SMALLER MAMMALS OF NORTH AMERICA 



407 



leaves and other small decaying vegetable mat- 

 ter covering the ground under the trees. Occa- 

 sionally, when the surface soil becomes dry 

 and hard, the burrows are deeper, so that no 

 surface indications can be discovered. On ac- 

 count of the similarity of their burrows the 

 depredations of pine mice are commonly attrib- 

 uted to moles. 



Several inches below the surface pine mice 

 excavate oval chambers to be used for nests or 

 for storage purposes. The nest chambers have 

 several entrances from ramifying tunnels and 

 are rilled with short fine pieces of grass, mak- 

 ing a warm nest-ball. Here the several litters 

 of young are born each year. Pine mice are 

 less prolific than field mice, however, and the 

 litters contain only from one to four young. 



The food chambers are larger than the nest 

 chambers, and when full of stores are kept 

 closed with earth. In these are stored short 

 sections of green or dry grasses, bulbous grass 

 roots, and short sections of other edible roots. 

 One such store contained about three quarts of 

 the fleshy roots of a morning glory cut into 

 short sections. 



Pine mice obtain much of their food from 

 the bark about the bases and roots of trees, in- 

 cluding both coniferous and deciduous species. 

 They kill many small trees and shrubs by gird- 

 ling, or by cutting the roots below the surface, 

 and in this way frequently inflict severe dam- 

 age in orchards and nurseries. Owing to their 

 underground habits they are much more dan- 

 gerous to orchards than field mice. They also 

 do much damage by burrowing along rows of 

 potatoes and other root crops, upon which they 

 feed. 



Both pine mice and field mice are serious 

 pests to agriculture and only by vigilant care 

 can they be prevented from steadily reducing 

 the returns from farm and orchard. A mouse 

 appears so insignificant an enemy that the gen- 

 eral inclination among farmers is to ignore it, 

 but both field and pine mice exist in such enor- 

 mous numbers and are so generally distributed 

 that the aggregate annual losses from them are 

 great. 



Clean cultivation in orchards, especially for 

 some distance immediately about the trees, is 

 an excellent protective measure against both of 

 these mice. The shrubbery and fruit trees of 

 orchards, lawns, and gardens may be protected 

 by the use of poisoned baits and traps as soon 

 as signs of pine mice or field mice are observed. 



THE RED-BACKED MOUSE (Evotomys 

 gapperi and its relatives) 



{For illustration, see page 421) 



With the exception of the banded lemmings 

 the red-backed mice are the most brightly col- 

 ored of the smaller northern rodents. They 

 are close relatives of the common field mice, 

 which they about equal in size, but from which 

 they are distinguished externally by rufous col- 

 oration, finer and more glossy pelage, larger 

 ears, and proportionately longer tails. 



The red-backed mice form a group contain- 



ing a considerable number of species distrib- 

 uted throughout the northern circumpolar 

 lands, except on the barren islands of the Arctic 

 Sea. In North America they occur from the 

 Arctic tundras north of the limit of trees 

 southward throughout Alaska and Canada to 

 the northern United States. With other north- 

 ern species of mammals, birds, and plants they 

 follow the high mountain ranges still farther 

 southward to North Carolina, New Mexico, 

 and middle California. 



It is true that in the far North they are nu- 

 merous on the moss-grown tundras, and in the 

 South range above timber-line on high moun- 

 tains. As a general rule, however, they are 

 woodland animals, whether among the spruces, 

 birches, and aspens of the North or farther 

 south in the United States in the cool fir and 

 aspen-clad slopes of mountains. They also fre- 

 quent old, half-cleared fields, brush-grown or 

 rocky areas, and similar places where cover is 

 abundant. 



Although so closely related to the field mice, 

 the red-backed species are not known to be- 

 come excessively abundant nor seriously to in- 

 jure crops. One reason for their harmlessness 

 in this respect may be their strong preference 

 for forest haunts. 



I once found them numerous in the grass- 

 grown streets and yards of an abandoned min- 

 ing camp in the forest at the head of Owens 

 River, in the Sierra Nevada, of California. The 

 mice were making free use of the congenial 

 shelter afforded by the old log cabins, and their 

 runways and entrances to burrows were all 

 about under scattered boards and similar cover. 



They are abroad equally by day and by night, 

 and for this reason are better known to woods- 

 men than most of the small w r oodland animals. 

 When foraging by day among the fallen leaves 

 and deep green vegetation they present a most 

 graceful and attractive sight, now moving about 

 with quick and pretty ways, now pausingto sit 

 up squirrel-like to eat some tid-bit held in the 

 front paws and then on the alert to detect a 

 suspected danger and poised in quivering readi- 

 ness for instant flight. 



Red-backed mice usually live in underground 

 burrows similar to those of field mice, but gen- 

 erally located with more care in dry situations, 

 the entrances sheltered by a stump, old log, 

 root of a tree, rock, or other object. Ordina- 

 rily they do not make such w r ell-defined run- 

 ways as do many field mice, and sometimes no 

 trace of a trail can be found leading away from 

 their burrows. But where they travel about 

 through small dense vegetation, under logs and 

 about stumps and rocks they often make well- 

 marked trails. 



Their nests are bulky and formed of a mass 

 of fine dry grass, moss, and other soft mate- 

 rial, which is sometimes located in an under- 

 ground chamber opening off the burrow and 

 sometimesin hollow stumps and logs or under 

 other surface shelters. But little is known 

 about the home life of these mice except that 

 they are prolific, and between April and Octo- 

 ber have several litters containing from three 

 to eight young in each. 



