Field Mice as Farm and Orchard Pests

by David E. Lantz

CULTIVATING THE LAND.

Thorough cultivation of fields and the elimination of fence rows between them is the most effective protection against field mice. Cultivation destroys weeds and all the annual growths that serve as shelter for the animals. This applies equally well to orchards and nurseries. Clean tillage and the removal from adjoining areas of the weeds and grass that provide hiding places for mice will always secure immunity to trees from attacks of the animals.

PROTECTING NATURAL ENEMIES OF MICE.

Field mice are the prey of many species of mammals, birds, and reptiles. Unfortunately, the relation that exists between the numbers of rodents and the numbers of their enemies is not generally appreciated; otherwise the public would exercise more discrimination in its warfare against carnivorous animals. It is the persistent destruction of these, the beneficial and harmful alike, that has brought about the present condition of growing scarcity of predacious mammals and birds and corresponding increase of rodent pests of the farm, especially rats and mice. The relation between effect and cause is obvious.

Among the mammalian enemies of meadow and pine mice are coyotes, wildcats, foxes, badgers, raccoons, opossums, skunks, weasels, shrews, and the domestic cat and dog. Among birds, their enemies include nearly all the hawks and owls, storks, ibises, herons, cranes, gulls, shrikes, cuckoos, and crows. Among their reptilian foes are black snakes and bull snakes. Not all these destroyers of mice are more beneficial than harmful, but the majority are, and warfare against them should be limited to the minority that are more noxious than useful.

OWLS AND FIELD MICE.

Owls as destroyers of mice are deserving of special mention. Not one of our American owls, unless it be the great horned owl, is to be classed as noxious. Especially beneficial are the short-eared, long-eared, screech, and barn owls. All these prey largely upon field mice, and seldom harm birds. Unfortunately, the short-eared and barn owls, which are the more useful species, are not plentiful in the sections most seriously infested by field mice.

The short-eared owl, while widely distributed, is not abundant, except locally, within the United States, but wherever field mice become excessively numerous these owls usually assemble in considerable numbers to prey upon them. Examinations of stomachs of these owls show that fully three-fourths of their food consists of short-tailed field mice.

The barn owl is rather common in the southern half of the United States and breeds as far north as the forty-first parallel of latitude. That mice form the chief diet of this bird has been demonstrated by Dr. A. K. Fisher, of the Biological Survey, through examination of stomachs of many barn owls and also of large numbers of pellets (castings from their stomachs) found under their roosts. In 1,247 barn-owl pellets collected in the towers of the Smithsonian Building in Washington, D. C., he found 1,991 skulls of short-tailed field mice, 656 of the house mouse, 210 of the common rat, and 147 of other small rodents and shrews. Very few remains of birds were found. Figure 7 illustrates the contents of some of these pellets.