2 BULLETIIS^ 1091, U. S. DEPARTMENT OF AGRICULTURE. {B^'ll.''Na''l, 



been found that such rodents as prairie dogs, pocket gophers, mar- 

 mots, ground squirrels, and rabbits take appreciable and serious toll - 

 of the forage on the open grazing range; in fact, that the}' reduce 

 the carrying capacity of the range to such an extent that expenditures 

 for control measures are amply justified. Current estimates place 

 the loss of goods due to rats and mice in warehouses and stores 

 throughout the United States at no less than $2*00,000,000 annually, 

 and damage to the carrying capacity of the open range and to culti- 

 vated crops generally by native rodents in the Western States at , 

 $300,000,000 additional ; added together, we haA^e an impressive total 

 from depredations of rodents. 



The distribution and life habits of rodents and the general con- 

 sideration of their relation to agriculture, forestry, and grazing, with 

 special reference to the carrying capacity of stock ranges, is a subject 

 that has received attention for many years from the Biological Sur- 

 vey of the United States Department of Agriculture. As a result 

 of the investigations conducted much has been learned concerning 

 the economic status of most of the more important groups, and the 

 knowledge already gained forms the basis of the extensive rodent- 

 control work already in progress, and in which many States are co- 

 operating with the bureau. If the work is to be prosecuted intelli 

 gently and the fullest measure of success achieved, it is essential that 

 the consideration largely of groups as a whole be supplemented by 

 more exhaustive treatment of the life histories of individual species 

 and of their place in the biological complex. The present report is 

 based upon investigations, chiefly in Arizona, of the life history, 

 habits, and economic status of the banner-tailed kangaroo rat, Dipo 

 domys sfectabilis spectahilis Merriam (PL I). 



INVESTIGATIONAL METHODS. 



Some 18 years ago (in 1903) a tract of land 49.2 square miles in 

 area on the Coronado National Forest near the Santa Rita Mountains 

 Pima County, southeirn Arizona, was closed to grazing by arrange- 

 ment between the Forest Service and the Agricultural Experiment 

 Station of the University of Arizona. Since that time another small 

 tract of nearly a section has been inclosed (Griffiths, 1910, 7 ^) . Thi; 

 total area of approximately 50 square miles is laiown as the United 

 States Eange Reserve, and is being devoted to a study of grazing con 

 ditions in this section and to working out the best methods of adminis 

 tering the range (PI. II, Fig. 1). 



f. 



"^ References in parentheses are to the Bibliography, p. 40 (the last figure being to thi 

 page of the publication). References to authorities where no citation of literature if 

 appended relate for the most part to manuscript notes in the files of the Biological Survej 

 or the University of Arizona Agricultural Experiment Station. 



