August 10, 1917] 



SCIENCE 



125 



swine ; and a note in Nature* suggests that 

 the causative organism of epidemic jaun- 

 dice, which has occurred of late on the 

 western front in Europe, probably has its 

 natural habitat in the rat. Examples of 

 other mammal-borne diseases are found in 

 the Rocky Mountain spotted fever, trans- 

 mitted through the agency of ticks borne 

 by rodents in Montana and Idaho, and 

 rabies, carried by coyotes and dogs in Ne- 

 vada and California. 



Third, the resources of nature are dis- 

 tinctly limited in amount, and man should 

 know what and where these resources are, 

 that accurate determination may be made 

 of the amount and kind of iise which may 

 be permitted as being compatible with a 

 regai'd for the rights of all the people, and 

 of future generations. 



In the matter of conservation of her nat- 

 ural resources America has been perhaps 

 the most backward of all civilized peoples. 

 She has permitted iindue exploitation of 

 all of her resources by selfish commercial- 

 ism. In no province is this more apparent 

 than in that of the wild life, where it is 

 well known that some of the most valuable 

 and interesting mammals and birds have 

 been exterminated, and others dangerously 

 reduced. 



Fourth, the perpetuation of interesting 

 and rejuvenating natural objects, includ- 

 ing scenery, forests and wild life, demands 

 detailed and accurate knowledge of all the 

 objects to be preserved. 



Many signs indicate that the people are 

 coming to realize, as never before, the 

 recreative value of the preservation of na- 

 ture. The hearty support given the De- 

 partment of the Interior in its epoch-ma- 

 king work for the national parks and that 

 accorded the Department of Agriculture in 

 its comprehensive forest, bird and game 

 protective activities are full of meaning in 

 this connection. 



* January 18, 1917, p. 393. 



Fifth, a more intensive agriculture brings 

 man into more strenuous competition with 

 certain insect and mammalian pests; for 

 the successful maintenance of farming and 

 horticulture man must know both his 

 friends and enemies in the animal world; 

 he must be prepared to perpetuate bene- 

 ficial species, and he must be ready to con- 

 trol or exterminate those which are detri- 

 mental. 



Disturbance of the balance of nature, 

 having to do with increased competition be- 

 tween man and certain pests, is efi'ected in 

 several ways, of which the following are 

 important: Destruction of carnivorous or 

 predatory birds and mammals; reduction 

 in numbers of game birds and mammals; 

 introduction of useful domesticated species 

 of plants and animals ; involuntary or mis- 

 taken introduction of harmful exotic spe- 

 cies of plants and animals; cultivation of 

 the soil and the raising of crops ; removal of 

 the natural cover of forest and brush. 



Some of these disturbing factors, notably 

 the increase in the supply of rodent food 

 provided by growing crops, and, all too 

 often, the ill-advised destruction of natural 

 checks on rodent increase, such as hawks, 

 owls, badgers, skunks, weasels and other 

 predatory animals, indicate that rodent out- 

 breaks may be expected to occur more fre- 

 quently in the future than they have in the 

 past, and it is well known that plagues of 

 rodents have harassed mankind at intervals 

 since the dawn of history. 



In Nevada in 1907 and 1908 meadow 

 mice of the genus Microtiis overran four 

 fifths of the cultivated area in the lower 

 Humboldt valley leaving a "dismal scene 

 of destruction," and necessitating the com- 

 plete replanting of much alfalfa land.^ 

 Depredations of cotton rats (Sigmodon) in 

 certain sections of the middle west, notably 

 southern Kansas and Oklahoma, in the 



6 Piper, Yearbook, TJ. S. Department of Agri- 

 culture for 1908, 1909, p. 302. 



