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Fishers in Our Forests

When we first moved to Vermont with two small dogs in the 90s, I received a stern warning from a neighbor and native Vermonter: “Better keep them little dogs inside or they’ll be fisher cat food”.  I thought I knew all of the cat species likely to occur in New England, and was wondering if “fisher catswere something locals invented to scare flatlanders.  I quickly learned that I had stumbled upon a real animal that is still defined by fiction more than fact. 

Fishers”, although known as “fisher cats” are not cats at all.  Rather, fishers, or Pekania pennanti, are in the family Mustelidae along with weasels, mink, wolverines, and otters. 

 

  

While sharp-eyed naturalists may wonder where I came up with the genus Pekania” and perhaps wonder “Why sent an entomologist to do a mammalogist’s job?” DNA analysis completed in 2008 determined that fishers are not as closely related to martens (another mustelid) as previously thought.  And so after referring to fishers as Martes pennanti since 1843, scientists placed them in the new genus Pekania along with two extinct relatives. 

Adding to the confusion about names, “fisher” might suggest that the animal eats fish, but it turns out that fishy dietary choices are more the provenance of the fisher’s cousins the mink and otter.  Fishers are actually fonder of dining on rodents, carrion, and will balance out their diets with fruits and even the occasional nut.   

Fishers famously eat porcupines. For most predators, porcupines are just not worth the risk, and are prey of last resort.  Fishers, on the other hand, are adept at hunting the large spiky rodents. There are reports of fishers chasing porcupines out to the lightest tree branches, forcing them to fall to the ground.  Once on the ground, they tenaciously circle until they can get a grip on the rodent’s face and crush its skull.  They are certainly not the only porcupine predators, but they may well be the most effective.  In some circumstances, fishers have been introduced to control burgeoning porcupine populations that were doing significant tree damage.  

Skunks and groundhogs also find their way onto the fisher’s menu, which may have fed speculation that fishers go after similarly sized pets, most notably cats, and perhaps the bichon and miniature poodle that shared our house in the 1990s. 

Roland Kays, former curator of mammals at the New York State Museum addressed the cat issue head on in a New York Times article.  He used radio collars to track fishers to kill sites; not one of the 25 prey was a house cat. He examined 24 fisher scat and stomach content samples; again, no cat.  A Massachusetts study of fisher diets used 226 diet samples and found cat hair or bone in just 2% of those; consumption of already dead cats could not be ruled out even in those cases. Kays considered the canine teeth and claws of a typical cat to be formidable deterrents to fisher predation.  So what may have eaten your cat?  According to Kays, coyotes were a far more likely candidate. And cars, much more common than coyotes, may pose an even greater risk. 

As the Massachusetts study showed, the possibility exists that a fisher will eat your kitty, but that’s not very high on the list of reasons to keep your cat indoors.  From a conservation point of view, the destructive impacts of housecats on bird populations are well documented. Cats are especially deadly to young birds who spend time on the ground as they learn to fly.  Special cat collars don’t help these helpless young birds who may be aware of the cat’s presence but can’t fly away.  Perhaps most compelling from a cat lover’s point of view, according to the Humane Society of the United States, outdoor cats have an average lifespan of three years while their home-body compatriots live between twelve and eighteen years. 

In addition to porcupines, snowshoe hares are often mentioned as important food sources for fishers.  But a fisher in Burlington would pass many a hungry night waiting for either of these species to amble by.  So how’s an urban fisher to supplement its meal plan?  A New Hampshire study placed birds, apples, shrews, mice, and beavers higher on the fisher menu than hares.  The twelve food items listed included deer, muskrats, and squirrels, but no porcupines.   

You might wonder how a fisher gets hold of a squirrel? With reversible rear feet due to incredibly flexible ankles, fishers are fast, adept climbers and use their claws to grip bark and literally run head-first up and down tree trunks.  They circle around trunks and attack squirrels from above and below.  Once they seize the rodents by the head or neck they tend to jump or fall to the ground and squirrel stands little chance of escape.  

Fishers were trapped to extinction in large portions of their range in the early twentieth century.  Legal protections and reintroductions permitted recovery, but pelt prices spiked in the early 1970s leading to another population crash.  Following some years with closed seasons and then short-season trapping with bag limits, populations have climbed.  The recovery has not been uniform, and in the western portions of their range, fishers are a rare, elusive species rarely found and then only in the deep woods. 

Northeastern fisher populations offers a sharp contrast to those out west.  While New England fishers are certainly found in the deep woods, it’s fair to say that they have also come to town!  In my first year using trail cameras on the Saint Michael’s College campus, I detected three fishers in a two month period.  Cameras I placed in Centennial Woods on the Burlington town line revealed a fisher on the second night. 

My literal and figurative snapshot seems to reflect patterns across Vermont. According to Vermont Fish and Wildlife, fishers are common and found in nearly every Vermont town.  There are 461 records in iNaturalist of fisher sightings including trail camera photographs, footprints, scat, roadkill, and a recent animal in a trap intended for groundhogs.  The observations span the state but with significant clusters that seem to say more about the observers than the animals. 

A conspicuous cluster of observations around Marlboro for example seems to be largely the work of a single individual and accounts for more than half of the state’s records.  In Burlington, where there may be more people looking for evidence of wildlife, there are 22 records, and exactly half of them were recorded by Sophie Mazowita, Director of The Burlington Mammal Tracking Project.  This summer I’m collaborating with the Intervale Center to document mammals in the lower Winooski River valley; we shall see if our cameras reveal the locations of even more urban fishers. 

Urban fishers face similar risks of vehicular encounters as other mammals in town.  But Scott LaPoint’s study of fishers in the Albany area indicated that the timing of fisher foraging minimizes vehicular encounters.  While fishers are typically considered to be active around the clock, fishers in urban Albany curtailed their activities before the morning vehicular traffic peak, also known as rush hourLaPoint also found that on weekends, when the morning traffic peak was later, fishers foraged a little longer. These patterns were absent in fishers living in nearby rural woodlands. 

It may or may not be the case that Burlington’s fishers have adjusted to the comings and goings of your neighbor’s minivan, but one thing is certain, fishers are here and unlikely to leave any time soon.  Despite the well documented presence in our midst, it is unlikely that most people will encounter one.  These secretive animals have no interest in making contact with any of us and they find plenty of prey without tracking down your cat or mine.  My dogs lived long lives, and their only wildlife encounter was a near miss with a skunk one evening. But fishers may well be part of the reason why the rat population is quite small in Vermont, and for that, I am profoundly grateful! 

 

Declan McCabe is a professor of biology at Saint Michael’s College. He conducts camera-trap surveys with student researchers on and off campus.. 

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