CHIPMUNKS 183 



Few data are available concerning the exact time or duration of the 

 breeding season in this or any of our other species of chipmunks. Among 

 ground squirrels one species is known to take somewhat less than one 

 month for gestation, and it seems probable that the period is at most not 

 longer in chipmunks. This would require, on the basis of young being 

 born in late June or early July (as shown by the data given beyond), 

 mating toward the end of May. At this season, though the ' ' high Sierras ' ' 

 are still fairly well covered with snow, the daily temperature reaches a 

 relatively high point, and spots of bare ground are beginning to appear. 



Our records for the Tahoe Chipmunk, based upon the taking of speci- 

 mens, show pregnant females as follows : 



Crane Flat, 6400 feet, June 16, 1915, 6 small embryos 



Mono Meadow, 7400 feet, June 16, 1915, 3 embryos 



Mono Meadow, 7400 feet, June 18, 1915, 3 large embryos 



Porcupine Flat, 8100 feet, June 27, 1915, 4 embryos 



Porcupine Flat, 8100 feet, June 28, 1915, 3 large embryos 



Porcupine Flat, 8100 feet, July 1, 1915, 6 large embryos 



Many young were abroad at Tuolumne Meadows by July 31, 1915. The 

 number of young in a litter we may infer to vary from 3 to 6, and to 

 average about 4. 



Allen Chipmunk. Eutamias senex (Allen) 



Field characters. — Size large for a chipmunk (head and body about 5^2. inches long, 

 tail about 41/1 inches). (See table in footnote 15, page 177, for detailed measurements.) 

 Usual chipmunk pattern, markings indistinct; general tone of coloration dark grayish. 

 (See pi. 3^1.) Distinguished from frater by larger size, duller coloration, and less con- 

 spicuous light striping on sides of head and back; from quadrimacxdatus by more 

 grayish coloration, shorter ears, and less conspicuous light spots behind bases of ears; 

 from alpinus by much larger size and by duller and darker coloration. Voice: Similar 

 to that of the Long-eared Chipmunk. 



Occurrence. — Common resident in Canadian Zone on west slope of Sierra Nevada. 

 Eecorded from Aspen Valley, Cascade Creek (near Gentrys) and Chinquapin eastward 

 to Glen Aulin and Washburn Lake, at altitudes of 6200 to 7700 feet regularly, and 

 exceptionally at 4600 feet (Lady Franklin Eock) and 8100 feet (Porcupine Flat). 

 Lives in thickets and about logs, rarely going over 5 feet above the ground. 



The Allen Chipmunk is the common brush and log inhabiting species 

 in the belt of country on the west slope of the Sierra Nevada characterized 

 by the presence of huckleberry oak, chinquapin, and snow bush (C. cordu- 

 latus). By reason of its large size (pi. 3(7), gray coloration, and terrestrial 

 proclivities it may be told at a glance from the smaller, more brightly- 

 marked tree-climbing Tahoe Chipmunk sharing the same belt. 



Along the lower margin of the Canadian Zone the Allen and Long-eared 

 chipmunks are found together. The former exhibits a grayer-toned pelage, 

 with more obscured striping, shorter ears, and a much less conspicuous 



