THE GROUND SQUIRRELS OF CALIFORNIA. 



785 



In comparison with syrups, albumen, cereal pastes, gelatines and 

 commercial gums, starch mucilage proved most satisfactory as the 

 medium for the poison coating. It makes a very thin coating that 

 readily liberates the strychnine into the squirrel's cheek pouches. The 

 addition of soda bicarbonate and saccharin in the poison coating has 

 a marked effect in delaying the bitter taste of the strychnine, so that 

 squirrels are less likely to refuse the poisoned grain. Small amounts 

 of heavy corn syrup and glycerin are added to the coating to prevent 

 the grinding and dusting off of the poison which occurs when the grain 

 becomes dry. Shellac, other resins, fats and vegetable oils were tried 

 as coating mediums in attempts to make a rain-resistant poison that 

 could be used effectively during the wet season of winter and early 

 spring, but these materials do not liberate the poison freely enough to 

 kill the animals. Moreover, the squirrels, to a great extent, cease car- 

 rying grain in their cheek pouches soon after the coming of the rainy 

 season ; instead they then hull out the kernels where the grain is found. 

 It is evident that a satisfactory winter poison — as yet not determined — 

 must be based on some other form of strychnine or other peculiarity of 

 the animal. 



An effective poison was only half the battle. The method of distrib- 

 uting it is quite as important. The first impulse in distributing poisoned 

 grain, still followed by many, was to place it in the holes or in a small 

 heap at the very entrance of the squirrel's burrow. But squirrels do 

 not look for food in these locations, and much of the poisoned grain is 

 lost by being covered by the animal running over it. Nature did not 

 drop the squirrel's food into the burrows nor place it in neat little 

 piles in front of them; she scattered it in locations" not always near the 

 burrows. Accordingly, the poisoned grain is now scattered on clean 

 areas within three to ten feet of the burrows, around trees or rockpiles, 

 along squirrel trails and in places where the animals feed. 



The standardized formula resulting from these investigations, and the 

 method for applying it, have been of immense economic value to Cali- 

 fornia. Used in the dry season and properly distributed, the poison 

 is entirely reliable. If prebaiting with clean, unpoisoned barley be 

 practiced in advance of poisoning, the squirrel pest can be prac- 

 tically eradicated by a single poison treatment in any given locality. 

 The common mistake is in attempting to use the poison during the wet 

 season, when results are less certain, though even under such conditions 

 it is among the most effectual of strychnine preparations. In general 

 use in the state for the past six or seven years, it has very largely 

 replaced the use of proprietary poisons at a small fraction of the cost 

 of the latter. In clearing the squirrel pest from valuable agricultural 

 areas, from irrigation systems, from nut groves and grainfields, the 

 aggregate saving to the state must be expressed in millions. 



Carbon disulphid has proved valuable during the wet seasons, espe- 

 cially for completing extermination of ground squirrels following the 

 use of the poisoned baits. It is very volatile and explosive, so should 

 be handled with care. There are two ways of using it, either by using 

 a pump which forces the gas into the burrow, or by saturating an 

 absorbent ball of some sort with the liquid and dropping it into the 

 burrow. The latter method is more commonly used. A convenient 



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