40 AN ECONOMIC STUDY OF FIELD MICE. 



numerous to have much effect, good or bad, upon the interests of the 

 farmer. 



The various species of weasels and wild ferrets are persistent 

 destroyers of meadow mice. The smaller weasels easily traverse the 

 surface runways of the larger species of Jlicrotus and even follow 

 them into underground burrows. The larger weasels feed upon 

 pocket gophers, prairie dogs, ground squirrels, and various kinds of 

 mice and rats. AYhile occasionally they capture game or song birds, 

 as well as poultry, their principal food consists of injurious rodents. 



The small American weasels, like European species, have an evil 

 reputation among game preservers and farmers, who assert that 

 weasels destroy the eggs and young of game birds, as well as young 

 chickens and other fowls. However, stomach examinations, supple- 

 mented by careful field observations, show that small mammals form 

 the principal food of weasels. Among their prey are cottontail rab- 

 bits, little chief hares (Ochotona), prairie dogs, ground squirrels, 

 wood rats, field mice, and the house mouse and brown rat. 



A recent advance in the price of weasel skins in white, or winter, 

 pelage has alread}^ caused a marked scarcity of these animals in some 

 of the Northern States. The present abundance of meadow mice in 

 the same States is attributable partly to the destruction of weasels. 

 A correspondent in Minnesota, in a letter dated April 14, 1906, states 

 that field mice were very abundant in his neighborhood during the 

 preceding winter and caused much damage in orchards and nur- 

 series. He adds : " The animals have never been so numerous here 

 as during the last two years. I think weasels used to keep mice in 

 check, but the high price of fur has made them very scarce." 



Badgers, when not employed in unearthing larger rodents, devote 

 much time and labor to digging out field mice. One will patiently 

 excavate every burrow on an acre or more of ground, and, besides the 

 litters of young, evidently get a large share of the old mice. Badgers 

 have been caught with their intestines full of pellets of fur and bones 

 of Microtus. Nevertheless, while doing almost no harm and while in 

 general highly beneficial, badgers are destroyed almost everywhere, 

 partly for sport, partly because on rare occasions one raids an unpro- 

 tected chicken coop. 



Foxes destroy many field mice and other rodents as well as many 

 insects, especially grasshoppers, and thus do much to compensate for 

 the poultry and game they kill. Although reliable testimony to the 

 destruction of domestic fowls by the red fox {Vulpes fulva) is not 

 wanting, the habit is by no means common, as is shown by the con- 

 tents of stomachs examined by the Biological Survey. In three cases 

 remains of the Gambel partridge were found and in one other a 

 small bird. On the other hand, harmful rodents, including field mice, 

 were found in over 20 stomachs. Besides these, a mole, a lizard, 



