The North American wilderness is home to many intriguing creatures, among them the fisher and the marten. Both are members of the Mustelidae family, which also includes weasels, otters, and mink. These agile carnivores share characteristics that often lead to confusion for observers. However, fishers and martens possess distinct traits that allow for their differentiation. This article will explore these differences across their physical appearance, preferred habitats, dietary habits, and characteristic behaviors.
Physical Distinctions
A primary way to distinguish a marten from a fisher is by their size, as fishers are noticeably larger. Martens typically measure 16.5 to 20.5 inches in body length with a tail adding 9 to 11 inches, and usually weigh between 1 to 3 pounds. In contrast, fishers can reach a body length of up to 30 inches, with a 12 to 17-inch tail, and their weight ranges from 4.5 to 12 pounds, making them roughly twice the size of martens.
Subtle differences also exist in their fur coloration and texture. Martens often display a distinct orange or buff patch on their throat and chest, with fur ranging from yellowish-brown to dark brown. Fishers generally have a darker brown, sometimes almost black, coat and typically lack the prominent throat patch seen on martens. Their fur can appear “grizzled” due to variations in the coat, and male fishers may have lighter guard hairs around their necks.
Further distinctions can be observed in their facial features and tail. Martens possess relatively larger ears in proportion to their head size compared to fishers, which have smaller, more rounded ears. Both have small, dark eyes and thin bodies. The tails of fishers are well-furred and make up about one-third of their total body length.
Habitat and Range
Fishers and martens inhabit forested environments across North America, though their specific preferences and geographical distributions show variations. Fishers are widespread throughout the northern forests of North America, found in the boreal and mixed deciduous-coniferous forest belt stretching from Nova Scotia to British Columbia and north to Alaska. Their range extends south into the Appalachian Mountains, New England, and are also found in the Sierra Nevada of California.
Fishers prefer areas with continuous overhead canopy cover, ideally greater than 80%, and tend to avoid areas with less than 50% coverage. They are often found in old-growth forests, as female fishers require moderately large trees for denning, and they also select forest floors with abundant coarse woody debris. These animals typically inhabit low to mid-elevations, and may be confined to lower elevations during heavy snow periods.
American martens, while sharing some distribution with fishers in the southern parts of their range, extend farther north to the tree line in arctic Alaska and Canada. Their distribution also reaches south to New Mexico in the Rocky Mountains and the southern Sierra Nevada in the Pacific states. Martens are closely associated with late-successional stands of mesic conifers, particularly those with complex physical structure near the ground. While generally found in or near coniferous forests, martens may inhabit talus fields above the treeline but are rarely found below the lower elevational limit of trees.
Diet and Hunting
The dietary habits and hunting strategies of fishers and martens reflect their different sizes and adaptations. Fishers are known for their ability to prey on porcupines, a feat few other North American carnivores accomplish. A fisher’s strategy involves repeatedly biting the porcupine’s face, exhausting it by forcing it to turn and expose its vulnerable areas, then flipping the animal over to access its unprotected belly. Beyond porcupines, their diet is diverse and opportunistic, including small mammals like mice, squirrels, and shrews, as well as ground-nesting birds and their eggs.
While fishers are generalist predators, their diet can vary regionally. Fishers utilize their long, slender bodies and semi-retractable claws to hunt in tree hollows and ground burrows, and they are agile climbers.
Martens, being smaller, primarily hunt small mammals, such as voles, mice, hares, and squirrels, especially in winter. Their diet also includes bird eggs, nestlings, insects, and fish in the summer, with berries and other fruits becoming important in the fall. Martens are adept at exploiting subnivean spaces, the area beneath the snow, to catch prey like voles and shrews. They also make occasional forays into trees due to their climbing abilities.
Behavioral Characteristics
Fishers and martens exhibit distinct behavioral patterns that further differentiate them in their natural environments. Fishers are largely solitary animals, displaying activity patterns that are primarily crepuscular and nocturnal, meaning they are most active during dawn, dusk, and nighttime hours. They are agile climbers, capable of descending trees head-first due to their highly mobile ankle joints. When denning, female fishers require moderately large trees or hollow logs for shelter and raising their young.
Martens, like fishers, are also solitary creatures, but their activity patterns can be more flexible, showing activity at various times of day and night. Compared to fishers, martens engage in more arboreal activity and utilize subnivean spaces more extensively for foraging and resting, which also helps them reduce energetic costs and escape predators during winter. Martens have been described as “wilderness animals” due to their shy nature, often being difficult for humans to observe in the wild.