SOME COMMON MAMMALS OF WESTERN MONTANA IN RELATION 

 TO AGRICULTURE AND SPOTTED FEVER. 



INTRODUCTION. 



There are few localities in the West where the commoner species 

 of native mammals, especially rodents, are so important as in certain 

 parts of western Montana ; for there the}' must be considered in rela- 

 tion not only to agriculture but also to the Rocky Mountain spotted 

 fever. Especially serious is the damage done to crops and young 

 orchards by ground squirrels, pocket gophers, and rabbits; while in 

 areas intended to be reforested the destruction of the tree seed by 

 chipmunks and Avhite-footed mice renders the extermination of these 

 rodents necessary. 



The Rocky Mountain spotted fever is a germ disease which is com- 

 municated from wild animals to human beings by the bite of the 

 spotted-fever tick {Dermacentor venustns). In a number of experi- 

 ments carried on by Dr. H. T. Ricketts 1 and others, spotted fever has 

 been repeatedly communicated to healthy guinea pigs by the bites 

 of wood ticks which had previously fed on animals sick with the fever. 

 Not only has the fever been thus carried from one guinea pig to 

 another, but it has been communicated directly to these animals by 

 ticks picked up in regions where cases of the fever are known to 

 have been contracted by men. Moreover, the germ which causes 

 spotted fever is transmitted from infected female ticks to their off- 

 spring, and in a number of experiments the disease has actually been 

 communicated simply by the injection into a healthy guinea pig of a 

 few crushed eggs of an infected tick. Such experiments as these — and 

 numbers have been made, all with similar results — are enough to 

 prove that ticks can and do transmit spotted fever. Only a small 

 percentage of ticks, however, even in the worst " fever country," are 

 infected, and thus people may be bitten by ticks many times without 

 bad results. Moreover, infected ticks may bite people and communi- 

 cate the disease and then become detached without being noticed, 

 there thus being in such cases no assignable cause for the infection. 



One of the current local theories is that spotted fever is caused 

 by drinking impure of very cold water — in other words, that the 



i Fourth Biennial Report (for 1907 and 1908) of State Board of Health of Montana, 

 pp. 106-111 and 161-183. 



484 5 



