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.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Fishers range from Quebec, the Maritime Provinces, and New England west across boreal Canada to southeastern Alaska, south in the western mountains to Utah, Wyoming, Idaho, and California, and formerly south to Illinois, Indiana, Tennessee, and North Carolina. Recently the species has expanded its range in the eastern United States, and it has been reintroduced in areas from which it was extirpated, including West Virginia, with some of the latter individuals wandering into Virginia (Handley 1991). The species is relatively abundant in the eastern provinces of Canada, with low populations in British Columbia (USFWS, Federal Register, 1 March 1996).

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.

Range mass: 2000 to 5000 g.

Range length: 750 to 1200 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

Length: 103 cm

Weight: 8200 grams

• Terrestrial

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.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: taiga ; forest ; mountains

Habitat Type: Terrestrial

Comments: Fishers inhabit upland and lowland forests, including coniferous, mixed, and deciduous forests. They occur primarily in dense coniferous or mixed forests, including early successional forest with dense overhead cover (Thomas et al. 1993). Fishers commonly use hardwood stands in summer but prefer coniferous or mixed forests in winter. They generally avoid areas with little forest cover or significant human disturbance and conversely prefer large areas of contiguous interior forest (see USFWS 2004). Powell (1993) concluded that forest type is probably not as important to fishers as the vegetative and structural aspects that lead to abundant prey populations and reduced fisher vulnerability to predation, and that they may select forests that have low and closed canopies. Several studies have shown that fishers are associated with riparian areas (see USFWS 2004), which are in some cases protected from logging and generally more productive, thus having the dense canopy closure, large trees and general structural complexity associated with fisher habitat (Dark 1997). Riparian areas may be important to fishers because they provide important rest site elements, such as broken tops, snags, and coarse woody debris (Seglund 1995).

Fishers are regarded as habitat specialists in the western United States (Buskirk and Powell 1994), occurring only at mid- to lower elevation in mature conifer and mixed conifer/hardwood forests characterized by dense canopies and abundant large trees, snags, and logs (Powell and Zielinski 1994). In contrast, fishers in the northeastern United States and the Great Lakes region inhabit areas with a large component of deciduous hardwood forest containing American beech (Fagus grandifolia), sugar maple (Acer saccharum), and other broadleaf species (Powell and Zielinski 1994). The majority of conifer forest habitat in Canada is characterized as boreal forest, which is different from the relatively dryer environmental conditions associated with Washington, Oregon, and California. In the Rocky Mountains of north-central Idaho, certain all-conifer habitat types, which include grand fir and Engelmann spruce appear to be important to, and preferentially selected by fishers (Jones 1991).

Fishers are adapted for climbing but are primarily terrestrial. When inactive, they occupy a den in a tree hollow, under a log, or in the ground or a rocky crevice, or they rest in branches of conifer (warmer months). In Connecticut, Kilpatrick and Rego (1994) found that tree with a dbh of 32 cm or more may provide cavities for rest sites in hardwood-dominated forests.

Young are born in a den in a tree hollow (usually), or under a log or in a rocky crevice. Large snags (greater than 50 cm dbh) are important as maternal den sites (Thomas et al. 1993). Of 19 tree dens documented by Truex et al. (1998) across three study areas in California, the average diameter was 115 cm for conifers and 63 cm for hardwoods. Of 16 maternal and natal dens located on managed timberlands in northwestern California, nine were in cavities in hardwoods and seven were in conifer snags: diameters of den trees ranged from 62.5 cm to 295 cm (Simpson Resource Company 2003). See USFWS (2004) for further details on dens used by fishers in California and British Columbia.

West Coast Distinct Population Segment:

The key aspects of fisher habitat are best expressed in forest stands with late-successional characteristics. Fishers use habitat with high canopy closure, large trees and snags, large woody debris, large hardwoods, multiple canopy layers, and avoidance of areas lacking overhead canopy cover (see references in USFWS 2004). Fishers also occupy and reproduce in some managed forest landscapes and forest stands not classified as late-successional that provide some of the habitat elements important to fisher, such as relatively large trees, high canopy closure, large legacy trees, and large woody debris, in second-growth forest stands (Klug 1997, Simpson Resource Company 2003). However, intensive management for fiber production on industrial timberlands does not typically provide for retention of these elements. It is unlikely that early and mid-successional forests, especially those that have resulted from timber harvest, will provide the same prey resources, rest sites and den sites as more mature forests (see USFWS 2004). Late-successional coniferous or mixed forests provide the most suitable fisher habitat because they provide abundant potential den sites and preferred prey species (Allen 1987). Forest structure of good quality fisher habitat should provide high diversity of dense prey populations, high vulnerability of prey to fishers, and natal and maternal dens and resting sites (Powell and Zielinski 1994). Younger forests in which complex forest structural components such as large logs, snags, and tree cavities are maintained in significant numbers, and which provide a diverse prey base, may be suitable for fisher (Lewis and Stinson 1998). [from USFWS (2004), which see for further details on habitat in California]

See also Zielinski et al. (2004) for information on habitat characteristics in California.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

See Zielinski et al. (2004) for information on home range characteristics in California.

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.

Animal Foods: birds; mammals

Plant Foods: fruit

Primary Diet: carnivore (Eats terrestrial vertebrates)

Comments: Diet consists primarily of mammals (small rodents, shrews, squirrels, hares, muskrat, beaver, porcupine, raccoon, deer carrion); also birds, other small animals, carrion, and fruit.

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.

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

Known Predators:

• hawks
• red foxes
• lynx
• bobcats
• hawks (Accipitridae)
• red foxes (Vulpes vulpes)
• lynx (Lynx canadensis)
• bobcats (Lynx rufus)

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: In the absence of good occurrence specifications and adequate population data, an estimate of the number of occurrences is not possible. But surely there are hundreds of fairly distinct populations.

10,000 to >1,000,000 individuals

Comments: Total population size is unknown but probably is at least in the low hundreds of thousands; for example, the harvest in North America during the 1983-1984 trapping season was about 20,000 (Novak et al. 1987), and the average in the 1960s and 1970s was about 13,000 (Strickland et al. 1982).

Solitary except during the breeding season.

Home range has been estimated at 10-800 sq km by snow tracking, 7-78 sq km by telemetry using minimum convex polygon model; generally the ranges of adults of the same sex do not overlap. In Maine, home ranges of females were stable between seasons and years, but males moved extensively in late winter and early spring and their ranges shifted between years. In New Hampshire, mean annual home range was about 15-25 sq km, with daily movements usually were 1.5-3.0 km. In southern Quebec, mean home range size was 5.4 sq km for females and 9.2 sq km for males (Garant and Crete 1997). Has been recorded moving 90 km in 3 days (see Nowak 1991).

Population density in favorable habitat has been estimated at up to about 1 per 3-11 sq km in summer, 1 per 8-20 sq km in winter (Arthur et al. 1989). In southern Quebec, density was estimated at about 3 individuals per 10 sq km; the high density was atrributed to the absence of trapping (Garant and Crete 1997).

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

Communication Channels: chemical

Other Communication Modes: scent marks

Perception Channels: visual ; acoustic

Comments: Active both day/night. Mainly nocturnal/crepuscular in summer and diurnal in winter. In south-central Maine, most activity occurred shortly before sunrise and after sunset; activity was reduced in winter (Arthur and Krohn 1991); females caring for weaned offspring showed increased diurnal activity (Paragi et al., 1994, Can. Field-Nat. 108:52-57.

Fishers can live up to ten years in the wild.

Range lifespan

Status: wild: 10 (high) years.

Little is known about mating in fishers. Copulation may last up to seven hours.

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.

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: 3.

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 (male): 2 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous ; delayed implantation ; embryonic diapause ; post-partum estrous

Average birth mass: 35 g.

Average number of offspring: 2.5.

Average age at sexual or reproductive maturity (male)

Sex: male: 365 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 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.

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)

Reportedly breeds late February-April or March-May, peak in March (late March-April in Manitoba); females mate probably within days of giving birth. Gestation lasts l year, including an 11-month period before implantation. Litter averages about 3 throughout the range. Births occur primarily from March to mid-April (sometimes in February or May in some areas). Young are mobile by 8 weeks, weaned in 2.5-4 months; separation from the mother occurs in the fifth month, in late summer or early fall. In Maine, young are weaned from mid-May to early June, independent probably in late August or early September (Arthur and Krohn 1991). Sexually mature in 1-2 years; not all adult females breed in a given year. Apparently promiscuous breeding. Very few males live more than 4 years, and less than 10% of females live more than 4 years.

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.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Large range in northern North America; extirpation from southern portion of range, due mainly to habitat loss, has been counteracted by recent natural and human-aided range expansions in the eastern U.S.; adequate population data are unavailable for much of the range, but the species currently is regarded as secure. See also information on the West Coast Distinct Population Segment.

Intrinsic Vulnerability: Highly vulnerable

Comments: Low fecundity retards the recovery of populations from declines, further increasing their vulnerability (USFWS 2004).

Global Short Term Trend: Unknown

Degree of Threat: C : Not very threatened throughout its range, communities often provide natural resources that when exploited alter the composition and structure over the short-term, or communities are self-protecting because they are unsuitable for other uses

Comments: The fisher's range was reduced dramatically in the 1800s and early 1900s through overtrapping, predator and pest control, and alterations of forested habitats by logging, fire, and farming (Douglas and Strickland 1987, Powell 1993, Powell and Zielinski 1994, Lewis and Stinson 1998). Since the 1950s, fishers have recovered in some of the central and eastern portions of their historic range in the United States as a result of trapping closures, changes in forested habitats (e.g., forest regrowth in abandoned farmland), and reintroductions (Brander and Books 1973, Powell and Zielinski 1994). However, fishers are still absent from their former range southeast of the Great Lakes (Gibilisco 1994). [from USFWS 2004]

The extent of past timber harvest is one of the primary causes of fisher decline across the United States (Powell 1993), and it may be one of the main reasons fishers have not recovered in Washington, Oregon, and portions of California as compared to the northeastern United States (Aubry and Houston 1992, Powell and Zielinski 1994, Lewis and Stinson 1998, Truex et al. 1998). Timber harvest can fragment fisher habitat, reduce it in size, or change the forest structure to be unsuitable for fishers. Habitat loss and fragmentation appear to be significant threats to the fisher. Forested habitat in the Pacific coast region decreased by about 8.5 million ac (34,400 sq km) between 1953 and 1997 (Smith et al. 2001). Forest cover in the Pacific coast is projected to continue to decrease through 2050, with timberland area projected to be about 6 percent smaller in 2050 than in 1997 (Alig et al. 2003). Thus fisher habitat is projected to decline in Washington, Oregon, and California in the foreseeable future. [from USFWS 2004, which see for further details]

Although exact numbers are unknown, trapping caused a severe decline in fisher populations. Aubry and Lewis (2003) state that overtrapping appears to have been the primary initial cause of fisher population losses in southwestern Oregon. The high value of the skins, the ease of trapping fishers (Powell 1993), year-round accessibility in the low to mid-elevation coniferous forests, and the lack of trapping regulations resulted in heavy trapping pressure on fishers in the late 1800s and early 1900s (Aubry and Lewis 2003). [from USFWS 2004]

See also threats information for the West Coast Distinct Population Segment.

Management Requirements: In the Pacific Northwest, habitat conservation measures proposed/implemented for the spotted owl and marbled murrelet, and for riparian zones, generally are sufficient to prevent the extirpation of this species, but ongoing management reassessment, monitoring, and adaptive management are important (U.S. Forest Service et al. 1993; see also Thomas et al. 1993).

Because fisher populations are extremely low in northern Oregon and Washington, U.S. Forest Service et al. (1993) recommended that kill trapping of American martens should be prohibited within the overlapping ranges of marten, fisher, and spotted owl until the rate of accidental take of fishers is determined to be insignificant.

Fishers from several source populations were released in Oregon in 1961 and from 1977 to 1981; successful reintroductions (beginning in the early 1960s) have occurred in Montana and Idaho (USFWS 2004).

There are currently efforts underway to implement a conservation strategy to reintroduce the fisher into its former range along the Pacific Coast. Additional populations of fishers will reduce the probability that a stochastic event would result in extirpation of the species. Genetic data indicate that British Columbia would be the most appropriate source population for future translocations that may be necessary to recover populations in Washington and portions of Oregon and California (Drew et al. 2003).

As of 2004, the Pacific Region (Region 5) of the U.S. Forest Service was due to complete a conservation assessment for the fisher in the Sierra Nevada Mountains. This effort is part of the Sierra Nevada Framework planning document and is a collaborative effort including scientists from the State and Federal agencies. The assessment may be used to develop a conservation strategy for the Sierra Nevada fisher populations in California. The timber industry and their representatives, including Sierra Pacific Industries, Simpson Timber Company and the California Forestry Association have indicated willingness to develop a conservation strategy to, if appropriate, conduct a reintroduction and/or relocation strategy in California. Their participation could include funding, staffing, and assistance with analysis and planning. [from USFWS 2004]
The State of Washington has completed a reintroduction feasibility study and has identified several sites in the Washington Cascades and the Olympic Peninsula where sufficient potential habitat exists to support a fisher population. Reintroduction efforts and evaluation by the State are ongoing and would potentially compliment efforts to establish additional populations throughout the range of the fisher (USFWS 2004).


USFWS will evaluate a completed conservation strategy in accordance with their Policy on Evaluating Conservation Efforts (68 FR 15100, March 28 2003) to determine whether it sufficiently removes threats to the fisher so that it no longer meets the definition of threatened under the Act (USFWS 2004).

See Berg (1982) for information on fisher reintroduction.

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: At least several populatons are protected in national parks.

Needs: Protect large tracts of habitat in areas well distributed throughout the range. Prevent excessive harvest.

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)

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

Comments: Total harvest in Canada and the U.S. was about 20,200 in the early 1980s; pelts sold for an average of about $50. The highest quality pelts sold for $450 in Ontario in 1986. See Strickland et al. 1982 and Nowak 1991 for further (though somewhat dated) information on harvest and fur prices.

Comments: Nominal subspecies are questionable, but population subdivision is occurring within the species (Drew et al. 2003). Genetic data suggest that gene flow once occurred between fisher populations in British Columbia and those in the Pacific states, but extant populations in those areas are now genetically isolated due to extirpation of fishers in Washington and northern Oregon (Drew et al. 2003). The extant populations in California and Oregon are both discrete and biologically significant and thus qualify as a distinct population segment.

"Multiple lines of paleontological and genetic evidence suggest that the fisher recently (<5,000 years ago) expanded into the mountain forests of the Pacific coast. The reduced dimensionality of the distribution of the fisher in western coastal forests appears to have contributed to the high levels of structure and decreasing diversity from north to south. These effects were likely exacerbated by human-caused changes to the environment. The low genetic diversity and high genetic structure of populations in the southern Sierra Nevada suggest that populations in this part of the geographic range are vulnerable to extinction." [from Wisely et al. 2004]

Stone and Cook (2002) placed the fisher in the subgenus Pekania and suggested that M. pennanti and Gulo gulo may form a monophyletic group, which would make Martes paraphyletic.