Gila Monsters — Reading Comprehension Lesson

Reading Passage

Gila Monsters

The Gila monster is one of only two venomous lizards native to North America, the other being the closely related Mexican beaded lizard. Gila monsters are large, slow-moving lizards that can reach up to two feet in length and weigh up to five pounds. They are found in the Sonoran and Mojave Deserts of the southwestern United States and northwestern Mexico, living in rocky areas, desert scrub, and dry grasslands.

Gila monsters have distinctive beaded skin covered with bumpy scales called osteoderms, which contain small bones for added protection. Their skin is typically patterned in orange or pink and black, which may serve as a warning to predators that the animal is venomous. Unlike venomous snakes, Gila monsters deliver venom through grooved teeth in their lower jaw rather than through hollow fangs, chewing the venom into a wound rather than injecting it.

Gila monsters are well-adapted to desert life. They store fat in their thick tails, which allows them to survive for months without food. In fact, Gila monsters spend up to 98 percent of their lives underground in burrows, emerging mainly in spring and early summer to feed and find mates. Their metabolism is so slow that they may eat fewer than ten large meals per year. They feed mainly on bird and reptile eggs, small rodents, and nestlings.

Despite their fearsome reputation, Gila monsters are not aggressive toward humans and rarely bite unless handled. Their venom is primarily defensive rather than used to subdue prey. Gila monsters are protected by law in the United States and are listed as near threatened due to habitat loss and collection for the illegal pet trade. A compound derived from Gila monster saliva led to the development of a widely-used diabetes medication.

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