Fisher (Martes pennanti)

Webpage Author: Michael Sedon

[Picture of Fisher]

     The fisher one of the largest members of the weasel family disappeared from Pennsylvania in the late 1800’s and early 1900’s as a result of deforestation and unregulated trapping Today fishers are repopulating the state of Pennsylvania.  The range of the fisher which was limited to five sites in the state and has now expanded to thousands of square miles.  This was due to a reintroduction of the population which started in 1994 when 22 fishers were released in Sproul State Forest which is located in Centre and Clinton counties.  Overall about 190 fishers were released in Pennsylvania (PGC).

      Fishers in the state of Pennsylvania never really held the title of “public enemy” like some of the other larger predators such as wolves and mountain lions.  Nor was there ever a bounty placed on it’s hide.  This low densisty species was more of a victim of circumstance due to the loss of habitat when the wood’s of Pennsylvania were cleared in the latter 1800’s.  Their loss was not  even noticed by most people since they have a very elusive nature and they inhabit the more rugged parts of the state (PGC).

       Fishers are similar to the much smaller weasels. They have a long body with short legs. Adults range in length from about 2.5 to 4 feet. Males weigh about 7 to 13 pounds, females about 3 to 5.5 pounds.  The fisher has a broad and flat head with a  sharp pronounced muzzle.  The eyes on a fisher face forward and the ears are rounded (Pack and Cromer 1981).  The fur on the fisher ranges from 1 inch to 2.75 inches long and the color ranges from light brown to dark brown.  It also has a large bushy tail.  Fishers have five toes on all four feet with retractable claws like a cat. They can also rotate their hind paws almost 180 degrees allowing them to come down trees head first like a squirrel and grasp limbs (Wallace 1985). Fishers are predators with a diverse diet that includes birds, porcupines, snowshoe hare, squirrels, mice, shrews, voles, reptiles, insects, deer carrion, vegetation and fruit. The breeding season for fisher begins in February and ends in the middle of April.  Litter sizes can range anywhere from 1 to 4 but have been known to get as high as 5 or 6 (Powell 1993).

     The primary threat is the loss and fragmentation of fisher habitat, which is due to timber harvest, roads, urban development, recreation, and stand-replacing fire (Berg 1982).  Other factors cited include poaching and incidental capture and injury, predation, mortality by vehicle collision, limited population size, and isolation of populations (Halfpenny 1995).

 [Picture of Fisher distribution  in Pennsylvania:]

[picture 3]

Habitat Requirements:

The requirements for habitat for the fisher are continuous forested areas, since they very rarely ever travel into unforested areas (Hagmeier 1956).  It has long been thought that coniferous forests were needed for the survival of fishers but it seems that, in Pennsylvania fisher  are getting away from this and thriving well  in mixed forests as well as hardwoods (Serfass 2001).

Taxonomy of the Fisher

Kingdom:  Animalia

Phylum:  Chordata

Class:    Mammalia

Order: Carnivora

Family:  Mustelidae

Genus: Martes

Species:  pennanti

Common Names: fisher, tree fox, and  black cats

 [animal diversity pictures]


Berg, W. E. 1982. Reintroduction of fisher, pine marten and river otter. Pages 159–173 in G. C. Sanderson, editor. Midwest furbearer management. University of Illinois.

Hagmeier, E. M. 1956. Distribution of marten and fisher in North America. The Canadian Field-Naturalist 70:149–168.

Halfpenny, J. C., R. W. Thompson, S. C. Morse, T. Holden, and P. Rezendes. 1995. Snow tracking. Pages 91–163 in W. J. Zielinski and T. E. Kucera, eds. American marten, fisher, lynx, and wolverine: survey methods for their detection. U.S. Forest Service General Technical Report PSW-GTR-157.

Pack, J. C., and J. I. Cromer. 1981. Reintroduction of fisher in West Virginia. Pages 1431–1442 in J. A. Chapman and D. Pursley, editors. Proceedings of the Worldwide Furbearer Conference, 3-11 August 1980, Frostburg, Maryland, Worldwide Furbearer Conference, Inc.

Powell, R. A. 1993. The fisher: life history, ecology, and behavior. University of Minnesota Press, Minneapolis and London.

Serfass, T. L., R. P. Brooks, and W. M. Tzilkowski. 2001. Fisher reintroduction in Pennsylvania. Final Project Report, Frostburg University, Maryland. 221pp.

Wallace, K., and R. Henry. 1985. Return of a Catskill native. The Conservationist 40:17–19.