FIELD MICE 



425 



(Fig. 412). This is set over the ridge made by a mole burrowing 

 just beneath the surface in search of food. If this surface burrow 

 is still in use, the trap hardly ever fails to catch the animal. 



Moles work ordinarily in the early morning and late afternoon, 

 and when the earth of a mound moves, indicating the addition 

 of fresh material from below, a manure fork driven into the moving 

 mass generally impales the animal; or a light charge of powder 

 and shot is effective. 



F. E. Wood, in "A Study of the Mammals of Champaign 

 County, Illinois" (Bull. 111. State Lab. Nat. Hist., vol. viii, 1910), 

 states that moles are very sensitive to odors and 

 may be driven away by placing naphthalin, 

 moth-balls, carbon bisulfid, or formalin in and 

 around their runs. 



Field mice (Fig. 413) destroy at least three 

 million dollars' worth of crops in the United 

 States every year. During the last few years 

 farm losses have greatly increased through the 

 work of these animals. Their extreme fecundity 

 is emphasized by a published statement by 

 D. E. Lantz, based upon scientific observation, 

 that "a single pair and their progeny in five 

 seasons would amount to nearly one million 

 individuals." 



Field mice begin breeding in the spring, 

 probably early in April in the North, and pro- 

 duce several litters of from four to eight each 

 in a season. The period of gestation is about FIG. 412. A successful 

 twenty days. Their round nests are found at mole trap ' 



the ends of very short burrows, under stumps or brush heaps, 

 or even directly on the surface of the ground, fastened stoutly 

 to surrounding stems. They seek concealment later under hay 

 stacks, shocks of corn, and similar places. They do not hiber- 

 nate, but continue their depredations during winter in their hiding 

 places and under the protecting snow. 



Doubtless the war of extermination carried on by man against 

 hawks, owls, crows, skunks, foxes, weasels, and snakes, all natural 

 enemies of mice, is to a large extent responsible for present-day 

 losses through the work of field mice. Other enemies of these 

 mice are wolves, raccoons, bitterns, and herons. Perhaps the 

 most effective way to keep down the numbers of field mice is to 



