Page:Natural History of the Ground Squirrels of California.djvu/118

696 Type locality.—Tipton, Tulare County, California (Merriam, 1893, p. 129).

Distribution.—Occupies the floor of the southern end of the San Joaquin Valley, and adjacent arid hills and included valleys immediately to the westward (see fig. 24). Life-zone Lower Sonoran. More specifically, extends from vicinity of Bakersfield (8 miles northeast) and Poso, in central Kern County, west to the Carrizo Plains and Cuyama Valley, in southeastern San Luis Obispo County, south to the mouth of San Emigdio Creek, 12 miles due east of Maricopa, Kern County, and north to Huron, Fresno County, and Tipton, Tulare County.

Specimens examined.—A total of 43, from the following localities in California. Kern County:eight miles northeast of Bakersfield, 32;twelve miles due east of Maricopa, 5;McKittrick, 3. San Luis Obispo County:Carrizo Plains, 3.

The Nelson Antelope Ground Squirrel is called Antelope Chipmunk by many of the people who live in the southern San Joaquin Valley. No distinction is made by them between the present species and the Antelope Squirrel of the Mohave and Colorado deserts. This is not surprising when we consider the rather close general resemblance between the two. When specimens of the two animals are in hand, tone of coloration alone suffices for distinguishing them. The ground color of the Nelson Squirrel is distinctly clay color, while that of the Desert Antelope Ground Squirrel is pinkish buff. In the former, too, the under side of the tail is creamy buff, while in the latter it is pure white. In bulk the Nelson is approximately 50 per cent the larger.

The Tehachapi Mountains on the south and the Greenhorn Mountains to the east help to form a continuous barrier between the range of these two near-related squirrels. We find the Nelson Squirrel to be restricted for the most part to the Lower Sonoran life-zone in that portion of the San Joaquin Valley which lies south of Tulare Lake. It is notably numerous in the oil districts. The Nelson Squirrel may be distinguished from all other rodents that occur in this region by having a very short, flat-haired tail (less than 3 inches in length) and by the presence of a single white stripe on each side of the body. The name borne by this species was given to it by its original describer (Merriam, 1893, p. 129) as a recognition of the contributions to mammalogy of Edward W. Nelson, now chief of the United States Bureau of Biological Survey.

During the rainy season many of the smaller streams in the southern and western foothills around the San Joaquin Valley cut deep and narrow channels, but when the flood waters of such streams reach the upper plains of the great valley their course is marked by broad washes with low, perpendicular banks. The silt-bearing waters finally spread out, forming broad, alluvial fans, and often sink into the thirsty soil before they reach the lower alkaline plains. The lower reaches of such stream courses, dry and desertlike most of the year, are the preferred haunts of the Nelson Ground Squirrel. Here burrows are easily dug between the hard layers of the stratified banks of the washes, affording safe retreats from such predators as the coyote and badger. A luxurious though brief-lived growth of vegetation results from the thorough natural irrigation of the rich soil of the alluvial fans and the squirrels are thus afforded an abundant food supply the rest of the year. Individuals and even colonies are to be found along the little gullies and ridges of the upper slopes between the mouths of the streams and the foothills, while a few may be found along the edges of the alkali ground