The ferret (Mustela furo) is a small domesticated species belonging to the family Mustelidae. The ferret is most likely a domesticated form of the wild European ferret or polecat evidenced by their interfertility. Other mustelids include the stoat badger and mink. Physically ferrets resemble other mustelids because of their long slender bodies. Including their tail the average length of a ferret is about 50 cm (20 in); they weigh between 0.7 and 2.0 kg (1.5 and 4.4 lb); and their fur can be black brown white or a mixture of those colours. In this sexually dimorphic species males are considerably larger than females.