GRAY GOPHER. 45 



the dispositions of the Gophers. In South Dakota Geomys inhabits 

 the mellow soil of the James Eiver Valley and its western branches, 

 while Thomomys inhabits the high rolling prairies with heavy, clay 

 soil that is waxy when wet and hard when dry. Thus the two species 

 come nearest together where sandy valleys penetrate the high prairie. 

 That Geomys invariably avoids hard or stony soils is shown by its absence 

 from south western Missouri and the Ozark Mountains; from the clay 

 prairies of southeastern Kansas, and the wax lands of Texas.. On the 

 other hand, Thomomys delights in the hardest soils and stony moun- 

 tain sides. Thus it is easy to account for the limit of range of Geomys 

 by soil. But while Thomomys inhabits hard soils it does not object to 

 sandy and mellow soils. The reason it does not invade the range of 

 Geomys may be that the latter, being the larger and more powerful ani- 

 mal, will not permit, it to occupy the same ground. 



The Gray Pocket Gopher is abundant over nearly the whole of the 

 great prairie region of North and South Dakota. The little mounds of 

 fresh, black soil thrown up along its lines of subterranean tunnels show 

 the various turns and windings of its galleries. Save for these mounds 

 there is nothing to indicate the presence of the animal or its burrows. 

 Often one individual works all summer without going beyond the limits 

 of an acre of ground. It is rarely seen above ground, coming out of its 

 hole just far enough to push back the loose earth brought from its 

 excavations and quickly returning for other loads, until enough is 

 ejected at one place, when it retires and closes the entrance of the hole 

 with damp earth. The progress of the burrow seems to be wholly 

 without aim or design, bending and turning in conformity to the charac- 

 ter of the soil, or following such roots and plants as suit the animal's 

 taste. 



The burrows, nests, and mounds of this species and the Prairie Gopher 

 are much alike except that the Gray Gopher, being a smaller animal, 

 makes smaller burrows and throws up mounds more frequently. Usually 

 after some familiarity with both species it is not difficult to distinguish 

 the mounds. While Thomomys ordinarily produces small bills, it often 

 forms large ones by reopening the same hole and throwing out additional 

 earth. Sometimes the Gopher throws out fresh earth at the same place 

 every night, closing the hole during the day, until a compound hill of 

 considerable size is formed. Following are the dimensions of some hills 

 that I measured at Pembina, N. Dak., in 1887 : 4 by 4 feet in diameter 

 and 10 inches high; 4 by 5 feet and 9 inches high; 3 by 3 feet and 7 

 inches high; 4 by 5 feet and 6 inches high. The ordinary hill is about 

 12 inches across and 2 or 3 inches high. 



Near the large hills there are usually no small ones, but the tunnel 

 extends a considerable distance before another hill is started. Twenty- 

 seven feet is the greatest distance I have measured between two hills. 

 The ordinary sized hills are usually 4 to 10 feet apart. 



In habits the Gray Gopher is as solitary as the other Gophers, 



