They are abroad equally by day and by night, and for this reason are better known to woodsmen than most of the small woodland 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 pausing to 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 readiness for instant flight. Red-backed mice usually live in underground burrows similar to those of field mice, but generally located with more care in dry situations, the entrances sheltered by a stump, old log, root of a tree, rock, or other object. Ordinarily they do not make such well-defined runways 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 material, which is sometimes located in an underground chamber opening off the burrow and sometimes in 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 October have several litters containing from three to eight young in each. [Illustration: ARCTIC HARE _Lepus arcticus_] [Illustration: COTTONTAIL RABBIT _Sylvilagus floridanus_] [Illustration: MARSH RABBIT _Sylvilagus palustris_] [Illustration: PIKA, LITTLE CHIEF HARE, or CONY _Ochotona princeps_] They feed upon a great variety of seeds, fruits, roots, and succulent vegetable matter and lay up stores for winter in underground chambers or in hollow logs and similar places above ground. With the coming of winter they gather about cabins and other habitations in their territory and become as persistent as house mice in searching out and raiding food supplies of all kinds. When the more appreciated kinds of food fail they resort to gnawing the bark from roots and bases of trunks of small deciduous trees of various kinds. During my sledge journeys in the region about Bering Strait I found the skins of many red-backed mice among the Eskimo children. The small boys kept them with lemming skins as evidences of their prowess with miniature dead-fall traps and blunt-pointed arrows, and the little girls kept them as prized robes for the dolls carved by their fathers from wood or walrus ivory. =THE RUFOUS TREE MOUSE= (=Phenacomys longicaudus= and its relatives) (_For illustration, see page 523_) The genus Phenacomys, to which the rufous tree mouse belongs, includes a number of species closely similar in size and external appearance to some of the well-known field mice. The structure of their teeth, however, shows that they form a distinct group of animals.