340 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



1. POISONING 



The four things necessary to poison gophers successfully are: (a) 

 an effective poison such as strychnine ; ( ft ) succulent bait that will be 

 relished by the gopher; (c) a bait large enough that the gopher 

 must eat it at once and not put it in his pocket and carry it away to 

 his storehouse; and (d) placing of the bait in the main run with the 

 least disturbance possible, so that the gopher can readily find it and 

 not cast it out with the dirt, as would often be the case were it placed 

 in an open hole or in a lateral. 



In poisoning ground squirrels, it has been found that strychnine 

 is more readily absorbed through the membranous cheek pouches, 

 which open inside the mouth, than through the stomach. But 

 the fur-lined pockets of the gopher which open outside the mouth do 

 not readily absorb the strychnine. Hence poisoned bait, such as 

 strychnine-coated barley, which is effective on the ground squirrel, is 

 not effective on the gopher. The gopher often puts the poisoned grain 

 in its pockets and carries it away to the storehouse, where the poison 

 soon loses strength. 



The cheapest and best method of destroying gophers, where a large 

 territory is involved, is by the use of vegetable baits poisoned with 

 strychnine. Such baits are easily placed in the main runways or bur- 

 rows of the gopher by aid of a probe (see fig. 1). The outstanding 

 advantage of the probing method is that the burrows can be readily 

 located and the poisoned baits placed in them with a minimum dis- 

 turbance. This is important since recent field tests have shown that 

 where the burrows were but little disturbed the gopher's suspicions 

 were only slightly aroused or not at all. As a result of placing the 

 bait by aid of a probe, 40 per cent more of the poisoned baits were 

 taken by the gophers than where the burrows were dug open and the 

 bait placed in the holes in the usual manner. Probing is also much the 

 quicker method. One man, after becoming familiar with the use of 

 the probe, can treat several hundred burrows in a day. As much as 

 five acres of heavily infested alfalfa have been gone over by one man 

 in one day. 



The great disadvantage of the probing method lies in the fact that 

 in order to use the probe successfully the surface of the ground must 

 be damp or wet to the depth of the ordinary gopher run — six to eight 

 inches. The probing method is not successful in dry soils. It is futile 

 to probe for gopher runs in dry adobe or any other soil which cracks 

 upon drying, because the probe drops just as readilj^ into a crack in 



