8 



COMMON MAMMALS <>l' WKSTKliN MONTANA. 



tend (o cause immunity. Although ii is almost tasteless, ground 

 squirrels and chipmunks refuse to eat it except when their natural 

 food is very scarce, and then strychnine also would be eaten and 

 would be much more effective. During the spring and summer of 

 1911 the author tried arsenic thoroughly and was forced to the con- 

 clusion that it is not a satisfactory poison for any of the rodents 

 mentioned herein, except woodchucks and possibly wood rats. 



Potassium cyanide is an exceedingly deadly and dangerous poison, 

 which has been much used to destroy ground squirrels and prairie 

 dog-. Although cheap, it absorbs moisture and quickly decomposes 

 when exposed to the air. and is therefore unsatisfactory. It is not 

 recommended. 



Corrosive sublimate, barium carbonate, squill, and mix vomica each 

 have such serious faults that they are not at present recommended. 



METHODS OF USING STRYCHNINE. 



Three methods of applying strychnine to baits are recommended 

 in this bulletin. In one the food is soaked in a solution of sulphate 

 of strychnine, in another it is coated with starch or flour paste con- 

 taining powdered alkaloid of strychnine, and in the third it is mixed 

 with starch containing the alkaloid and is then compressed into 

 squares or ''biscuits." 



Grain soaked in sulphate solution is very bitter and is not recom- 

 mended except when the bait is to be soaked in tallow to render it 

 waterproof. A sulphate solution is valuable in preparing baits for 

 rabbits and meadow mice 



Starch or (lour paste containing powdered alkaloid is recommended, 

 localise baits coated with these materials can be prepared much more 

 easily than those soaked in sulphate solution, because animals carry- 

 ing coated baits are often killed simply by the absorption of part of 

 the poison directly into the blood through the mucous membranes of 

 the mouth or cheek pouches, and because the centers of kernels of 

 coated grain remain sweet and are more freely eaten than those made 

 bitter all through by soaking in sulphate solution. 



It is sometimes necessary to take special precautions to avoid killing 

 birds, and in such cases ••oatmeal biscuits'" are recommended. 



NECESSITY OF SPRING POISONING. 



Ground squirrels, chipmunks, and mice usually refuse to take poi- 

 soned baits when natural food is abundant, and preparations which 

 are effective at one time of the } 7 ear are often of no use at another. 

 The best time to use poison is in early spring, and the work should 

 be done then if possible. Columbian ground squirrels can not be suc- 

 cessfully poisoned at any other season. Thus, although 27 dead 



484 



