Alfalfa in Kansas. 



355 



about. This is evidenced by the sudden appearance in late summer and 

 in autumn of new mounds, like pioneer shanties, in fields remote from 

 other gopher habitations. At this season we occasionally encounter a 

 claim seeker abroad even in the day time. In late autumn and early 

 winter, too, the males no doubt wander about more or less. 



FIG. 304. View of a gopher-infested alfalfa field. 

 [Courtesy Kansas Experiment Station.] 



THE BURROW. Except where an invader has recently established him- 

 self in new territory, it is practically impossible to determine the limits 

 of a gopher's burrow. The work of excavating is usually carried on at 

 a depth of eight to ten inches below the surface of the ground, but the 

 animal sometimes ranges lower in loose, sandy soil, where succulent roots 

 penetrate deeper. The average diameter of the burrow of the prairie 

 pocket gopher is about three inches; large enough that one may usually 

 thrust the hand and arm back into it as far as he can reach. These 

 data are easily obtained, but when one undertakes to map out the course 

 of the main runway, the branch tunnels and their intersections, the 

 pockets and the short laterals, he has before him a task that might well 

 appall a military engineer in the wilds of a jungle. In a field that is 

 even fairly well populated by gophers the runways of different individ- 

 uals must of necessity frequently intersect each other, for it can not be 

 supposed that all the numerous subway crossings one exposes in digging 

 along the tunnels are parts of one animal's private labyrinth. A prairie 



