REPORT OF THE SECRETARY. 125 



mammals in and near the valley. It does not follow, however, that 

 all ticks found on mammals are capable of transmitting the fever. 

 The ticks discovered and all mammals showing symptoms of disease 

 were given to experts for examination. The results of the work of 

 the past season should go far to aid in a solution of this important 

 problem. Should it prove, as seems probable, that the Columbia 

 ground squirrel or some other rodent is responsible for the spread of 

 the disease through the agency of ticks, it is believed that a practi- 

 cable plan can be devised for reducing the numbers of the animals 

 within the confines of Bitterroot Valley and other inhabited locahties 

 in the Rocky Mountain region where the fever is prevalent, so that in 

 future it need be little feared. 



PRAIRIE DOGS. 



In certain regions of the j\Iiddle West prairie dogs exist in great 

 numbers, and so numerous are their colonies in certain places that 

 they seem to form one continuous settlement. In such areas, where 

 the little rodents number many thousands, the damage they do to 

 forage grasses and other vegetation is very great. The extent of 

 this damage can be realized when it is known that 35 prairie dogs 

 during their season of activity eat as much grass as one sheep and 

 210 eat as much as a range steer. In the days of unhmited public 

 pasturage such losses passed almost unnoticed, but the increasing 

 value of grass lands for stock ranges makes it impossible to ignore 

 them longer. In thickly settled farming communities the extermi- 

 nation of prairie dogs is comparatively easy, since it is possible to 

 secure the necessary cooperation between landowners; but in sparsely 

 settled areas and on large stock ranges cooperation is difficult or 

 impossible to obtain, and the cost of extermination bears heavih^ on 

 individual owners. To discover methods of destruction of the utmost 

 efficiency and at a minimum of cost has been the endeavor of the 

 Survey, and investigations to this end have been made during the 

 past year in New Mexico, Colorado, Wyoming, and Montana, and are 

 still in progress. Oats poisoned with strychnine have proved to be the 

 most attractive bait so far experimented with, but as the use of this 

 grain endangers the lives of valuable birds like shore larks and long- 

 spurs, further experiments will be made with a view to obviating 

 this disadvantage. 



BIRDS IN RELATION TO THE CODLING MOTH. 



The codling moth occurs in every apple-growing region of the 

 United States, and where no effort is made to check its ravages it 

 destroys from a fourth to three-fourths of the crop. It has been 

 estimated by assistants of the Bureau of Entomology that the 

 annual loss in the United States due to the codling moth, including 



