Page:Natural History of the Ground Squirrels of California.djvu/70

654 into conflict with man's interests. Extensive clearing of the sagebrush and seeding of these clearings to grain and hay has doubtless benefited the squirrels. Indeed, this is likely one of the factors that accounts for their increase of late years as testified to by several of the old-time residents whom we have interviewed.

In Butte Valley, Siskiyou County, the Oregon Ground Squirrels are popularly known as "bull dogs," in Modoc County as "short-tails" (evidently as distinguished from the longer tailed Douglas Ground Squirrel), and elsewhere, locally, as "bobbies," "prairie dogs," "gophers," and "woodchucks." The last three names, of course, are misapplications of names properly belonging to quite different kinds of rodents.

In the latter part of May, 1918, the senior author accompanied Mr. W. C. Jacobsen, State Superintendent of Rodent Control, in a tour through northeastern California for the particular purpose of studying the Oregon Ground Squirrel. In traveling eastward from Shasta Valley, we first encountered this species toward the head of the Little Shasta River, on the Mills ranch at about 4,200 feet altitude. Here we found a field of vetch to be riddled with the burrows and secured one of the animals to verify this, the westernmost record station for the species. At Bull Meadows, a little east of Goose Nest Mountain, the squirrels were exceedingly numerous on the uncultivated open ground among scattering lodgepole pines. Subsequently we found them plentiful around the margins of Grass Lake, nearly as far west, but due south of Goose Nest. But it was on the floor of Butte Valley, from the vicinity of Bray north to Dorris, wherever there were open grass lands, that the Oregon Ground Squirrels simply swarmed. The following observations made May 16, 1918, on a ranch seven miles south of Macdoel, will give an idea of the abundance of the animals where conditions are most favorable to them.

Taking a position at the right-angled intersection of two fences, the observer counted the animals in the quarter-circle gaze thus bounded and found that there were sixty-five squirrels in plain sight within a distance of one hundred yards of him. This was about nine o'clock in the forenoon of a bright day, when the squirrels were at about the height of their daily activity aboveground. Young of the year were included.

Again, three adjacent plots of pasture were paced off, thirty-nine paces square, and the open burrows counted. In one plot there were 151, in the second 182, in the third 194, an average of 176. This, figured out, makes 560 open burrows to the acre! If we allot one adult squirrel to each five openings, which our observations showed to be about the proper ratio, there would be 112 adults to the acre, not counting young. Figuring, further, this would make somewhat over 70,000 squirrels per square mile! This, however, would pertain only in limited areas and to those pasture lands where little effort had yet been made to reduce the pests. The population of the sagebrush plains and pine woods of Butte Valley would be much smaller. It is, of course, the pasture lands and grainfields where the squirrels come into chief conflict with man's interests, and this is where they are most abundant. Some further estimates in this connection are likely to prove worth while.