Tracking Tips: Fishers Aren’t Cats

Study this photograph of a right front fisher paw. Four asymmetrically arranged toes form an arc above the knobby metacarpal pads beneath them. Slightly offset to the right side (where the forceps are pointing), a smaller toe is found on the inside of the paw (where our thumb would be). Photos by Susan C. Morse ©

Though it’s often called “fisher cat” or “black cat,” the fisher (Pekanis pennanti) rarely fishes and is not a cat. The fisher’s only likeness to the domestic cat is its long tail, sharp curved claws, reflective eye-shine at night, and its ability to climb trees. As a member of the weasel family, the fisher’s long torso, rounded ears, short stout legs, small dark eyes, and elongated skull with a wedge-shaped face and a narrow muzzle are not at all catlike.

Both domestic cats and fishers will climb trees to escape from enemies. However, the fisher’s climbing abilities are far superior, and the observant tracker will find sign and learn about the more diversified purposes that motivate fishers to climb up into trees in the first place.

Five sharp, semi-retractable claws and a flexible spine enable lithe fishers to climb, cling to branches, and balance in tree crowns, where they occasionally seek prey, including songbirds and their eggs, porcupines, and, especially, nesting squirrels. Unusually flexible ankle joints further equip the fisher to rotate its hindfeet nearly 180 degrees, such that the fisher can climb down a tree headfirst like a squirrel. Photo by Susan C. Morse ©

When I spotted this handsome creature in the crown of an oak tree, I was blessed with a first-hand appreciation of yet another reason fishers climb trees. Apparently, soft new acorns were this fisher’s meal of choice. Acorns that have been bitten and partially chewed can sometimes be found beneath oaks. Look for small canine tooth marks that pierce and scratch the hulls. Photo by Susan C. Morse ©

A fisher’s razor-sharp claws leave very fine scratches and subsequent scars on the thin bark of beeches and serviceberry trees. Trees climbed by a fisher will display the diagnostic features shown here – most notably the wider space between the thumb toe and the other toes. Look for smaller width spaces between the placement of right and left paws, as well as shorter distances between the forelimbs and hindlimbs that grasped the trunk while climbing. These measurements will show that the tree was climbed by a mammal much smaller than a black bear. Photo by Susan C. Morse ©

When threatened, fishers may seek refuge in trees, but researchers have learned that the nimble mustelids also simply rest and relax in trees. One curious resting perch is found in conifer “witches’ brooms” – the nest-like hypertrophic growth of twigs and needles. Such structures must be warm and comfortable. Tree cavities provide important security habitats, especially for female fishers that are seeking to safely give birth and care for their newborn offspring. What goes up must come down, and occasionally we find evidence of this in the deep snowpack. Instead of climbing down the trunk, the fisher leaps away and tries skydiving, sailing downward to make a perfect soft landing. Photo by Susan C. Morse ©