Monday, November 21, 2011


The wolverine gets all the press.

But the wolverine isn't the only tough, solitary, mysterious and tough member of the weasel family.

Meet the fisher.

The fisher roams the forest in search of any prey it can catch. It's one of the few predators that successfully and regularly hunts porcupines (but, contrary to popular outdoor lore, it doesn't flip over the porcupine and scoop out its soft underside).

Due to their solitary nature, wide home range and preference for heavy forest cover, fishers are not well studied.

In Idaho, they're also quite rare. In fact, fishers were exterminated from the state by the early 1900's due to a deadly combination of over-trapping and clear cutting.

Fishers were reintroduced to Idaho in the 1960's. How are they doing? That answer is unclear, but it's undeniable that they remain one of the state's rarer mammals.

Fishers require heavy forest cover. Conservationists often list them as one of those animals that can only thrive in large, unbroken, roadless tracts of forest--the kind of forests Idaho has in abundance.

And that is true...sort of.

Fishers do require heavy forest cover, and they do need room to roam. But fishers might require a bit more--and a bit less--than we imagine.

Fishers were eliminated from my home state of Pennsylvania, as in Idaho, more than a century ago. With much of the state clearcut, fishers were concentrated into remaining pockets of forest--where they became easy for trappers to catch.

From 1994 through 1998, 190 fishers were reintroduced to six areas of northern Pennsylvania.

Pennsylvania is a smaller state than Idaho, but has 10 million more residents. The forests are today a mix of deciduous hardwoods and conifers. There are far more roads, and far more people recreating in the forests.

And yet, fishers thrive in Pennsylvania. They've spread over much of the state, including into areas considered unsuitable for their needs. The state now allows a limited trapping season, and still the fishers appear to be spreading and thriving.

It's a similar story throughout the eastern United States. Fishers in West Virginia, New York and New England flourish while those in less populated regions of the Rockies do not.

This may in part be due to the maturity of forests in the east. Fishers require heavy forest cover, and seem to prefer hunting around dead tree snags on the ground. They do not survive well in second-growth forest.

There is also an abundance of prey in eastern forests. Despite their specific habitat requirements, fishers adapt readily to any available prey. The fisher's most common prey of Canadian boreal forest--snowshoe hares--are not common in Pennsylvania. But they have adapted to the abundant gray squirrels, cottontail rabbits and even carrion from road-killed deer.

Conservation is complicated. The fisher does have specific habitat needs. But that doesn't mean it can only survive in huge, roadless areas. In this case, the forests of Pennsylvania--while more fragmented and less "wild"--appear to be much more suited to fishers today than Idaho.

Clearly, though, there is much room for research on this little known carnivore. Perhaps as we learn more, we can bring back this fascinating animal to the Rockies, much as has been done in the eastern forests. -- Matt Miller

1 comment:

Patrick Murtha said...

I very much enjoyed reading this post (which I learned about at MammalWatching). I have always been interested in fishers, although I don't believe I have ever seen a live one, even in a zoo.