| Six-lined racerunner | |
|---|---|
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| Male six-lined racerunner (Aspidoscelis sexlineata). | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Family: | Teiidae |
| Genus: | Aspidoscelis |
| Species: | A. sexlineatus |
| Binomial name | |
| Aspidoscelis sexlineatus (Linnaeus, 1766) | |
| Synonyms | |
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The six-lined racerunner (Aspidoscelis sexlineatus) is a species of lizard native to the United States and Mexico.
The six-lined racerunner is found throughout much of the southeastern and south-central portion of the United States, from Maryland to Florida in the east, across the Great Plains to southern Texas and northern Mexico. [3] [4] In a study conducted on A. sexlineata in Mexico, the majority of the individuals found were inhabiting areas near the seashore that were formed and influenced from maritime climate and hurricanes. [5] The species' range also reaches north to Wisconsin and Minnesota. A small disjunct population is found in Tuscola County, Michigan. [6]
The six-lined racerunner is typically dark green, brown, or black in color, with six yellow or green-yellow stripes that extend down the body from head to tail. Between stripes are dark-colored fields ranging from dark brown to black and pale-colored fields near ventral scales on each side. There is a distinct lemon-yellow coloration on the sides of the head both above and below the lateral stripe. There are also white mental and gular stripes. The posterior gular fold is bordered by enlarged mesoptychial scales. The postantebrachial scales on the forearms are granular-like and only slightly enlarged. [7] The underside is usually white in color on females, but they may have some pale blue as adults. Males have a brightly blue-hued chest and abdominal stripes. [7] Males also sometimes have a pale green-colored throat. They are slender-bodied, with a tail nearly twice the body length. It is hypothesized that its long tail may serve as a counter-balance, allowing it to flee quickly from predators. [8]
Like other species of whiptail lizards, the six-lined racerunner is diurnal and insectivorous. A. sexlineata is most active between 9:00 am and 11:30 am on clear days between late spring and early summer when the temperature is closest to 90 °F. [9] In a different study, they found six-lined racerunners were most active between 11:00 am and 3:00 pm. [10] They are wary, energetic, and fast moving, with speeds of up to 18 mph (29 kmh), darting for cover if approached. Aggressive behavior is common, as the dominant will chase the subordinate and often follow up with a bite to signify dominance. [11]
Due to its extensive range, A. sexlineata is found in a wide variety of habitats including grasslands, woodlands, open floodplains, or rocky outcroppings. Populations have also been found abundantly in areas that experience frequent fires. [12] It prefers lower elevations, with dry loamy soils as well as open xeric environments. [13] In the lower elevations, the six-lined racerunner can be found in human-made disturbances like under voltage towers or along highways and railroads. [14] They lay their nests around activity burrows along secondary highways and dirt roads where it is well drained. [15]
Breeding takes place in the spring and early summer, with up to six eggs being laid in mid-summer and hatching six to eight weeks later. A second clutch of eggs may be laid several weeks after the first. Males have been seen to perform an act termed "cloacal rubbing" to show arousal during breeding. This act entails the male rubbing its cloaca and pelvic region rapidly on the ground, sometimes in a figure eight, while simultaneously moving forward. [16] [9] When he finds a receptive female, the male will straddle her, curve his body over hers, and bite her on the opposite side to where his cloacal region is in order to start copulation. [9] Males will also perform an act termed "female tending" where the male will repeatedly charge at a female trying to leave its burrow until the female allows for the male to approach and begin the reproductive process. [17]
A. sexlineata are opportunistic insectivores; they target a prey that is currently abundant in their area. [18] The principal foods of A. sexlineata are spiders (Araneae 16.8%), grasshoppers (orthoptera 16.8%), and leaf hoppers (Homoptera 14.1%). [18] A. sexlineata also prey upon beetles and butterflies. [18]
Red-imported fire ants are a predator of the six-lined racerunner. [18]
There are three recognized subspecies of A. sexlineatus:
The six-lined racerunner is listed as a species of concern in the states of Michigan and Wisconsin, due to its limited population but otherwise holds no official conservation status. In Michigan, the population is found in a single public game reserve, 322 km separated from the closest known other populations in Indiana. [19] This species has been observed to benefit from human development in some locations, with stable populations existing along road cuts and railroad tracks. [20] Playa Bagdad in Mexico has seen a large decrease in six-lined racerunner populations due to recreational vehicle damage to sand dunes. [21]
Teiidae is a family of Lacertoidean lizards native to the Americas. Members of this family are generally known as whiptails or racerunners; however, tegus also belong to this family. Teiidae is sister to the Gymnopthalmidae, and both families comprise the Teiioidea. The Teiidae includes several parthenogenic species – a mode of clonal reproduction. Presently, the Teiidae consists of approximately 150 species in eighteen genera.
Cnemidophorus is a genus of lizards in the family Teiidae. Species in the genus Cnemidophorus are commonly referred to as whiptail lizards or racerunners. The genus is endemic to South America, Central America, and the West Indies.
Aspidoscelis is a genus of whiptail lizards in the family Teiidae.
The western whiptail is a species of lizard in the family Teiidae. The species is found throughout most of the southwestern United States and northern Mexico. Most of its populations appear stable, and it is not listed as endangered in any of the states comprising its range. It lives in a wide variety of habitats, including deserts and semiarid shrubland, usually in areas with sparse vegetation; it also may be found in woodland, open dry forest, and riparian growth. It lives in burrows. Major differences between this species and the checkered whiptail include the lack of enlarged scales anterior to the gular fold and the presence of enlarged postantebrachial scales. It was previously known as Cnemidophorus tigris, until phylogenetic analyses concluded that the genus Cnemidophorus was polyphyletic. Since it does not migrate, a number of forms have developed in different regions, several of which have been given subspecific names – for example the California whiptail, Aspidoscelis tigris munda.
The desert grassland whiptail lizard is an all-female species of reptiles in North America. It was formerly placed in the genus Cnemidophorus. A common predator of the whiptail lizard is the leopard lizard that preys on A. uniparens by using ambush and stalk hunting tactics. These reptiles reproduce by parthenogenesis. In this process, eggs undergo a chromosome doubling after meiosis, developing into lizards without being fertilized. However, ovulation is enhanced by female-female courtship and mating (pseudo-copulation) rituals that resemble the behavior of closely related species that reproduce sexually.
The orange-throated whiptail is a species of lizard in the family Teiidae. The species was previously placed in the genus Cnemidophorus. Three subspecies are recognized as being valid, including the nominotypical subspecies.
The Texas spotted whiptail is a species of long-tailed lizard, in the family Teiidae. The species is endemic to the south central and southwestern United States and northern Mexico. Six subspecies are recognized as being valid.
The gray checkered whiptail, also known commonly as Dixon's whiptail and the gray-checkered whiptail, is a species of lizard in the family Teiidae. The species is native to northern Mexico, and to the United States in southern New Mexico and western Texas.
The Laredo striped whiptail is a species of lizard found in the southern United States, in Texas, and northern Mexico in Coahuila, Nuevo Leon, and Tamaulipas. Some sources believe it to be the result of extensive hybridization between the Texas spotted whiptail, Aspidoscelis gularis and the six-lined racerunner, Aspidoscelis sexlineatus. It is one of many lizard species known to be parthenogenic.
The New Mexico whiptail is a female-only species of lizard found in New Mexico and Arizona in the southwestern United States, and in Chihuahua in northern Mexico. It is the official state reptile of New Mexico. It is one of many lizard species known to be parthenogenetic. Individuals of the species can be created either through the hybridization of the little striped whiptail and the western whiptail, or through the parthenogenetic reproduction of an adult New Mexico whiptail.
The checkered whiptail is a species of lizard found in the southwestern United States in Colorado, Texas and New Mexico, and in northern Mexico in Chihuahua and Coahuila. Many sources believe that the species originated from the hybridization of the marbled whiptail, Aspidoscelis marmorata, the plateau spotted whiptail, Aspidoscelis septemvittata, and possibly the six-lined racerunner, Aspidoscelis sexlineata. It is one of many lizard species known to be parthenogenic. It is sometimes referred to as the common checkered whiptail to differentiate it from several other species known as checkered whiptails.
The little striped whiptail is a species of lizard found in the southwestern United States and in northern Mexico. A significant amount of research was done on the species during the mid-1990s, with several new subspecies being added, many of which some sources consider to be distinct enough to warrant full species status, and the research is ongoing. It is called little to distinguish it from many other species known as striped whiptails and to indicate that it is the smallest of those species.
Cnemidophorus sexlineatus viridis, commonly known as the prairie racerunner, is a subspecies of lizard endemic to the United States. It is a subspecies of Cnemidophorus sexlineatus, which is commonly known as the six-lined racerunner lizard.
The Trans-Pecos striped whiptail is a subspecies of the little striped whiptail lizard. It is found in the semiarid, sandy habitats of the Chihuahuan Desert, in the United States from West Texas across southern New Mexico to Arizona, as well as northern Mexico. It is sometimes referred to as the Arizona striped whiptail or seven-striped whiptail.
The canyon spotted whiptail is a species of lizard in the family Teiidae. The species is native to northwestern Mexico and the adjacent southwestern United States.
Aspidoscelis costatus, also known as the western Mexico whiptail, is a species of whiptail lizard endemic to Mexico, including Guerrero, Morelos, and Puebla in southern Mexico, as well as other Mexican states. Its range spans both temperate and tropical habitats, and even densely populated urban areas. Its common name, the Western Mexico Whiptail, can easily be confused with the Western Whiptail, which refers to a different lizard, Aspidoscelis tigris.
Aspidoscelis danheimae, also known commonly as the Isla San José whiptail, the San Jose Island blue-throated whiptail, and el huico de la Isla San José in Spanish, is a species of lizard in the family Teiidae. The species is endemic to Isla San José in Baja California Sur, Mexico.
Aspidoscelis deppii, known commonly as the blackbelly racerunner, is a species of lizard in the family Teiidae. The species is native to Central America and southern Mexico. There are three recognized subspecies.
Aspidoscelis rodecki, also known commonly as Rodeck's whiptail, is a species of lizard in the family Teiidae. The species is endemic to Mexico.
Aspidoscelis sackii, known commonly as Sack's spotted whiptail, is a species of lizard in the family Teiidae. The species is endemic to Mexico. There are three recognized subspecies.
Data related to Aspidoscelis at Wikispecies 
Media related to Aspidoscelis sexlineata at Wikimedia Commons
