178 SEEDING AND PLANTING 



tremely varying in its effectiveness. Hunger 1 states that the 

 control of rodents in large field operations has never been dem- 

 onstrated to be practical. The many species of squirrels, chip- 

 munks, gophers, and mice are scarcely ever the same in their 

 relative destructiveness even on contiguous areas. Not only does 

 each species appear to have distinctive food habits, but the food 

 and activities of the same species differ at different times of the 

 year. Poisoned bait distributed without regard to the destruc- 

 tive species and their habits is ineffective. The, kind of bait, 

 and the season and manner of applying it must be adapted to the 

 particular species to be destroyed. If there is an abundance of 

 rodent food on the area where the poison is distributed, it is rela- 

 tively ineffective. It is, however, under such conditions that 

 rodent damage is the least. Usually it is most effective when 

 distributed in the spring. Poisoning the seed itself before sowing 

 is not so effective. as poisoned bait distributed over the area before 

 the seeding. Cox 2 concludes from the investigations of the 

 Biological Survey that rodents can be greatly reduced in numbers 

 and their depredations practically stopped by systematic poisoning. 



When rodents are abundant, it may be necessary to distribute 

 poisoned bait several months before the seeding and again a few 

 days before the seed is sown. When the rodents have been de- 

 stroyed and a given area is practically free from the pests when 

 the seed is sown, others may come in from unpoisoned adjacent 

 areas and destroy the seed. It is usually desirable, therefore, to 

 scatter the poisoned bait over a strip from 8 to 10 rods wide entirely 

 around the seeded area and to keep this strip well poisoned until 

 the seed has germinated. 



When the area is poisoned in the autumn, it should be done 

 several weeks in advance of the seeding or before the rodents 

 begin to store their winter food supply. 



Experiments made by the U. S. Biological Survey in cooper- 

 ation with the Forest Service show that strychnine baits are the 

 most effective in destroying seed-eating rodents. The following 

 methods are recommended for preparing the bait. With slight 

 variations in the proportion of strychnine to the other ingredients 



1 Munger, T. T.: Natural versus artificial regeneration in the Douglas fir 

 region of the Pacific coast. (Proc. Soc. Am. For., vol. VII, pp. 187-196. 1912.) 



2 Cox, W. T. : Reforestation on the national forests. (U. S. Forest Service, 

 Bui. 98. 1911.) 



