Size of an individual's range would vary with food availability and type and quality of cover. Least Weasel The least weasel is the world's smallest carnivore. It is found in Europe, northern Asia and North America. In Pennsylvania, Mustela nivalis is most common in the Allegheny Plateau area of our northwest and in the southcentral part of the state. They weigh 1-2 ounces.
Males are slightly larger and heavier than females.
Coloration is brown above, white below. The chin and feet are white, and the brown tail has no black tip. Sexes are colored alike. Least weasels are just as aggressive and predatory as the larger weasels and kill in the same manner. If disturbed near its nest, an adult least weasel will chirp at its enemy.