Six-Lined Racerunner Aspidoscelis sexlineatus

Adult from Newton County

Identification

Racerunners are interesting lizards that occur in localized populations associated with sandy (western Indiana) or rocky (southern Indiana) substrates and open canopies. Of note in identifying this species, is that they are apt to escape by running quickly along the ground, into thickets or under rocks, as opposed to climbing trees, as do skinks and fence lizards. Six-Lined racerunners get their name from the six yellow stripes that run from their head to tail. As in some skinks, juvenile Six-Lined Racerunners have a bright blue tail that fades with age. However, they are not as smooth-scaled as skinks and glass lizards, or as rough-scaled as fence lizards. Adult Six-Lined Racerunners grow to around 9 inches (20 cm) long.

Adult from northern Illinois
Juveniles from southern Illinois

Six-Lined Racerunners are similar in appearance to both Five-Lined Skinks and Broad-Headed Skinks. This species’ scalation is notably different; they sport many tiny dorsal scales and lack the shiny smooth appearance of skinks.

Ecology and Conservation

A sun-loving lizard, the Six-Lined Racerunner can be found in drier open grassland areas. In dreary situations, they hide out in burrows under rocks or logs, some of which they dig themselves. These burrows also serve for hibernation. A very quick lizard, they are named because of their ability to outrun humans attempting to capture them.

Sandy scrub in Newton County
Sheet metal pile in northern Illinois

Distribution

Six-Lined Racerunners have a distribution unlike any other Indiana reptile or amphibian. They are most abundant in sand prairies and among the sand dunes of northwestern Indiana. However, they have also been found in scattered, sandy-soiled open areas in southwestern Indiana, along the Wabash River. Six-Lined Racerunners were historically known from Floyd and Clark Counties, on scattered rocky glades but these populations may now be gone. Glades are fire-maintained ecosystems and many of these glades occurred on private property and have since become overgrown and shaded.

Taxonomy

Six-Lined Racerunners were once described as members of the genus Cnemidophorus, with the Six-Lined Racerunner known as C. sexlineatus. Reeder et al. (2002) demonstrated this genus to be paraphyletic and placed Six-Lined Racerunners in the genus Aspidoscelis. Today, two subspecies are commonly recognized in Indiana: the Eastern Six-Lined Racerunner (A. s. sexlineata) and the Prairie Racerunner (A. s. viridis). The former is found in the southwestern Indiana, while the latter is found in northwestern Indiana.

Literature Cited

Reeder, T. W., C.J. Cole and H. C. Dessauer. 2002. Phylogenetic relationships of whiptail lizards of the genus Cnemidophorus (Squamata: Teiidae): a test of monophyly, reevaluation of karyotypic evolution, and review of hybrid origins. American Museum Novitates:1-61.

Distribution Map
Distribution map of Six-Lined Racerunner (Aspidoscelis sexlineatus)
Photographs