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Northern Chuckwalla

Sauromalus ater

What do they look like?

Common chuckwallas are stout lizards with skin folds near the neck, shoulders, and stomach. They have five digits on each limb and the tail thicker near the body and rounded at the tip. Common chuckwallas come in various colors, depending on where they live, temperature, and mood. Their heads are usually darker and are dark brown to yellow. Males are slightly larger than females and males tend to be darker in color, overall, than females or young common chuckwallas. They have a snout to vent length of 80 to 197 mm and weigh from 24 to 315 grams. Their tails are about half their body length.

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • male more colorful
  • sexes shaped differently
  • Range mass
    24 to 315 g
    0.85 to 11.10 oz
  • Average mass
    245 g
    8.63 oz
  • Range length
    80 to 197 mm
    3.15 to 7.76 in
  • Average length
    162 mm
    6.38 in

Where do they live?

Common chuckwallas are found in deserts in the western United States and Mexico and 30 known islands in the Gulf of Mexico. They can be found as far west as southeastern California and Nevada, and are abundant in Arizona, New Mexico, Texas, Utah, and parts of Colorado. (Hammerson, 2007; Hollingsworth, 1998; Johnson, 1965)

What kind of habitat do they need?

Common chuckwallas are found in deserts with rocks and crevices for hiding, such as areas of past lava flows, rocky hillsides, and outcrops. They use underground burrows and crevices for hibernation in the winter. Common chuckwallas can be found between sea level and 1400 m elevation. (Cliff, 1958; Hammerson, 2007; Johnson, 1965; Montanucci, 1997)

  • Range elevation
    1400 (high) m
    4593.18 (high) ft
  • Range depth
    0 (low) m
    0.00 (low) ft

How do they grow?

Females lay eggs in an underground nest and the young hatch after about a month, after which they are independent. Common chuckwallas grow at a rate of about 17 mm a year. They reach sexual maturity at around ages 2 or 3. Growing to adult size takes about 25 years, after which they continue to grow but at a significantly decreased rate of about 5.5 mm a year. Their rate of growth is determined by temperature and food abundance, they grow more and shed their skin during the spring and summer, when food is plentiful and it is warm. (Hammerson, 2007; Johnson, 1965)

How do they reproduce?

Common chuckwalla males use head-bobbing, licking, circling, nudging, jaw-rubbing, and other methods to persuade females to mate. They generally mate with several females that are found within their territory. Mating usually takes place in the early spring after hibernation. (Montanucci, 1997; Nagy, 1973)

Common chuckwallas breed between April and August when food is most abundant. Females lay from 5 to 16 eggs each year or every other year, depending on food availability and rainfall. Females incubate the eggs until they hatch, after about 35 days. Males reach sexual maturity when they reach a 125 mm snout-vent length, or at about 2 years old. Females reach sexual maturity at the same length, but may take 2 to 3 years to reach that length. (Friends of the Rosamond Gifford Zoo Education Volunteers, 2008; Johnson, 1965; Montanucci, 1997)

  • How often does reproduction occur?
    Common chuckwallas may not breed every year, but they breed in years of heavy rainfall and abundant food.
  • Breeding season
    Breeding takes place from April to August.
  • Range number of offspring
    5 to 16
  • Average number of offspring
    8
  • Range gestation period
    33 to 50 days
  • Average gestation period
    35 days
  • Average time to independence
    immediate minutes
  • Range age at sexual or reproductive maturity (female)
    2 to 3 years
  • Average age at sexual or reproductive maturity (female)
    2-3 years
  • Average age at sexual or reproductive maturity (male)
    2 years

Females prepare an underground nest in an area with dry soil that is unlikely to be disturbed. Females protect their eggs from predators and other threats while they incubate. However, after hatching, females no longer care for their young. Males do not provide parental care. (Friends of the Rosamond Gifford Zoo Education Volunteers, 2008; Hammerson, 2007; Johnson, 1965)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

How long do they live?

Common chuckwallas live 10 years or more in the wild. The oldest known common chuckwalla in the wild was 30 years old. The oldest common chuckwalla in captivity lived to 65 years old. (Abts, 1987; Friends of the Rosamond Gifford Zoo Education Volunteers, 2008; Johnson, 1965; Montanucci, 1997; Sullivan and Sullivan, 2008)

  • Range lifespan
    Status: wild
    30 (high) years
  • Range lifespan
    Status: captivity
    65 (high) years
  • Average lifespan
    Status: wild
    15 years

How do they behave?

Common chuckwallas are solitary and diurnal. They leave rock shelters during the day to eat foliage, but remain close to their shelters. They are active from mid-March to mid-August, but may aestivate in the summer months when food is scarce. From November through March they may go through brumation (similar to hibernation). To prevent overheating, they move in and out of the shade and assume different orientations towards the sun. Most of their time is spent basking on rocks when they are not looking for food. They retreat into crevices and shallow holes during the hottest portion of the day and use these crevices to avoid predators.

  • Range territory size
    1000 to 7000 m^2
  • Average territory size
    3500 m^2

Home Range

Male home ranges are typically larger than female home ranges and do not overlap with those of other males. Females have smaller home ranges, so that male home ranges generally overlap with those of several females.

How do they communicate with each other?

Not much is known about communication and perception in common chuckwallas. They are solitary, so most communication happens during the mating season, when males compete for mating opportunities and females choose males. When looking for food, common chuckwallas use chemical cues (smell and taste) to decide what to eat. They have acute eyesight and perceive movement within 30 m. Their sense of hearing is not well-developed. (Cooper and Al-johany, 2002; Johnson, 1965; Montanucci, 1997; Sullivan and Kwiatkowski, 2007)

What do they eat?

Common chuckwallas are herbivores, eating leaves and fruit and occasional insects found on the plants they eat. They eat leaves and the fruit of creosote bushes, browneyes, and desert ragweed. In captivity they are fed various greens, vegetables, fruits, and flowers. They obtain water from the plants they eat.

  • Animal Foods
  • insects
  • Plant Foods
  • leaves
  • fruit
  • flowers

What eats them and how do they avoid being eaten?

Common chuckwallas are experts at detecting and evading predators. They hide in crevices and rocks when they feel threatened or scared. Tight holes and crevices between rocks are inaccessible to larger predators and common chuckwallas take refuge in those crevices to escape predators. Once in the crevice, they inflate their lungs to wedge themselves even tighter against the rocks and they position the tail towards the crevice opening and against their body for added protection. Their neutral-colored scales serve as camouflage in their desert landscapes. (Cooper Jr., et al., 2000; Hollingsworth, 1998)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Common chuckwallas eat plants and occasional insects and may impact their habitats through their feeding, they are also preyed on by their predators and act as hosts for several mite species and other parasites. (Montanucci, 1997; Nagy, 1973)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • Saurian malarial parasites (Plasmodium mexicanum)
  • mites (Hirstiella pyriformis)
  • mites (Hirstiella trombidiiformis)

Do they cause problems?

Common chuckwallas are shy and solitary and don't harm humans. (Nagy, 1973)

How do they interact with us?

Humans keep chuckwallas as pets. Currently, Nevada is the only state that allows commercial pet collection because of the large population there. (Brodie, Jr, et al., 2003; Montanucci, 1997; Nagy, 1973)

  • Ways that people benefit from these animals:
  • pet trade
  • research and education

Are they endangered?

Common chuckwalla populations are protected by national parks and naturally protected due to their remote habitat (rugged terrain and harsh climate). Trends towards developing desert areas of of the United States and parts of Mexico are affecting common chuckwalla habitat; however the population status as a whole has been reported as large, and stable. Populations throughout most of their range are considered stable. (Hollingsworth, 1998)

Some more information...

Contributors

Tanya Schultz (author), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Amer. Suppl. 1996. Influences of environmental conditions on life history tactics of herbivorous Mojave Desert lizards. Bull. Ecol. Soc., 77/3: 446 (abstr.).

Abts, M. 1987. Environment and variation in life history traits of the chuckwalla, Sauromalus obesus. Ecological Monographs, 57: 215-232.

Brodie, Jr, E., T. Edwards, Jr, P. Ustach. 2003. "Status of distribution, populations, and habitat relationships of the common chuckwalla, Sauromalus obesus, in Nevada" (On-line pdf). Division of Wildlife, Department of Conservation and Natural Resources, State of Nevada. Accessed December 04, 2013 at http://www.clarkcountynv.gov/Depts/dcp/Documents/Library/other%20reports/collab/ChuckWallaReport030703.pdf.

Cliff, F. 1958. A new species of Sauromalus from Mexico. Copeia, 1958: 259-261.

Cooper Jr., W., J. Van Wyk, P. Mouton, A. Al-Johany, J. Lemos-Espinal, M. Paulissen, M. Flowers. 2000. Lizard antipredatory behaviors preventing extraction from crevices. Herpetologica, 56: 394-401.

Cooper, W., A. Al-johany. 2002. Chemosensory responses to foods by an herbivorous acrodont lizard, Uromastyx aegyptia. Journal of Ethology, 20.2: 95-100.

Friends of the Rosamond Gifford Zoo Education Volunteers, 2008. "Desert Chuckwalla" (On-line). Rosamond Gifford Zoo. Accessed November 15, 2013 at http://rosamondgiffordzoo.org/assets/uploads/animals/pdf/DesertChuckwalla.pdf.

Hammerson, G. 2007. "IUCN Red List of Threatened Species. Version 2013.2" (On-line). Sauromalus ater. Accessed September 11, 2013 at http://www.iucnredlist.org/details/64054/0.

Hollingsworth, B. 1998. The systematics of chuckwallas (Sauromalus) with a phylogenetic analysis of other iguanid lizards. Herpitological Monographs, 12: 38-191.

Johnson, S. 1965. An ecological study of the chuckwalla, Sauromalus obesus Baird, in the western Mojave Desert. Amer. Midl. Nat., 73/1: 1-29.

Lappin, A., P. Hamilton, B. Sullivan. 2006. Bite-force performance and head shape in a sexually dimorphic crevice-dwelling lizard, the common chuckwalla [Sauromalus ater (= obesus)]. Biological Journal of the Linnean Society, 88/2: 215-222.

Macey, J., T. Papenfuss. 1991. Reptiles. Pp. 291-360 in C Hall, ed. Natural History of the White-Inyo Range: Eastern California. Berkeley, California: Univ. Calif. Press.

Montanucci, R. 1997. Captive management, behavior and conservation of chuckwallas, Sauromalus obesus (Lacertilia: Iguanidae). Bull Chicago Herp. Soc., 32/6: 121-127.

Nagy, K. 1973. Behavior, diet and reproduction in a desert lizard, Sauromalus obesus. Copeia, 1973/1: 93-102.

Sullivan, B., M. Kwiatkowski. 2007. Courtship displays in anurans and lizards: theoretical and empirical contributions to our understanding of costs and selection on males due to female choice. Functional Ecology, 21/4: 666–675.

Sullivan, B., K. Sullivan. 2008. Common chuckwalla (Sauromalus ater) populations in the Pheonix metropolitan area: stability in urban preserves. Herpetological Conservation and Biology, 3/2: 149-154.

Zimmerman, L., C. Tracy. 1989. Interactions between the environment and ectothermy and herbivory in reptiles. Physiological Zoology, 62/2: 374-409.

 
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Schultz, T. 2014. "Sauromalus ater" (On-line), Animal Diversity Web. Accessed February 19, 2019 at http://www.biokids.umich.edu/accounts/Sauromalus_ater/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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