organ which they utilize when food is scarce and they can survive several months without eating.
Gila monsters are nocturnal and are one of only two known venomous lizards.
Their venom is produced in glands along the lower jaw and is not injected like snakes but rather it flows into the open wound as the lizard chews on its victim. Most prey can be taken without venom and it appears that the venom is used primarily for defense instead of killing prey. Their jaws are extremely powerful and well known for its persistent death grip. Gila monsters are carnivores who seem to rely more on taste and smell to hunt than on vision. They often track prey by licking the ground to pick up scents with their forked tongues.