REPORT OF THE SECRETARY. 117 



to stimulating activity on the part of resident farmers and land- 

 owners generall}" in the work of ridding their lands of ground squir- 

 rels. "\^nien fully advised of the importance of the work, they have 

 usually shown themselves ready to do their part. The present law 

 of California, which requires the cooperation of all landowners in 

 the work of exterminating ground squirrels, will, if fully enforced, 

 go far toward providing a remedy, especially if the State, through 

 county and other officials, arranges for furnishing poison or poisoned 

 bait in necessary quantities to landowners at cost. By providing 

 centers of distribution the poison can be supplied ready for use at 

 comparatively low cost, which will greatly stimulate its use by 

 farmers and others. 



RELATION or NATIVE MAMMALS TO SPOTTED ^E^^ER. 



The recently ascertained agency of certain of our native mammals 

 in the transmission of diseases vastly increases the importance of a 

 knowledge of the exact range of the species concerned and their 

 habits. It is now known that the so-called spotted fever of the Rocky 

 Mountain region is transmitted from certain native mammals to 

 men through the agency of ticks. In its most virulent form this 

 fever, fortunately, has a restricted range, being confined to a portion 

 of Bitterroot Valley, western Montana; but in milder form it pre- 

 vails in parts of Idaho, Wyoming, Utah, and Nevada, and probably 

 elsewhere in the Rocky Mountain region. During the past year the 

 Biological Survey, the Bureau of Entomology, and the Agricultural 

 Experiment Station of Montana cooperated in a field and labora- 

 tory study of the agencies and manner by which the disease is trans- 

 mitted to human beings. The work of the Biological Survey was 

 chiefly confined to ascertaining the species of native mammals which 

 carry ticks in any stage of development, since presumably one or 

 more of these mammals is, if not the original, the chief source of 

 infection. 



A collection of the mammals of the valley and adjacent mountains 

 was made and the ticks discovered were turned over to the assistants 

 of the Bureau of Entomology for experiment and study. No fewer 

 than 18 species of mammals were found to harbor fever ticks — proof 

 of the great difficulty that must necessarily attend any attempts to 

 exterminate all the wild hosts of the ticks over the region in which 

 the fever prevails. The mammal found to be most frequently in- 

 fested — possibly in this respect equaling all other wild mammals 

 combined — is the common ground squirrel of the region {Citellus 

 columbianus) , which abounds over much of the valley. As a very 

 important step in the suppression of the disease, a thoroughly organ- 

 ized campaign to exterminate this squirrel within the limits of the 



