It is well that weasels are not abundant, for beasts with such innate ferocity and love of killing would otherwise be a menace to the existence of many useful species of birds and mammals, especially the game birds. In many places they live almost entirely on mice, and there they should be left unmolested; but whenever they locate in the vicinity of a chicken yard the owner will do well to take proper measures for protection. =THE LEAST WEASEL= (=Mustela rixosus= and its relatives) (_For illustration, see page 554_) In addition to the larger members of the tribe briefly described in the foregoing sketch, the true weasels include another group of species, so small they may appropriately be termed the dwarfs of their kind. They vary from a half to less than a fourth the size of the larger weasels, but have the same characteristic form and proportions, except that the tail is very short and never tipped with black. Like the larger species, they change their brown summer coat for white at the beginning of winter and back again in spring. The least weasels are also circumpolar in distribution, but are limited to the northern parts of Europe, Asia, and North America. In England and other parts of the Old World the group is represented by the well-known species _Mustela vulgaris_. In North America several species are known which, between them, share all the continent from the Arctic coast south to Nebraska and Pennsylvania. On the desolate islands extending from the mainland far toward the Pole their place seems to be taken by the ermine. [Illustration: THE COMMON BROWN RAT The large series shows the ordinary foraging gait; the smaller one, to the right, shows the travel at low speed. In all, the tail mark is a strong feature (see pages 525 and 531).] The dwarf weasels appear to be less numerous and, as a consequence, less known in most parts of America than in England and northern Europe. Our most northern species, _Mustela rixosa_, sometimes called the “mouse weasel,” occupies Alaska and northern Canada and has the distinction of being the smallest known species of carnivore in the world. In this connection it is interesting to note that in Alaska we have associated on the same ground the least weasel and the great brown bear, the smallest and the largest living carnivores.