The fisher (Martes pennanti) is a small carnivorous mammal native to North America. It is a member of the mustelid family (commonly referred to as the weasel family) and a part of the marten genus. Names derived from aboriginal languages include pekan, pequam, wejack, and woolang. It is also called a fisher cat, although it is not a feline.
Fishers are a medium-sized mammal, comparable in size to the domestic cat, and the largest species in the marten genus. Their bodies are long, thin, and low to the ground. The fisher is closely related to but larger than the American marten (Martes americana). The sexes look similar but are dimorphic in size: Males are 90 to 120 cm (35–47 in) in length and weigh 3.5 to 6 kg (8–13 lb). Females measure 75 to 95 cm (30–37 in) and weigh 2 to 2.5 kg (4–6 lb).
The fisher's fur changes with the season and differs slightly between sexes. Males have coarser coats than females. In the early winter, the coats are dense and glossy, ranging from 30 mm (1 in) on the chest to 70 mm (3 in) on the back. The color ranges from deep brown to black, although it appears to be much blacker in the winter when contrasted with white snow. From the face to the shoulders, fur can be hoary-gold or silver due to tricolored guard hairs. The underside of a fisher is almost completely brown except for randomly placed patches of white or cream-colored fur. In the summer, the fur color is more variable and may lighten considerably. Fishers undergo moulting starting in late summer and finishing by November or December.
Fishers are most active at dawn and dusk. They are active year-round. Although fishers are competent tree climbers, they spend most of their time on the forest floor and prefer continuous forest to other habitats. Fishers are solitary, associating with other fishers only for mating purposes. After 4 months, kits become intolerant of their litter mates, and at 5 months, the mother pushes them out on their own. After one year, juveniles will have established their own range.
An omnivore, the fisher feeds on a wide variety of small animals and occasionally on fruits and mushrooms. It prefers the snowshoe hare and is one of the few animals able to prey successfully on porcupines. Despite its common name, the fisher seldom eats fish. They are not averse to eating carrion; fishers have been observed to feed on the carcasses of deer left by hunters. While uncommon, fishers have been found to kill larger animals, such as wild turkey, bobcat and lynx.
- The largest male fisher ever recorded weighed 9 kg (20 lb).
- They have highly mobile ankle joints and can rotate their hind paws almost 180 degrees, allowing them to maneuver well in trees and climb down head-first. The fisher is one of relatively few mammalian species with the ability to descend trees head-first.