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UN I VERSITY^F~ CALIFORNIA 

 COLLEGE OF AGRICULTURE 



BERKELEY, CALIFORNIA 



AGRICULTURAL EXPERIMENT STATION 

 THOMAS FORSYTH HUNT, DIRECTOR 



CIRCULAR No. 82 



(NOVEMBER, 1912.) 



THE COMMON GROUND SQUIRRELS O 



H. C. BRYANT. 



Two rodents in the State of California give the rancher more trouble 

 than all the other animal pests combined, insects excepted. One, the 

 pocket gopher (Thomomys sp.), feeds largely on the roots of plants and 

 trees and hence is one of the worst pests of the garden and orchard. 

 The other, the ground squirrel (Citellus sp., Ammospermophilus sp., 

 Gdllospermopkilus sp.) is especially destructive to grain, but it is also 

 destructive to nuts and fruit. The established fact that the California 

 ground squirrel is instrumental in spreading bubonic plague has made 

 these animals of more than ordinary economic importance. 



These two principal rodent pests are easily distinguished by their 

 general appearance, size, habits, and burrows. The pocket gophers have 

 very short ears, small eyes, short tails, and cheek pouches which open 

 externally ; they are relatively small (6 to 10 inches), largely nocturnal, 

 and live almost entirely in their burrows. Ground squirrels have rela- 

 tively large ears and eyes, longer tails, and the cheek pouches do not 

 open externally ; most of them are larger in size, diurnal, and forage for 

 food above ground. The burrow of the pocket gopher can be distin- 

 guished by a mound of earth surrounding the entrance, and by the fact 

 that the opening is nearly always kept plugged full of earth. The 

 burrow of the ground squirrel on the other hand is usually open, with 

 the excavated earth thrown out on one side of the entrance only. One 

 or more runways lead away from the burrow. 



According to Merriam, 1 the ground squirrels of California may be 

 arranged in four groups: (a) the large, long-eared gray ground squirrel 

 (subgenus Otospermophilus) (b) the small, short-eared, brownish 

 species (genus Citellus) ; (c) the small, white-striped, antelope ground 

 squirrel of the deserts (genus Ammospermophilus) (d) the golden- 

 mantled ground squirrel of the mountains (genus Callospcrmophilus). 



The "digger" ground squirrels (Citellus sp.), which belong to the 

 siibuvnus Otospermophilus, are not only the most destructive, but are 

 the disease carriers (Fig. 1). These ground squirrels usually live in 

 colonies, their burrows often being connected for a considerable dis- 

 tance. Food in the shape of grain, seeds, and fruit is stored for the 

 winter season. The call note is a single loud whistle. The warning 

 note is a similar short whistle followed by two or three chattering trills. 

 Young, numbering from five to ten, are usually born in March and 

 April. This ground squirrel has been found infected with bubonic 

 plague, and several cases of human plague have been traced to a bite 



riam. r. 

 no. 52. pp. 1-8. 



Hart. 



California Ground Squirrels. Treas. Dept., Public Health Reports, rol. 23, 



294980 



