Dipsosaurus dorsalis

Geographic Range

Desert iguanas are endemic to the Sonoran Desert of the Southwestern United States and Northern Mexico and to the Mojave Desert of the Western United States. They can also be found on several islands in the Sea of Cortez.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Desert iguanas inhabit desert environments. Their preferred habitats include creosote flats and thornscrub forests. They are terrestrial animals but are capable of climbing at least one meter above the ground in creosote bushes. They are capable of withstanding high temperatures and are often active during the hottest part of the day, becoming less active when the sun is not shining. They are most active at 40°C (104°F) and are capable of handling temperatures up to 46°C (115°F). Higher temperatures, ranging from 55° to 60°C (131° to 140°F) are fatal. When inactive or at night, they take shelter in small mammal burrows, usually found at the base of creosote bushes or cacti.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• desert or dune desert or dune
• savanna or grassland savanna or grassland
• scrub forest scrub forest

Physical Description

Desert iguanas are medium-sized lizards. They have a stout, rounded body with a small head. Their snout to vent length (SVL) is about 13 cm (5.25 inches). Their tail is long and tapered, and generally measures a little less than twice the body length. They are typically 33 to 36 cm in total length (13 to 14 inches), with a maximum overall length of 40.6 cm (16 inches). Hatchling desert iguanas are only about 3.75 inches long. Desert iguanas have a grayish brown coloring with a reticulated dark, reddish brown pattern on their dorsal surface. Their ventral surface is a pale gray or cream that lacks any reticulations. The tail is decorated with small reddish brown dots. Both female and male desert iguanas exhibit areas of pinkish pigment on their lateral-ventral surfaces during mating season. Female and male desert iguanas appear very similar to one another, although males are usually characterized by reddish markings near their tails. Desert iguanas have fine, granular dorsal scales and a faint serrated crest that runs from the neck onto the tail. Desert iguanas have large, oval ear holes, well formed limbs, and are equipped with femoral pores that are used for marking territory.

• Sexual Dimorphism
• sexes colored or patterned differently
• male more colorful

Development

Currently, there is no information available regarding specific aspects of the development and life cycle of desert iguanas.

• Development - Life Cycle
• indeterminate growth indeterminate growth

Reproduction

Desert iguanas are a polygynous species. Their mating system centers around the cooler microhabitats created by the creosote bushes and other desert shrubs. The bushes and shrubs are a major food source for desert iguanas but they also provide the coolest midday temperatures and females develop their home ranges around them. Desert iguanas are a territorial species and aggression between sexually mature males competing for females and resources is common. Aggressive displays between males that are designed to attract females often include push-ups, as in many other iguanid species. Dominant males will also establish their territory around desert shrubs, allowing better access to more females.

• Mating System
• polygynous polygynous

The breeding season begins in spring and continues through midsummer. Peak breeding intervals occur in May and June. Desert iguanas are oviparous, usually laying eggs in early to late summer. Females generally lay one clutch of eggs per season, although under optimal conditions they can lay two clutches per season. Egg clutches typically contain from three to eight eggs. Females dig burrows in the ground, then position themselves over the burrow to deposit their eggs. The eggs are then covered with soil and left alone. Desert iguanas reach sexual maturity around 31-33 months of age. Both male and femalese exhibit pinkish pigment on the sides of their ventral surfaces during mating season. There is little known about the actual reproductive process and gestation in this species.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• oviparous oviparous

Desert iguanas provide very little parental investment for their offspring. Females will dig a burrow, lay the eggs, and cover them. Once the eggs hatch there is no parental involvement.

• Parental Investment
• no parental involvement
• pre-hatching/birth
  • provisioning
    • female

Lifespan/Longevity

The lifespan of desert iguanas in captivity averages about 7 years, with the longest lifespan recorded in captivity being 14.6 years. Little is known about the lifespan of wild individuals, although it is likely to be less than those in captivity.

Behavior

Desert iguanas are diurnal. They are active during midday in the spring, summer, and fall. They are extremely heat tolerant, being most active at an average temperature of 40°C (104°F). Most of their day is spent foraging or basking in the sun. Being active during midday in summer is possibly an adaption to avoid predators, which may not be able to tolerate such high temperatures. Desert iguanas frequently climb creosote bushes to find food. They carry their bodies high off the ground when running or walking and are capable of running very fast (occasionally bipedally).

Desert iguanas create shelter from predators and high temperatures by burrowing under shrubs or near knolls, but will also use burrows made by mammals. Desert iguanas begin hibernating in late October, continuing through the winter. Hibernating individuals and will burrow anywhere from a few inches up to two feet under the soil. Young desert iguanas will burrow at shallower depths than adults. They normally emerge from hibernation in March. Desert iguanas are territorial and aggressive.

Aggressive behavior in males includes push-ups. Males will establish territories around shrubs and females will form home ranges, with both sexes marking their territories using fluorescent chemicals from their femoral pores. Desert iguanas are very alert to their surroundings and will quickly retreat to their burrows when threatened. They are also able to appear twice their actual size by inflating their bodies as a defensive display, when fleeing is not possible. When hiding from predators, desert iguanas will often wedge themselves into crevices, where being able to inflate their bodies has the added benefit of preventing predators from removing them from these hiding spots. They are also able to autotomize their tail in order to escape predators.

• Key Behaviors
• cursorial
• terricolous
• diurnal diurnal
• hibernation hibernation
• territorial territorial

Home Range

While male desert iguanas are territorial and females will form home ranges, there is little information about the size of these areas. There is also little information regarding any restriction of movement to these areas.

Communication and Perception

Desert iguanas are equipped with femoral pores that absorb ultraviolet wavelengths and then produce fluorescent chemicals that are used as territory markers. These markers are only visible to species that can detect ultraviolet wavelengths. Little is known about sensory perception in desert iguanas. They appear to have color vision, as demonstrated by their affinity for yellow flowers, yellow mealworms and yellow flagging tape. They also are able to communicate through aggressive displays, such as push-ups.

• Communication Channels
• visual visual
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• visual visual
• ultraviolet
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Desert iguanas are primarily folivores, but will also occasionally eat insects. They feed on the buds, leaves and flowers of a variety of annual and perennial plants, with vegetation making up over ninety percent of their diets. The types of plants eaten change seasonally. In spring they will particularly eat yellow flowers, especially those of the creosote bush ( Larrea tridentata ). Alfalfa leaves ( Medicago sativa ) are also a part of their diet, as are the feces of other herbivores. Occasionally they will eat arthropods, such as crickets and mealworms , but this behavior is rare in the wild. Captive desert iguanas will eagerly consume yellow mealworms, with wild individuals also taking mealworms, when offered. Desert iguanas in captivity have also been known to eat dandelion flowers ( Taraxacum sp ). They have even been observed eating yellow flagging tape, which suggests that the color yellow plays an important role in their foraging strategy.

• Primary Diet
• herbivore herbivore
  • folivore folivore
• coprophage coprophage

• Animal Foods
• insects

• Plant Foods
• leaves
• fruit
• flowers

• Other Foods
• dung

Predation

Raptors, snakes, and foxes are all predators of desert iguanas. Coachwhip snakes ( Masticophis flagellum ) are also a major predator of desert iguanas and other lizards in the Sonoran Desert of the Southwestern United States. The desert iguana’s grayish-brown body coloring is advantageous for desert environments and may act as camouflage. Desert iguanas will retreat to their burrows when threatened, but are also capable of inflating themselves to keep from being pried out of their hiding places. In the open, this behavior allows them to seem larger and discourage predators. Desert iguanas also have autotomous tails which, when lost, distract their predators and potentially allow the lizard to escape.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Desert iguanas are a food source for the predators in their geographic range, including foxes, raptors, and snakes. Desert iguanas also serve as hosts to a number of parasitic microbes. In order to keep the microbes from excessively multiplying and causing internal damage, infected desert iguanas maintain higher than normal body temperatures. If an infected individual is prevented from achieving a higher internal body temperature, then the microbes can have detrimental effects. Aside from these microbes, there are currently no known parasites specific to this species.

Economic Importance for Humans: Positive

Desert iguanas often serve as pets for humans and are also used in research.

• Positive Impacts
• pet trade pet trade
• research and education

Economic Importance for Humans: Negative

There are no known adverse effects of desert iguanas on humans.

Conservation Status

The IUCN Red List classifies desert iguanas as a species of least concern. It is estimated that their population exceeds 100,000 adults. Some local populations have experienced decline due to habitat destruction and highways.

Additional Links

Encyclopedia of Life

Contributors

Amanda Sloan (author), Sierra College, Jennifer Skillen (editor), Sierra College, Jeremy Wright (editor), University of Michigan-Ann Arbor.

References

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Hammerson, G., D. Frost, H. Gadsden. 2007. "Dipsosaurus dorsalis" (On-line). The IUCN Red List of Threatened Species. Accessed October 30, 2010 at http://www.iucnredlist.org/apps/redlist/details/64053/0 .

Mayhew, W. 1971. Reproduction in the Desert Lizard, Dipsosaurus dorsalis. Herpetologica , Vol. 27, No. 1: 57-77. Accessed November 17, 2011 at http://www.jstor.org/pss/3890824 .

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Schmidt, K., R. Ingers. 1957. Living Reptiles of the World . Garden City: Doubleday and Company, Inc..

Smith, H. 1949. Handbook of Lizards: Lizards of the United States and of Canada . New York: Comstock Publishing Co..

2001. "AnAge entry for Dipsosaurus dorsalis" (On-line). AnAge: The Animal Ageing and Longevity Database. Accessed October 30, 2011 at http://genomics.senescence.info/species/entry.php?species=Dipsosaurus_dorsalis .

2010. "Desert Iguana - Rosamond Gifford Zoo" (On-line pdf). Rosamond Gifford Zoo. Accessed October 30, 2011 at rosamondgiffordzoo.org/assets/uploads/animals/.../Desert_Iguana.pdf .

2011. "Some Facts About The Desert Iguana" (On-line). Iguanas As Pets. Accessed November 17, 2011 at http://iguanasaspets.com/some-facts-about-the-desert-iguana/ .