Martes pennantifisher

Geographic Range

Fishers are found only in North America, from the Sierra Nevada of California to the Appalachians of West Virginia and Virginia. They range along the Sierra Nevada to their southernmost extent and south along the Appalachian mountain chain. They do not occur in the prairie or southern regions of the United States. Populations have declined in the southern parts of their range in recent history.


Fishers prefer coniferous forests, but they are also found in mixed and deciduous forests. They prefer habitats with high canopy closure. They also prefer habitats with many hollow trees for dens. Trees typically found in fisher habitats include spruce, fir, white cedar and some hardwoods. Also, as would be expected, their habitat preference reflects that of their favored prey species.

Physical Description

Males fishers are, on average, larger than females, with a body length of 900 to 1200 mm and a body weight of 3500 to 5000 grams. Females range from 750 to 950 mm in length and 2000 to 2500 grams in weight. Tail length of males is between 370 and 410 mm and tail length of females is between 310 and 360 mm. Their coats range from medium to dark brown, with gold to silver hoariness on their head and shoulders, and with black legs and tail. They may also have a cream chest patch of variable size and shape. Fur color and pattern varies among individuals, sexes and seasons. Fishers have five toes on their feet, and their claws are retractable.

  • Sexual Dimorphism
  • male larger
  • Range mass
    2000 to 5000 g
    70.48 to 176.21 oz
  • Range length
    750 to 1200 mm
    29.53 to 47.24 in


Little is known about mating in fishers. Copulation may last up to seven hours. (Powell, 1981)

The breeding season is late winter and early spring, from March to May. After fertilization, the embryos sit in suspended development for 10 to 11 months, and resume developing late in the winter following mating. Overall, gestation lasts almost a full year, 11 to 12 months. The average number of young in a litter is 3, ranging from 1 to 6. Shortly after giving birth, females experience a postpartum estrus and mate again. Healthy females first breed at age 1, produce their first litter at age 2, and probably breed every year after that. So females essentially spend almost all of their adult life in a state of pregnancy or lactation. Males breed for the first time when they are two years old. Females reach adult weights at 5.5 months, whereas males reach adult weights after 1 year old. (Kurta, 1995; Powell, 1981)

  • Breeding interval
    Fishers breed once per year.
  • Breeding season
    Fishers breed in the late winter to early spring, from March to May. Breeding times vary with location.
  • Range number of offspring
    1 to 6
  • Average number of offspring
  • Average number of offspring
  • Range gestation period
    11 to 12 months
  • Range weaning age
    8 to 16 weeks
  • Range time to independence
    5 (low) months
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    365 days
  • Average age at sexual or reproductive maturity (male)
    2 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    365 days

Young fishers are born blind and nearly naked. Each weighs about 40 grams at birth. The eyes open after about 53 days. Young begin to be weaned at 8 to 10 weeks, but may nurse occasionally for up to 4 months after birth. By the time they are four months old, the young are able to hunt for themselves, and they disperse at least one month later. Most dens in which young fishers are raised are high up in hollow trees, and females may choose to move their young up to several times if the litter is disturbed. Male fishers do not help raise their young. (Kurta, 1995; Powell, 1981)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female


Fishers can live up to ten years in the wild. (Kurta, 1995)

  • Range lifespan
    Status: wild
    10 (high) years


Fishers are agile and speedy tree climbers, but they usually move on the ground. They are quite solitary; there is little evidence that they ever travel together, except possibly during the mating season. There has been some observed aggression between males, which supports the notion that they are solitary.

Fishers use "resting sites", such as logs, hollow trees, stumps, holes in the ground, brush piles and nests of branches, during all times of the year. Ground burrows are most commonly used in the winter, and tree nests are used all year, but mainly in the spring and fall. During the winter, fishers use snow dens, which are burrows under the snow with long and narrow tunnels leading to them.

Fishers are active during the day and night and may be agile swimmers.

  • Range territory size
    4 to 50 km^2
  • Average territory size
    25 km^2

Home Range

Home range size varies from 15 to 35 square kilometers in area, averaging about 25 square kilometers. Home ranges of males are larger than those of females and may overlap with them, but they usually do not overlap with the home ranges of other males. (Kurta, 1995)

Communication and Perception

Fishers have good senses of smell, hearing and sight. They communicate with each other by scent marking.

Food Habits

Fishers are predators, and most of their prey are herbivores. Fishers eat mice, porcupines, squirrels, snowshoe hares, birds, and shrews, and sometimes, other carnivores. They may also feed on fruits and berries, such as beechnuts and apples.

They have also been seen to eat white-tailed deer, though they are most likely scavenging a deer carcass.

Fishers and American martens are the only medium-sized predators agile in trees that also possess the ability to elongate themselves to seek prey in holes in the ground, hollow trees and other small areas. Fishers are solitary hunters, and seek prey that is their own size or smaller, although they are capable of taking on prey larger than themselves.

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • Plant Foods
  • fruit


Young fishers fall prey to hawks, red foxes, lynx and bobcats. Adult fishers are generally safe from predation. (Kurta, 1995)

Ecosystem Roles

Fishers are important predators in their ecosystems. They are often in competition for food with foxes, bobcats, lynx, coyotes, wolverines, American martens and weasels. Fishers have a low incidence of diseases.

Economic Importance for Humans: Positive

Fishers are trapped and killed for their pelts. Trapping, in the past, had a significant effect on fisher populations, but the problem is not as severe now. Fishers hunt porcupines, and can effectively control porcupine populations (porcupines are known to damage timber crops by debarking and killing trees).

  • Positive Impacts
  • body parts are source of valuable material

Economic Importance for Humans: Negative

In recent years fisher populations in some areas, particularly southern Ontario and New York, have been recovering. In these areas they may be becoming habituated to human presence and venturing into suburban areas. There have been numerous reports of fisher attacks on domestic animals and even children. It is important to recognize that fishers are simply trying to find food and protect themselves. It is important to restrict access to garbage, pet foods, pets, and domestic fowl. When startled, fishers may react aggressively to the perceived threat. Diseased individuals may react unpredictably.

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Logging of forests greatly impacts fishers and fisher populations by destroying their preferred habitat--continuous or nearly continuous coniferous forests.

Zoos have had a hard time breeding fishers in captivity, but there has been some success. Because there are numerous thriving and healthy fisher populations, there has been little pressure or initiative to develop fisher breeding or maintaining programs in captivity.

In some areas of North America, such as Michigan, Ontario, New York, and some areas of New England, fisher populations seem to have rebounded in recent years.

Fisher populations in the southern Sierra Nevada have been proposed as candidates for protection under the Endangered Species Act.

Other Comments

Fishers are generally thought of as secretive and rarely observed. This may be changing in parts of their range as populations re-expand and become habituated to human presence.


Tanya Dewey (editor), Animal Diversity Web.

Allison Poor (editor), University of Michigan-Ann Arbor.

Cynthia Rhines (author), University of Michigan-Ann Arbor.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate

delayed implantation

in mammals, a condition in which a fertilized egg reaches the uterus but delays its implantation in the uterine lining, sometimes for several months.

  1. active during the day, 2. lasting for one day.
embryonic diapause

At about the time a female gives birth (e.g. in most kangaroo species), she also becomes receptive and mates. Embryos produced at this mating develop only as far as a hollow ball of cells (the blastocyst) and then become quiescent, entering a state of suspended animation or embryonic diapause. The hormonal signal (prolactin) which blocks further development of the blastocyst is produced in response to the sucking stimulus from the young in the pouch. When sucking decreases as the young begins to eat other food and to leave the pouch, or if the young is lost from the pouch, the quiescent blastocyst resumes development, the embryo is born, and the cycle begins again. (Macdonald 1984)


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


uses touch to communicate


Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Macdonald, David. (editor) The Enclopedia of Mammals. Facts on File Publications, NY. 1984

Powell, Roger A. The FIsher: Life History, Ecology, and Behavior. University of Minnesota Press, MN. 1993.

Johnson and Todd. Fisher, Behavior in Proximity to Human Activity. Canadian Field Naturalist 99 (3) 1985.

Arthur, Krohn and Gilbert. Habitat Use and Diet of Fishers. Journal of Wildlife Management 53 (3) 1989.

Kurta, A. 1995. Mammals of the Great Lakes Region. Ann Arbor: University of Michigan Press.

Powell, R. 1981. Martes pennanti. Mammalian Species, 156: 1-6.