606 THE MONTHLY BULLETIN. 



The species now under discussion is restricted in its distribution 

 mainly to the state of California. It extends a little ways south into 

 Lower California; and to the eastward it barely crosses the Nevada 

 line in the vicinity of Lake Tahoe. To the northward in the coast 

 belt it is cut off sharply by the Golden Gate and San Francisco Bay, 

 but in the interior it extends to the headwaters of the Feather River. 

 Southeastwardly toward the deserts the race heecheyi blends into the 

 race fisheri, which in turn is wholly cut off by the hottest deserts 

 beyond. (See map, fig. 17.) In the coast belt north of San Fran- 

 cisco Bay and from the upper Sacramento Valley northward the 

 Beechey Squirrel is replaced by the Douglas Ground Squirrel. 



Altitudinally the California Ground Squirrel ranges from sea level, 

 as on the shores of Monterey Bay, up to an altitude of at least 8200 

 feet, as in the Yosemite National Park. It is most abundant on the 

 plains of the San Joaquin and in the Coast Ranges and Sierra foot- 

 hills. As regards life-zone, the metropolis of the species lies in the 

 Lower and Upper Sonoran (see fig. 23). It is less numerous in the 

 yellow pine belt (Transition zone), and is but rarely or sparingly 

 represented in the Canadian zone, still higher on the mountains^ 

 Its preferences as to local conditions are not closely limited, except 

 that it avoids dense chaparral and thick woods. It frequents pasture 

 lands, grain fields, orchards, sparsely tree-covered slopes, small moun- 

 tain meadows, rock outcrops on the tops of ridges, and even granite 

 talus slopes. It is always most abundant, however, in the open situa- 

 tions, and its decided preferences are such that it thickly populates 

 much of the best farming and grazing lands in the state, to the great 

 reduction of their producing value from the human standpoint. 



This squirrel secures shelter for itself and young, and safety from 

 its enemies, by burrowing in the ground. Where possible it chooses 

 to excavate its retreats in hillsides or in low earth banks. Here some 

 at least of the necessary digging can be done in a horizontal direction. 

 But, of course, those members of the species which live on the plains 

 or on small flats or meadows in the foothills or mountains must dig 

 down vertically for considerable distances to gain the requisite pro- 

 tection. Many of the squirrels which live in the granite country 

 make their homes under large boulders or in rock taluses where a 

 minimum of burrowing is necessary to insure safe retreats. On wooded 

 hillsides special safety from enemies that dig is secured by location 

 of the burrows under tree-roots or old stumps. 



In the foothill region at the southern end of the San Joaquin Valley 

 there seems to be a decided tendency on the part of the ground squirrel 

 to select alluvial fans for home sites. This preference may be accounted 

 for by the fact that the plants upon which the squirrel feeds make a 

 better growth in the deep alluvial soil there than they do on the adjoin- 

 ing hillsides which are often steep and with but shallow cover of soil. 

 For the same reason the alluvial fans afford easier digging to consider- 

 able depth and hence better protection. In seven burrows in different 

 localities, in which the squirrels were gassed and then dug out (J. 

 Dixon, MS), the extent, diameter and depth were found to vary and to 

 depend largely upon the nature of the soil. In shallow adobe or clayey 

 soil, underlaid by broken rock, the burrows were found to be short, of 



14 



