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THE NATIONAL GEOGRAPHIC MAGAZINE 



two or three feet into the open, bite off a tender 

 little grass blade and dash back to the sheltered 

 road. There they would sit up squirrel-like, 

 holding the grass blades in their forepaws and 

 eating them rapidly, or would sometimes carry 

 the food back to the burrows. 



Occasionally as the mice darted into the open 

 I made a slight squeaking noise and perhaps 

 two or three in sight at the time would in- 

 stantly turn and dash back into the sheltered 

 road, sometimes not reappearing for a long- 

 time. Again and again I saw them come into 

 the open for food, and before securing it sud- 

 denly scamper back in a panic without apparent 

 cause for alarm. 



Eternal vigilance is the only defense such 

 animals have, and despite their watchfulness 

 myriads of them are devoured daily by a large 

 number of rapacious birds and mammals, in- 

 cluding even such huge beasts as the great 

 Alaskan brown and grizzly bears, which dig 

 them from their burrows on grassy northern 

 mountain sides. 



Despite their numerous natural enemies field 

 mice are so prolific they continue among the 

 most destructive of agricultural pests. They 

 are so obssure and the damage by a single 

 mouse appears so insignificant, that it requires 

 a knowledge of their habits, their wide distri- 

 bution, and their enormous numbers to appre- 

 ciate what a serious drain they are on the 

 farmer's income, even when in their normal 

 numbers. 



In summer they feed on growing grass, 

 clover, alfalfa, and grain, seeds, bulbs, root 

 crops, and garden vegetables. In fall they con- 

 gregate under shocks to feed on the grain, and 

 in winter often do enormous injury to young 

 or even well-grown fruit and other trees by 

 gnawing off the bark on the base of the trunk 

 and roots, sometimes in this way destroying 

 entire orchards and nurseries. 



One species in California destroys large 

 quantities of raisins drying in the field by car- 

 rying them off to some shelter, where they cut 

 out the seeds and leave the rest of the fruit. I 

 have seen half a pound of raisins under a piece 

 of board, the result of the night's work of a 

 single mouse. 



While field mice are always destructive, at 

 intervals they have sudden and mysterious ac- 

 celerations of increase and become so exces- 

 sively abundant that they are a veritable plague. 

 Many instances of this are on record in the Old 

 World, where they have become so numerous 

 as to call forth governmental intervention. 



The most notable recent outbreak of this 

 kind in the United States took place in the 

 Humboldt Valley, Nevada, where, during the 

 winters from 1906 to 1908, they swarmed over 

 the cultivated parts of the valley and completely 

 destroyed 18,000 acres of alfalfa, even devour- 

 ing the roots of the plants. During this out- 

 break the mice in the alfalfa fields were esti- 

 mated to number as high as 12,000 to the acre. 



Whenever field mice become over-abundant 

 notice appears to go out among their natural 

 enemies, and in extraordinary numbers hawks, 

 owls, crows, ravens, sea gulls, coyotes, foxes, 



bobcats, weasels, and other animals appear to 

 prey upon them. 



At no season of the year are they free from 

 their foes, for they remain active throughout 

 the winter, and most species apparently lay up 

 no winter store of food. They travel to winter 

 feeding places through series of tunnels under 

 the snow, and it is mainly at this season that 

 they do the most serious damage to orchards 

 and shrubbery. 



In the far North at the beginning of winter 

 they gather in large numbers about the fur- 

 trading stations and other habitations, where 

 they persistently invade the food supplies. 



Some of the northern mice, however, gather 

 stores of food for winter. A species living 

 along the coast of the Bering Sea and else- 

 where on the Arctic tundra of Alaska accumu- 

 lates a quart or more of little bulbous grass 

 roots, which are delicious when boiled. They 

 are hidden in nests of grass and moss among 

 the surface vegetation, and before the first 

 snowfall I have seen the Eskimo women 

 searching for them by prodding likely places 

 with a long stick. The roots thus taken from 

 the mice are kept to be served as a delicacy 

 to guests during winter festivals. 



THE PINE MOUSE (Pitymys pinetorum 



and its relatives) 



{For illustration, see page 420) 



The pine mice form a small group of species 

 peculiar to North America and closely related 

 to the field mice. They are similar in form to 

 the common field mice of the Eastern States, 

 but are usually smaller, with much shorter tails 

 and shorter, finer, and more glossy fur. 



Most of the pine mice are limited to the 

 wooded region of the States between the At- 

 lantic coast and the eastern border of the Great 

 Plains, and from the Hudson River valley and 

 the border of the Great Lakes south to the 

 Gulf coast. Strangely enough, one species lives 

 in a restricted belt covered with tropical forest 

 along the middle eastern slope of the Cordil- 

 lera, which forms the eastern wall of the Mex- 

 ican tableland, on the border between the 

 States of Vera Cruz and Puebla. 



Pine mice occupy the borders of thin forests 

 and brushy areas, from which they work out 

 into the open borderlands, especially in or- 

 chards or other places where there are scat- 

 tered trees amid a rank growth of weeds. In- 

 stead of making their runways among growing 

 vegetation on the surface of the ground like 

 field mice, they live in little underground tun- 

 nels or burrows which extend in all direc- 

 tions through their haunts. These tunnels are 

 closely like those of the common mole except 

 that they are smaller and have frequent open- 

 ings to the surface, through which the owners 

 make short excursions for food. They often 

 utilize the tunnels of moles when conveniently 

 located for their purposes. 



The tunnels are often so near the surface 

 that the ground is slightly uplifted or broken 

 as by a mole, or they are made under the fallen 



