Page:Natural History of the Ground Squirrels of California.djvu/65

Rh The Douglas, as is known of most other ground squirrels, is fond of flesh when this can be obtained. Many have been taken in the meat-baited steel traps kept out in various localities for carnivores.

Hibernation seems to be more prevalent with douglasii than with beecheyi, for all of the population of the former is reported to disappear for weeks at a time, even in the lower valleys. At the higher altitudes, where there is more or less heavy snow, all the squirrels disappear over a period of some months. In Hayfork Valley, Trinity County, the senior author was assured by several different people living there that the Douglas Squirrels hibernate regularly and completely "from November till April." The earliest spring record we have for a mountainous region is of one squirrel caught in a box trap February 25 (1911) near Helena, Trinity County (A. M. Alexander, MS).

The natural enemies of this squirrel probably include practically all those already specified in our chapter on the California Ground Squirrel. Only one specific instance is at hand. A gopher snake found run over in a road near Chico, June 7, 1912, was found to contain in its stomach a young Douglas Ground Squirrel (T. I. Storer, MS). Coyotes are locally reputed to levy considerable toll upon this rodent. We have heard the argument advanced against the poisoning of ground squirrels on wild mountain land in the northwest coast district that reducing the squirrel population will deprive the coyote of one of his chief sources of subsistence and that he will thereupon be forced to seek food elsewhere and so be more prone to raid the poultry of the valley ranches and the flocks of sheep in the mountains. On the other hand, it may be advanced that the total coyote population is adjusted to the total amount of food available at the season of least supply, and that removal of any one important kind of food will in course of time reduce the total coyote population able to exist in any general territory.

A high natural mortality for this species may account for its relative lack of aggressiveness as compared with the California Ground Squirrel. The testimony of a number of people from localities widely scattered over the range of the Douglas Ground Squirrel is to the effect that every few years there is a great reduction in its numbers. Some fairly close observers, forest rangers in the Trinity region, for instance, think this is due to the effects of severe winter weather, as when there is an exceptionally heavy snowfall or torrential rains of unusual amount. In either case the squirrels are thought to be drowned in large proportion when lying dormant underground. Other persons think there are recurrent epidemics of some disease fatal to the ground squirrels. We have no good evidence bearing upon either hypothesis.

Because of this observed reduction in numbers during some winters, certain ranchers have objected to carrying on poisoning operations in the fall, since their efforts might prove to have been unnecessary. They prefer to. deal with the naturally reduced squirrel population of the springtime, at the close of the dormant period.

The general range of the Douglas Ground Squirrel has not changed within history as far as definite records show. But, locally, there have been marked fluctuations. On the western side of the Sacramento Valley the animals have been almost completely cleaned out on many large tracts as a result of systematic poisoning. This is particularly true, as we are assured by W. C. Jacobsen, State Superintendent of