(Mustek nivalis), also short-tailed weasel and common weasel, a predatory mammal of the family Mustelidae. It is one of the smallest predators, with a body length of 13–26 cm, a tail length of 1.4–9 cm, and a weight of 30–250 g. It is smaller in northern regions and larger in southern regions. The body is slender and very flexible. The fur is dense but short. The summer coloring is yellowish brown above and white below. In the winter the fur becomes completely white, except for weasels in the south.
The snow weasel is distributed in Europe, Asia (except in the south), and North America. In the USSR it is distributed almost everywhere. Its habitats are varied—from forests to tundras, deserts, and mountains—and it is even found in villages. The snow weasel feeds on small rodents, which it hunts by entering their burrows. It reproduces year-round; there are three to nine offspring in a litter. Snow weasels are beneficial because they destroy harmful rodents. Their fur is of little value.