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Dipsosaurus dorsalisDesert Iguana

By Amanda Sloan

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. (Pianka and Vitt, 2003; Smith, 1949)

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. (Bartlett and Bartlett, 2009; Pianka and Vitt, 2003; Smith, 1949)

  • Range elevation
    Below sea level to 5,000 m
    to ft

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. ("AnAge entry for Dipsosaurus dorsalis", 2001; Bartlett and Bartlett, 2009; Ditmars, 1936; Smith, 1949)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • male more colorful
  • Average mass
    69.5 g
    2.45 oz
  • Range length
    33.02 to 40.64 cm
    13.00 to 16.00 in

Development

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

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. (Pianka and Vitt, 2003; Schmidt and Ingers, 1957)

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. ("Desert Iguana - Rosamond Gifford Zoo", 2010; Mertz, 2003; Schmidt and Ingers, 1957)

  • Breeding interval
    Desert iguanas generally breed once a year, although they may breed twice if conditions are optimal
  • Breeding season
    Copulation typically occurs in May and June
  • Range number of offspring
    3 to 8
  • Range age at sexual or reproductive maturity (female)
    31 to 33 months
  • Range age at sexual or reproductive maturity (male)
    31 to 33 months

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. (Schmidt and Ingers, 1957)

  • 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. ("AnAge entry for Dipsosaurus dorsalis", 2001; "Desert Iguana - Rosamond Gifford Zoo", 2010)

  • Range lifespan
    Status: captivity
    14.6 (high) years
  • Average lifespan
    Status: wild
    less than 7 years
  • Average lifespan
    Status: captivity
    7 years

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 Iguana - Rosamond Gifford Zoo", 2010; Bartlett and Bartlett, 2009; Pianka and Vitt, 2003; Smith, 1949)

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. ("Desert Iguana - Rosamond Gifford Zoo", 2010; Bartlett and Bartlett, 2009)

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. ("Desert Iguana - Rosamond Gifford Zoo", 2010; Bartlett and Bartlett, 2009; Pianka and Vitt, 2003)

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. (Mertz, 2003; Pianka and Vitt, 2003)

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. (Pianka and Vitt, 2003)

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. ("Desert Iguana - Rosamond Gifford Zoo", 2010; Mertz, 2003; Pianka and Vitt, 2003; Schmidt and Ingers, 1957)

  • 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. (Hammerson, et al., 2007; Pianka and Vitt, 2003)

  • Anti-predator Adaptations
  • 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. (Benes, 1985; Pianka and Vitt, 2003)

Commensal/Parasitic Species
  • Cyrtosomum scelopori (Family Atractidae, Phylum Nematoda)
  • Ozolaimus sp. (Family Oxyuridae, Phylum Nematoda)

Economic Importance for Humans: Positive

Desert iguanas often serve as pets for humans and are also used in research. ("Some Facts About The Desert Iguana", 2011; Hammerson, et al., 2007; Mayhew, 1971)

  • Positive Impacts
  • 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. (Hammerson, et al., 2007)

Contributors

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

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

chemical

uses smells or other chemicals to communicate

coprophage

an animal that mainly eats the dung of other animals

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
folivore

an animal that mainly eats leaves.

herbivore

An animal that eats mainly plants or parts of plants.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynous

having more than one female as a mate at one time

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

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/.

Bartlett, R., P. Bartlett. 2009. Guide and Reference to the Turtles and Lizards of Western North America (North of Mexico) and Hawaii. Gainesville: University Press of Florida.

Benes, E. 1985. Helminth parasitism in some central Arizona lizards. The Southwestern Naturalist, 30/4: 467-473.

Ditmars, R. 1936. The Reptiles of North America; A Review of the Crocidilians, Lizards, Snakes, Turtles and Tortoises Inhabiting the United States and Northern Mexico. Garden City: Doubleday, Doran and Company, Inc..

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.

Mertz, L. 2003. Anoles, Iguanas, and Relatives (Iguanidae). Pp. "243-257" in M Hutchins, A Evans, J Jackson, D Kleiman, J Murphy, D Thoney, eds. Grzimek's Animal Life Encyclopedia. Grzimek's Animal Life Encyclopedia, Vol. Volume 7: Reptiles, 2nd edition Edition. Detroit: Gale. Accessed October 20, 2011 at http://go.galegroup.com/ps/retrieve.do?sgHitCountType=None&sort=RELEVANCE&inPS=true&prodId=GVRL&userGroupName=rock89639&tabID=T003&searchId=R2&resultListType=RESULT_LIST&contentSegment=&searchType=BasicSearchForm&currentPosition=1&contentSet=GALE|CX3406700445&&docId=GALE|CX3406700445&docType=GALE&role=.

Pianka, E., L. Vitt. 2003. Lizards: Windows to the Evolution of Diversity. London, England: University of California Press.

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..

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