THE GROUND SQUIRRELS OF CALIFORNIA. 645 



boundary of Modoc County. (See map, fig. 17.) Life-zone, Upper Sonoran aiid 

 Transition, ranging down into Lower Sonoran along the western side of the Sacra- 

 mento Valley. Altitudinally, the species ranges from near sea level up to as high as 

 6,500 feet (near South Yolla Bolly Mountain) and even 6,800 feet (on the Scott 

 Mountains, Siskiyou County). 



More in detail : The southern limit of the range of douglasii is not known to reach 

 the Golden Gate; it falls, on the sea-coast, somewhere not far to the north of Point 

 Reyes Station, and extends from there to the vicinity of Petaluma, leaving the south- 

 ern two-thirds of Marin County uninhabited. It extends nearly or quite to Benicia 

 and to the southern end of the range of hills west of Vacaville. The flood-plain of 

 the Sacramento River forms the eastern boundary north to beyond the Marysville 

 Buttes, Thence northeastward, across the Sacramento Valley, there is no obvious 

 barrier. In Butte, Plumas and Lassen Counties the ranges of douglasii and beecheyi 

 approach very closely, but so far as known they do not overlap ; nor have undoubted 

 hybrids or geographic intergrades been reported. 



Specimens examined. — A total of 65, from the following localities in California: 

 Modoc County : Sugar Hill, 3 ; Parker Creek, Warner Mts., 3 ; Deep Creek, Warner 

 Mts., 1. Siskiyou County : Mayten, 1 ; six miles northwest of Callahan, Scott River 

 Valley, 6 ; Summerville, 1 ; Castle Lake, 3. Shasta County : McCloud River, near 

 Baird, 7. Tehama County : Mill Creek, 2 miles northeast of Tehama, 4 ; four miles 

 south of South Yolla Bolly Mountain, 1. Butte County : four miles southeast of 

 Chico, 4 ; Dry Creek, on Oroville-Chico road, 3. Glenn County : Winslow, 4. Yolo 

 County : Rumsey, 1. Solano County : three miles west of Vacaville, 2. Humboldt 

 County : Eureka, 1 ; Fair Oaks, 2 ; Ferndale, 1 ; Ouddeback, 1. Trinity County : Hay- 

 fork, 2 ; Helena, 2. Mendocino County : Sherwood, 3 ; three miles south of Covelo, 1 ; 

 six miles north of Willets, 1 ; Mount Sanhedrin, 3. Sonoma County : seven miles west 

 of Cazadero, 4. 



The Douglas Ground Squirrel belongs to the group of large, bushy- 

 tailed, tall-eared ground squirrels which include the California, Fisher, 

 Catalina Island and Rock Squirrels, and in common with the first and 

 second of these at least it is often called Digger Squirrel. Although 

 the differences are not great, they are evident and should be recognized 

 in economic work, for they not only concern color, but apparently also 

 habitat and food preferences. The Douglas Squirrel differs from its 

 next neighbor of the ''digger" category, the California, in having a 

 conspicuous blackish wedge-shaped patch on the middle of the back 

 between the shoulders, in having the shoulder region more extensively 

 grayish white, and in having the tail a little longer and grayer. 



The name of the squirrel now under discussion was bestowed upon it 

 (Richardson, 1829, p. 172) in acknowledgment to an early English 

 explorer in western America, David Douglas, for having brought home 

 specimens of the animals met with, many of which proved to be new 

 to science. Douglas's travels carried him through parts of Oregon 

 and probably northern California ; but the type of this ground squirrel 

 was a hunter's skin received from the Columbia River. There is no 

 telling now exactly where it really came from originally, though prob- 

 ably from much south of the Columbia, since the species is not known 

 to have existed within history that far north. 



In northern California the Douglas Ground Squirrel occupies a wide 

 area ; in fact, at the extreme north from the Pacific Ocean to the Nevada 

 line. To the southward its range includes all of the upper Sacramento 

 Valley, and its western half lower down, and the whole coast region 

 (hills and included valleys) south nearly to San Francisco Bay. Refer- 

 ence to the map (fig. 17) will show that the range of the Douglas is 

 almost exactly complementary to that of the Beechey; at no point do 



