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The Fisher Can’t Shake its Bad Reputation

Reports of fishers wreaking havoc on game populations occasionally circulate among hunters and trappers, according to the Pennsylvania Game Commission. This predatory furbearer has been blamed for decimating turkey populations, reviled for gleefully dining on spotted fawns, and despised for its perceived unquenchable thirst for hot blood. The number of colorful metaphors used to describe them is endless – and very few are flattering.

However, when this furbearer is examined without emotional bias, what emerges is a fascinating animal deserving of a little more understanding.

The name fisher offers no description of the animal itself. Known as fisher cat, fisher weasel, and even tree otter, the secretive predator is saddled with an identity issue. It rarely eats fish and is certainly no cat.

So why the confusing moniker? The name was likely derived from a corruption of the antiquated word “fichet,” a polecat found in Europe. The common use of “fisher cat” seems to validate the theory, much to the chagrin of biologists and game wardens trying to explain its name to a confused audience.

Handsome devils?

The fisher is an omnivorous predator of the family Mustelidae – animals that are characteristically nocturnal, solitary and active year-round. Other mustelids include weasels, martens, mink, badgers and wolverines. Fishers are more closely related to the wolverine than to any of the other weasel species.

It has a well-furred long body with a full tail that makes up one third of its length. The striking coat of the fisher is mostly chocolate with legs, tail and rump a midnight black. Fur on the shoulders and head is grizzled with gold and silver, enhanced by tricolored guard hairs. The head is triangular with wide, rounded ears. A fisher’s eyes have horizontal oval pupils that produce a green eyeshine at night. Five toes on each paw sport formidable sharp, curved, semi-retractable claws. Adult males tip the scales at 7-15 pounds while females weigh significantly less. 

The female usually gives birth to one to six cubs high up in a tree cavity in late March or early April. She will cycle into estrous and breed again within 10 days after giving birth, resulting in most adult females being pregnant for nearly the entire year! The pregnant fisher develops a small fertilized egg mass called a blastocyst that floats freely in the uterus. The blastocyst does not increase in size until it attaches to the wall of the placenta around 40 days prior to birth. This adaptation, known as delayed-implantation, also is seen in bears and bats. It allows young of the year to be born under the most favorable environmental conditions.

Fisher cubs weigh less than two ounces at birth with eyes closed and completely dependent on maternal care. They initially sport silver-gray fur until their coat transitions into chocolate brown at 3-4 weeks. Canine teeth erupt at 7-9 weeks and, at four months, fishers are already developing into efficient predators, attacking the head and neck region of small mammals.      

Disappearing act

Ideal fisher habitat is older conifer and deciduous forests with good overhead cover and an abundance of woody vegetation on the forest floor. Their population once spread throughout Pennsylvania forests, but fisher numbers sharply declined as a result of unregulated trapping and intensive deforestation that peaked in the late 1800s. The last remnant populations were found in Clearfield, Elk, Cameron, Clinton, Potter and Sullivan counties. When fishers entirely disappeared from Pennsylvania has been lost to history.    

The return of the fisher in Pennsylvania became possible when much of the state became reforested through natural succession providing suitable fisher habitat. Successful reintroduction efforts by conservation agencies in West Virginia and New York were already expanding fisher populations into the state by the mid-1990s. The Game Commission’s fisher reintroduction started in 1994 and continued for four more years releasing 190 fishers trapped in New Hampshire at six release sites throughout northern Pennsylvania.

Food for thought

A fisher is a diet generalist and opportunistic predator, taking what’s easiest to catch. The ability to forage effectively within the forest canopy and on the forest floor offers them a diversity of food options. 

A fisher diet study conducted by biologists from the Indiana University of Pennsylvania

and the Game Commission between 2002 and 2014, revealed some fascinating information. Ninety one fisher carcasses were collected from road-killed, incidental trapper-killed and legally harvested fishers from 30 Pennsylvania counties. Their stomach contents were rinsed, separated, dried, examined and identified. The results were eye-opening.

Mammal species were found in 83 percent, and bird species were found in 12 percent, of fisher stomachs. Fruit and seeds (12 percent), foliage (12 percent), egg shells (4 percent), reptiles, amphibians and insects (all round 1 percent) rounded out other documented food items. Rodents were the most common order of animal consumed and porcupine (a large rodent) parts were found in 11 percent of the stomachs. Fishers are considered effective porcupine predators but, as food generalists with multiple options, are not believed to greatly reduce porcupine populations.

White-tailed deer was found in 13 percent of the samples. Fishers preying on fawns has been documented, but is considered a rare event. Scavenging road-killed deer, and entrails left in the woods during hunting seasons, (most fishers for this study were collected in the fall and winter) likely account for this finding. Despite the fisher’s notoriety for slaughtering wild turkeys, not a trace of turkey parts turned up in the study samples. Fisher predation on adult turkeys and turkey poults is likely minor.   

Population dynamics

The oddest finding of the diet study was that 12 percent of fisher stomachs contained the remains of other fishers, including hair, feet, claws, flesh and bone. Such cannibalistic behavior among fishers hadn’t been reported in scientific literature.

The majority of fisher stomachs containing fisher remains were from adults collected between November and February, a period of fisher dispersal. Fishers defending their territories might play a role in cannibalism and this behavior might reflect increasing population densities within a geographical area.

Because they are secretive and occur at low population densities, determining a reliable estimate of Pennsylvania’s current fisher population is difficult. However, Game Commission biologists use a number of techniques to monitor changes in fisher distribution and relative abundance. Techniques include monitoring the number of fishers sightings reported to game wardens, incidental captures by trappers, roadkill data, and fishers harvested during the trapping season.   

The Game Commission created a fisher trapping season in 2011 and the harvest limit has been one fisher per trapper each year since. Furtakers harvested 126 fishers in that initial year. The 2018 fisher trapping season that ran from Dec. 15-26 saw a record high of 503 fishers taken in 15 of 23 Pennsylvania wildlife management units.

“Fishers continue to expand numerically and geographically in Pennsylvania,” said Game Commission Furbearer Management Section Chief Matt Lovallo.  “It was once thought that they required large tracts of unbroken forests to thrive. However, they can now be found everywhere from big woods to small suburban woodlots.”

The Game Commission’s 10-year fisher management plan is due to be updated in the near future. Lovallo expects there will be some changes contained in the plan that will provide sportsmen with more opportunities to take fishers.

Evil, mean, and nasty?

Projecting human characteristics upon wild animals is unfortunate and unreasonable. The fisher is no more evil than an owl is wise, no meaner than a fox is sly, and no nastier than a newborn fawn is adorable. Many find elements of fisher behavior boorish and their eating habits downright unpalatable. But in contemporary parlance, the fisher “is what it is” – a fascinating furbearer, diet generalist and efficient predator that has returned to resume its place among Pennsylvania’s wildlife community.

If you are lucky enough to catch a glimpse of one bounding around in Penn’s Woods, consider yourself fortunate. And if you have to choose some adjectives to describe this fascinating furbearer – try to be nice.     

Photo Fisher in tree cavity

Photo Credit: Zane Miller/U.S. Forest Service Photo