38 AN ECONOMIC STUDY OF FIELD MICE. 



EPIDEMIC DISEASES. 



Excessive multiplication of any mammal to the point of over- 

 crowding is sure to be followed sooner or later by a fatal epidemic. 

 Numerous instances of the prevalence of such diseases among rodents 

 are known, and several of the historic mouse plagues were terminated 

 by them. So complete was the destruction that several years of 

 almost total absence of mice followed. 



NATURAL ENEMIES OF FIELD MICE. 



Prominent among the recognized causes for the great increase of 

 rodent pests in recent years is the persistent destruction of the birds, 

 mammals, and snakes that habitually prey upon them. Warfare 

 against the natural enemies of noxious rodents' is not confined to 

 America. In the British Islands and on the Continent gamekeepers 

 have systematically killed foxes, weasels, stoats, hawks, and owls, 

 on the plea that they destroy game, and even farmers have joined in 

 the warfare against the so-called " A^ermin." In America the same 

 mistaken sentiment exists, and too often has led to ill-advised legis- 

 lation against mammals and birds that are beneficial to the farmer. 

 Wise measures for game protection can not be too highly commended, 

 but ignorance of the true relations of animals and birds of prey to 

 game is widespread even among lawmakers and sportsmen's clubs. 



One of the most common mistakes made by sportsmen in the sup- 

 posed interests of game protection is the offer of prizes for the de- 

 struction of alleged " game-destroying " mammals and birds. In one 

 instance nine competitors for a club's prizes destroyed during twelve 

 months 184 weasels, 48 foxes, 54 minks, 343 skunks, 15 great horned 

 owls, 6 " common owls," and 148 hawks. The fact that only 21 

 owls were killed in an entire year by nine men trying for a record 

 reveals a scarcity of these useful birds that is not complimentary to 

 the intelligence of the community. The large number of skunks 

 killed indicates ignorance or disregard of the usefulness of that ani- 

 mal in destroying insects and mice. Apparently, too, there was no 

 discrimination as to the species of hawks destroyed, and it is prob- 

 ably safe to say that field mice in a single year have damaged the 

 farmers of the region concerned a hundredfold more than the value 

 of all the game and poultry saved through the offer of prizes. 



The evidence presented to a committee of the British Board of 

 Agriculture, who were investigating the Scottish vole plague of 1892, 

 showed conclusivel} T that in the affected district before the outbreak 

 carnivorous animals and birds had been very scarce. The committee 

 in their report emphasized the importance of protecting the birds, 

 whose absence in the district in question was regarded as an impor- 

 tant cause of the enormous multiplication of voles. 



