The fisher (Martes pennanti) is a member of the Mustelid family of weasel-like animals. Its common name is derived from that name of the European polecat, “fitchet”, “fitche” or “fitchew”. Other common names include “pekan”, “black cat”, “wejack” and “Pennant’s marten”.
Fisher are found in all provinces except Prince Edward Island and Newfoundland. They do not live as far north as do marten, and are rare in the Northwest Territories, the Yukon and northern British Columbia. Fisher inhabits Michigan, Minnesota, Wisconsin and most of the New England states. They can also be found in the mountains of the American west.
The fisher’s wedge-shaped head is set on a stout neck. It has short, heavy legs, sharp claws and a long, bushy, tapering tail. The adult male usually weighs from 3.6 to 5.4 kg (8 to 12 lbs) and measures 90 to 120 cm (35 to 47 in) from the nose to the tip of the tail. The adult female weighs from 2 to 2.5 kg (4 to 6 lbs) and has a total length of 75 to 95 cm (30 to 37 in). Fisher uses two types of scent glands to mark their territories: a pair of anal glands and a set of small glands on the pads of the hind paws. The pelt ranges in colour from grey-brown to black, and is lighter on the sides and darker towards the rump and tail. The face, neck and shoulders are often heavily frosted with grey or pale brown. A few white patches are found on the neck, throat, belly and inner part of the upper leg, as well as around the anus. Immature fishers are somewhat darker in colour than adults. The adult male’s fur is fairly coarse and grizzled, while the female’s is lighter and silkier. Moulting causes the spring and summer fur to become lighter in colour and less dense. By November, the fur is dense, glossy and prime. It is no longer at its peak prime after late January.
The female fisher is sexually mature by and breeds at 12 months, and has her first litter when she is 24 months. Although the male produces sperm by the age of 11 months, his breeding success at this age is not known. Both sexes may have more than one mate. Breeding begins in March or April a few days after the birth of the young from the previous year’s mating. Fisher have delayed implantation, breeding 51 weeks before the kits are born. Active pregnancy lasts only eight weeks. The average litter contains three kits. The blind and helpless new-born is partially covered with a growth of fine hair. They utter cries like those of domestic kittens. Their eyes usually open by the fifty-third day. The kits nurse for about four months and begin to eat meat before they are weaned. The average life span of the male fisher that survives the first year is from four to five years. The female lives longer, and individuals as old as 14 years have been reported. The skull characteristics of the juveniles distinguish them from the adults. A bony crest begins to form down the middle of the skull at 6 months of age and becomes progressively larger with age, particularly in males.
Fisher are adaptable animals that will live in a variety of forested areas so long as there is something to eat. They avoid open areas, preferring dense forests of mixed conifers and hardwoods, or second growth stands and swamps. Hollow trees and logs, holes in rocky ledges, old porcupine dens and cavities in the snow are likely den sites. Fisher also make dens under large boulders and brush piles. A favourite spot for a nesting den is high in a hollow hardwood tree.
Food and Feeding Behaviour
The fisher eats what it can find – snowshoe hares, small mammals, ruffed grouse, small birds and their eggs, amphibians, fish, insects, fruit and nuts. Carrion can be important to its winter diet. It is especially noted for preying on porcupine, which it kills by repeatedly attacking the face and head. Little of the dead porcupine is wasted. The fisher eats everything except the skin, the large bones, the feet and the intestines.
Except for brief periods during the breeding season, fisher lead solitary lives, travelling extensively as they search for food. They are most active at night, and can also be active during the day. They usually remain on the ground but can climb trees and swim if necessary. They travel in rough circles 10 to 30 km in diameter, repeating each circuit every four to twelve days. Using their scent glands to mark their territories, the males establish home ranges of about 25 square km (9 square mi), and the females, of about 17 square km (6 square mi). These ranges vary in size according to habitat quality and the food supply. Like marten, fisher demonstrate a good deal of curiosity, and are, therefore, readily baited and trapped.
Ontario’s annual fisher harvest has varied from year to year, but except in recent years has rarely exceeded 5,000 pelts. This fluctuation in the harvest figures is due to a variety of factors including trapping pressure and changes in habitat. It is not due to diseases or parasites, neither, of which has a significant impact on the fisher population.
One-quarter of North America’s fisher harvest comes from Ontario. To ensure that the yield is sustained, Ontario uses a quota system. In areas for which information is available the trapping of approximately one fisher for every 25 square km (9 square mi) maintains a sustained harvest. A sudden influx of fisher to a particular area may call for the local quota to be raised temporarily. In co-operation with trappers and conservation officers, the local district offices set the yearly quotas. These are based on the harvest size in past years, the age and sex ratios of previous harvests, and the size of the area to be trapped. A fisher transplant program was begun in 1979-80 to the Bruce Peninsula and to Manitoulin Island. Live-trapped fisher were outfitted with radio transmitters and released individually. This project provided information about the extent of movements, home range sizes and survival rates of fisher.