Fisher (Pekania (martes) pennanti)

Introduction

The Fisher (Pekania (martes) pennanti) is a slender medium-sized forest-dwelling mammal indigenous to northern mixed forests and mountainous areas of North America. Also known as fisher cats (in New England dialect), tree fox, or pekan (in Canadian dialect), the fisher is a member of the mustelid family (commonly known as the weasel family), and is in the monospecific genus Pekania. Adapted to climbing trees, the fisher is a skilled predator of both squirrels and porcupines, while also hunting for small rodents and mast on the forest floor.

Coat color ranges from a light rusty brown to dark chocolate brown to almost black depending on season, with winter seasons presenting a darker, glossier shimmer. During the summer months, fur color becomes more mottled through a molting cycle. Males and females look similar, with adult males averaging 35–47 inches in length and weighing 8–13 pounds. Adult females are smaller and more slender, at 30–37 inches long and weighing approximately 4–6 pounds. Males will often have a lighter grizzled coloration on the face, head and over the shoulders. Older male specimens may also be identified by a pronounced bulbous forehead, resulting from development of the sagittal crest. Fur on males tends to be coarser than that of females. Two small, white triangular patches of fur are found in the front armpit and crotch areas.

Five toes are present in fisher tracks and the inside toes appear smaller and placed behind the other four. Despite the nickname “fisher cat”, the fisher is not aquatic, nor can it retract it's claws like felines. At a distance, female fisher may often be confused for large mink (a cousin of the fisher) to the untrained eye. Similar to other mustelids, a pair of anal musk glands are present on both males and females and their musk is often released when the animal is frightened or angry. Fishers are generally crepuscular, being most active at dawn and dusk, although they commonly hunt at night and it is not uncommon to observe fisher active during the daylight hours. Hunting range varies from 3 - 5 square miles. Hunting and travel ranges up to 8 square miles are common depending on the quality of the habitat.

Habitat / Range

Destruction of woodlands and unregulated hunting caused population declines throughout the 19th and early 20th centuries. Regulated management and reintroduction efforts throughout the 20th century have encouraged healthy fisher populations to rebound in many suitable habitat types throughout their traditional ranges. Recovery is cited as being due to a mixture of translocation efforts, natural recolonization, habitat modification, and even beneficial effects from climate change. A combination of forest regrowth in abandoned farm country and improved forest management practices increased available habitat, which is believed to have allowed remnant fisher populations to recover. Populations have since rebounded enough that the species is no longer considered endangered in most of its range throughout North America. Maintaining increased forest cover in eastern North America is integral to the health of fisher populations for the near future.

Today, the fisher holds healthy or steady populations throughout the Northeast United States and most eastern/central Canadian provinces, with populations increasing in places like Montana, Minnesota, Wisconsin, and southern expanses of West Virginia, and Pennsylvania. In the northern reaches of its range, the fisher prefers boreal forest and conifer groves throughout Canada and southeast Alaska which protect from high snow accumulation and provide shelter. In central and southeastern expanses of the range, the fisher prefers mixed deciduous hardwoods and conifer groves which offer similar shelter protections from the elements while allowing the animal to take advantage of mast such as acorns, and utilize hollows of hardwood trees for denning sites.

Although fishers are competent tree climbers, they spend considerable time on the forest floor and prefer continuous forest to other habitats. Some studies have found preference to areas with continuous overhead cover with greater than 80% coverage and avoidance to areas with less than 50% coverage.

In greater New England specifically, fisher have adapted well to mixed agricultural land, commonly observed skirting dense forest edges of farm fields and suburban development throughout Maine, Vermont, New Hampshire, and upstate New York. They are commonly observed traveling miles of old colonial stone wall structures to flush out small rodents such as mice and chipmunks. They have become regular fixtures in urban areas of southern New Hampshire, Massachusetts, Connecticut, and even rural portions of New Jersey. Reports of fisher sightings in Brooklyn, New York have also been documented. Fisher populations were virtually wiped out after the construction of the Cape Cod Canal in the early 1900s, however recent reports conclude populations have become re-established on Cape Cod. They remain one of several furbearer species that have shown proof of adapting well to urban environments alongside human activity, although their presence remains limited in these settings compared to that of species like skunks and raccoons.

In the Pacific Northwest, fragmented populations of fisher exist today. Throughout the 1970’s and 80’s, fishers from British Columbia and Minnesota were reintroduced in Oregon, and later in Washington state by the mid-2000’s. Today, reintroduction efforts successfully continue in the Cascade Mountain range. Fisher were reintroduced in the northern Sierra Nevada, which had reportedly complemented populations along California's northern boundary.

Breeding / Reproduction

Fisher are active year-round, and are solitary, associating with other fishers only for mating. Males become more active during mating season. Females are least active during pregnancy and gradually increase activity after the birth of kits. Male and female fishers have overlapping territories. Fishers exhibit what is known as Embryonic diapause, or “delayed implantation.” The female fisher begins to breed at about one year of age and her reproductive cycle is an almost year-long event. Mating takes place in late March to early April. Implantation is then delayed for ten months until mid-February of the following year when active pregnancy begins. After gestating for about 50 days, the female gives birth to 1-4 kits. The female then enters estrus 7–10 days later and the breeding cycle begins again.

Females den in hollow trees. Kits are born blind and helpless. They are partially covered with fine hair. Kits begin to crawl after about three weeks. After about seven weeks, they open their eyes. They start to climb after eight weeks. Kits are completely dependent on their mother's milk for the first eight to ten weeks, after which they begin to switch to a solid diet. After four months, kits become intolerant of their litter mates, and at five months, the mother pushes them out on their own. After one year, juveniles will have established their own range.

Diet

Fisher are one of the only species of animal that can effectively kill a porcupine. Fisher are the same height as porcupines and are able to attack the face at face-level. Quills which guard the porcupine’s face from above are rendered useless against fisher coming from below. An attack usually ensues in a circle, and can last over a half hour as the porcupine continuously rotates to keep its quills towards the fisher in order to shield the face. Though a fisher is not completely immune to the porcupine’s quill strikes, it is able to fend off serious infections from quill injuries that would otherwise kill most animals. Tagged fishers have been found with quills embedded deep within the skin from previous encounters.

Fisher will prey on smaller-sized livestock such as chickens and ducks, and domestic pets left unattended. Despite being synonymous with depredation on house cats in suburban settings, the fisher is only one of several predatory wildlife species that will prey on domesticated pets; which also includes coyotes, fox, owls, and others.

Fisher are not particularly picky, feeding on varied food types. While they are carnivores, fishers will also feed on nuts, seeds, berries, and mushrooms. Staple foods include porcupines and snowshoe hares, although common fare includes birds, fish, small mammals, small deer other predators and carrion. Fishers hunt alone, and can only kill prey that they can take down on their own.

Management Notes

Fisher remain a protected species in Oregon, Washington, and Wyoming, while receiving ESA status in California. In June 2011, the U.S. Fish and Wildlife Service recommended that fishers be removed from the endangered list in Idaho, Montana, and Wyoming. The animal is considered healthy and abundant throughout most of its Canadian and Northeast ranges. Concerns have been raised in New Hampshire with regard to population trends over several decades, but professionals assert the population continues to remain steady, despite potential impacts from habitat loss and disease mortality such as Canine Distemper Virus (CDV). Thanks to reintroduction efforts and input from local trappers, limited hunting/trapping seasons have been recently opened for fisher in states like Pennsylvania and Wisconsin. The fisher remains a favored and staple species for fur trappers in places like Alberta, Ontario, Quebec, Maine, New Hampshire, Vermont, and Massachusetts.

Due to larger home range travel during winter months, setting traps for fisher during this time may become tedious, as two-three week intervals may incur between regular visits from individuals to locale where traps are placed.

Due to its significantly larger size, the fisher remains a dominant inter-specific competitor of the American marten, which some studies assert may contribute to the marten’s lack of strong presence in those shared territories on the southern fringes of its range. In addition to being a competitor for the same habitat and food as marten, the fisher is also known to be a direct predator of marten in areas where their ranges overlap, which may prohibit expansion of the less abundant marten. In Maine, studies have shown that large male fisher may impact Canadian Lynx kittens. In the mid-west United States, studies have found bobcats and wolves contribute to fisher mortality as direct competitors for resources and depredation.

Although considered fierce, human conflict with fishers are typically relegated to depredation on livestock (such as chickens). Attacks on humans are incredibly rare, with few reported cases, including a 12-year-old boy in Rehoboth, Massachusetts in 2014, and an attack on a 6-year-old boy in Hopkinton, Rhode Island in 2009.

The fisher is a susceptable host to several parasites, including nematode Baylisascaris devosi, tapeworm Taenia sibirica, nematode Physaloptera sp., trematodes Alaria mustelae and Metorchis conjunctus, nematode Trichinella spiralis, and Molineus sp. Diseases include Canine Distemper Virus (including a specific strain discovered in New England populations), and the Rabies Virus.