Wildlife Portfolio of the Western National Parks
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THE FISHER GROUND SQUIRREL is frequently known as the "digger" squirrel because of its habit of digging extensive burrows in the alluvial soil. It is a large, heavy-set squirrel, about the size of a regular gray squirrel, with a moderately bushy tail. The ears are comparatively small, and the tail is much narrower than that of the tree squirrel. The general coloration of the upper parts is mixed gray and light brown, with a definite mottled pattern on the back and rump. There is a white silvery patch over the shoulders, and the long hairs of the tail have white tips. The total length is about 17 inches; tail about 7 inches.

The digger squirrel formerly occurred in great numbers over the plains of the San Joaquin Valley in California. With the settlement irrigation, and cultivation of much of this area, the squirrel population in the valley was reduced or crowded into the noncultivated land in the adjacent foothills. There it has taken advantage of human association, increased its numbers, and extended its range back into the mountains by following along the regular pack trail routes.

This species is clever at letting other squirrels do the hard work. Many times I have watched one waiting on the ground beneath a tree in which a chickaree was cutting and dropping the large green cones of the western yellow pine. Whenever the digger squirrel heard a pine cone hit the ground he would rush over and carry it off to his own den. When the chickaree came down the tree he was surprised to find that the cone, which he had just cut, had "walked off."

Digger squirrels have a high rate of reproduction. From 3 to 11, with an average of 6 young, are born in a litter. These young squirrels mature rapidly and are able to leave their underground burrows within a few weeks after birth. Frequently their dens are located under logs or between boulders, apparently in order to give better protection from badgers and other natural digging enemies. Digger squirrels are the basic food supply of many carnivorous birds and mammals of the West. They form the staff of life for the western red-tailed hawk and golden eagle and are extensively preyed upon by coyotes, wildcats, and gray foxes.


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Last Updated: 01-Jul-2010