To recapitulate: judging from the number of nests examined—of course, another such series might give different results—the winter retreats or bush-nests of the white-footed mice are usually modified birds' nests; but in some cases the modification appears to be extended to practically a new construction.
Once within their nests, the white-footed mice are not readily disturbed during the day; and, unless the smilax or other growth is greatly agitated, they will not even take the trouble to look about them. By gently cutting my way toward the nest with a pair of shears, snipping here and there a branch or two, and drawing others gently aside, I have never failed to successfully surprise the timid occupants in their snug retreats. It is fairly safe, therefore, to conclude that I procured a pretty accurate knowledge of the number of occupants of each nest, the relative proportion of the one to the other sex, and of old and young. Thirty-six nests contained each a female mouse, and of these twenty-two were associated with young able to walk, while the others were burdened with the care of helpless offspring but a few days old. In not a single instance did I find a male mouse in these nests, while in the six other nests each was found to contain a single adult male mouse and no other occupant.
This unsocial condition of affairs seems to me the more strange, as in several nests placed upon the ground—many such nests are occupied the year round—both parents were found. They were not accompanied by any offspring, however; and it would seem as though a separation took place on the birth of a litter. Such facts tempt one to theorize, but I desist.
It was a pretty sight to see the mice when forced to quit their airy quarters in a thicket of smilax. Be the vine ever so slender, they took no uncertain steps, but tripped lightly down from point to point, and never arriving at a confusing corner. One female mouse turned just twenty times before she reached the ground. Once there, although she had proceeded very cautiously before, she suddenly disappeared. This, indeed, is always the case; but just where they go when they reach terra firma remains to be shown.
The prevalent impression is that every mouse has a subterranean retreat directly beneath the nest in the bushes, and passes from one to the other as fancy dictates. Their actions seem to bear out the truth of this, but I have never been able to discover such underground retreats in positions that conclusively showed they were frequently visited by the bush-dwelling mice above them. On the other hand, I have found the evicted mice to take shelter under dead leaves, pieces of bark, or limbs of trees. If disturbed from such lurking-places, they very seldom attempt to re-enter the elevated bush-nests, but scamper off over the weedy, leaf-strewed meadow.
Besides reconstructing nests of birds as dwellings for themselves, they convert others into magazines stored with carefully selected
