Cnemidophorus sexlineatusSix-lined Racerunner

Geographic Range

Six-lined racerunners occur from Maryland and Rhode Island through Florida, west to approximately southeastern Wyoming and extreme southern Texas, north in the Mississippi-Missouri Valley to Lake Michigan, western central Wisconsin and south-western South Dakota. A very small population exists in Michigan's Tuscola County.

Habitat

This lizard lives in relatively dry regions on sandy or other loose soil, in short grass, sparse woods, or areas with scattered, subxerophytic vegetation. Dryness seems more essential than any other factor; a loose porous soil is generally more often frequented than a loamy soil. Dense vegetation, unless low and not of a moisture-retaining type, is avoided. Within these limits a tremendous variety of habitats are utilized. The land may be flat or hilly, the soil rocky or uniformly fine. In the east they reach elevations as great as 1400 feet above sea level; in the west greater altitudes are attained on the high flat plains. However, nowhere do they reach high elevations in mountains.

Physical Description

Length: 30cm (12in). Maximum snout-vent length about 75mm. (3in); tail about 2 times the head-body length, very slender. Color: Six well-defined, narrow, longitudinal, light, pale blue to yellowish lines on body in females and juveniles, all extending from head to base of tail or groin; the stripe nearest the middle on each side begins near the median edge of the parietal; lateral to this another stripe (dorsolateral) begins at posterior corner of eye; and a lateral stripe begins below the eye and passes through the upper edge of the ear. Dimly evident may be another line extending from the lower part of the ear opening to the upper edge of the arm insertion. The sides between these three stripes are usually black: below the lateral stripe is a narrow dark area blending with the light ventral color; and between the median stripes is a broad brownish area. The median light stripes are indistinguishable on the tail, but the dorsolateral ones extend a considerable distance on it; bordering it below is a black stripe in turn borderd by a light stripe which extends upon the otherwise uniformly dark posterior surface of the thigh. The belly is white in life, sometimes tinged with blue in preserved specimens. Adult males have the same dorsal pattern, except that the lateral stripes and the dark areas above them are indistinct, merged with the belly color; and the black between the dorsolateral and median stripes on each side is less intense. Ventrally the entire belly and throat are suffused with pale blue; the limbs and subcaudal surfaces are cream below. This ventral color may become blackish in formalin.

Scalation: Dorsal scales are very small, granular, 76 to 93 from one side to the other at about the middle of the body. Large, flat, quadrangular, belly plates in 8 longitudinal rows; 2 gular folds, the primary (posterior) overlapped anteriorly by enlarged scales. Large head plates. Scales on posterior surface of lower foreleg all small in both sexes, the central ones not, or seldom, more than 3 times as large as adjacent dorsal scales of the arm.

Reproduction

Mating occurs in spring, probably not over 2 or 3 weeks after emergence from hibernation. A regular courtship pattern is followed. The male, without stimulus from a female, rubs his cloaca on the ground by moving his hips quickly from side to side while moving in a figure eight. At various times he stops to chase others, not distinguishing betwen males and females. He attempts to ride their backs, nipping the skin in the neck region and scraping their backs with his femoral pores. These attentions are accepted by willing females but fought off by males. Finding a receptive female, the male curls the tail under the female until the cloacas are together. He loops his body in a half coil and grasps the posterior part of the the back in his jaws, at the same time that one hemipenis is inserted. Copulation continues some 5 minutes, after which the female moves away. The eggs, 4 to 6 in number, are laid from early June to middle July. About a week after deposition the eggs measure about 17 x 9.5 mm. They are laid 4 to 12 inches below the surface, frequently under some object on the surface such as a log. Racerunners frequently use mole tunnels, making small side tunnels from them in which the eggs are laid. The young hatch in early August.

Lifespan/Longevity

  • Average lifespan
    Status: captivity
    6 years
    AnAge

Behavior

Moderately wary, these lizards seek cover, generally in holes or under objects such as boards, rails, stones, etc., when disturbed by close approach of an observer. They never or rarely climb; they seem completely terrestrial. If an observer remains at a distance of 15 feet or so, generally the lizards go on about their business much as usual. Although it is difficult to approach closely enough to capture them by hand before they seek cover, their habitat of entering small holes or crevices frequently makes it possible to dig them out easily. They can dig their own burrows, but they do not hesitate to use mammal or other ready-made burrows. In digging they use their front legs to remove soil. The burrows are said to extend to a depth of some 8 to 10 inches. The burrows have two openings; when the lizard is within, one of the openings is closed from the inside. The burrows are used as retreats during night and on cool days, and for egg laying. It is not known how closely restricted they are to one burrow or how many burrows are usually made during a season. Hibernation occurs in the fall when temperatures drop (October in North Carolina). Whether they use the same kind of burrow for hibernation is not known; upon emergence in April they are sometimes covered with soil, which wears off shortly.

Activity begins early in the morning on warm days and falls off during the afternoon. In late afternoon they disappear completely. They are not active on cool or cloudy days. They are completely diurnal.

Food Habits

Food consists primarily of insects but also includes other arthropods and snails. Stomach contents studies show the normal diet includes grasshoppers, crickets, spiders ants, flies, small moths, and moth or butterfly larvae. Soft-bodied insects are preferred, as beetles are not frequently found. Large butterflies, although killed, may not be eaten. Some insects, as ladybird beetles, are distasteful and are ejected promptly upon being taken into the mouth, and the lips are then usually wiped on the ground, the lizard displaying great discomfort. Racerunners are said to be voracious feeders.

Economic Importance for Humans: Positive

These insect predators are of considerable value in the control of pests in various parts of the country. They important as predators of the beet leafhopper in Utah, and in Florida they are significant in the control of celery pests.

Conservation Status

This species is listed as special concern in the state of Michigan, but it is not nationally or globally threatened at this time.

Other Comments

Recognition Characteristic: One of only two lizards occuring in the same territory that have 8 rows of enlarged ventrals, minute dorsals, big scales on the head, a long slender body and tail, and well-developed legs. Other one is Cnemidophorous g. gularis.

Interesting Facts: - Black snakes and collared lizards are known to eat these lizards. Probably other snakes and lizards do so at times.

  • When well warmed up they can attain a surprising speed, measured at 18 miles an hour.
  • Although more is known of the natural history of this species than of many other lizards of this country, there are many points on which there have been no observations.

Contributors

Brad McFarlane (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

native range

the area in which the animal is naturally found, the region in which it is endemic.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References