BUREAU or BIOLOGICAL SUEVEY. 279 



Wyoming. Preliminary conferences were held in reference to the 

 organization of similar work in Iowa, Minnesota, and Texas. In- 

 vestio-ations for bettering the methods of destroying injurions rodents 

 as well as improving the organization are being conducted, and the 

 work is becoming increasingly effective. 



Field investig^ations through inclosed trial plots for the purpose 

 of securing accurate data as to the destruction of forage by rodents 

 on the open range have been continued during the year in coopera- 

 tion with tlie Forest Service, the State University of Arizona, and 

 the Carnegie Institution of Washington. Interesting and valuable 

 residts are being secured. 



The demands from the States for increased activities in rodent- 

 control work, and the money offered by States and counties for co- 

 operative purposes, are far greater than the bureau can possibly 

 meet with its available funds. The opportunity for useful expansion 

 in this work is obvious in view of the fact that native rodents destroy 

 each year field crops and forage worth approximately $300,000,000, 

 while the losses from house rats and mice approximate nearly $200,- 

 000,000, a large proportion of which can be eliminated at moderate 

 cost. 



Through a system of contracts the bureau has been able to assist 

 the States in securing poison supplies for use in rodent campaigns 

 at a discount amounting to many thousands of dollars, thus increas- 

 ing the effective use of their funds. 



PRAIRIE DOGS. 



Prairie dogs occupy more than 100,000,000 acres of public and 

 private lands. Wherever the}^ occur in abundance they are exceed- 

 ingly destructiA'e to cultivated crops and to forage on the open 

 range. In cooperation Avith the extension services of the agricultural 

 colleges in Arizona. Colorado. Montana, New Mexico, North Dakota, 

 Oklahoma, South Dakota, Utah, and Wyoming, the campaign against 

 these animals has been pushed aggressively. In Arizona and New 

 Mexico the State councils of defense joined actively in the work 

 and contributed funds for the purpose. The participation of farmers 

 and stockmen has been fuller than ever before, and the saving of 

 crops and forage has been correspondingly great. During the year 

 from 75 to 95 per cent of the prairie dogs were destroyed on nearly 

 2,000,000 acres of privately owned crop and forage lands and on 

 more than 200,000 acres of public domain, the latter making more 

 than 3,700,000 acres of public lands which have been largely freed 

 from tiiese pests. In many places private landowners were so inter- 

 ested that they volunteered their services to clear adjacent Govern- 

 ment lands, the bureau supplying the poison to be used in the work. 

 With cooperation of this character it will be possible to clear large 

 areas of the public domain at almost a nominal cost to the Gov- 

 ernment. 



GROUND SQUIRRELS. 



Numerous species of ground squirrels occur in the West, several 

 of them having such wide ranges and existing in such abundance 

 that their depredations on crops and forage are most serious. As 

 with the prairie dogs, continued investigations are being made to 

 devise improved methods of poisoning and of organization for their 

 destruction. The poisoned grain used for operations against ground 

 squirrels on private lands is prepared under the supervision of field 



