The fisher (Pekania pennanti) is a carnivorous mammal native to North America, a forest-dwelling creature whose range covers much of the boreal forest in Canada to the northern United States. It is a member of the mustelid family and is the only living member of the genus Pekania. Although it is sometimes referred to as a fisher cat, it is not a feline.
The fisher is similar to, but larger than, the American marten (Martes americana) and Pacific marten (Martes caurina). In some regions, the fisher is known as a pekan, derived from its name in the Abenaki language, or wejack, an Algonquian word (cf. Cree , Ojibwa ) borrowed by fur traders. Other Indigenous names for the fisher are Chipewyan and Carrier , both meaning "big marten", and Wabanaki uskool.
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 became locally extinct in 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 historical 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.
Male and female fishers look similar, but can be differentiated by size, with males being up to twice as large as the females. 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 the 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, it 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, it rarely eats fish. The reproductive cycle lasts almost a year. Female fishers give birth to a litter of three or four kits in the spring. They nurse and care for them 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.
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 or . In the French language, the pelt of a polecat is also called or . Alternatively, Dr. James DeKay, as reported by John James Audubon and John Bachman, claimed the name "fisher" may have been attributed to the animal's "singular fondness for the fish used to bait traps", although this may have been local lore.
Taxonomy
The Latin specific name pennanti honors 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.Coues, p. 66. The fisher was eventually placed in the genus Martes by Smith in 1843.Powell, pp. 11–12. In 2008, advances in DNA analysis allowed a more detailed study of the fisher's evolutionary history. The fisher and the genus Martes were determined to have descended from a common ancestor, but the fisher was distinct enough to put it in its own genus. It was decided to create the genus Pekania and reclassify the fisher as Pekania pennanti.
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: Powell, p. 12.
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, Pekania palaeosinensis and P. anderssoni, have been found in eastern Asia. The first true fisher, P. diluviana, has only been found in Middle Pleistocene North America. P. diluviana is strongly indicated to be related to the Asian finds, which suggests a migration. P. pennanti has been found as early as the Late Pleistocene era, about 125,000 years ago. No major differences are seen between the Pleistocene and the modern fishers. Fossil evidence indicates that the fisher's range extended farther south than it does today.
Three subspecies were identified by Goldman in 1935, Martes pennanti 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.Powell, p. 14.
Physical characteristics
Fishers' bodies are long, thin, and low to the ground. The sexes have similar physical features, but they are sexually dimorphic, with the male being much larger than the female. Males are in total length and weigh . Females measure and weigh . Head and body lengths for both sexes range from ; the tail adding a further . The largest male fisher ever recorded weighed .Powell, p. 3.
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 on the chest to 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.Powell, pp. 4–6.
Fishers have five toes on each foot, with unsheathed, retractable claws. Their feet are large, making movement on top of snowpacks easier. 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.Powell, p. 9. 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.Fergus, p. 101. The fisher is one of relatively few mammalian species with the ability to descend 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 they can mate.
Biology and behavior 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. They have been observed eating small apples during winter. 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 indicating that they are not averse to eating carrion.Fergus, p. 102. While the behavior is not common, fishers have been known to kill larger animals, such as wild turkey, raccoon, fox, marten, mink, otter, bobcat, and Canada lynx. Raccoons may be killed by a large fisher in trees or on the ground. Fishers can also catch martens on the ground or in the trees, and usually there is either a good population of fisher or marten but not both. Researchers in Maine have found "about a dozen" cases of confirmed fisher predation on Canada lynx, and several more suspected cases, in a four-township area of Maine. According to Maine Department of Inland Fisheries and Wildlife wildlife biologist Scott McClellan, the fishers involved in these kills attacked lynx bedded down in snowstorms with a quick "powerful grip" bite to the lynx's neck. Signs of struggle indicated that some lynx attempted to defend themselves but McClellan states that "the fishers would finish the cats off pretty quickly. There was some struggle certainly, but it didn't appear to last very long. There were some broken branches, tufts of fur, and claw marks where the lynx was trying to get away." The McClellan study in The Journal of Wildlife Management documents 14 fisher-caused mortalities of Canada lynx from 1999 to 2011 in northern Maine, and found that predation was the leading source of mortality of lynx in the study area (18 deaths, 14 by fisher).
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". This was identified as an exaggerated misconception as early as 1966. Observational studies show that fishers make repeated biting attacks on the face of a porcupine and kill it after about 25–30 minutes.Powell, pp. 134–6.
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 ten 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.Burt, Henry W. (1976) A Field Guide to the Mammals. Boston, p. 55. . The female then enters estrus 7–10 days later and the breeding cycle begins again.Feldhamer, pp. 638–9.
Females den in hollow trees. Kits are born blind, helpless, and 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.
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.
A fisher's hunting range varies from in the summer to in the winter. Ranges up to 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.Feldhamer, p. 641.
Predators and parasites