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"The quantity of green vegetation eaten by a single adult field 

 mouse in the course of a year has been calculated at from 24 to 36 

 pounds. When one considers in connection with this estimate the 

 great numbers of these animals in our meadows, swamps, and forests, 

 the total quantity of food consumed by them appears so enormous as 

 apparently to exceed the productive capacity of the soil. A thousand 

 meadow mice in a meadow would require at least 12 tons of grass 

 or other vegetation to maintain them for a year. 



THE COMMON MEADOW MOUSE. Microtus pennsylvanicus (Ord). 



The most familiar of American species of Microtus is the common 

 meadow mouse (M. pennsylvanicus). The average measurements of 

 adults are about as follows: Total length, 6.6 inches; tail vertebrae, 

 1.8 inches; hind foot, 0.83 inch. The tail is always at least twice 

 as long as the hind foot. The fur is long and overlain with coarse 

 black hairs. In summer the ears overtop the fur. In winter the fur 

 is longer, and of a duller color, and almost conceals the ears. The 

 usual color above is a dark brown, against which the black hairs are 

 not conspicuous. This shades off gradually into gray or tawny on 

 the under parts. 



"The vast range of this species has already been given. This 

 mouse has its natural habitat in moist meadows and grassy borders 

 of swamps, but it habitually extends its range into neighboring culti- 

 vated fields, waste lands, and open spaces on the border of timber 

 lands. Wherever it occurs, it is normally the most abundant rodent. 

 Nearly all meadows are full of the animals. 



"In swamps meadow mice nest in burrows in dry tussocks or in 

 bunches of grass above the surface of the moist ground. The nests 

 are composed of grass or fibers of weeds made into balls, loose and 

 of coarser materials outside, but compact and of finer stuff within, 

 each having a small opening on the side near the bottom. From this 

 opening two or more trails diverge, one usually leading into an under- 

 ground tunnel which opens at some distance from the nest. Nests 

 intended to receive the young are lined with the softest of accessible 

 materials. 



"The species under consideration never live in barns or out- 

 buildings. Its nearest approach to human habitations is the stackyard 

 or piles of wood or boards left on the edge of orchards or fields near 

 houses. 



"The common meadow mouse is especially noted for long winter 

 excursions from its summer abode, hiding its movements under cover 

 of deep snow. The journeys of the animals are not suspected until 



