Habits Tracks in the snow are often the only sign easily noticed when fisher are present in an area, as the species is not usually observed in the wild. Fisher are solitary animals throughout most of the year, although snow tracking often indicates that two or more fishers will hunt in parallel patterns. Activity is mostly at night, although it appears that fishers hunt frequently during daylight hours in wilderness habitats. Male territories are larger than female territories and the sizes of these regularly patrolled areas vary according to the availability of prey species. Circuits are irregularly patrolled although fishers travel pretty much in a straight line when they have determined to go to a certain location.
Males usually pass through a given area in their territory about once every two weeks.
Female circuits in winter usually vary from 3 days to a week. Both male and female fisher are highly skilled predators and territory relocation are sometimes necessary as fishers are capable of overharvesting prey species. Fisher are aggressive hunters and competition with other furbearers is not only for the same prey species, but by direct contact. Raccoon may be killed by a large fisher in trees or on the ground. Fisher can also catch marten on the ground or in the trees, and usually there is either a good population of fisher or marten but not both.