Nature’s Way: Venomous Reptiles in Our Neighborhood

Gila monster (photo by Gerry Tietje)

Gerry Tietje

If you have seen a Gila monster in the wild, you are fortunate, because it’s a rare occurrence for most people. I’ve been fortunate to see two of them in the wild, one that was crossing South Reddington Road near San Manuel and the other on a trail in Saguaro National Park East.

Gila monsters were first discovered in the late 1800s in the Gila River Basin and were named after this region. They are the largest lizards native to the United States, some reaching a length of two feet, and the only ones that are venomous. Their jet-black bodies, interspersed with bright orange, yellow, or pink patterns, are covered from snout to tail with pearl-shaped bony bumps that act as protective armor and give them a bead-like appearance. Grooved teeth in their lower jaws allow venom to reach a victim when they chew, unlike venomous snakes that inject venom through fangs. Gila monsters use their venom primarily for defense, and not to disable and kill prey. If bitten, a human will have painful swelling and other reactions to the bite, but there is little chance of death; therefore, no antivenom has been developed. However, a peptide in the venom of Gila monsters has been synthesized to provide a type 2 diabetes medicine.

Gila monsters spend most of their lives in burrows of other mammals, in pack rack nests, and under large rocks. They hibernate from November to March. When they emerge, it is usually to find food, find mates, and procreate. They are most active in April through June, when their food sources are readily available. Gila monsters are too slow to chase their prey, and are instead nest robbers. With a flick of their bluish-black, forked tongues they collect scent particles that are transmitted to their Jacobson’s organ, a scent-detecting organ found in many reptiles. This allows them to readily find nests and devour eggs and young birds, reptiles, and small mammals. Gila monsters can even climb trees and cacti to reach bird nests. Since they have a very slow metabolism and store fat in their large, plump tails, they can live on three or four large meals a year! They also store water in their bladders and can go without drinking for more than two months. Male Gila monsters wrestle other males for dominance, going several rounds before pinning the loser to the ground. Although they attempt to bite their opponent, its bony body armor usually allows the loser to meander away unscathed. The dominant males mate with females that later lay four to six eggs; the eggs hatch in October, when the young Gila monsters begin their secluded lives.

I hope you will consider it a real treat if you encounter a Gila monster in the wild. They are not a threat unless handled, although they may produce a hissing sound if you get too close to them. Gila monsters are another wonder of nature found in our neighborhood.