Gila monsters spend 95 percent of their time underground. ... Their bulky bodies, slow-moving stride, thick forked tongue, and snorting hisses reinforce the name Gila monster. They live in the dry, arid regions such as the Mojave..In fact, the Gila monster is the largest lizard in the U.S. Gila monsters can grow 2 feet long, but they only weigh about 5 pounds. They have a thick tail that stores fat. Gila monsters are one of the few lizards that have a venomous bite. Get facts and watch videos about these cold-blooded creature.