Page:Natural History of the Ground Squirrels of California.djvu/43

Rh dependent upon the sequence in which they become available. Thus, alfilaria is eaten during winter and early spring; then the foxtail crop claims attention; and the bur clover, after its seeds ripen, is harvested all through midsummer and autumn. Of course the above statements are only of local application.

Examination of the food stores of ground squirrels would go far toward providing adequate knowledge of their food habits. Such investigations should be made preferably in the fall. Specific information now available is as follows:

In digging out a colonial burrow near Bakersfield, Kern County, on May 3, 1918, a storehouse was uncovered. This consisted of a cavity or pocket off the main run (see a, fig. 8), which measured five and a half by eight inches in two diameters and was eighteen inches beneath the surface of the ground. The stored food consisted of a double handful of nearly dry heads of foxtail grass carefully packed in dry sand. A few alfilaria seeds were also included with the foxtail, but alfilaria was scarce at this locality.

Upward of fifty of the button-like seeds or "cheeses" of the mallow (Malva) were observed at the entrance of another burrow at the same place, but the observer was unable to determine whether or not these seeds were being stored. The mallow seeds were found for the most part on the lookout station at the entrance to the burrow.

"At Modesto in May, 1909, Piper found stores of alfilaria seeds packed in cavities and well mixed with dry sand. In December of the same year he examined a number of stores of grain unearthed by a farmer while scraping and leveling his land. Each of these caches consisted of from a pint to a quart of oats stored in cavities and packed in dry sand. They varied from 8 to 18 inches in depth beneath the surface; some were in short blind holes; others at the ends of branches, of the main burrow" (Merriam, 1910, p. 5).

An idea of the quantity of food eaten by the California Ground Squirrel can be derived from the following data:

A female taken near Coulterville, Mariposa County, on June 3, 1915, weighed 553.5 grams, or about a pound and a quarter. The stomach and its contents alone weighed 77.5 grams, or about 2¾ ounces (C. L. Camp, MS). Figuring out the ascertained weight of the stomach in other individuals, 5 grams, the ratio of stomach contents to total weight in this squirrel proves to have been about 1 to 7. The material represented is presumed to have been fresh green stuff.

Some experiments have been carried on at the Museum with captive squirrels with the purpose of determining the amount of green forage consumed daily. Fifty grams, or nearly two ounces, of green alfilaria was found to be the average daily ration for an average-sized squirrel. In cases where all food had been withheld from the squirrels the previous day, the greatest amount of succulent alfilaria, the favorite food of the squirrel, consumed in one day was 80 grams, or somewhat less than three ounces.

Five immature ground squirrels taken July 26, 1918, near Walnut Creek, Contra Costa County, gave an average total weight of 504.3 (427.2–517.2) each in grains. The average weight of the stomach contents in these five squirrels was 13.2 (10.3–19.0), so that the avejrage ratio of the weight of the stomach contents to the total weight was