20 AN ECONOMIC STUDY OF FIELD MICE. 



lows: Total length, 125 mm. (about 5 inches) ; tail vertebra?, 20 mm. 

 (0.78 inch) ; hind feet, 16.3 mm. (0.64 inch), 



Owing to their peculiar habits, pine mice are not so well known as 

 are meadow mice. Their natural habitat is the forest, although they 

 are b}^ no means restricted to pine woods or forested areas. While 

 often inhabiting pine woods and the edges of adjacent fields, they live 

 also in forests and copses of deciduous trees, usually on uplands. 



The life of pine mice is largely spent in underground tunnels, 

 which so closely resemble those of the mole that generally they are 

 mistaken for the work of that animal. The ridges of loose soil over 

 the tunnel are exactly like those thrown up by the mole, but the inner 

 diameter of mouse tunnels is less. When moles and pine mice live 

 in the same vicinity, the mice often use the runways made by 

 the moles. It is this habit that has helped to bring moles into dis- 

 repute with farmers, who blame them for damages inflicted upon 

 potatoes and other crops by pine mice. 



In marked contrast with the pine mouse, the mole (genus Scalopus) 

 is almost exclusively carnivorous, eating mainly earthworms and 

 insects. While it sometimes cuts off the roots of growing plants 

 when they interfere with its tunneling operations, it apparently eats 

 no roots. Stomach examinations of moles show that they eat a very 

 small percentage of vegetable matter, and this mainly waste corn or 

 other grain previously softened by long contact with wet soil. On 

 the other hand, pine mice eat little insect food, if any, and are largely 

 consumers of vegetable substances. Nearly always when moles are 

 charged with destro3 T ing root crops, the real culprits are pine mice. 



Thin, open woodlands used for pasture, and thickets along the 

 edges of forests are favorite resorts of pine mice. Like nearly all 

 voles, they prefer moist soil, but it must also be loose and somewhat 

 sandy. From their intricate tunnels under the leaf mold frequent 

 burrows descend into the soil. Some of these burrows are utilized 

 as nesting places. Nests are built also at the surface of the ground, 

 under fallen logs, brush heaps, flat stones, fences, or other shelter. 



The number of young at a birth evidently averages less than is 

 usual in the genus Jficrotus, as is shown by the small number of 

 mamma?. Observations as to the number of litters in a season seem 

 to be lacking, but the rate of reproduction is probably less in the 

 pine mice than in any other American group of field mice. Blasius 

 says concerning M. subterraneus of Europe, that " it produces five 

 or six times a year three to five young, which are blind for ten days 

 after birth;'' l and this statement is probably true, with slight modi- 

 fication, for all the species of the group. To compensate for slower 

 multiplication, their liability to attack by -natural enemies is much 



a N. A. Fauna No. 17, p. 64, 1900. 



& Naturgeschichte der Saugethiere Deutschlands, p. 390, 1857, 



