Reproduction
Fishers reach sexual maturity from 1-2 years of age. Both sexes are predominantly solitary except during the breeding season, which occurs in the beginning of March. Gestation lasts about 51 weeks. The gestation period is long because the fertilized egg is delayed several months before implanting on the uterine wall. An average size litter of three young are born from late February through April in dens situated high in hollow trees. Females mate almost immediately after giving birth, and are therefore pregnant most of the time.

Life Cycle
Young are born blind and helpless, but after four weeks are able to eat meat. At about 7 weeks their eyes open, and they begin to walk at approximately 9 weeks. The female may move her young several times to alternate dens. By 17 to 18 weeks, they are weaned and ready to leave the den. Except for raising young, fishers normally do not have a permanent den. Instead, they seek temporary shelter in hollow trees and logs, stumps, holes in the ground, or wherever they can find seclusion. The fishers home range appears to encompass one to four square miles (2.6-10.4 sq km). Home ranges of males seldom overlap, and males are not tolerant of one another. There is wide overlapping of territories between males and females. Territories are identified through scent marking.

Opportunistic Hunters
The fisher is largely an opportunist when hunting. Most of its hunting consists of the chance investigation of sites where small mammals are likely to be found. Fishers kill all prey, except porcupines, by biting them through the back of the head. The fisher is one of the few predators that eats porcupines. The hunting of a porcupine is hard work and a successful kill may take half an hour. The arrangement of quills on a porcupine protects it from an attack to the back of the neck. To counter this pointy defense, the fisher circles the porcupine and bites at its face until the porcupine suffers shock or is unable to protect itself. The fisher then overturns the porcupine and begins to feed on its belly. As would be expected, fishers may sustain some injury from the quills of their victims, but even though quills sometimes penetrate a fisher's intestines, they seldom appear to cause serious damage to the animal. Porcupines are not an essential part of the fisher's diet because fishers live in areas not inhabited by this prey species.

Bigger and Stronger
The fisher is a close relative of the marten. Similar in structure and body proportions, the fisher is nearly twice as large as a marten, and four times as heavy. Their coats also differ. The fisher's coat is very dark brown to blackish brown with gold to silver hoariness on the head and shoulders. Fishers have strong, moderately large feet with hairy soles. Each foot has five toes that terminate in sharply curved, partially retractable claws. The legs and tail are black. The chest has a variable cream-colored patch.

Woodland Park Zoo no longer exhibits fishers. Other animals that can be seen along the Northern Trail are gray wolves, brown bear, mountain goat, porcupine, bald eagle and Roosevelt elk.

During the late 19th century through the 1920s, fishers were extensively trapped for their pelts. Loss of required forest habitat due to extensive logging also contributed greatly to their population decline during this century. By the 1930s, the fisher was essentially eliminated in the United States. The demise of the fisher had a positive effect on porcupine populations. With the removal of their primary predator, porcupine populations expanded. This in turn led to the extensive damage to forests, caused by the porcupines debarking and killing of trees. With the realization that fishers are important for controlling porcupine populations, fishers were reintroduced to certain areas during the 1950s and 1960s. Legal trapping of the fisher for the fur market continues today in areas of the United States and Canada.

How You Can Help!
The effort to save endangered species requires cooperation and support at the international, national, regional and individual levels. You can help in this cause. Join and become active in Woodland Park Zoo and other conservation organizations of your choice. Let your elected representatives know your views about protecting endangered species and wild habitats.

Contact Woodland Park Zoo at webkeeper@zoo.org to find out about ways you can support conservation efforts at the zoo. Learn other ways you can help conserve wildlife and the habitats they require for survival by visiting our How You Can Help page.

Sources and Suggested Reading
Chapman, Joseph A. and George A. Feldhamer, ed. 1982. Wild Mammals of North America: Biology, Management, Economics. The Johns Hopkins University Press, Baltimore, MD. 1147 p.

Nowak, Ronald M. ed. 1991. Walker's Mammals of the World. 5th Edition. The Johns Hopkins University Press, Baltimore and London. 1629 p.

More References

* Taxonomic classification varies between references. Classification information used in this fact sheet was taken from Mammal Species of the World: A Taxonomic And Geographic Reference, edited by Don E. Wilson and Dee Ann M. Reeder, Second Edition, 1993.

**Woodland Park Zoo identifies an animal or plant endangered if it is listed as endangered (in any part of its range) on the federal list of Endangered and Threatened Species, or if is listed on Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).