Dr. Matthew Lovallo
The fisher is a mid-sized carnivore, the second largest member of the weasel family in Pennsylvania; the river otter being the largest. Fisher are characterized by a well-furred long body, short legs, and a full tail that comprises about one third of its total length. While mostly dark to chocolate brown, fur on the tail, legs and rump is usually black, whereas fur on the back and shoulders is grizzled with gold and silver and enhanced by tricolored guard hairs. White areas or patches are common and most frequently found in the genital areas and under the forelimbs. The face is triangular with wide and rounded ears. Eyes have horizontal oval pupils that produce a bright green eye-shine at night. Fishers have five toes on each paw and sharp, curved, semi-retractable claws.
In the most general sense, fisher occupy forests with abundant downed woody debris or other structure on the forest floor. Fisher are generally believed to avoid areas lacking overhead cover, but the degree to which fisher will tolerate varying levels of forest fragmentation and human encroachment has not been well studied. During recent decades, fisher populations have expanded into highly fragmented, human-altered forest ecosystems throughout many areas of the northeast, including Pennsylvania.