2018-02-15 / Nature

Fishers on Aquidneck Island?

By Charles Avenengo

Fishers are known to prey on domestic cats, rabbits and poultry, but are not dangerous to humans. Fishers are known to prey on domestic cats, rabbits and poultry, but are not dangerous to humans. We know coyotes, otters and mink are present on Aquidneck Island, but what about fishers?

Some residents in Portsmouth swear they have seen the medium sized member of the weasel family. There has also been a sighting reported as far south as Brenton Point State Park.

However, Dr. Charles Brown, state mammalogist and principal biologist of the Rhode Island Department of Environmental Management, wants evidence.

“My perspective is that while it’s possible, I have been monitoring fishers for a long time and we have no photographs and no specimens,” he says. “Up to this point, it’s not likely that there are fishers on any of the Narragansett Bay islands.”

Ascertaining populations of certain mammals is difficult. It’s not like observing birds, who are usually colorful and can be seen during the day. Mammals are primarily black, brown, gray or white, and, except for squirrels, they are nocturnal. Therefore, mammalogists use different measurements for these animals.

One method is examining roadkill, which is how Brown conducted a study on the fishers’ presence in the state. From 1999 to 2008, he documented and examined approximately 200 mostly male fishers killed on state roads, including a high of 30 in 2006. But most of the roadkill came in the wooded portions of the state, with none from Aquidneck Island.

The island has six species of carnivores: mink, otter, skunk, raccoon, coyote and red fox. After the notoriety that coyotes have received locally involving the taking of pets, the possibility of adding the formidable fisher might not be greeted with much enthusiasm. Locals have heard the stories of the fisher’s ferocity. It includes raiding chicken coops and snagging pets, all while issuing blood-curdling shrieks, before disappearing into the woods. A woman in Coventry was attacked by a fisher in 2016, requiring 10 stitches to her leg.

Mammalogists divide mammals into groups based on their dentition, which is the arrangement of their teeth. Carnivores in North America include felines, canines, bears and weasels. In addition to being primarily flesh-eaters, carnivores all have dentition marked by elongated canine teeth. These “fangs” enable them to puncture and tear.

Fishers, which are between a mink and otter in size, are recognizable by their bushy tails and superb ability to climb trees. Fishers have hind feet that can rotate nearly 180 degrees, allowing them to ascend headfirst down tree trunks. Males are larger than females, with lengths up to four feet and weighing as much as 15 pounds. Compared to mink and otters, which hunt mainly along streams, fishers rely more on small mammals, birds and even fruit.

After being rooted out from southern New England for a couple of centuries, the fishers expanded their range as the area reforested. Tracking south from New Hampshire and Maine, a fisher was shot in Burriville in 1966. This represented the first specimen in Rhode Island in modern times. Moving ahead through the years, a colonization of fishers began in the wooded portions of the state, until they were colonized in Little Compton and Tiverton around five years ago, Brown says.

But the expansion appears to have stopped short of the bridges. “They don’t like the open exposure,” Brown says. “They wouldn’t be likely to actually cross the bridges.”

Unlike coyotes, otter, mink and deer, fishers are not prolific swimmers capable of crossing the distances required to reach the island, Brown says.

In addition to the lack of concrete evidence of fishers on Aquidneck Island, other factors precluding the animals from colonizing here include large home ranges that require unbroken canopied forests. The range of a male fisher can extend to 100 square miles, and the island doesn’t harbor that number of forests.

Also, in order to even begin a population, much less sustain it, there must be enough male and female fishers to reproduce a second generation.

“Maybe the sightings could be of mink, otters, or possibly even woodchuck,” Brown says when asked to explain the reported sightings of fishers.

While the official word is that they aren’t on the island, despite claims to the contrary, what is known is that, should evidence ever be produced proving the fisher’s existence here, they will be fearsome and rarely seen phantoms.

“It’s not out of the realm,” said Brown.

Naturalist Charles Avenengo has been chasing Aquidneck Island wildlife for more than 40 years.

Terrestrial Mammals on Aquidneck Island

Little brown bat
Silver-haired bat
Big brown bat
Red bat
Eastern cottontail
Eastern chipmunk (introduced)
Grey squirrel
White-footed mouse
Meadow vole
Norway rat (introduced)
House mouse (introduced)
Red fox
River otter
Striped skunk
White-tailed deer

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