Page:Natural History of the Ground Squirrels of California.djvu/109

Rh surface of tail broadly pure creamy white, with an outer black border around the terminal half, and succeeding this a white fringe.

Adult in summer pelage: Coat short and harsh instead of long and silky. General pattern of coloration as in winter, but tone of upper surface more buffy, especially so on top of head; hairs on whole lower surface pure white to bases (no lead-color); tail as in winter.

Color variations.—The sexes are alike in coloration. The young closely resemble summer adults save that the pelage is not so harsh. There is some individual variation in tone of gray on back and in intensity of cinnamon on flanks and shoulders, but we are unable to find any correlation in these respects with locality. In other words, we are unable to find any tendency within the range of Ammospermophilus leucurus in California to form subspecies. The range of the animal is continuous from the Mexican border to the head of Owens Valley and there are no hindrances to continuous mixing of breed, such as seem essential to subspecific differentiation in other ground squirrels.



The two seasonal coats, winter and summer, are interchanged through a clearly defined process of molt. That from winter to summer begins as early as April 23 and continues in different individuals as late as June 18; that in the fall extends from September 12 to October 23. These dates are as shown by the specimens available. The spring molt commences on the forehead and proceeds backwards; the last remnants of the winter coat are to be seen on the hind neck and rump. In the fall the order is reversed, and the rump first acquires the new winter pelage, the crown and forehead being the last areas to show the short harsh summer hairs. The hairs of the tail seem to be involved only in the fall molt, in other words they are not replaced in the spring when the rest of the pelage is.

Wear, fading, and contact with alkaline soil bring about some modification in the tones of coloration. In some cases the tails are dirty light brown and the ends of the hairs are all curled up as if scorched by heat. In April specimens from the sand-dunes at the edge of Owens Lake near Keeler, the worn winter pelage shows a curious yellowish tone, but September examples from the same place, in process of molt, show the new winter pelage to be normal and exactly like that in specimens from Riverside County.

We are unable to find any grounds for recognizing a separate race of leucurus from the Inyo region (vinnulus of Elliot, 1903, p. 241, type from Keeler, Inyo County).

Measurements.—Average and extreme measurements, in millimeters, of twenty adult specimens from Inyo County are as follows: Ten males: total length, 215, (200–235); tail vertebræ, 61.5 (50–70); hind foot, 37.7 (35–40); ear from crown, 5.7 (5.0–7.0); greatest length of skull, 38.7 (37.5–40.6); zygomatic breadth, 22.3 (21.5–23.1); interorbital width, 9.6 (9.4–10.1). Ten females: total length, 211 (200–220); tail vertebræ, 57.7 (46.0–65.0); hind foot, 36.5 (35.0–38.0); ear from crown, 5.5 (4.0–8.0); greatest length of skull, 38.1 (37.1–39.4); zygomatic breadth, 22.1 (20.6–22.9); interorbital width, 9.6 (8.9–9.9).