In a battle there are always two sides and at its finish one side always runs away while the other pursues. Thus it is in the wars of nature, only here the timid ones are always ready to flee, while the strong are equally prepared to pursue. It is only by constant vigilance that the little mice can save themselves from disappearing down the throats of their enemies, as under cover of darkness they snatch nervous mouthfuls of grain in the fields,—and hence their gray colour and their large, watchful eyes; but on the other hand, the baby owls in their hollow tree would starve if the parents were never able to swoop down in the darkness and surprise a mouse now and then,—hence the gray plumage and great eyes of the parent owls.
The most convincing proof of the reality of protective coloration is in the change of plumage or fur of some of the wild creatures to suit the season. In the far north, the grouse or ptarmigan, as they are called, do not keep feathers of the same colour the year round, as does our ruffed grouse; but change their dress no fewer than three times. When rocks and moss are buried deep beneath the snow, and a keen-eyed hawk appears, the white-feathered ptarmigan crouches and becomes an inanimate mound. Later in the year, with the increasing warmth, patches of gray and brown earth appear, and simultaneously, as if its feathers were really snowflakes, splashes of brown replace the pure white of the bird’s plumage, and equally baffle the eye. Seeing one of these birds by itself, we could readily tell, from the colour of its plumage, the time of year and general aspect of the country from which it came. Its plumage is like a mirror which reflects the snow, the moss, or the lichens in turn. It is, indeed, a feathered chameleon, but with changes of colour taking place more slowly than is the case in the reptile.
We may discover changes somewhat similar, but furry instead of feathery, in the woods about our home. The fiercest of all the animals of our continent still evades the exterminating inroads of man; indeed it often puts his traps to shame, and wages destructive warfare in his very midst. I speak of the weasel,—the least of all his family, and yet, for his size, the most bloodthirsty and widely dreaded little demon of all the countryside. His is a name to conjure with among all the lesser wood-folk; the scent of his passing brings an almost helpless paralysis. And yet in some way he must be handicapped, for his slightly larger cousin, the mink, finds good hunting the year round, clad in a suit of rich brown; while the weasel, at the approach of winter, sheds his summer dress of chocolate hue and dons a pure white fur, a change which would seem to put the poor mice and rabbits at a hopeless disadvantage. Nevertheless the ermine, as he is now called (although wrongly so), seems just able to hold his own, with all his evil slinking motions and bloodthirsty desires; for foxes, owls, and hawks take, in their turn, heavy toll. Nature is ever a repetition of the “House that Jack built”;—this is the owl that ate the weasel that killed the mouse, and so on.
The little tail-tips of milady’s ermine coat are black; and herein lies an interesting fact in the coloration of the weasel and one that, perhaps, gives a clue to some other hitherto inexplicable spots and markings on the fur, feathers, skin, and scales of wild creatures. Whatever the season, and whatever the colour of the weasel’s coat,—brown or white,—the tip of the tail remains always black. This would seem, at first thought, a very bad thing for the little animal. Knowing so little of fear, he never tucks his tail between his legs, and, when shooting across an open expanse of snow, the black tip ever trailing after him would seem to mark him out for destruction by every observing hawk or fox.
But the very opposite is the case as Mr. Witmer Stone so well relates. “If you place a weasel in its winter white on new-fallen snow, in such a position that it casts no shadow, you will find that the black tip of the tail catches your eye and holds it in spite of yourself, so that at a little distance it is very difficult to follow the outline of the rest of the animal. Cover the tip of the tail with snow and you can see the rest of the weasel itself much more clearly; but as long as the black point is in sight, you see that, and that only.
“If a hawk or owl, or any other of the larger hunters of the woodland, were to give chase to a weasel and endeavour to pounce upon it, it would in all probability be the black tip of the tail it would see and strike at, while the weasel, darting ahead, would escape. It may, morever, serve as a guide, enabling the young weasels to follow their parents more readily through grass and brambles.
“One would suppose that this beautiful white fur of winter, literally as white as the snow, might prove a disadvantage at times by making its owner conspicuous when the ground is bare in winter, as it frequently is even in the North; yet though weasels are about more or less by day, you will seldom catch so much as a glimpse of one at such times, though you may hear their sharp chirrup close at hand. Though bold and fearless, they have the power of vanishing instantly, and the slightest alarm sends them to cover. I have seen one standing within reach of my hand in the sunshine on the exposed root of a tree, and while I was staring at it, it vanished like the flame of a candle blown out, without leaving me the slightest clue as to the direction it had taken. All the weasels I have ever seen, either in the woods or open meadows, disappeared in a similar manner.”
To add to the completeness of proof that the change from brown to white is for protection,—in the case of the weasel, both to enable it to escape from the fox and to circumvent the rabbit,—the weasels in Florida, where snow is unknown, do not change colour, but remain brown throughout the whole year.