CALIFORNIA WHIP-TAILED LIZARD. Cnemidophorus tigris mundus Camp

Field characters.—Body and especially tail long and slender; legs stout, the hinder pair much the larger; toes long; a well marked fold of skin across throat; back and sides of body covered with minute rounded bead-like scales; under surface of body with flat rhomboid scales arranged in eight lengthwise rows; tail with ridged or keeled scales. (See pl. 57c.) Coloration varying with age, striped in young, becoming spotted in adults. Ground color of body blackish, with lengthwise stripes (young) or with scattered small spots of buff, yellow or white (adults); sides of head and legs blotched with dusky; under surface white, with scale edgings of black; tail dark brown above, yellowish beneath. Head and body measuring to 4 inches; tail to 10 inches.

Occurrence.—Resident in small to moderate numbers on west side of Yosemite region, chiefly in Upper Sonoran Zone. Recorded from Pleasant Valley eastward to Smith Creek, 6 miles east of Coulterville, and to foot of Big Oak Flat road in western part of Yosemite Valley. To be seen on surface of ground in open gravelly or sandy places.

The swiftest of all the lizards in the Yosemite region is the California Whip-tailed Lizard which occurs at certain locations in the western part of the section. This reptile is ordinarily thought of as an inhabitant of desert regions, and in truth it is; but it also occurs, or did occur formerly, on much of the floor of the San Joaquin Valley, and it penetrates into the foothills wherever there are conditions suitable for its existence. Its distribution in the Yosemite section is not continuous. We found it at Pleasant Valley, about Coulterville, at Smith Creek, in the neighborhood of Kinsley, and at two locations in the lower end of Yosemite Valley, namely, at the foot of the Coulterville grade and at the foot of the Big Oak Flat grade.

The whip-tailed lizard is specialized in somewhat the same manner as the kangaroo rat, and to achieve the same result. Its whole organization is modified for the attainment of speed in running on the surface of the ground. The body is slender and the tail is fully twice the length of head and body together, and finely and evenly tapered to the end. (See pl. 57c.) The legs are stout, especially the hinder pair, and the toes are long, particularly those of the hind feet. When frightened, one of these animals appears to get over the ground, for a short distance at least, faster than a man can run. Its usual procedure is to start up suddenly, make a rapid dash of 50 to 100 feet or so, then stop abruptly, often dodging around behind a bush at the instant of stopping. The long tail serves as a counter poise and perhaps also as a rudder, in movement. The sudden start, extremely swift run and quick stop are, to the human eye, confusing, and may have the same effect on any animal, such as the Road-runner, which might attempt to prey on the lizards. When undisturbed the Whip-tail forages about with jerky movements of the body. The tail is then usually dragged on the ground and leaves a characteristic trail between the marks of the feet. When pursued, one of these lizards will often take shelter in some hole in the ground, usually at the base of a bush. One was seen to enter a ground squirrel burrow. In places where there are no open rodent burrows, and where the soil is sufficiently loose, Whip-tails dig their own burrows.

At Smith Creek a small whip-tailed lizard was seen in a pool of water, where it had evidently jumped when frightened by the approach of the observer. The animal was obviously unadapted to this element, for after a few strokes it sank to the bottom and was drowned.

The Whip-tail subsists upon insects. Some of these, such as grasshoppers, are obtained by stalking, just as a carnivorous mammal such as a coyote stalks a ground squirrel. Other prey, such as cutworms (moth larvae) and beetle larvae, are picked up by the Whip-tail from the surface of the ground about the bases of plants. This lizard does not climb at all, even over rocks.