AUG 14 19P 



Issued Auf^ust 3, 1911. 



United States Department of Agriculture, 



BUREAU OF BIOLOGICAL SURVEY— Circular No. 82. 

 HENRY W. HENSHAW, Chief of Bureau. 



THE MAMMALS OF BITTERROOT TALLEY, MONT., IN 

 THEIR RELATION TO SPOTTED FEYER. 



By Henry W. Henshaw, Chief, Biological Survey, 

 and 



Clarence Birdseye, Assistant, Biological Survey. 



INTRODUCTION. 



The present report contains the results of investigations carried 

 on from March 12 to July 14, 1910, and continued in 1911 in coopera- 

 tion with the Bureau' of Entomology and the State Experiment 

 Station of Montana. In addition it embodies numerous data obtained 

 by assistants of the Biological Survey in previous years. 



As has long been known, the so-called s^potted fever of many 

 parts of the Eocky Mountain region is peculiarly virulent in Bitter- 

 root Valley, Mont., and the present investigations were undertaken 

 for the primary purpose of ascertaining the particular species of 

 wild mammals in and near the valley which harbor ticks, especially 

 the form Dermacentor venustus, believed to be chiefly responsible 

 for the spread of this fever. Incidentally also it Avas intended to 

 obtain ticks in various stages of development for determination and 

 study by the Bureau of Entomology and for experimental purposes. 

 It was further expected that in the course of the season's trapping 

 animals stricken by the fever would be taken which might be made 

 to yield valuable data regarding the etiology of the disease. But 

 the untimely death in Mexico of Dr. H. T. Ivicketts, who had 

 planned to carry on these studies, put an end for the season to this 

 part of the investigation, and, although animals were trapped show- 

 ing unmistakable signs of disease, in the absence of experts in this 

 branch of the work the nature of the sickness could not be determined. 



The almost complete restriction of the fever to the western side 

 of the valley has occasioned much speculation and given rise to 



[Cir. 82] 



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