Mustela pennantii Erxleben, 1777
The fisher (Martes pennanti) is a medium-sized 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 (Martes americana). 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. Names derived from aboriginal languages include pekan, pequam, and wejack. It is also sometimes referred to as a fisher cat, although it is not a feline.
Males and females are similar in appearance but the males are larger. Males are 90–120 cm (35–47 in) in length and weigh 3.5 to 6 kilograms (8–13 lb). Females measure 75–95 cm (30–37 in) and weigh 2–2.5 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. 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 fallen dead wood on the forest floor. 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 successfully hunt porcupine. Despite their name, fishers seldom eat fish.
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 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. There are anecdotal reports of fishers attacking pets and, in a 2009 case in Rhode Island, a 6-year-old boy.
Despite the name fisher, the animal is not known to eat fish. The name comes from colonial Dutch fisse or visse due to its resemblance to the European polecat (Mustela putorius). In the French language, the pelt of a polecat is also called fiche or fichet.
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 and Carrier chunihcho, both meaning "big marten", and Wabanaki uskool.
The Latin specific name pennanti is named for Thomas Pennant who described the fisher in 1771. Buffon had first described the creature in 1765, calling it a pekan. Pennant examined the same specimen but called it a fisher, unaware of Buffon's earlier description. Other 18th-century scientists gave it similar names, such as Schreber, who named it Mustela canadensis, and Boddaert, who named it Mustela melanorhyncha. The fisher was eventually placed in the genus Martes by Smith in 1843.
Members of the genus Martes are distinguished by their four premolar teeth on the upper and lower jaws. Its close relative Mustela has only three. The fisher has 38 teeth. The dentition formula is:
There is evidence that ancestors of the fisher migrated to North America during the Pliocene era between 2.5 and 5 million years ago. Two extinct mustelids M. palaeosinensis and M. anderssoni have been found in eastern Asia. The first true fisher, M. divuliana, has been found only in North America. There are strong indications that M. divuliana is 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. There are no major differences between the Pleistocene fisher and the modern fisher. Fossil evidence indicates that the fisher's range extended farther south than it does today.
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 it is recognized that the fisher is a monotypic species with no extant subspecies.
Biology and behavior
Fishers are a medium-sized mammal, comparable to the size of domestic cat, and the largest species in the marten genus. Their bodies are long, thin, and low to the ground. The sexes have similar physical features but they are sexually dimorphic in size, with the male being much larger than the female. Males are 90–120 cm (35–47 in) in length and weigh 3.5–6 kg (8–13 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 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.
Fishers have five toes on each foot with unsheathed, retractable claws. 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, they are likely used to make a scent trail to allow fishers to find each other so that they can mate.
Hunting and diet
Fishers are generalist predators. Although their primary prey is snowshoe hare and porcupine 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 to their size. Analyses of stomach contents and scat have found evidence of birds, small mammals, and even moose and deer. The latter food sources shows that they are not averse to eating carrion. Fishers have been observed to feed on the carcasses of deer left by hunters. While uncommon, fishers have been found to kill larger animals such as wild turkey, bobcat and lynx.
Fishers are one of the few predators that seek out and kill porcupines. There are stories in popular literature that fishers can flip a porcupine onto its back and "scoop out its belly like a ripe melon." This was identified as an exaggerated misconception as early as 1966. Observational studies show that fishers will make repeated biting attacks on the face of a porcupine and kill it after about 25–30 minutes.
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 six 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 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.
Social structure and home range
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.
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 of 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 desire to increase mating success.
Although fishers are competent tree climbers, they spend most of their time on the forest floor. They prefer continuous forest to other habitats. Fishers have been found in extensive conifer forests typical of the boreal forest but are also common in mixed hardwood and conifer forests. Fishers prefer areas with continuous overhead cover with greater than 80% coverage and will avoid areas with less than 50% coverage. Fishers are more likely to be found in old-growth forests. Since female fishers require moderately large trees for denning, forests that have been heavily logged and have extensive second growth appears to be unsuitable for their needs.
Another factor that fishers select for are forest floors that have large amounts of coarse woody debris. In western forests where fire regularly removes understorey debris, fishers show a preference for riparian woodland habitat. Fishers tend to avoid areas with deep snow. Habitat is also affected by snow compaction and moisture content.
Fishers are widespread throughout the northern forests of North America. They are found from Nova Scotia in the east to the Pacific shore of British Columbia and Alaska. They can be found as far north as Great Slave Lake in the Northwest Territories and as far south as the mountains of Oregon. There are isolated populations in the Sierra Nevada of California and the Appalachian Mountains of West Virginia.
In the late 19th century and early 20th century, fishers were virtually eliminated from the southern and eastern parts of their range including most American states and eastern Canada including Nova Scotia. Over-trapping and loss of forest habitat were the reasons for the decline.
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 farm lands and improved forest management practices increased available habitat and allowed remnant populations to recover. 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 reestablished, porcupine numbers returned to natural levels.
Scattered fisher populations now exist in the Pacific Northwest. In 1961 fishers from British Columbia and Minnesota were re-introduced in Oregon to the southern Cascades near Klamath Falls and also to the Wallowa Mountains near La Grande. From 1977-1980 fishers were introduced to the region around Crater Lake. In January 2008, fishers were reintroduced into the Olympic National Park in Washington State. From 2008 to 2011, about 40 fishers were re-introduced 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. 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; however, it is expected that in California the fisher will probably be granted listing under the Endangered Species Act in 2014. In June 2011, the U.S. Fish and Wildlife Service recommended that fishers be removed from the endangered list in Idaho, Montana, and Wyoming. It also recommended further study to ensure that current populations are managed properly.
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.
Fishers and people
Fishers have had a long history of contact with humans but most of the contact has been to the detriment of fisher populations. Eliminated in many areas due to excessive trapping and logging practices in the early 20th century, 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.
In 2003, a new minor league baseball team based in Manchester, New Hampshire held a "Name The Team" contest; the name New Hampshire Fisher Cats was chosen by the public from a list of suggestions reflecting the local culture and environment.
Fur trade and conservation
Fishers have been trapped since the 18th century. They have been popular with trappers due to the value of their fur. Their fur has been used for scarfs and neck pieces. The best pelts are from winter trapping with secondary quality pelts from spring trapping. The lowest-quality furs come from out of season trapping when fishers are moulting. They are easily trapped, and the value of their fur was a particular incentive for catching this species.
Prices for pelts have varied considerably over the past 100 years. They were highest in the 1920s and 1930s, when average prices were about $100 US. In 1936, pelts were being offered for sale in New York City for $450–750 per pelt. 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. In 1999, 16,638 pelts were sold in Canada for $449,307 (CAN) at an average price of $27.
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 fishers were still abundant enough in Canada to maintain a harvest of over 3,000 fishers per year (see figure). Limited protection was afforded in the early 20th century, but it was not until 1934 that total protection was finally given to the few remaining fishers. Closed seasons, habitat recovery, and reintroductions have restored fishers to much of their original range.
Trapping resumed in the U.S. after 1962 once numbers had recovered to sufficient numbers. During the early 1970s, the value of fisher pelts soared, leading to another population crash in 1976. After a couple of years of closed seasons, fisher trapping re-opened 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.
Fishers have been captured live for fur farming, zoo specimens, and scientific research. From 1920–1946, pelt prices averaged about $137 CAN. 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 it was thought that the same techniques could be applied 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.
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. Yet there is at least one example of a fisher kept in captivity that lived to be ten years old, well beyond its natural lifespan.
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 in order 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 the Upper Michigan peninsula.
In some areas, fishers can become pests to farmers because they can get into a pen and kill large numbers of chickens. Unprovoked attacks on humans are extremely rare, but they will attack if they feel threatened or cornered. In one case a fisher was blamed for an attack on a six-year-old boy.
There have been a few instances of fishers preying on cats and small dogs. A 1979 study examined the stomach contents of all fishers trapped in the state of New Hampshire; cat hairs were found in only 1 of over 1,000 stomachs. While there is popular belief for more frequent attacks on pets, zoologists suggest bobcats or coyote are more likely to prey upon domestic cats and chickens. In 2012, a UC Davis study showed that the fisher population was falling victim to rat poison, commonly used on marijuana farms in northern California.
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.
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.
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.
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- "Fisher". Encyclopedia Americana. 1920.
- "Fisher". The American Cyclopædia. 1879.