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The fisher: Minnesota's mysterious mammel

One November morning about three years ago while hunting deer from an elevated tree stand in Kittson County, I heard what I thought was the telltale sound of an approaching deer. Alerted to the noise, I turned myself toward the sound and waited. And waited. And waited some more.

About the time I had figured out that the sound I was listening to wasn't a deer, I at last discovered the source: a fisher! The dark brown animal, which was surprisingly large (no wonder it sounded like a deer), climbed an aspen tree about 25 yards from where I stood.

Despite my standing as motionless as I could, the fisher seemed to have noticed me. Clutching the trunk of the tree with his long sharp claws, the fisher peered at me for a moment and then climbed down the tree as quickly as he had just climbed up. In the next instant the fisher disappeared in the opposite direction.

I was thrilled for having observed a rare and pleasurable sight. And while Minnesota does indeed harbor plenty of fishers, few people ever see one. In fact, some people don't even realize that fishers are around at all.

Fishers are members of the weasel family. Other relatives of the fisher include the pine marten, river otter, mink, badger and wolverine. The fisher is reputed as the fastest tree-climbing mammal in North America. These rather large and powerful animals with bear-like claws can literally run up and down trees as they hunt for prey such as squirrels and porcupines, or to escape possible predators.

The fisher has a curious name. There are only a few records in existence of a fisher actually observed eating or catching fish. Undoubtedly an opportunistic creature that will take advantage of most any available food and prey, fishers were nonetheless named in reference to fishes. That said, these highly intelligent and swift hunters of the forest are better known at finding and killing forest dwelling, terrestrial prey.

Other names for the fisher include pekan, black cat or black fox, and Pennant's cat, evidently in reference to T. Pennant, the man who gave the fisher its Latin scientific name, Martes pennanti. But perhaps a more fitting name for the fisher was what the Ojibwe traditionally called the animal: "tha-cho", which means "big marten".

Undeniably marten-like in appearance and habits, the fisher is much larger than its smaller cousin the pine marten. Both species are arboreal weasels, that is, tree-loving weasel-like mammals. And both species are known to hunt similar prey such as red squirrels, mice and voles, rabbits and hares, and birds. However, the two species are not believed to be competitors.

Elusive in everyway, fishers are adept at avoiding detection. In part, this stems from its nature as a nocturnal hunter. In order to capture fleet-of-foot prey like rabbits and squirrels, and sometimes even young deer, fishers are deliberate and determined hunters that take advantage of their natural surroundings and abilities. What's more, the fisher is one of the only mammals known to actively hunt and kill porcupines for food.

Fishers accomplish this by first being fast, but also by being extremely cunning. Porcupines, which are well armed with a coat of quills that can inflict serious harm to would-be predators, are creatures known for their defense strategies, not their ability to outrun or outsmart their enemies.

When confronted, a porcupine will often turn its rear toward the aggressor, puff out its quills and rely on its protective armor -- or a well-placed slap of its heavily quilled tail across the snout or body of its attacker -- in order to repel it. But what the fisher will do to counter the porcupine's defenses is to repeatedly attack the facial portion of a porcupine until the animal is disoriented or wounded badly enough in order to quickly and safely kill the porcupine without causing undue injury to itself.

Another of the many amazing attributes of a fisher is its physiology. Female fishers are only receptive to mating for a very short period of time in the spring after giving birth to her litter. Once mating commences and successful fertilization occurs, female fishers enter into an incredibly long gestation period -- about 350 days.

Actually, this is common in all members of the weasel family. Still, timed so the fertilized egg attaches to the female fisher's uterine wall just months before the baby fishers are born in the springtime, this "delayed implantation" helps to ensure that the young fishers are born at the right time and have the best chance of survival.

Ranging mostly in forested lands, especially in mixed deciduous-coniferous forests throughout Minnesota's northern third, fishers are also found in other not-so-typical habitats. I have seen fishers bounding along creek bottoms in western Marshall and Polk counties and have observed their tracks in the snow in Norman and western Becker counties, too. They also occupy suitable habitats in central Minnesota.

Fishers are distinctive and interesting animals that few people observe in the wild. Trapped for their valuable fur during the state's closely regulated fisher trapping season, this large member of the weasel family continues to thrive while remaining virtually unseen. Once nearly extirpated from the state because of deforestation and unregulated trapping, this mysterious Minnesota mammal is abundant once again as we get out and enjoy the great outdoors.

(Klemek is the DNR Area Wildlife Supervisor in Detroit Lakes. You can contact him at