The ferret (Mustela putorius furo) is the domesticated form of the European polecat, a mammal belonging to the same genus as the weasel, Mustela of the family Mustelidae. They typically have brown, black, white, or mixed fur. They have an average length of 51 cm (20 in) including a 13 cm (5.1 in) tail, weigh about 1.5–4 pounds (0.7–2 kg), and have a natural lifespan of 7 to 10 years. Ferrets are sexually dimorphic predators with males being substantially larger than females.