Prairie Racerunner

Aspidoscelis sexlineata viridis

(Cnemidophorus sexlineatus viridis)

Prairie Racerunner

Distribution in Wyoming

 

 

 

 

 

 

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The Prairie Racerunner is distributed in the south-central plains of Wyoming, South Dakota, and Nebraska, south through Colorado and Kansas, into Oklahoma and Texas. It is a peripheral species in Wyoming, residing in Platte and Goshen counties where it inhabits the brushy rock outcrops and yucca covered hillsides of the grassland community in the prairie life zone. It prefers loose soils associated with mosaics of open cover mixed with dense patches of weedy vegetation—especially those areas along the base of the white sandstone cliffs and floodplain terraces belonging to the White River geologic formation.

Prairie Racerunner Prairie Racerunner

During the day these insectivorous lizards forage on grasshoppers, crickets, spiders, moths, and beetles. They have a long and forked tongue which they frequently flick when capturing airborne chemical cues from their surroundings. They then use the tongue to wipe those samples on to sensors on the roof of the mouth (the vomeronasal organ) for assessment—something like a combination of smelling and tasting.

While thermo-regulating to avoid overheating during the day or when resting during the night, they seek shelter in burrows made by them or, more commonly, made by mammals such as ground squirrels and kangaroo rats. They are extremely fast and run with somewhat erratic or jerky movements; they are difficult to catch—either by hand or by noose. (It may sound a bit masochistic, but they will inflict a most “pleasant and satisfying” bite if you have been fortunate enough to have chased down one of these critters and have it in hand.)

Prairie Racerunner Prairie Racerunner

This is a large lizard with a long, slender body and a SVL of about 3 inches. Its elongated head has a distinct ear opening, a pointed snout, and 2-3 gular folds at the base of its thickened neck. The dorsal surface of the body and legs is covered with small granular scales which become keeled, rectangular, and overlapping at the base of the long tail—which is more than twice the length of the body. The brown, tan, or gray dorsal background is disrupted with 6 light stripes running along the body; these longitudinal stripes begin as an iridescent yellow or green just behind the eye and often grade to a pale blue before fading to white as they near the waist. The ventral surface is white and made of large rectangular scales aligned in 8 rows. Males in breeding condition have a bluish throat and belly. Juveniles have a blue tail.

Prairie Racerunner Prairie Racerunner

 

Courtship and breeding take place in May and June when the larger and more aggressive males begin chasing and fighting each other. When approaching a female, a male will investigate with tongue flicking and, if she is somewhat receptive, he will bite and grasp her by the neck as he mounts and copulates. Egg laying occurs a week or so later when the gravid female buries 1-5 eggs in loose soil. Incubation takes 7-9 weeks and hatchlings start appearing in August (and in September if second clutches have been laid). Sexual maturity is reached in 2-3 years. There are populations of Aspidoscelis/Cnemidophorus in Colorado and the Southwest that are comprised entirely of females; these species reproduce without males or fertilization in a process known as parthenogenesis.