On The Desert Chuckwalla
NOTE: This is the first article in a two-part series on the chuckwalla by Dr. Kristin Berry, zoologist on BLM's Desert Plan Staff at Riverside.
By Dr. Kristin Berry
BLM Zoologist
THE chuckwalla is a large lizard that is closely related to the marine and land iguanas of the Galapagos Islands, the large green iguana of Mexico, and the spiny iguanas of Mexico and Central America. All of these lizards feed on plant material, and all. with the exception of our chuckwalla, are tropical or subtropical lizards.
Geographic Range and Habitat
The chuckwalla occurs in the deserts of California, southern Nevada, southern Utah, and western Arizona south into Sonora, Mexico. In California, the northernmost extension of the geographic range is at Westgard Pass in the Inyo Mountains; the extreme western edge is at Red Rock and Jawbone Canyons in eastern Kern County.
Chuckwallas have specialized habitat requirements. They are rock-dwellers and live in large rock outcrops, boulder jumbles, lava flows, and sometimes in sandstone cliffs. Their bodies are specialized for living under rocks and in crevices. When disturbed, they gulp air, inflate the lungs, and tightly wedge into a crevice or crack. Often they can be removed only by destroying the rocks.
The habitats vary considerably throughout the geographic range. In Mexico, chuckwallas live along the coast at sea
Research Project
My research project. which spanned four years between 1968 and 1971 , focused on the ecology, social behavior, and adaptive strategies of the chuckwalla for living in a harsh environment. A study site was selected in the Argus Range on the Naval Weapons Center, China Lake, in an area untouched by man for over 30 years. The chuckwalla populations were believed to be undisturbed and at high densities. During the study. 116 chuckwallas were captured and marked.
Growth and Aging
Chuckwallas are long-lived lizards. Males may live to be 20 or more years of age and females 40 or more. Growth rates vary considerably and depend upon sex, age, food availability, and social position.
All chuckwallas grow rapidly after hatching; they double in body length by the end of the first spring. After the first year, growth slows. The time to reach adulthood or sexual maturity varies with sex, with males growing about twice as fast as females. It takes a male a minimum of 3 to 6 years to reach maturity and a female 6 to 9 years. The time to reach maturity may be lengthened considerably if food is not available, as during a drought.
Males and females are adults when their body length is 6 inches (the length without the tail). The maximum body size is slightly over 8.5 inches. With the added length of about 9