THE GROUND SQUIRRELS OF CALIFORNIA. 



68? 



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 varia- 

 tion 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. 



Fig. 26. Feet of ground squirrels to show extent of hairing on soles and posi- 

 tion and shape of tubercles, a, Desert Antelope Ground Squirrel ; b, Stephens 

 Soft-haired Ground Squirrel ; c, California Ground Squirrel. Natural size ; 

 drawn from specimens. 



The two seasonal coats, winter and summer, are interchanged through a clearly 

 defined process of molt. That from winter to summer begias 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 vertebrae, 61.5 (50-70) ; hind foot, 37.7 (35-40) ; ear from crown, 

 j 5.7 (5.O-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 vertebrae, 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). 



