When researchers cut open the stomachs of 91 dead fishers collected across the central Appalachians between 2002 and 2014 to see what the growing population was living on, they found something nobody expected.
Fisher was the second most common food item in the stomachs, tied with eastern cottontail rabbit and trailing only white-tailed deer carrion. Out of the 91 stomachs examined, 11 of them, or about 12 percent, held the remains of another fisher.
Even stranger was which part of the animal they were eating. Eight of those 11 stomachs held at least one whole fisher claw, and several contained multiple claws alongside foot bones and fur. When the biologists measured the swallowed claws, they were the exact same size as the claws on the animals that had eaten them. These were adult fishers eating other adult fishers, and they were mostly eating the feet.
In their 2017 paper in the American Midland Naturalist, lead author Darin McNeil and his colleagues went through the obvious explanations one by one and ruled them out.
It was not adult males raiding dens to eat helpless kits, because 10 of the 11 stomachs were collected between November and February, outside the spring birthing season. It was not trapped animals chewing on their own feet to get out of a foothold trap, because five of the carcasses came from trapped fishers whose own four paws were completely intact. The researchers also doubted the fishers were scavenging roadkill of their own kind or stealing fisher paws used as trap bait, since both would be far too rare in the woods to show up in 12 percent of the stomachs.
That left a puzzle. A fisher paw is mostly bone, tendon, fur, and keratin. It carries almost no nutritional value compared to the rest of a carcass, leading the researchers to call the paw-heavy diet perplexing and to suspect that hunger was not the main reason it was happening.
Their best guess was that Pennsylvania's fishers were thriving a little too well. As the reintroduced population multiplied and expanded across the mountains, young adults striking out for new territory were likely running into established fishers in crowded woods. In the violent territorial fights or breeding-season clashes that followed, one animal may have bitten off or chewed the paws of another. Because nobody actually watched these encounters happen in the wild, the stomach contents only prove that one fisher ate another, not whether it killed the animal outright or chewed on a rival after a fight.
Whatever was happening out in the winter woods, it did not slow the population down. Thirty years after those first 190 animals were turned loose in the northern timber, fishers have reclaimed most of Pennsylvania. In 2024, when a trail camera photographed a fisher wandering through Murrysville, a suburb just east of Pittsburgh, a state Game Commission furbearer biologist noted that seeing one near town was no longer that out of the ordinary.
Image is for illustration purposes only.
Source: McNeil et al. (2017), American Midland Naturalist 177(2): 200–210 / Pennsylvania Game Commission / Outdoor News (2024).
Pennsylvania Fishers Ate the Paws of Other Adult Fishers
