The Grand Canyon Chuckwalla

The stout-bodied chuckwalla is the second largest lizard in the United States, next in size only to the gila monster. A male individual can measure up to 18 inches in total length, while the female is somewhat smaller. I swear this one was over two feet. They are found primarily in arid regions of the southwestern United States and northern Mexico. I stumbled upon this big fellow basking on a rock along the banks of the Colorado River at the bottom of the Grand Canyon. That day it reached 120 degrees!

The “chuck” is, not surprisingly, a relative of the iguana. These large, plump lizards have loose folds of skin around the neck and shoulders. The chuckwalla is a diurnal lizard that emerges in the morning, and before seeking food, basks in the sun until its optimum body temperature of 100-105 degrees F. is reached. The chuckwalla is an herbivore, feeding on wildflowers, fruits and leaves of creosote and, to a lesser extent, on other perennials and annuals.

Harmless to humans, these lizards are known to run from potential threats. When disturbed, a chuckwalla will wedge itself into a tight rock crevice, gulp air, and inflate its body in order to entrench itself. Chuckwallas may live for 25 years or more. This species requires rocky cover such as large rock outcrops, boulder piles or scattered large rocks, usually on a slope but often on a flat. Chucks like to position themselves high on a rock, so that they can survey their surroundings. They are big and they look mean, but are harmless.