Its stores of food are often communal, a colony of mice contributing, for it is not always of solitary habit. These stores are of the most varied character. Of the very miscellaneous items on its menu a few may be mentioned: leaves of clover and dandelion, with flower-buds of the latter, nuts of all kinds, apples, grapes, gooseberries, crocus and hyacinth bulbs (Millais says the Dutch were taught to multiply hyacinths by division of the bulbs through observing the effects of this mouse's attacks), acorns, rose and bramble seeds, slow-worms, eggs and—putty! It has been known to enter beehives, and not only to eat the honeycomb, but impudently to construct its nest there. Deserted birds' nests are often adapted to its use, either as a dining-room when seeking haws in the hedges, or as a permanent habitation, in this case roofed with moss.
The breeding nest is a globular structure of dry grass, and is usually built in a separate chamber of the underground run, but occasionally is on the surface or under a heap of hedge débris. Some of the burrows may extend as much as three feet underground.
Towards the end of last century, Mr. de Winton called attention to what was considered to be a new British mouse—the Yellow-necked Mouse (Apodemus flavicollis), distinguished from the Wood Mouse by its larger size, the head and body measuring four and a quarter inches, and the brown spot on the chest commonly found in the Wood Mouse developed into an orange cross whose arms are connected with the upper side coloration—described as golden brown. This is a feature that at once attracts attention where this form occurs; but there is another distinction out of sight—there being three additional bony joints in the tail, that is thirty instead of the twenty-seven in the tail of an ordinary Wood Mouse. Whether it is a really distinct species or the typical form of the Wood Mouse is at present open to question. It is found chiefly in the southern and eastern portions of England, but its distribution also includes Northamptonshire, Herefordshire, and Northumberland.
Other local races have been distinguished also as distinct species or sub-species under the name of Hebridean Field Mouse (A. hebridensis) with the white of the under parts tinted with buff; Fair Isle Field Mouse (A. fridariensis), like the Yellow-necked but without the collar; St. Kilda Field Mouse (A. hirtensis) with brown under parts; and Bute Field Mouse (A. butei), darker, with shorter tail and ears.
House Mouse (Mus musculus, Linn.).
The most familiar, the most widely distributed and most numerous of the mammals of our country, the Common or House Mouse, stands in little need of nice description. Although of a timid and retiring nature, it can on occasion exhibit not only bold familiarity, but actual friendliness to mankind to which it has been attached for ages, preferring to live in palace or hovel with human beings to the open-air life of woods and fields. Not that he is not to be found in the open air; but then it is mostly in the immediate neighbourhood of a house, where he can make his runs in ricks of corn—mountains of food. It is this easy method of despoiling man of his goods that caused the Mouse in ancient days to attach himself to the huge creature that is so impotent in ridding himself of small adversaries. The domestic Mouse is considered to have had its home, its place of origin, in Asia, whence it has spread to every part of the world where man has gone. In most cases, it may be presumed with safety, it has travelled cosily stowed away in his stores and merchandise, so that as soon as the human migrant has built himself a home he finds that the Mouse is in occupation, and demanding a share of his food. In spite of all his serious depredations, our literature teems with evidence that the victim has always retained some kindly feeling for his pretty four-footed oppressor.
For the sake of uniformity, let us say that the head and body of the House Mouse measure a little more than three and up to four inches, and the tapering, flexible, and sparsely haired, scale-ringed tail may slightly exceed that measurement. It has a pointed snout, the bright, bead-like eyes are black, the large, sensitive brownish ears are nearly half the length of the head, and the soft, brownish-grey fur is only a little paler on the under parts. Outdoor specimens are often more yellow-brown in coloration. As compared with the Wood Mouse we have this more dusky and uniform coloration, shorter whiskers, smaller eyes, stouter and less flexible tail, and shorter legs. The thumb of the hand is reduced to a mere tubercle.
It is very active and silent in its movements, emerging from a tiny hole in floor-board or skirting and gliding without sound over the floor, ascending with ease table-legs or walls, and then, if alarmed, springing with a prodigious leap back to its hole. Concrete floors will not suffice to keep it out of a house, for it will climb the outer walls and enter the upper windows, thence making itself secret ways to the lower floors behind woodwork or plastered walls, till it reaches the kitchen, the larder or the storeroom. Though it shows by its preferences that its natural rôle is that of grain thief, it will eat any kind of human food and much besides: in a word, it is omnivorous.
Its great success as a species is due to this adaptability and to its astonishing fecundity. It produces four or five litters during the year, each consisting of five or six, or even up to twelve, blind and naked young which develop so rapidly that in a fortnight they are capable of independence. At the age of six weeks they may begin to breed.