Mustelidae (weasel family) 101.
Mink, weasels, ferrets, woverines, fisher and marten are all members. Common trade names encountered in the fur industry are: Ermine (winter white weasel), Sable (fisher), Sable Nordique (pine marten) and Minque nordique (wild brown mink). Weasels are the only one that change color.
In order of size, smallest to largest are weasel, ferret, mink, marten, fisher, wolverine. Mink and fisher are a deep brown "sable" color all year with some variation occasionally seen, especially near commercial mink farms due to interbreeding with ranch mink. Weasels are more of a fawn color in warmer months. Winter they are white with a black tip on tail. Pine marten are a lighter brown than fisher and mink and have big tufty ears. In all mustelids, Males are significantly larger than females.
They are all solitary hunters. They are only found together when rearing young or during brief mating season. Males mate and run, they do not help raise young. They are all territorial and will mark territory with their musk glands and defend it vigorously. Males range much farther than females.