Males and females look similar. Adult males are 90 to 120 cm (35–47 in) long and weigh 3.5 to 6.0 kilograms (8–13 lb). Adult females are 75 to 95 cm (30–37 in) long and weigh 2.0 to 2.5 kg (4–6 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 moulting cycle. The fisher prefers to hunt in full forest. Although an agile climber, it spends most of its time on the forest floor, where it prefers to forage around fallen trees. 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 rarely eats fish.
The reproductive cycle of the fisher lasts almost a year. Female fishers give birth to a litter of three or four kits in the spring. They nurse and care for their kits 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 besides humans. 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 usually avoid human contact, encroachments into forest habitats have resulted in some conflicts.
Etymology
Despite the name "fisher", the animal is not known to eat fish. The name is instead related to the word "fitch", meaning a European polecat (Mustela putorius) or pelt thereof, due to the resemblance to that animal. The name comes from colonial Dutch equivalent fisse or visse. In the French language, the pelt of a polecat is also called fiche or fichet.[3]In some regions, the fisher is known as a pekan, derived from its name in the Abenaki language. Wejack is an Algonquian word (cf. Cree wuchak, otchock, Ojibwa ojiig) borrowed by fur traders. Other American Indian names for the fisher are Chipewyan thacho[4] and Carrier chunihcho,[5] both meaning "big marten", and Wabanaki uskool.[3]
Taxonomy
Skull diagram
Members of the genus Pekania are distinguished by their four premolar teeth on the upper and lower jaws. Its close relative Mustela has just three. The fisher has 38 teeth. The dentition formula is: 3.1.4.12.1.4.2[9]
Evolution
Some evidence shows that ancestors of the fisher migrated to North America during the Pliocene era between 2.5 and 5.0 million years ago. Two extinct mustelids, M. palaeosinensis and M. anderssoni, have been found in eastern Asia. The first true fisher, M. divuliana, has only been found in North America. M. divuliana is strongly indicated to be related to the Asian finds, which suggests a migration. M. pennanti has been found as early as the Late Pleistocene era, about 125,000 years ago. No major differences are seen between the Pleistocene fisher and the modern fisher. Fossil evidence indicates that the fisher's range extended farther south than it does today.[3]Three subspecies were identified by Goldman in 1935, M. p. columbiana, M. p. pacifica, and M. p. pennanti. Later research has debated whether these subspecies could be positively identified. In 1959, E.M. Hagmeier concluded that the subspecies are not separable based on either fur or skull characteristics. Although some debate still exists, in general, the fisher is recognized to be a monotypic species with no extant subspecies.[10]
Biology and behavior
Physical characteristics
Fisher in winter coat
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.[14]
Fishers have five toes on each foot, with unsheathed, retractable claws.[3] Their feet are large, making it easier for them to move on top of snow packs. In addition to the toes, four central pads are on each foot. On the hind paws are coarse hairs that grow between the pads and the toes, giving them added traction when walking on slippery surfaces.[15] Fishers have highly mobile ankle joints that can rotate their hind paws almost 180°, allowing them to maneuver well in trees and climb down head-first.[16][17] The fisher is one of relatively few mammalian species with the ability to descend trees head-first.[18]
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, they are likely used to make a scent trail to allow fishers to find each other so they can mate.[15]
Hunting and diet
Fishers are generalist predators. Although their primary prey is snowshoe hares and porcupines, they are also known to supplement their diet with insects, nuts, berries, and mushrooms. Since they are solitary hunters, their choice of prey is limited by their size. Analyses of stomach contents and scat have found evidence of birds, small mammals, and even deer—the latter two indicating that they are not averse to eating carrion. Fishers have been seen to feed on deer carcasses.[19] While the behavior is not common, fishers have been known to kill larger animals, such as wild turkey, bobcat, and lynx.[20][21][22]Fishers are one of the few predators that seek out and kill porcupines. Stories in popular literature indicate that fishers can flip a porcupine onto its back and "scoop out its belly like a ripe melon".[23] This was identified as an exaggerated misconception as early as 1966.[24] Observational studies show that fishers make repeated biting attacks on the face of a porcupine and kill it after about 25–30 minutes.[25]
Reproduction
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. Blastocyst implantation is then delayed for 10 months until mid-February of the following year when active pregnancy begins. After gestating for about 50 days, the female gives birth to one to four kits.[26] The female then enters estrus 7–10 days later and the breeding cycle begins again.[27]Females den in hollow trees. Kits are born blind and helpless. They are partially covered with fine hair. Kits begin to crawl after about 3 weeks. After about 7 weeks, they open their eyes. They start to climb after 8 weeks. Kits are completely dependent on their mother's milk for the first 8–10 weeks, after which they begin to switch to a solid diet. 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.[27]
Social structure and home range
Fishers are generally crepuscular, being most active at dawn and dusk. They 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 birth of their kits.[27]A fisher's hunting range varies from 6.6 km2 (3 sq mi) in the summer to 14.1 km2 (5 sq mi) in the winter. Ranges up to 20.0 km2 (8 sq mi) in the winter are possible depending on the quality of the habitat. Male and female fishers have overlapping territories. This behavior is imposed on females by males due to dominance in size and a male's desire to increase mating success.[28]
Parasites
Parasites of fishers include Baylisascaris devosi, Taenia sibirica, nematode Physaloptera sp., Alaria mustelae, trematode Metorchis conjunctus, nematode Trichinella spiralis, and Molineus sp.[29]Habitat
A fisher in the woods near Ipswich, Massachusetts
Fishers also select for forest floors with large amounts of coarse woody debris. In western forests, where fire regularly removes understory debris, fishers show a preference for riparian woodland habitat.[28][32][33] Fishers tend to avoid areas with deep snow. Habitat is also affected by snow compaction and moisture content.[34]
Distribution
A fisher climbing a tree at night
In the late 19th and early 20th centuries, fishers were virtually eliminated from the southern and eastern parts of their range, including most American states and eastern Canada including Nova Scotia. Overtrapping and loss of forest habitat were the reasons for the decline.[37][38]
Most states had placed restrictions on fisher trapping by the 1930s, coincidental with the end of the logging boom. A combination of forest regrowth in abandoned farmlands and improved forest management practices increased available habitat and allowed remnant populations to recover. Populations have since recovered sufficiently that the species is no longer endangered. Increasing forest cover in eastern North America means that fisher populations will remain sufficiently robust for the near future. Between 1955 and 1985, some states had allowed limited trapping to resume. In areas where fishers were eliminated, porcupine populations subsequently increased. Areas with a high density of porcupines were found to have extensive damage to timber crops. In these cases, fishers were reintroduced by releasing adults relocated from other places into the forest. Once the fisher populations became re-established, porcupine numbers returned to natural levels.[39] In Washington, fisher sightings were reported into the 1980s, but an extensive survey in the 1990s did not locate any.[40]
Scattered fisher populations now exist in the Pacific Northwest. In 1961, fishers from British Columbia and Minnesota were reintroduced in Oregon to the southern Cascades near Klamath Falls and to the Wallowa Mountains near La Grande. From 1977–1980, fishers were introduced to the region around Crater Lake.[41] Starting in January 2008, fishers were reintroduced into Washington State.[42] The initial reintroduction was on the Olympic peninsula (90 animals), with subsequent reintroductions into the south Cascade Mountains. The reintroduced animals are monitored by radio collars and remote cameras, and have been shown to be reproducing.[43] From 2008 to 2011, about 40 fishers were reintroduced in the northern Sierra Nevada near Stirling City, complementing fisher populations in Yosemite National Park and along California's northern boundary between the Pacific Coast Ranges and the Klamath Mountains.[44] Fishers are a protected species in Oregon, Washington, and Wyoming. In Idaho and California, fishers are protected through a closed trapping season, but they are not afforded any specific protection;[45] however, in California the fisher has been granted threatened status under the Endangered Species Act.[46] In June 2011, the U.S. Fish and Wildlife Service recommended that fishers be removed from the endangered list in Idaho, Montana, and Wyoming.[12]
Recent studies, as well as anecdotal evidence, show that fishers have begun making inroads into suburban backyards, farmland, and periurban areas in several US states and eastern Canada, as far south as most of northern Massachusetts, New York,[47][48] Connecticut,[49] Minnesota and Iowa,[50] and even rural New Jersey.[51] Having virtually disappeared after the construction of the Cape Cod Canal in the early 1900s, some reports have shown that populations have become re-established on Cape Cod,[52][53][54] although the populations are likely smaller than the populations in the western part of New England.[55][56]
Fishers and people
Fishers have had a long history of contact with humans, but most of it has been to the detriment of fisher populations. Unprovoked attacks on humans are extremely rare, but fishers will attack if they feel threatened or cornered. In one case, a fisher was blamed for an attack on a 6-year-old boy.[57][58] In another case, a fisher is believed to be responsible for an attack on a 12-year-old boy.[59]Fur trade and conservation
Prices for pelts have varied considerably over the past 100 years. They were highest in the 1920s and 1930s, when average prices were about US$100.[63] In 1936, pelts were being offered for sale in New York City for $450–750 per pelt.[64] Prices declined through the 1960s, but picked up again in the late 1970s. In 1979, the Hudson's Bay Company paid $410 for one female pelt.[64] In 1999, 16,638 pelts were sold in Canada for C$449,307 at an average price of $27.[65]
Between 1900 and 1940, fishers were threatened with near extinction in the southern part of their range due to overtrapping and alterations to their habitat. In New England, fishers, along with most other furbearers, were nearly exterminated due to unregulated trapping. Fishers became extirpated in many northern U.S. states after 1930, but were still abundant enough in Canada to maintain a harvest over 3,000 fishers per year. Limited protection was afforded in the early 20th century, but total protection was not given to the few remaining fishers until 1934. Closed seasons, habitat recovery, and reintroductions have restored fishers to much of their original range.[3]
Trapping resumed in the U.S. after 1962, once numbers had recovered sufficiently. During the early 1970s, the value of fisher pelts soared, leading to another population crash in 1976. After a few years of closed seasons, fisher trapping reopened in 1979 with a shortened season and restricted bag limits. The population has steadily increased since then, with steadily increasing numbers of trapped animals, despite a much lower pelt value.[60]
Captivity
Fishers have been captured live for fur farming, zoo specimens, and scientific research. From 1920–1946, pelt prices averaged about C$137. Since pelts were relatively valuable, attempts were made to raise fishers on farms. Fur farming was popular with other species such as mink and ermine, so the same techniques were thought to be applicable to fishers. However, farmers found it difficult to raise fishers due to their unusual reproductive cycle. In general, knowledge of delayed implantation in fishers was unknown at the time. Farmers noted that females mated in the spring but did not give birth. Due to declining pelt prices, most fisher farms closed operations by the late 1940s.[66]
Fishers have also been captured and bred by zoos, but they are not a common zoo species. Fishers are poor animals to exhibit because, in general, they hide from visitors all day. Some zoos have had difficulty keeping fishers alive since they are susceptible to many diseases in captivity.[67] Yet at least one example shows a fisher kept in captivity that lived to be 10 years old, and another living to be about 14 years old,[68] well beyond its natural lifespan of 7 years.[69][70]
In 1974, R.A. Powell raised two fisher kits for the purpose of performing scientific research. His primary interest was an attempt to measure the activity of fishers to determine how much food the animals required to function. He did this by running them through treadmill exercises that simulated activity in the wild. He compared this to their food intake and used the data to estimate daily food requirements. The research lasted for two years. After one year, one of the fishers died due to unknown causes. The second was released back into the wilderness of Michigan's Upper Peninsula.[71]
Interactions with domestic animals
Fisher raiding a farmer's duck coop
Poisoning
Male
fisher killed by anticoagulant rodenticide on a marijuana grow site on
US Forest Service lands, southern Sierra Nevada mountains
Literature
One of the first mentions of fishers in literature occurred in The Audubon Book of True Nature Stories. Robert Snyder relates a tale of his encounter with fishers in the woods of the Adirondack Mountains of New York. He recounts three sightings, including one where he witnessed a fisher attacking a porcupine.[83]
In Winter of the Fisher, Cameron Langford relates a fictional encounter between a fisher and an aging recluse living in the forest. The recluse frees the fisher from a trap and nurses it back to health. The fisher tolerates the attention, but being a wild animal, returns to the forest when well enough. Langford uses the ecology and known habits of the fisher to weave a tale of survival and tolerance in the northern woods of Canada.[84]
Fishers are mentioned in several other books, including The Blood Jaguar (an animal shaman), Ereth's Birthday (a porcupine hunter) and in The Sign of the Beaver, where a fisher is thought to have been caught in a trap.[85][86][87]
Pekania pennanti
(Erxleben, 1777)
Fisher range
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