Page:Natural History of the Ground Squirrels of California.djvu/23

Rh on the campus at Berkeley, that were plainly caused by the presence of squirrel burrows which had concentrated and conducted the water in narrow channels instead of permitting it to spread out and soak in or run off in the natural way. The presence of squirrels along irrigation canals results in the embankments becoming undermined by their burrows, with ensuing disastrous breaks in the canals, especially at times of high water.

Digger Squirrels are firm believers in the daylight saving plan. Their activities above ground are restricted to the hours between sunrise and sunset. They love the warm sunshine and may often be seen sprawled upon the summits of stumps, rocks or other points which afford safety as well, basking in the morning or later afternoon sunshine. During spring and summer they come out of their burrows soon after sun-up. They are at those seasons most active during the middle of the forenoon and again during the late afternoon, but avoid the intensest heat of midday. During midwinter those squirrels which do not remain underground altogether make their appearance only late in the forenoon of bright sunny days. Light and warmth seem to be essential to their successful existence aboveground.

The observer afield often comes upon ground squirrels which are some distance from their holes. Such animals usually run, with bodies and tails undulating and closely paralleling the ground, to the near vicinity of their burrows, where they then post themselves in upright position. They can then watch the intruder, yet be in readiness to dart down into their holes at an instant's warning. While thus on watch a squirrel is wont to repeat, at regular intervals of from two to five seconds, its characteristic "bark." This note is really a double one, and may be indicated by the syllables, clink-sup. The second syllable, however, is not audible for any great distance, while the first is loud, staccato, and of decided metallic quality, calling to mind the sound produced by the blow of a light hammer on an anvil. The impression is enhanced by the regularity and frequency of its utterance, and this will be kept up five minutes at a time. Sometimes, when a squirrel is startled, it gives a more prolonged note, clink-sup-sup-sup-sup, the last syllables running together as a sort of chuckle. In any event, it is the clink which is the metallic syllable, and which one hears a long ways, more or less mellowed by distance.

If closely pressed the squirrels drop down at once into the protection of their subterranean retreats. Ordinarily when thus frightened down they do not reappear at the surface of the ground for some minutes, five to twenty-five minutes in tested cases, as if to give the suspected enemy a chance to tire of his waiting and depart. Occasionally, when surprised at a distance from its burrow, a squirrel will crouch motionless, it may be almost at the feet of the observer, as if to escape detection by the "freezing" ruse. Extreme fear also on occasion may be part of the basis for this mode of behavior.

In some respects the California Ground Squirrel is much "wiser" than is generally supposed. This has been forcibly impressed upon the junior author during his endeavors to secure photographs. Living squirrels were then observed at close range in their various activities under natural conditions. Several species of chipmunk, as well as the Golden-mantled Ground Squirrel and the Nelson Antelope Ground