The fisher ($Pekania pennanti$) is a carnivorous mammal native to the forested regions of North America, ranging from Canada’s boreal forests to the northern United States. Despite the common misnomer “fisher cat,” this animal is not a feline but a large member of the weasel family, Mustelidae. The fisher’s diet is highly diverse, reflecting its adaptability as a forest predator, and changes with the seasons and local availability.
Primary Food Sources: Small Mammals and Rodents
The fisher’s diet is predominantly carnivorous, focusing heavily on small to medium-sized mammals readily available within its forest habitat. The snowshoe hare ($Lepus americanus$) is a primary target, often forming a significant portion of the fisher’s intake across its northern range. The fisher’s size and agility enable it to pursue and capture these lagomorphs both on the ground and through dense underbrush.
Rodents, including mice, voles, and shrews, also constitute a major part of their diet. The fisher is an adept climber, allowing it to successfully prey on tree-dwelling species like the American red squirrel and Douglas squirrel. This ability to hunt in both arboreal and terrestrial environments makes the fisher a highly effective generalist predator. Mammalian remains dominate their diet, especially during winter when other food sources are less accessible, providing consistent energy for all fishers, including females raising young.
The Unique Role of the Porcupine Specialist
One notable aspect of the fisher’s diet is its specialized ability to hunt the North American Porcupine ($Erethizon dorsatum$), a feat few other predators can accomplish. This quill-defended prey is systematically attacked using a complex technique to bypass its formidable defense mechanism. The fisher repeatedly bites the porcupine’s face, the only area not protected by quills, often circling the animal to exploit any opening.
The hunting process can be protracted, sometimes lasting up to 30 minutes until the porcupine is weakened. Once the porcupine is dispatched, the fisher feeds safely by accessing the unprotected underside. This predation provides a large, caloric meal, especially during winter or when common prey, such as the snowshoe hare, is scarce. Fishers have been intentionally introduced to certain areas to help control porcupine populations due to this unique skill.
Opportunistic Eating and Seasonal Foraging
Beyond its staple diet of mammals, the fisher is a highly opportunistic forager, readily supplementing its intake with non-mammalian items. This flexibility is evident in its consumption of carrion, such as deer remains, which provides a substantial meal with minimal energy expenditure. During warmer months, the diet diversifies further to include insects, small birds and their eggs, and reptiles.
Plant matter also becomes a significant component during the spring and summer, including various fruits, berries, and nuts when they are ripe. In certain regions, the diet includes fungi, specifically subterranean species like false truffles. While fishers generally avoid human settlements, their opportunistic nature means they occasionally prey on domestic fowl or small pets, which sometimes brings them into conflict with people.