Fisher vs Marten: How to Tell Them Apart

If you see a small brown furry animal in a tree or on the ground in a forest, the quickest way to tell if it is a fisher or marten is by size. Fishers are substantially larger and heavier, about the size of a small house cat or larger. Martens are slender and light, about as big as a squirrel. The second tell is coloring. Fishers are dark brown or nearly black all over, including their chest and throat. Martens have a distinctly different look with light brown or yellowish fur and noticeably paler, almost cream-colored patches on their chest and throat. The third tell is the tail. Fishers have thick, bushy, relatively long tails. Martens have longer, thinner tails relative to body size. Both animals move quickly and with grace, but martens move with lighter, quicker bounds while fishers move with a heavier, loping gait. For more information about forest animals, visit the wildlife identification guides.

The most obvious difference between fishers and martens is their size. Fishers are much larger animals. An average fisher weighs between 4 and 15 pounds depending on sex, with males being substantially heavier than females. A fisher's body measures about 16 to 20 inches from head to rump, and the tail adds another 12 to 16 inches. This makes a fisher roughly the size of a small dog or large house cat. Martens, by contrast, are tiny. An adult marten weighs only 1 to 3 pounds, making them much lighter than fishers. A marten measures just 7 to 9 inches from head to rump with a tail of 8 to 10 inches. A marten is about the size of a large squirrel and weighs less than a pound of butter. Both animals have sleek, long bodies built for climbing and hunting in trees, but the fisher is a powerful predator while the marten is a nimble tree dweller. When you see one of these animals, size is the first clue to identification. For more forest animal comparisons, explore wildlife identification.

Beyond size, the most noticeable difference between these two mustelids is their fur coloring. Fishers have uniformly dark fur that can range from dark brown to nearly black. Their entire body, including the chest, throat, and belly, is the same dark color. Some fishers have slightly grizzled or gray-tipped fur on the head and shoulders, but the overall impression is of a dark animal. Martens, on the other hand, have a much lighter overall color that is tan, yellowish, or light brown. What really sets martens apart is their distinctive pale markings. Martens have a bright yellow, pale cream, or sometimes white patch on their chest and extending down their throat. This bicolored pattern is one of the most reliable ways to tell a marten from a fisher from a distance. A fisher simply does not have these pale markings. If you see a small weasel-like animal in a tree with a pale throat and chest, you can be confident you are looking at a marten. Check local wildlife guides for regional variations in coloring.

Fishers and martens have overlapping but distinct ranges in North America. Fishers are found in scattered populations across the northern United States and into Canada. They live in the Northeast from Maine south to Pennsylvania and westward, with populations in the Pacific Northwest and scattered in western mountains. Fishers prefer dense forests with a mix of tree types and are known for living in mature hardwood and coniferous forests. They are more adaptable to human forests and will use woodlots and fragmented forests. Martens are found in more limited ranges in far northern forests and high mountain elevations. In the US, martens occur mainly in northern Minnesota, Wisconsin, parts of Michigan, and scattered high elevations in the western mountains. Martens require boreal forest and dense conifer forests and are highly sensitive to habitat loss. They are not found in southern or central regions at all. If you live in a dense forest in the Northeast or Pacific Northwest, you might encounter a fisher. Martens are far more restricted and are rarely seen.

Fishers and martens have different hunting styles and behaviors adapted to their size and environment. Fishers are powerful predators that hunt on the ground and climb trees with ease. They hunt rabbits, squirrels, birds, and other small mammals. Fishers are one of the few predators that regularly kill porcupines, flipping them to attack the underside. They also eat fruits, nuts, and carrion. Fishers are crepuscular and nocturnal, meaning they hunt at dawn, dusk, and night. Martens are also tree climbers but are more specialized for hunting in the canopy. Martens spend much of their time high in trees hunting squirrels, their preferred prey. They also hunt voles, insects, and gather berries and seeds. Martens are extremely agile acrobats in the trees, able to chase and catch squirrels in the highest branches. Both animals are solitary and territorial, marking their ranges with scent. Fishers have larger home ranges than martens and will travel farther nightly. For more information on forest predators, see wildlife resources.

One common confusion is between martens and the American mink or weasels, which are also small mustelids. However, minks are water-loving animals found near streams and lakes, while martens are tree specialists of dry forests. Another myth is that fishers are aggressive or especially dangerous. While fishers are skilled hunters, they avoid people entirely and will flee from humans. Fishers do not attack people and are generally shy. Some people believe that all dark weasels are fishers, but there are other mustelids like wolverines and marten variants with different coloring. The term fisher is sometimes confused with fisher cat, which is an outdated name for the fisher. Martens and fishers are not cats, they are mustelids. Another misconception is that seeing a fisher or marten means danger to pet cats and dogs. While large fishers can be a threat to small pets left outside, they typically avoid human areas. Both animals are elusive forest dwellers that most people will never see.