The Pocket Gopher. 137 



and potato are used. The presence of freshly thrown up 

 mounds indicates that the animal is extending his runways in 

 that quarter, and it is best to confine one's poisoning opera- 

 tions to such places. If the field can be dragged over with a 

 harrow or plank a few days after the poison has been put out, 

 new mounds can be readily detected and fresh poison dis- 

 tributed. If the work was thoroughly done in the first place 

 it usually takes but a few minutes to go over the field a second 

 time. The few remaining gophers, if any, may become wary, 

 and in that case they should be trapped. 



The best time of the year to poison gophers is when they are 

 most active in extending their burrows. This is usually in the 

 late fall, for they are then laying in stores of provisions for the 

 winter. Spring is a period of renewed activity, and poison 

 may be successfully used at this time also. In fact, it will pay 

 to make war on pocket gophers at any time when they are seen 

 to be active. 



Fumigation. The use of carbon-bisulfid vapor or the fumes 

 of burning sulfur as agents for destroying the pocket gopher 

 is not recommended by this Station. It is true that fumigation 

 methods are occasionally followed by successful results, but 

 under ordinary conditions the game is not worth the powder. 

 We have other remedies for the pest that can be more easily, 

 more effectively and more cheaply employed. An older bulletin 

 of the United States Department of Agriculture recommends 

 carbon-bisulfid as the simplest agent for the destruction of 

 gophers, but later advices from the same source partially dis- 

 credit the former recommendations, and experiments at this 

 Station contribute to the same result. 



The ordinary method of using carbon-bisulfid for destroying 

 burrowing rodents is to pour the liquid upon a wad of cotton, 

 corn-cob, or other porous substance and then thrust the latter 

 into an opening made into the burrow, closing the opening at 

 once with earth. The bisulfid vaporizes rapidly, forming a 

 heavy gas which is supposed to flow along the runways, smoth- 

 ering the occupants. This it will do in the case of animals 

 whose burrows are short or penetrate deep into the soil. The 

 pocket gopher, however, in his search for food ranges so near 

 the surface of the ground that the introduced gas has plenty 

 of opportunity to escape through the loose earth or to be ab- 

 sorbed. The burrows are long and intricate, branching often 



