Alaska Weasels: Fisher

alaska is home to many mink
The Mustelidae, or weasel family is a large group of mammals. In Alaska there are eight types of Mustelidae. They include the wolverine, fisher, river otter, sea otter, marten, short tailed weasel, least weasel, and the mink.
The fisher (Martes pennanti) is a medium-size mammal native to North America. It is a member of the mustelid family, commonly referred to as the weasel family. The fisher is closely related to but larger than the American Marten. The fisher is a forest-dwelling creature whose range covers much of the boreal forest in Canada to the northern fringes of the United States. It is also sometimes referred to as a fisher cat, though it is not a feline.

The Fisher is a dark colored bushy-tailed member of the weasel family that is about the size of a small fox. It is a nocturnal hunter, so its eyes are on the larger side, and it is very aggressive. Humans, rarely see this solitary animal with a territory of about 10 square miles. Fishers have a life span over about 10 years.

Fishers are a medium-size mammal. Their bodies are long, thin, and low to the ground. In appearance the sexes are hard to distinguish, but they are sexually dimorphic in size, with the male being larger than the female. Males and females are similar in appearance but the males are larger in size. Males are 90–120 cm (35–47 in) in length and weigh 3.5 to 5 kilograms (8–11 lb). Females measure 75–95 cm (30–37 in) and weigh 2–2.5 kg (4–6 lb). The largest ever male fisher recorded weighed 9 kg (20 lb).

The fur of the fisher varies seasonally, being denser and glossier in the winter. During the summer, the color becomes more mottled, as the fur goes through a molting cycle. 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 molting starting in late summer and finishing by November or December.

The fisher has retractable claws, much like a cat, and preys on mice, porcupines, squirrels, snowshoe hare, birds, shrews, and can even kill deer and lynx.. Fishers have five toes on each foot. Their feet are disproportionately larger than their legs, making it easier for them to move on top of snow packs. In addition to the toes, there are four central pads on each foot. On the hind paws there are coarse hairs that grow between the pads and the toes, giving them added traction when walking on a variety of surfaces. Fishers have extremely mobile ankle joints, which can rotate their hind paws almost 180 degrees, allowing them to agilely move through tree branches and climb down trees head first.

A circular patch of hair on the central pad of their hind paws marks plantar glands that give off a distinctive odor. Since these patches become enlarged during breeding season, there is speculation that they are used for communication for reproduction.

Fishers prefer to hunt in full forest. While they are agile climbers most of their time is spent on the forest floor. They also prefer to forage where there is a lot of fallen dead wood on the forest floor. Despite their name, fishers seldom eat fish.  Fishers are omnivorous and feed on a wide variety of small animals and occasionally fruits and mushrooms. They show a preference for the snowshoe hare and are one of the few predators able to hunt porcupine.

Fishers are generally crepuscular. They are most active during dawn and dusk hours of the day. They are active year-round. Fishers are solitary, associating with other fishers only for mating purposes. Males become more active during mating season. Females are least active during pregnancy and gradually increase activity after birth of their kits

The reproductive cycle of the fisher lasts almost the entire year. Female fishers give birth to a litter of three or four kits in the spring. They nurse and care for their kits up until late summer, when they are old enough to set out on their own. Females enter estrus shortly after giving birth and leave the den to find a mate. Implantation of the blastocyst is delayed until the following spring when they give birth and the cycle is renewed.

Fishers have few predators aside from man. They have been trapped since the 18th century for their fur. Their pelts were in such demand that they were extirpated from several parts of the United States in the early part of the 20th century. Conservation and protection measures have allowed the species to rebound, but their current range is still reduced from its historic limits. In the 1920s, when pelt prices were high, some fur farmers attempted to raise fishers. However, their unusual delayed reproduction made breeding difficult. When pelt prices fell in the late 1940s, most fisher farming ended. While fishers are usually shy and elusive, humans are encroaching into their forest habitat.


fishers are sometimes called fisher cats but are weasels

An Alaskan fisher weasel getting a drink

Alaska Mammals:

With 112 mammal species, Alaska ranks 12th of the 50 U.S. states in mammalian diversity.

Learn more about Alaskan mammals

Shrewss Bats Cats
Canines Bears Weasels
Ungulates Rabbits Rodents