Chuckwalla Facts

The chuckwalla is a large, desert-dwelling lizard in the iguana family, Iguanidae. All of the chuckwalla species are in the genus Sauromalus, which roughly translates from Greek to mean "flat lizard." The common name "chuckwalla" comes from the Shoshone word tcaxxwal or Cahuilla word čaxwal, which Spanish explorers transcribed as chacahuala.

Species

Six chuckwalla species are recognized:

• Common chuckwalla (Sauromalus ater): Found in both the United States and Mexico
• Peninsular chuckwalla (S. australis): Inhabits Baja California
• Angel Island chuckwalla (S. hispidus): Also known as the spiny chuckwalla, found on Isla Ángel de la Guarda and several smaller islands in the Gulf of California
• Santa Catalina chuckwalla (S. klauberi): Also known as the spotted chuckwalla, found on the Baja California peninsula and several islands in the Gulf of California
• San Esteban chuckwalla (S. varius): Also known as the piebald or pinto chuckwalla, only found on San Esteban Island in the Gulf of California
• Monserrat chuckwalla (S. slevini): Also known as Slevin's chuckwalla, found on three islands in the Sea of Cortés

Description

Chuckwallas are wide-bodied, flattened iguanas with thick tails that taper to blunt tips. They are sexually dimorphic. Males are larger than females and have black heads and limbs with gray, yellow, orange, or pink bodies. Females and juveniles are colored in alternative gray and yellow bands or red or yellow spots. Males also possess femoral pores inside their legs that secrete fluid used to mark territory.

Common chuckwallas reach a length up to 20 inches and a weight up to 2 pounds. Island species grow larger and may reach lengths up to 30 inches and weights up to 3 pounds.

Habitat and Distribution

Chuckwallas live in rocky North American deserts. They are widely distributed in the Mojave and Sonoran deserts. The common chuckwalla occurs from southern California, Nevada, Utah, and Arizona, to Baja California and northwestern Mexico. The peninsular chuckwalla lives in the southern portion of Baja California, while the other species only live on islands off the Baja peninsula. Chuckwallas live from sea level up to 4.500 feet of elevation.

Diet

Chuckwallas are primarily herbivores. They feed on flowers, fruit, and leaves. The lizards primarily eat creosote bushes and cholla cacti, but they also feed on other yellow flowers. Sometimes they supplement their diet with insects.

Behavior

The lizards are well-adapted to desert living. They bask in the sun in the early morning and throughout the day in cooler weather, remaining active at temperatures up to 102°F. The lizards typically seek an elevated position to bask. When a threat is detected, they wedge themselves into crevices and inflate their lungs with air, making them difficult for predators to remove. When temperatures become too hot, chuckwallas retreat to a crevice and enter a period of inactivity called aestivation. They enter brumation (similar to hibernation, but with periods of wakefulness) in winter and emerge in February.

Reproduction and Offspring

Mating occurs between April and July. Males become territorial during the breeding season. They establish a dominance hierarchy and attract females using flashes of color from their skin and mouths and performing physical displays, such as head-bobbing, push-ups, and mouth-gaping. Females lay between five and 16 eggs in a nest in the summer, between June and August. The eggs hatch around late September, with development depending on temperature. Females do not guard the nest or raise the young. In general, iguanas reach sexual maturity after two to five years. Chuckwallas live for 25 years or longer.

Conservation Status

Chuckwalla conservation status varies according to species. The International Union for Conservation of Nature (IUCN) classifies the status of the common chuckwalla as "least concern." The Catalina chuckwalla and piebald chuckwalla are "vulnerable," while Slevin's chuckwalla is "near threatened" and the spiny chuckwalla is "endangered." The peninsular chuckwalla has not been evaluated for a conservation status. The common chuckwalla population is stable, but populations of the other species are unknown or decreasing.

Threats

Populations are threatened by excessive collection for the pet trade, which not only removes the lizards, but also typically results in microhabitat destruction, as rocks or vegetation are moved to expose the animals. Chuckwallas also suffer from habitat destruction and degradation by river damming and grazing by ranch animals.

Chuckwallas and Humans

Chuckwallas flee from threats, are not venomous, and pose no harm to humans. The Angel Island species was an important food source to the indigenous population.

Sources

• Hammerson, G.A. Sauromalus ater . The IUCN Red List of Threatened Species 2007: e.T64054A12740491. doi:10.2305/IUCN.UK.2007.RLTS.T64054A12740491.en
• Hollingsworth, Bradford D. The Evolution of Iguanas an Overview and a Checklist of Species. Iguanas: Biology and Conservation. University of California Press. 2004. ISBN 978-0-520-23854-1.
• Hollingsworth, Bradford D. "The Systematics of Chuckwallas (Sauromalus) with a Phylogenetic Analysis of Other Iguanid Lizards." Herpetological Monographs. Herpetologists' League. 12: 38–191. 1998.
• Montgomery, C.E.; Hollingsworth, B.; Kartje, M.; Reynoso, V.H. Sauromalus hispidus. The IUCN Red List of Threatened Species 2019: e.T174482A130061591. doi:10.2305/IUCN.UK.2019-2.RLTS.T174482A130061591.en
• Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians (3rd ed.). Houghton Mifflin Company. 2003. ISBN 0-395-98272-3.