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UNITED STATES DEPARTMENT OF AGRICULTURE

FARMERS' BULLETIN

WASHINGTON, D. C. 670 JUNE 3, 1915.

Contribution from the Bureau of Biological Survey, Henry W. Henshaw,
Chief.




FIELD MICE AS FARM AND ORCHARD PESTS.

By D. E. LANTZ, _Assistant Biologist_.


    NOTE.--This bulletin describes the habits, geographic
    distribution, and methods of destroying meadow mice and pine mice,
    and discusses the value of protecting their natural enemies among
    mammals, birds, and reptiles. It is for general distribution.




INTRODUCTION.


The ravages of short-tailed field mice in many parts of the United
States result in serious losses to farmers, orchardists, and those
concerned with the conservation of our forests, and the problem of
controlling the animals is one of considerable importance.

Short-tailed field mice are commonly known as meadow mice, pine mice,
and voles; locally as bear mice, buck-tailed mice, or black mice.
The term includes a large number of closely related species widely
distributed in the Northern Hemisphere. Over 50 species and races occur
within the United States and nearly 40 other forms have been described
from North America. Old World forms are fully as numerous. For the
purposes of this paper no attempt at classification is required, but
two general groups will be considered under the names meadow mice and
pine mice. These two groups have well-marked differences in habits,
and both are serious pests wherever they inhabit regions of cultivated
crops. Under the term "meadow mice"[1] are included the many species of
voles that live chiefly in surface runways and build both subterranean
and surface nests. Under the term "pine mice"[2] are included a few
forms that, like moles, live almost wholly in underground burrows. Pine
mice may readily be distinguished from meadow mice by their shorter and
smoother fur, their red-brown color, and their molelike habits. (See
fig. 1.)

[1] Genus _Microtus_.

[2] Genus _Pitymys_.

[Illustration: FIG. 1.--Field mice: _a_, Meadow mouse; _b_, pine mouse.]




MEADOW MICE.


Meadow mice inhabit practically the whole of the Northern Hemisphere--
America, north of the Tropics; all of Europe, except Ireland; and
Asia, except the southern part. In North America there are few wide
areas except arid deserts free from meadow mice, and in most of the
United States they have at times been numerous and harmful. The animals
are very prolific, breeding several times a season and producing
litters of from 6 to 10. Under favoring circumstances, not well
understood, they sometimes produce abnormally and become a menace to
all growing crops. Plagues of meadow mice have often been mentioned
in the history of the Old World, and even within the United States
many instances are recorded of their extraordinary abundance with
accompanying destruction of vegetation.

The runs of meadow mice are mainly on the surface of the ground under
grass, leaves, weeds, brush, boards, snow, or other sheltering litter.
They are hollowed out by the animals' claws, and worn hard and smooth
by being frequently traversed. They are extensive, much branched, and
may readily be found by parting the grass or removing the litter. The
runs lead to shallow burrows where large nests of dead grass furnish
winter retreats for the mice. Summer nests are large balls of the same
material hidden in the grass and often elevated on small hummocks in
the meadows and marshes where the animals abound. The young are brought
forth in either underground or surface nests.

Meadow mice are injurious to most crops. They destroy grass in
meadows and pastures; cut down grain, clover, and alfalfa; eat grain
left standing in shocks; injure seeds, bulbs, flowers, and garden
vegetables; and are especially harmful to trees and shrubbery. The
extent of their depredations is usually in proportion to their numbers.
Thus, in the lower Humboldt Valley, Nevada, during two winters (1906-8)
these mice were abnormally abundant, and totally ruined the alfalfa,
destroying both stems and roots on about 18,000 acres and entailing a
loss estimated at fully $250,000.

When present even in ordinary numbers meadow mice cause serious
injury to orchards and nurseries. Their attacks on trees are often
made in winter under cover of snow, but they may occur at any season
under shelter of growing vegetation or dry litter. The animals have
been known almost totally to destroy large nurseries of young apple
trees. It was stated that during the winter of 1901-2 nurserymen near
Rochester, N. Y., sustained losses from these mice amounting to fully
$100,000.

Older orchard trees sometimes are killed by meadow mice. In Kansas in
1903 the