The Common Chuckwalla is an impressive sight, a sizable lizard of the iguana family, some 16 inches long. His head is flat and loose skin sags at his neck and sides. His crowning glory is his tail, fat and orange like a carrot. Although his appearance is a bit scary, a chuckwalla’s method of defense is to scurry into a crevice and gulp air until inflated and tightly wedged.
Various chuckwallas have frequented the area behind our house over the years. We’ve learned that females’ tails are grey rather than orange, and juveniles’ tails are banded. For several years a particularly imposing chuckwalla reigned at the fountain location. “Chuckzilla” had a habit of cocking one front leg under his chin in a most imperious manner. He would drop behind the fountain if approached, but was fearless in a stare down. Once while I watched him, he noticed a smaller male chuckwalla near the property line. Moving with amazing speed, Chuckzilla chased the youngster down, rolled him on the ground a couple of times and dispatched him into the desert.
Several ASU grad students have made research projects of the South Mountain chuckwallas because the males’ orange tail color is unique among the species. Other common chuckwallas have black or white tails depending on where they live. The researchers have concluded that the rich plant diet found at South Mountain provides carotenoid pigments that make the tails orange. The males with territories supporting the lushest plant growth sport the brightest color. These are also the males that attract the most females. South Mountain is a good place to study chuckwallas as there is a higher concentration of the reptiles here than anywhere else. The mountain’s igneous rock (granodiorite) fractures into layers and forms stacks of boulders creating many crevice habitats.
Chuckwallas hibernate until mid February and lay eggs in the summer. The hatchlings emerge in the early fall. Only a very small percentage of the bulky lizards reach reproductive age, making the population vulnerable to habitat destruction and other pressures by humans. Poachers from the pet trade have been caught taking chuckwallas from South Mountain, attracted by the unusual tail color. If you are lucky to see a chuckwalla remember they are herbivores. They won’t hurt you, and you shouldn’t mess with them either.