38 AK ECONOMIC STUDY OF FIELD MICE. 
KIM 1>KM K DISEASES. 
Excessive multiplication of any mamma] 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 terminatec 
by (hem. So complete was the destruction that several years o: 
almost total absence of mice followed. 
NATURAL ENEMIES -OF FIELD MICE. 
Prominent among the recognized causes for the great increase oj 
rodent pests in recent years is the persistent destruction of the birds. 
mammals, and snakes that habitually prey upon them. Warfan 
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 " vermin." 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, -18 foxes, 54 minks, 343 skunks, 15 great hornec 
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 ol 
Agriculture, who were investigating the Scottish vole plague of 1892, 
showed conclusively 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. 
