Six-lined racerunner
Male six-lined racerunner (Aspidoscelis sexlineata).
Scientific classification Edit this 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

The six-lined racerunner (Aspidoscelis sexlineatus) is a species of lizard native to the United States and Mexico.

Geographic range

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]

Description

Adult, Indialantic, Florida

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]

Behavior

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] 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.[10]

Habitat

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.[11] It prefers lower elevations, with dry loamy soils. In the lower elevations, the six-lined racerunner can be found in human-made disturbances like under voltage towers or along highways and railroads.[12]

Reproduction

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.[13][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.[14]

Prey and Predators

A. sexlineata are opportunistic insectivores; they target a prey that is currently abundant in their area.[15] The principal foods of A. sexlineata are spiders (Araneae 16.8%), grasshoppers (orthoptera 16.8%), and leaf hoppers (Homoptera 14.1%).[15] A. sexlineata also prey upon beetles and butterflies.[15]

Red-imported fire ants are a predator of the six-lined racerunner.[15]

Subspecies

There are three recognized subspecies of A. sexlineatus:

  • Eastern six-lined racerunner, Aspidoscelis sexlineatus sexlineatus (Linnaeus, 1766)
  • Texas yellow-headed racerunner, Aspidoscelis sexlineatus stephensae Trauth, 1992
  • Prairie racerunner, Aspidoscelis sexlineatus viridis Lowe, 1966

Conservation status

The six-lined racerunner is listed as a species of concern in the state of Michigan, due to its limited population but otherwise holds no official conservation status. This species has been observed to benefit from human development in some locations, with stable populations existing along road cuts and railroad tracks.[16] Playa Bagdad in Mexico has seen a large decrease in six-lined racerunner populations due to recreational vehicle damage to sand dunes.[17]

See also

References

  1. ↑ Hammerson, G.A.; Lavin, P.; Mendoza Quijano, F. (2007). "Aspidoscelis sexlineata". IUCN Red List of Threatened Species. 2007: e.T64287A12753706. doi:10.2305/IUCN.UK.2007.RLTS.T64287A12753706.en. Retrieved 16 May 2023.
  2. ↑ The Reptile Database. www.reptile-database.org.
  3. ↑ Animal Diversity Web: Cnemidophorus sexlineatus
  4. ↑ Savannah River Ecology Laboratory Herpetology Program - Species Profile: Six-lined Racerunner (Cnemidophorus [Aspidoscelis] sexlineatus)
  5. ↑ Pérez-Ramos, Edmundo; Nieto-Montes de Oca, Adrián; Vargas-Contreras, Jorge A.; Cordes, James E.; Paulissen, Mark A.; Walker, James M. (September 2010). "Aspidoscelis Sexlineata (Sauria: Teiidae) in Mexico: Distribution, Habitat, Morphology, and Taxonomy". The Southwestern Naturalist. 55 (3): 419–425. doi:10.1894/GC-199.1. JSTOR 40801041. S2CID 86514210.
  6. ↑ Michigan Natural Features Inventory: Aspidoscelis sexlineata
  7. 1 2 Pérez-Ramos, Edmundo; de Oca, Adrián Nieto-Montes; Vargas-Contreras, Jorge A.; Cordes, James E.; Paulissen, Mark A.; Walker, James M. (September 2010). "Aspidoscelis sexlineata (Sauria: Teiidae) in Mexico: Distribution, Habitat, Morphology, and Taxonomy". The Southwestern Naturalist. 55 (3): 419–425. doi:10.1894/GC-199.1. ISSN 0038-4909.
  8. ↑ Ballinger, R. E., Nietfeldt, J. W., & Krupa, J. J. (1979). An Experimental Analysis of the Role of the Tail in Attaining High Running Speed in Cnemidophorus sexlineatus (Reptilia: Squamata: Lacertilia). Herpetologica, 35(2), 114–116. http://www.jstor.org/stable/3891774
  9. 1 2 3 Carpenter, Charles C. (1960-01-01). "Aggressive behaviour and social dominance in the six-lined racerunner (Cnemidophorus sexlineatus)". Animal Behaviour. 8 (1): 61–66. doi:10.1016/0003-3472(60)90010-5. ISSN 0003-3472.
  10. ↑ Carpenter, Charles C. (January 1960). "Aggressive behaviour and social dominance in the six-lined racerunner (Cnemidophorus sexlineatus)". Animal Behaviour. 8 (1–2): 61–66. doi:10.1016/0003-3472(60)90010-5. ISSN 0003-3472.
  11. ↑ Mushinsky, Henry R. (1985). "Fire and the Florida Sandhill Herpetofaunal Community: With Special Attention to Responses of Cnemidophorus sexlineatus". Herpetologica. 41 (3): 333–342. ISSN 0018-0831. JSTOR 3892279.
  12. ↑ Trauth, Stanley E. (1983). "Nesting Habitat and Reproductive Characteristics of the Lizard Cnemidophorus sexlineatus (Lacertilia: Teiidae)". The American Midland Naturalist. 109 (2): 289–299. doi:10.2307/2425409. ISSN 0003-0031. JSTOR 2425409.
  13. ↑ Carpenter, Charles C. (1962). "Patterns of Behavior in Two Oklahoma Lizards". The American Midland Naturalist. 67 (1): 132–151. doi:10.2307/2422824. ISSN 0003-0031. JSTOR 2422824.
  14. ↑ Carpenter, Charles C. (1960). "Reproduction in Oklahoma Sceloporus and Cnemidophorus". Herpetologica. 16 (3): 175–182. ISSN 0018-0831. JSTOR 3890059.
  15. 1 2 3 4 Taylor, H.L; Paulissen, M.A; Walker, J.M; Cordes, J.E (2011). "Breadth and Overlap of diet between syntopic populations of parthenogenetic Aspidoscelis tesselata C and gonochoristic Aspidoscelis sexlineata (Squamata: Teiidae) in southeastern Colorado". The Southwestern Naturalist. 56 (2): 180–186. doi:10.1894/F06-GC-211.1. S2CID 86594649. Gale A262145143.
  16. ↑ "Eastern Six-lined Racerunner". Virginia Herpetological Society. 2023. Retrieved 16 May 2023.
  17. ↑ Pérez-Ramos, Edmundo; de Oca, Adrián Nieto-Montes; Vargas-Contreras, Jorge A.; Cordes, James E.; Paulissen, Mark A.; Walker, James M. (2010). "ASPIDOSCELIS SEXLINEATA (SAURIA: TEIIDAE) IN MEXICO: DISTRIBUTION, HABITAT, MORPHOLOGY, AND TAXONOMY". The Southwestern Naturalist. 55 (3): 419–425. ISSN 0038-4909. JSTOR 40801041.

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