THE GROUND SQUIRRELS OP CALIFORNIA. 



753 



species were to be found, and furthermore the wood rat had been discov- 

 ered to harbor the plague flea. A possibility of the transmigration of 

 the Sierra Nevadas would thus be established by way of the low 

 mountain passes. After bubonic plague had been discovered east of 

 the San Joaquin River near Ripon, fears gained currency of the rapid 

 spread of the disease up through the foothills into the mountains, across 

 the mountains east into Nevada, where other rodents could carry the 

 flea harboring the bacillus of bubonic plague, and possibly the prairie 

 dog also would be instrumental in its dissemination still on to the east- 

 ward where city rats again might be the host of the flea. 



On the strength of the possibility, pointed out by the United States 

 Public Health Service, which might arise from the rapid spread of 

 bubonic plague among ground squirrels throughout California's valley, 

 even into the forests and mountains, allotments to prosecute the erad- 

 ication of rodents upon public lands and national forests were eagerly 

 sought, and a more plausible argument than safeguarding human health 

 had never been advanced hitherto, for economic losses did not seem to 

 appeal as being serious. An appropriation to eradicate noxious rodents, 

 particularly ground squirrels upon national forests, was turned over 

 to the Bureau of Biological Survey, United States Department of 

 Agriculture. 



In 1913 extensive operations were carried on by the Biological Survey 

 on national forests and public domain which have been continued up 

 to the present time. The only control methods applied upon national 

 forests prior to this time had been instituted by interested forest super- 

 visors or district rangers. In many localities excellent results had been 

 obtained which, when followed up properly, demonstrated an increased 

 value to those grazing stock on these forests. 



So far as records show, the plague was never found within any of 

 the national forests where the infestations of ground squirrels were 

 heavy. Nevertheless, the value of the work in eliminating a source of 

 reinfestation for agricultural areas adjacent to these timber reserves 

 or the prevention of greater damage to forage crops on the range can 

 never be estimated. Estimates have been made by numerous investi- 

 gators that from 15 per cent to 25 per cent of range value is depleted 

 which, if true, means that an enormous saving to stock men would be 

 effected, not to mention the slightly increased revenue to the forest 

 service from additional grazing fees. It was not until 1917, however, 

 that the bureau of biological survey took up extensive educational cam- 

 paigns in connection with the county horticultural commissioners, in 

 order that the co-operative action gained thereby might furnish a means 

 by which all public and privately owned lands could be cleared of 

 squirrels in a systematic manner. 



Every effort was made by the United States Public Health Service 

 to procure co-operation of all counties where plague had been found, 

 as well as some adjacent, especially in a financial way. Boards of 

 supervisors were petitioned to establish an inspector system, which for 

 the most part met with approval of these officers. They had been bur- 

 dened with the details of eradicating squirrels in their counties from 

 an economic angle and now comes an opportunity to unload some of 

 these duties upon a willing federal agency whose purpose had behind 

 it the safety of human lives. 



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