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Fisher

Scientific Name: Martes pennanti

Description

Fisher
Photo by Marty DeLong

The fisher, also known as the 'fisher cat', is a large, dark, long-haired member of the weasel family. Their stature is relatively low to the ground, with short legs, small ears and a well-furred tail. The color of their fur varies from dark brown to nearly black. Females and juveniles usually have a more uniform color, and males will have a blonde or grizzled appearance due to multi colored guard hairs around the neck, upper back and shoulders.

There is considerable evidence of dimorphism between the sexes, with males weighing between 7 and 13 pounds, and females between 3 and 7 pounds. Total lengths for males range from 35-47 inches, and females, 30-37 inches.

Fisher have large, wide feet with five toes on each foot and semi-retractable claws. This makes them well adapted for walking on snow, climbing trees and grasping and killing prey. They are capable of rotating their hind feet nearly 180º, which allows for a headfirst descent from trees. As with all members of the weasel family, both sexes have large anal scent glands which may be used to mark territories or attract potential mates.

Distribution and Habitat

Found exclusively in North America, fisher inhabit a band of forested and semi-forested land from coast to coast, and prefer extensive closed canopy forests. In the east, they range from Virginia north to Quebec and the maritime provinces of Canada. They use deciduous, coniferous and mixed forests. Historically, their numbers experienced a severe decline during the late 1800s and early 1900s due to over-exploitation and loss of forested habitat due to unregulated logging and the clearing of land for farms. Reintroduction programs have proven to be effective in restoring populations, along with regulation of trapping opportunities and the initiation of reforestation programs.

In New York State, fisher can be found throughout approximately 26,000 square miles of forested habitat within the northern, eastern and southeastern parts of the state. Recently they have begun to return to the southern tier of central and western New York, as some sightings and road kills have been reported from that region.

Food and Feeding

Fisher are a dietary generalist. They eat a wide variety of small to medium sized mammals and birds, and a variety of hard and soft mast such as beechnuts, acorns, apples and berries. However, they have been considered a specialist in that they are the only known North American mammal that succeeds in killing and consuming porcupines. They will consume the entire animal, leaving nothing but a quilled hide and a few of the larger bones.

Other prey items include rabbits, squirrels, mice, shrews, and carrion from large mammals such as whitetailed deer. Carnivores such as bobcat, coyote, red and grey fox and some raptors serve as competition for prey items, and fisher have been documented to travel over a hundred miles over the course of a few weeks in order to meet the demands of their dietary requirements.

Reproduction

Fisher reach sexual maturity in their first year of life, and females may be receptive at that time. Implantation of the fertilized embryo may be delayed until the following season, thus accounting for their first litter being born in their second year. Reproduction peaks in late March, and breeding may occur as late as May. Average litter size is 2-3 young, and kits are born partially furred with closed eyes and ears, essentially helpless at birth. Weaning occurs within 8-10 weeks, and dispersal of young may occur by their fifth month, as interfamilial aggression begins by the onset of autumn.

Behavior

Fisher use a variety of structures for year-round denning purposes such as the natural cavities found in older trees, hollow logs, cavities in rocky outcrops, brush piles and underground burrows. Dens used for birthing of young are usually found in hollow sections of trees, high above the ground.

Fisher lead a solitary lifestyle except for brief periods during the breeding season. They have been found to be active at any time during the day or night. Males generally have larger home ranges than females, and their territories seldom overlap that of other males, suggesting territoriality between the sexes.

Predators and Disease

Fisher have no natural enemies, save humans, and natural mortality remains largely undocumented. Trapper harvest and automobile collisions likely account for the majority of fisher deaths across their range. A few species of tapeworm, intestinal roundworm, and flatworm have been identified in fisher, and their effects on health are minimal. Rabies and distemper have been described in fisher in New York State, but are a minor source of mortality in the wild.