File:Control of field rodents on California farms (1965) (20665845646).jpg

Title: Control of field rodents on California farms
Identifier: controloffieldro535stor (find matches)
Year: 1965 (1960s)
Authors: Storer, Tracy I. (Tracy Irwin), 1889-1973; Jameson, E. W. (Everett Williams), 1921-
Subjects: Rodents
Publisher: (Berkeley, Calif. ) : Division of Agricultural Sciences, University of California
Contributing Library: University of California, Davis Libraries
Digitizing Sponsor: University of California, Davis Libraries

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9HHHHHHHHH* ""*â¢'â â *« t' â Fig. 14. Beechey ground squirrel at entrance to a well-used burrow from which trails lead out. (Photo by California Forest and Range Experiment Station.) pits of growing peaches and apricots. Sometimes they may also forage in truck patches. The feeding habits of ground squirrels cause greatest damage to grain and pas- turage. In fields they dig up sprouting grain, and later pull down the ripening heads. After harvest they may eat and carry off quantities of grain from shocks and stacks. On pasture lands they may take a good deal of grass and herbage that could otherwise be used by domestic stock. Green forage eaten daily by the average squirrel has been estimated at 2% ounces (70 grams) ; thus, 450 squir- rels would eat as much as one steer. Both on isolated ranches and in well- developed areas, they often seriously de- plete grain, nut, and fruit crops. Hibernation and estivation. All California ground squirrels living at high altitudes and some of the population, mostly adults, at lower elevations hole up for a part of each year. Before this period of inactivity, each animal acquires much fat. After going below ground the squir- rel plugs part of the tunnel just above the nest with earth to as much as 3 feet in length, and curls up in its nest below the tunnel plug. The burrow entrance remains open. While the squirrel is holed up, the rates of heartbeat and respiration are greatly reduced, and body tempera- ture drops nearly to that of the burrow. Emergence occurs in winter or early spring. Estivation ("summer sleep") be- gins as early as mid-May in the hills east of Livermore. and by late June in the hills of eastern Kern County, whereas it does not commence until early August in Siskiyou County. In mountain areas some do not enter hibernation until late in autumn. This habit of a prolonged sleep below ground explains why old breeding adults suddenly appear in spring, after all squir- rels active in a field during autumn had been killed and there seemed no chance for migration from the surrounding fields. During hot summer weather and in the fall and early winter, some of the squir- rels may be underground and out of reach. The exact extent of estivation among our ground squirrels is unknown because it is very difficult to follow an individual squirrel through its activities for any length of time. Therefore, it is extremely important to carry on intensive control in the late winter, spring, and early sum- (26)

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