Cnemidophorus uniparens

Geographic Range

Desert grassland whiptail lizards, Aspidoscelis uniparens , are a southwest American and Mexican species. Their geographic range extends into Arizona, stopping just south of Grand Canyon National Park and west of Tanto National Forest. In New Mexico, their range extends north to the city of Albuquerque while staying relatively close to the western border of the state. In Texas, their range only includes the very tip of the western border near the city of El Paso. In Mexico, their range extends southward to Chihuahua, staying northeast of the Sierra Madre Occidental. This range is continuous across these state and country borders.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Desert grassland whiptail lizards are found in desert and grassland habitats. Their habitats range in elevation from 1120 meters to 2100 meters. These lizards often reside in arid areas with sparse vegetation. They can also be found living in dense shrubbery or small valleys. These areas vary greatly in composition, switching between grasslands, dense mesquite such as brittlebush ( Encelia farinosa ), and arid desert. These lizards spend much of their time under rocks and dense shrubbery to escape heat. They also escape heat with a burrow, where they spend their time at night and lay eggs.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

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

Physical Description

Desert grassland whiptails are an all-female species with an olive-brown to black base color. They have six cream colored stripes that run longitudinal along their bodies from head to tail, separated from each other by about 4 to 8 scales. When these lizards are hatchlings, their tails are bright blue. This color fades into olive-brown to black as they become adults. Their ventral surfaces are white and sometimes the adults have some light blue tinting on their throat and chin. Some of these lizards also have the beginnings of a seventh stripe near their head. There are a few populations of desert grassland whiptails near Chihuahua, Mexico that have more vividly colored stripes, likely due to allopatric congeners. They have granular dorsal scales numbering in the range of 59 to 78 rows around the mid-body. Wright (1968) reports that average snout-vent length (SVL) is 52.8 mm and weight is 4.1 g (N=1117).

Desert grassland whiptails co-occur with two similar-looking species. Little striped whiptails ( Cnemidophorus inornatus ) are smaller on average, more blue-colored throughout their ventral surface as well as their tail even as adults, and they have a full set of seven longitudinal stripes. Plateau striped whiptails ( Cnemidophorus velox ) are larger on average, have a complete set of seven longitudinal stripes, and often times have spots on the olive-brown areas covering their bodies.

• Other Physical Features
• ectothermic ectothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

Development

When desert grassland whiptail lizards' eggs are laid, they weigh about 0.4 g, on average. Desert grassland whiptails are triploid, meaning that they have three sets of homologous chromosomes. These lizards are parthenogenic, meaning that they develop from an unfertilized egg. They are genetic clones of the female that laid the egg. Once hatched, the hatchling lizards grow at a rate of 0.012 g per day, on average, for the first 30 days of life. Like all other lizards, they have indeterminate growth, meaning that they grow for the rest of their lives. These lizards are fully developed sexually after an average of seven months.

• Development - Life Cycle
• indeterminate growth indeterminate growth

Reproduction

Desert grassland whiptail lizards are parthenogenic, meaning that they are all females and they do not mate to reproduce. Even though they do not mate sexually, they often display pseudocopulatory behavior. The female-like pseudocopulatory behavior consists of allowing dominance by another desert grassland whiptail, that is displaying male-like behavior. The male-like pseudocopulatory behavior consists of general aggression, biting, and mounting. Sometimes there is even an alignment of the cloacae as though mating will occur but it does not. They most often display female-like behavior while they are producing their clutches of eggs. They most often display male-like behaviors before and after laying their eggs and before their next production of eggs.

The reproductive season of desert grassland whiptail lizards extends from the beginning of May through July. These lizards reach sexual maturity at the minimum size of 60 mm (SVL) during the first reproductive season after they hatch, which is on average seven months old. These lizards are parthenogenic, meaning they develop in unfertilized eggs. They are also clones of their single parent, and so are siblings genetically. Each sexually mature individual produces 2 to 3 clutches per year with 21 to 28 days between each clutch. Clutches range from 1 to 4 eggs with an average of 2.77. The amount of eggs per clutch correlates strongly with the size of the lizard. Females of SVL length smaller than 65 mm are reported to have an average of 2 eggs per clutch. Females with SVLs ranging 65 to 70 mm averaged 3 eggs per clutch. Females larger than 70 mm averaged 4 eggs per clutch. Desert grassland whiptail eggs, freshly laid, are cream-colored, oval shaped, and on average 0.4 g. Eggs hatch after approximately 2-3 months. When desert grassland whiptails hatch they weigh, on average, 0.56 g with a range of 0.53 to 0.58 g. Lizard hatchlings are immediately independent from their parent.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• parthenogenic parthenogenic
• oviparous oviparous

These lizards are precocial, meaning they are well developed when hatched. There is no parental investment beyond the act of egg-laying.

• Parental Investment
• no parental involvement
• precocial precocial

Lifespan/Longevity

There is very limited information detailing lifespans of desert grassland whiptail lizards. There is no information concerning the longevity of captive desert grassland whiptail lizards because they are not kept in captivity. However, research on another species of whiptail lizards suggests that they have a minimal annual survival in adults of 54-60% and average lifespans of at least seven years in the wild. These data are based on western whiptails ( Cnemidophorus tigris ), and suggests a similar lifespan but does not confirm one. According to Carey and Judge (2002), the longest known lifespan of a western whiptail in captivity is 7.8 years.

Behavior

Desert grassland whiptail lizards are not a very social species. Most of their time during the day is spent foraging for food and basking in sunlight. Most interactions between desert grassland whiptails are not aggressive. This lack of aggressive behavior compared to other lizard species is likely because they are all female and have no need to compete for mates or establish dominance in most settings. Most interactions between lizards occur during their reproductive season. At nighttime, desert grassland whiptail lizards retreat into their burrows within their home ranges, until dawn when they come out and resume foraging. These lizards are active during overcast days, but activity ceases during rainfall.

• Key Behaviors
• terricolous
• fossorial fossorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

According to Eifler and Eifler (1998), desert grassland whiptails' median home ranges are 1080 square meters. This is the area that they use primarily for foraging and they spend an average of 50% of their time in one-tenth of this range. These lizards are not territorial.

Communication and Perception

Desert grassland whiptail lizards use their visual, tactile, and olfactory senses to perceive their environment. They have eyes to see their surroundings and they can use their limbs and bodies to feel their surroundings. Lizards hear their surroundings using an organ called the cochlea. Lizards have a Jacobson's organ, a specialized olfactory organ that allows them to use their tongues to smell their surroundings. Using this organ, they perceive chemical signals that tell them when prey is near. Desert grassland whiptail lizards use several means of communication, even though they are not very social lizards. They sometimes use touch to communicate through mounting and biting. They also use pheromones to communicate their intentions to other lizards about mating and homestead range.

• Communication Channels
• visual visual
• tactile tactile
• chemical chemical

• Other Communication Modes
• pheromones pheromones

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

Food Habits

Desert grassland whiptail lizards are insectivores. Eifler and Eifler (1998) found that their diets consisted of both fossorial and surface insects, 42.5% of which were termites. A second study reported that these termites were arid land subterranean termites, Reticulitermes tibialis . About 6.7% of their diet consisted of queen ants ( Formica perpilosa ), 0.6% beetles, 5.4% grasshoppers, 2.0% butterflies, and 42.5% unknown insects. When foraging for prey, desert grassland whiptails will use a series of movements and intermittent sessions of digging and searching. They also use their tongues to smell the surrounding area and locate prey. When predators are nearby, desert grassland whiptails search for prey far less often. This is likely because digging attracts the attention of said predators.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects

Predation

The known predators of desert grassland whiptail lizards are long-nosed leopard lizards ( Gambelia wislizenii ), greater roadrunners ( Geococcyx californianus ), burrowing owls ( Speotyto cunicularia ), and loggerhead shrikes ( Lanius ludovicianus ). There is no difference in predators between juveniles and adults. These lizards have been observed to behave differently in the presence of a predator. When a predator is near, foraging lizards keep movement short and infrequent. This is likely in an effort not to attract the attention of predators. Also, when digging for prey, they have a significantly lower likelihood of finding prey, likely because the lizards are distracted by the presence of the predator.

Ecosystem Roles

Desert grassland whiptail lizards act as both predator and prey within their ecosystem. According to Bursey and Goldberg (1992), 26% of desert grassland whiptails in Arizona are infected with cestodes Oochoristica bivitellobata . Mahrt (1979), observed no cases of infection of desert grassland whiptails with hematozoans ( Hematozoa ). Goldberg and Bursey (1990) reported no indications of desert grassland whiptails being infested with nematodes ( Nematoda ), but there were infections of acanthocephalans ( Acanthocephalus ) in the stomachs of 3% of tested lizards.

Economic Importance for Humans: Positive

Due to the fact that these lizards are insectivores, it is possible they could provide pest control on some insects. However, there is no conclusive evidence to confirm this.

Economic Importance for Humans: Negative

There are no known negative economic impacts of desert grassland whiptail lizards on humans.

Conservation Status

Desert grassland whiptails lizards are listed as a species of "least concern" on the IUCN Red List. These lizards are not listed under any special status on the United States Endangered Species Act list, CITES, or the state of Michigan list.

Because they are parthogenic, desert grassland whiptail lizards are all genetically similar. Therefore, any biological or environmental threats to an individual (e.g. disease, climate change) are a threat to the whole species.

Much of the geographic range of desert grassland whiptail lizards consists of government protected areas; this prevents dramatic loss of habitat. Therefore, there are no conservation efforts in place for these lizards.

Other Comments

Desert grassland whiptail lizards were originally scientifically named Cnemidophorus uniparens , but are now called Aspidoscelis uniparens .

Additional Links

Encyclopedia of Life

Contributors

Logan Platt (author), Radford University, Lauren Burroughs (editor), Radford University, Layne DiBuono (editor), Radford University, Lindsey Lee (editor), Radford University, Karen Powers (editor), Radford University, Galen Burrell (editor), Special Projects.

References

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