RODENTS IN SOIL FORMATION GRINNELL 343 



of its burrow. As an evident result of this timidity, each feeding 

 exit is the center of a small circle, shorn of vegetation, the radius 

 of which is less than the body length of the gopher. The haunches 

 of the animal, when it forages, remain in contact with the orifice 

 of the burrow, as a sort of anchor by means of which the gopher 

 can pull itself back into safety at an instant's warning. It is well 

 known to gardeners that a gopher will burrow underground to 

 some near-by plant, rather than risk capture by venturing forth 

 on the open surface. Many times gophers tunnel toward the sur- 

 face beneath plants and cut off roots and even main stems, without 

 any disturbance being evident above ground, until the plants begin to 

 wither and die, if they do not topple over before by reason of inse- 

 curity at the base. 



In digging, the earth loosened by the strong incisor teeth and 

 stout front claws is swept back underneath the body until a con- 

 siderable amount has accumulated. The animal then turns around 

 (being able to do so apparently almost within the diameter of its 

 own body, which is the diameter also of its burrow), and pushes the 

 earth along the tunnel to the surface opening where it is shoved out 

 on top of the ground or into some other part of the burrow system 

 no longer of use. Only the fore feet, in conjunction with the broad 

 furry face below the level of the nose, are used in moving the earth. 

 The outside-opening, fur-lined, cheek pouches, with which the animal 

 is provided, and which are situated at each side of the mouth, are 

 not used to carry earth, but solely to carry clean food materials. 

 Most of the surface openings are at the ends of side tunnels and 

 are but a few inches in length. After excavation has proceeded a 

 few inches beyond one surface opening, this opening is closed and 

 a new one is made at a more convenient location — nearer the point 

 where the earth is being removed. 



As already intimated, gophers occur veiy widely. In fact, in Cali- 

 fornia, we find them existing under the most extreme conditions of 

 climate, though different species are represented under the different 

 combinations of conditions. There are pocket gophers in abundance 

 in the vicinity of Yuma, and at Eureka; at Monterey, and around 

 Goose Lake ; at Fresno, and up to the limit of plentiful plant growth, 

 11,500 feet, on the slopes of Mount Whitney. 



1 will now give some facts and information relative to the gophers 

 in the Yosemite National Park, where Mr. Tracy Irwin Storer and 

 myself have made definite studies of their habits. 



The pocket gopher 2 is one of the few Sierran rodents that carry 

 on active existence throughout the entire year. It does not hibernate. 



2 The species here concerned is Thomomys monticola. 



