This advice from William Shakespeare has stood the test of time.  “Modest doubt is the beacon of the wise,” he explained.

It isn’t always easy being a doubter.  At Felix Neck, we receive reports of all types of wildlife sightings from the mundane to the unusual.  We appreciate them all, and, while we want to believe them all, science and responsibility require that we seek proof.

The appearance of dead fisher on the beach last week, while an exciting occurrence, doesn’t prove the existence of live fishers on the Island.  It is, however, our tradition at Felix Neck to ‘never say never’ to folks who share their sightings, even the most unusual. Nature can and does change, and changes in species’ range are possible.

The fisher find was very interesting and is a great reason to learn more about this literal washashore.

Fishers, also called fisher cats, don’t hunt fish and are not related to cats.  They hail from the Mustelid family, relations of skunk, mink, otter and weasel.  They are one of the larger Mustelids, second only to otters.  Size in this species varies by gender, with the males being significantly bigger.  In both otters and fishers, the tail is prominent, taking up one-third of the entire body length.

Seeing a fisher isn’t easy, as they are known for their secretive nature.  In the winter, fishers are diurnal (active during the day) and in the summer, they are nocturnal (night) or crepuscular (active at dawn and dusk).

February and March is breeding time for fishers, though they practice delayed implantation.  Females breed within days of giving birth to kits, and the fertilized eggs that result from their hour-long mating remain dormant for 10 to 11 months.  Then the fertilized eggs will implant and develop over 6 weeks, after which 2-4 kits will be birthed.  Shortly after, copulation again occurs and the cycle starts anew.

Populations of fishers have been variable over time.  Historically, they were extremely plentiful in New England and were valued for their pelts.  However, in the 1800s, fishers were extirpated here in Massachusetts due to the decline of forest habitat and unregulated hunting.

They are currently making a comeback. The decline of agriculture and the reforestation of landscapes increase fishers’ preferred habitat.  Hunting of the species has decreased due to wildlife regulations that greatly reduced the use of leg hold and body-gripping conibear traps.

And there was even a fisher reintroduction program in some states in New England in the 1950s. As fishers are known to target and eat porcupines, a prickly meal at best, a logging company reintroduced fishers to lower the population of porcupines that were damaging seedlings the company planted.

If fishers can consume porcupines, it is not surprising that they will make a meal of just about anything.  A few squirrels a week, up to 22 mice a day, or just one porcupine per month will sate even the hungriest fisher.  Nor are they picky, since they will also consume raccoons, reptiles, amphibians, insects and even carrion.

Not to worry, though, your pets are probably safe.  Fishers usually do not, contrary to some folks’ belief, often consume cats or small dogs.  In one study of the stomach contents of 1,000 fishers in New Hampshire, only one had evidence of feline consumption.

With this recent and provable report of a dead fisher, more sightings and stories will likely come in.  Please don’t take it personally if we maintain our reservations, as we will encourage the gathering of proof.

If the existence of live fishers on the Island is someday confirmed, I will not eat my words.  I will, rather, be excited at the powerful and transformative ways of nature; and remember the words English poet William Cowper who explained “Absence of proof is not always proof of absence.”

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature.