This is one of the few land animals which ranges completely round the pole. There is no difference to be noted between the Old-World and the New-World specimens. It is now an entirely northern form, but in Pleistocene times it reached as far south as this country. The fossil species seems to be Gulo luscus, and to be quite indistinguishable from the living forms.
Putorius, the genus which embraces the Weasel tribe, contains
many species known popularly as Weasels, Ermines, Stoats, Ferrets, Polecats, Minks, and Vison. Not only is the genus common to both Old and New Worlds, but in a few cases the species (e.g. P. erminea) range from Asia to America. The molar formula is Pm 3/3 M 1/2. The form of the body is an exaggerated one, the length of the trunk to the limbs being very great. The feet are more or less hairy beneath, and the animals are digitigrade. The nose is grooved. The dorsal vertebrae vary from thirteen to sixteen.
Fig. 221.—Polecat. Mustela putorius. × 1⁄6.
There are four British representatives of this genus:—
The Polecat, P. foetidus, is a dark brown-coloured animal. Its total length is about 2 feet, of which the tail occupies some 7 inches. It is a species banned by the gamekeeper, and hence is approaching extinction in this country. It is excessively bloodthirsty, as are apparently all the members of this genus, and kills out of mere wantonness. The Ferret is simply a domesticated variety of the Polecat.
The Stoat or Ermine, P. erminea, is reddish brown above, white beneath. In winter, in certain localities, it becomes white with the exception of the black tip of the tail. This colour-change bears some relation to the degree of latitude. It is universal in the north of Scotland, rare in the south of England. As is the case with some other animals that generally change
their colour in the winter, there are individuals which seem to have lost the power of change, and others which change in an apparently capricious manner, not influenced by season or cold. Like so many other animals, the Stoat appears at times to migrate, which it does in large parties. Such parties are said to be dangerous, and will attack a man who crosses their path.
The Weasel, P. vulgaris, has much the same colour as the Stoat, but is a smaller animal; it differs also by undergoing no seasonal change. It is equally agile and ferocious, and ought to be encouraged, as it vents its ferocity largely upon Voles and Moles, which it can pursue underground. Like other species of Putorius, it seems to kill its prey by biting through the brain-case.