| Common Names: fisher
The fisher is a medium sized carnivore, and the largest species of the Martes genus. It has a long, thin body and bushy tail. Its overall colour is a very dark brown, which often appears black. A lighter silver or blond colour is visible on the face neck, and shoulders, due to the presence of lighter-tipped guard hairs. Pelt colouration varies from individual to individual and also varies with the season, as the number and location of the guard hairs changes. A complete molt occurs yearly in late summer or early fall.
Fishers show a significant sexual dimorphism, females being the smaller of the two sexes. Average female size is 75-95 cm and 2 -2.5 kg. Average male size is 90-120 cm and 3.5-5.5 kg. Males up to 9 kg have been captured, but are very rare. Height in fishers has never been measured, but, like most members of the mustelid family, their legs are short relative to their body size. Adult male fishers have coarser coats than females and juveniles and thus they have not been targetted specifically in commercial harvesting operations.
Fishers have five toes per foot, which are exceptionally large for the size of the animal. They walk and run in a typical weasel fashion and their tracks are distinguishable on the basis of the following characteristics:
General Distribution and Habitat of Fisher Cat:
Found throughout New Brunswick, the fisher is restricted mostly by habitat suitability. It is also found in all of Canada’s southern provinces, south to New England and New York in the East, south to Northern California in the west, and in the Rocky Mountains to Utah. The fisher’s range limit in the north is the tree line, as they do not generally venture into untreed areas.Fishers prefer continuous forest that has high forest floor structural diversity. High structural diversity in the forest floor refers to the presence of a large number of leaning trees, dead trees, and fallen logs and debris. Late-successional forest is the forest type that best fits this description, and fishers thrive in areas where there are coniferous forests of this type. They may also be found in areas that are predominantly deciduous trees. However, in these cases, the snowfall must be only moderate so as not to decrease the fisher’s mobility. Fishers are most likely to be found in dense forests with a continuous canopy layer. In the winter, fishers are found at lower altitudes and often in swampy, riparian areas, where there is little snow accumulation.
There is much seasonal change in the distribution of the fisher. Warmer months find them at higher elevations and in areas that have higher deciduous content. Whereas, in the colder months the fisher moves to lower altitudes, with less snowfall and a larger coniferous tree population. In winter, fishers are also more likely to be found in riparian habitats. If there is adequate overhead coverage, a fisher will show preference for an area with a higher diversity of small mammal prey.Fishers den in hollow trees, rock crevices, slash piles, rockfalls, logs, abandoned beaver lodges, and snow dens. Generally, fishers use dens only once, though over the course of a number of years they may return to a few dens. Den use varies from season to season, with more enclosed dens seeing more use in the winter and with fishers often making use of tree branches and more open dens in the warmer months. Female fishers use almost exclusively hollows located high up in trees as natal dens, though a few nests have been witnessed in rockfalls. During the rest of the year, female fishers make use of dens in a similar fashion as males.
The type of rest site a fisher makes use of also depends on the type of forest the animal is in. A higher percentage of tree nests are used in coniferous forests, whereas tree cavities are more commonly used in deciduous forests. Obviously, this is closely related to the type of rest site available in each type of forest.
Fisher Cat: General Biology
Fishers, like most other carnivores, are fairly flexible in their food intake, and tend to be opportunistic. They mostly feed on deer, red squirrels, hare, porcupine, and small mammals ( red-backed mice, shrews, deer mice). Flying squirrels, mink, muskrat, insects, and birds often supplement the fisher’s diet. The deer ingested are not usually killed by the fisher, but are carrion from other animal kills or human shootings. Fishers benefit from human activity by killing and consuming trapped mink and muskrat and making use of deer that are killed and not removed from the forest.
Interestingly, fishers also commonly feed on a variety of berries and seeds including: swamp holly berries, black cherries, fern fronds, moss, and beechnuts. Beechnuts actually make up a large part of the diet for a number of fishers while the nuts are in season. It was previously thought that the nuts were only relied upon when the prey species fishers exploit are at low population levels. It has been noted, however, that the fishers usually make use of the seed availability regardless of the population levels of prey species.
A popular hypothesis suggests that fishers and porcupines coevolved in their predator-prey relationship. The fisher, though not immune to porcupine quills themselves, seems able to fend off serious infections from quill injuries that would result in death for individuals of similar species. Fishers that are tagged are often found with quills imbedded deep within the skin from obviously earlier encounters. Despite the presence of such evidence of injury, the fishers in these cases show no ill effects.
The fisher’s diet is affected by seasonality in much the same way as its range. As the temperature decreases, the prey species tend to become confined to lowland forests, which is where the fisher makes its winter home. The fisher also makes use of fruits and seeds when seasonally available.
Fishers have varying home ranges, with sizes from 7 to 40 square kilometres. The average home range seems to extend to around 15-20 square kilometres. Fisher movement is not as directed as that seen in foxes, but fishers do move in roughly circular patterns within their range. The speed at which fishers travel can be extraordinary, one witness tracked fresh fisher prints over 97 km in less than 4 days. Fishers are considered solitary animals, but there have been numerous sightings of a few fishers (especially males) travelling together.
Breeding season occurs almost immediately after parturition in early spring. The females must leave their nearly newborn young to find a mate. Once the female has successfully mated, the fertilized egg undergoes delayed implantation for approximately 11 months, at which time, 30 days of active gestation takes place. Females can mate as early as at 1 year of age. An average of 2-3 kits are born in late March or early April in a natal den in a hollow tree, rock crevice, or log. Newly born kits are nursed for about 6 weeks after which time there is close to 6 weeks of weaning. The young are no longer dependent on milk between 8 and 10 weeks of age. Fisher kits leave the nest in early fall to find their own territory.
Fishers are generally considered nocturnal animals. However, it is not unusual for a fisher to be active in the daytime. Some studies have shown no difference in the amount of fisher activity between day and night. Female fishers tend to be more active in the evening, and male fishers in the early morning. Female fishers increase their rate of daytime activity during the weaning period of the kits. This may be because of the need for increased foraging when caring for the weaned young, or because they are exploiting alternate prey types.
Fisher Cat :Conservation:
The fisher is not rated as endangered or threatened in any part of Canada or the U.S. However, there have been a number of attempts by various organizations to have the western populations of fishers listed as threatened because of their overall decline in their numbers and range. These attempts have all failed because the U.S. Fish and Wildlife Service does not distinguish between the western and eastern populations and will not list the species as threatened on the basis of one of the populations. The fisher has recently been placed on the IUCN blue list of sensitive or vulnerable animals in British Columbia.
The main threat to fishers is the destruction of suitable habitat. Managing and clearcutting forests have severely restricted the amount of appropriate habitat for the fisher. Management of forests necessitates the removal of dead trees and snags, both of which the fisher depends on for nesting and rest sites. Clearcutting results in forest fragmentation and the removal of late successional forest, which are also prime fisher habitats.
In the late 19th and early 20th centuries, fishers were harvested for their pelts. There were very few regulations on the trapping of these animals, and as a result a strong decline in population numbers was seen. This decline cannot be wholly blamed on hunting, as logging also had a large impact on fisher populations. Extirpation of the species was seen in both Eastern Canada and the Eastern United States, as well as, much of the Midwestern and Western United States. In the 1930s both Canada and the United States enacted legislation to protect fishers, many states went so far as to close the fisher-trapping season entirely. Fortunately, logging also decreased at this time, and the fishers that remained were able to increase in number.
There are a number of areas where fishers have been reintroduced after species extirpation. These areas include Nova Scotia ( site of the first release in 1947), Wisconsin, Michigan, Montana, Oregon, and Idaho. Vermont and New York also released fishers into the wild, however, though the population levels of fishers in these two states dropped dramatically in the early part of this century, the animals were never eliminated completely. Most of these reintroductions were very successful, with the exception of Oregon, where the fisher does not seem to have regained its previous range. A number of these areas first reintroduced the fisher as a biological means of controlling rapidly expanding porcupine populations, which many wrongly believed were responsible for significant damage to the timber harvest. Later, however, states reintroduced fishers purely because they wished to rebalance the biological communities in their wilderness.
There has not been a great deal of research conducted on fisher populations and behaviour in recent years. This helps explain the contradictory information commonly found in the literature. These contradictions can also be partially explained by the variation in biology seen in any animal with a range as large as the fisher’s. The variety in habitats and interactions the fishers encounter across their range leads to variation in a great number of behaviours. Fishers are considered fairly rare in New Brunswick, but because there is no data supporting this theory it is hard to say for sure. Fishers are not hunted in New Brunswick, but trapping is still pursued in Minnesota and Michigan and possibly in other states.