Page:Natural History of the Ground Squirrels of California.djvu/38

624 burrow some fifty feet distant from where the rattlesnakes had been. There was no way of determining whether the presence of the snakes had influenced this action, but it was evident that this squirrel made no effort to fill up the entrance to the burrow which had been preempted by the snakes. It is a popular notion that ground squirrels, when the opportunity offers, bury snakes alive.

As for mammals as enemies of ground squirrels, the evidence most readily obtainable is derived from examination of the excrement of the former. Coyotes have regular places for deposit of excrement, on hill tops or ridges. Bones and teeth of ground squirrels frequently have been found represented in these deposits (J. Grinnell, MS). The remains of two freshly eaten ground squirrels were found in the stomach of a wildcat killed in central San Diego County (J. Dixon, MS).

As to food, the California Ground Squirrel shows a wide range of taste, even though there are at the same time decided preferences. He cheerfully adopts substitutes when favorite foods are lacking; he is not averse to taking considerable barley with his wheat. A list of all the plants eaten by the ground squirrel would be a very long one, and if locality be taken into account great variation would doubtless be found from place to place. The above general statements will be borne out, in part at least, by the data presented in the paragraphs to follow.

On the University campus at Berkeley, on March 13, 1918, the majority of the California Ground Squirrels were feeding on the tender leaves of alfilaria (Erodium). A female squirrel was observed by the junior author at this time to eat the leaves of young plants of the star thistle (Centaurea). On San Emigdio Creek, Kern County, on April 28, 1918, a squirrel was seen to disappear down a hole carrying a sheaf of freshly cut heads of foxtail (Hordeum) held tightly in his mouth. A few minutes later this squirrel was gassed and when the burrow was dug out the fresh foxtail heads were found on the edge of the nest. Previously this squirrel was seen to gather heads of both foxtail and alfilaria, but preference was given to the latter (J. Dixon, MS). The young as well as the old squirrels seem to prefer alfilaria when obtainable to any other plant.

In the region about Walnut Creek, Contra Costa County, on July 26 and August 16, 1918, the authors found ground squirrels feeding extensively on seeds of bur clover (Medicago hispida). Dried burs of this plant were abundant on the hillsides in the near vicinity of the squirrel burrows, and although there was a plentiful supply of barley on the adjacent stubble fields this was in major part passed up in favor of the clover seeds. Hulled seeds of the bur clover were found to predominate in the cheek pouches and the stomachs of the score or more squirrels that were shot. This fondness on the part of the ground squirrels for bur-clover seed suggests a possibly better way of poisoning these rodents by using the entire bur of the clover than by the use of barley, wheat or other grains, which are now so badly needed for human consumption.

In southern California the seeds of the plant known as wild cucumber, manroot, or chilicothe (Echinocystis macrocarpa) is eagerly sought by ground squirrels. Gnawed hulls of the seeds of this plant are frequently found in large quantities near the summits of rock piles where the husking or lookout stations of the squirrels are located. In Yosemite