THE NATIONAL GEOGRAPHIC SOCIETY 



485 



pellets of fur and bones, representing 

 thousands of mice. While certain species 

 of hawks seldom frequent trees, others 

 habitually perch in them, notably the 

 large rough-leg, Swainson, and red-tail, 

 which were the most abundant and per- 

 sistent mousers. In nearly all of the 

 valleys, even those which have been 

 farmed for years, the absence of trees is 

 notable. More trees along ditches, about 

 the borders of fields, and in groves here 

 and there would doubtless increase the 

 number of valuable resident hawks and 

 owls and attract more winter visitors. 



It was estimated that during the height 

 of the outbreak birds and mammals de- 

 stroyed some 45,000 mice daily. Al- 

 though their combined assaults unaided 

 did not suffice to abate the plague, yet 

 when the number of mice was reduced 

 by poison, and long before it approached 

 the normal, they were able not only to 

 prevent increase, but to cause a rapid 

 decline, which continued until the mice 

 became so scarce that the predatory 

 birds and mammals were forced to scat- 

 ter and look elsewhere for food. It is 

 fair to infer that had these friends of 

 the farmer been protected in the begin- 

 ning they would have been able from the 

 first to hold the mice in check, preventing 

 the abnormal increase so that there 

 would have been no plague. 



The mouse which produced the plague 

 in Nevada, locally known as "black 



mouse" (see page 483), is the Carson 

 field mouse (Microtus montanus), one of 

 the numerous species of short-tailed field 

 mice or meadow mice, a group which 

 has caused widespread destruction in 

 various parts of the world. This field 

 mouse is rather widely distributed in the 

 valleys of Utah, Nevada, northeastern 

 California, and eastern Oregon. In 

 nearly all parts of the United States 

 short-tailed field mice are among the 

 most abundant of mammals, and a num- 

 ber of species in widely separated locali- 

 ties have occasionally exhibited the same 

 tendency to excessive increase, indicating 

 that favoring conditions may produce 

 mouse plagues wherever the mice exist. 

 Even when in small numbers they de- 

 stroy considerable clover and alfalfa and 

 injure orchards, nurseries, and root 

 crops. 



This is the first recorded instance of 

 an irruption of field mice in North 

 America attaining the proportions of a 

 plague. The experience indicates the 

 probability of future and even more dis- 

 astrous outbreaks. In the extensive re- 

 claimed areas of the West the abundant 

 food and luxurious cover furnished by 

 alfalfa fields and the miles of irrigation 

 ditches, which afford these mice suitable 

 homes along their banks, greatly favor 

 their increase,, while surrounding desert 

 conditions limit the spread of mice be- 

 yond the cultivated areas. 



THE NATIONAL GEOGRAPHIC SOCIETY 

 AND GEOGRAPHIC WORK 



THE extraordinary growth of this 

 Society has made it incumbent 

 on its Board of Managers to 

 correspondingly increase its power and 

 influence as an educative force in Amer- 

 ica. The main objects of the Society are 

 the increase and diffusion of geographic 

 knowledge, which must be done by three 

 distinct methods — those of publication, 

 of encouragement, and of research. The 

 Board of Managers has given much at- 



tention of late to a consideration of the 

 means best calculated to produce results 

 in keeping with the great importance and 

 with the high aims of the Society as a 

 whole. Definite policies with regard to 

 research work having been adopted dur- 

 ing the past month, their tenor is here- 

 with communicated to the members, 

 together with a general review of the 

 work of the Society. 



