Fishers make quick population comeback
We all have "once in a lifetime" moments. Lucky, keen-eyed naturalists have many over the years -- a brief glimpse of a rare bird or a bobcat crossing the road in the dead of night.
One of mine occurred a few years ago while walking an abandoned gas road near my home. A dark four-legged mammal crossed the path about 15 yards ahead of me. It stopped for a moment, checked me out, then disappeared into the brush. We stared at each other for no more than two seconds.
My heart raced because I knew I had never seen this animal before. It was about the size of a fox, but it was dark with a long, bushy tail. It was too big to be a ground hog or cat. It lacked a fox's distinct shape, and it was too small to be a coyote.
After a few minutes, I concluded I must have seen a fisher. A little book work confirmed my suspicions. Fishers are large members of the weasel family, the Mustelidae. Males measure up to 48 inches long, including a 12 to 18 inch tail, and weigh 8 to 12 pounds. Females are about a foot shorter and weigh half as much as males. The one I saw seemed big enough to be male.
I never expected to see a fisher so close to home. In my mind they were wilderness mammals most common in the north woods of New England and Canada. So I called Jim Evans, a wildlife biologist with the West Virginia DNR. When I repeated my story, he told me a fisher was entirely possible. "We've even had a few reports from within the city of Fairmont," he said.
Fishers disappeared from West Virginia and Pennsylvania in the late 1800s and early 1900s. Habitat destruction and unregulated trapping were the causes. The fisher's comeback can be traced to 1969 when the West Virginia Division of Wildlife Resources released 23 animals from New Hampshire at two sites in Tucker and Pocahontas counties. Just three years later, the population had grown large enough to support a legal trapping season. Since then, the West Virginia fisher population has continued to grow and expand so that now fishers might be seen in any forested area in the state.
And because animals do not respect state boundaries, fishers soon began to appear in the mountains of western Maryland, southwestern Pennsylvania and northern Virginia. Pennsylvania gave fishers another boost in 1994 when the Game Commission released 22 individuals in Centre and Clinton counties. Over the next four years, Pennsylvania released another 168 fishers.
The results of the fisher reintroductions in West Virginia and Pennsylvania have been astounding because the populations have grown and expanded so quickly. Fishers breed only once each year, and females bear just two or three cubs per litter.
Furthermore, thanks to a process called "delayed implantation," fishers have a prolonged pregnancy. They breed in the spring, but the embryo does not immediately implant on the female's uterine wall. After about 10 months, the embryo finally implants, and birth occurs 30 to 60 days later the following March or April, for a total gestation of about 11 months.
How they prospered
Fishers' rapid population growth may be due to unusually high survivorship.
Dens are almost always in high, inaccessible tree cavities where the young are safe from predators. And adult fishers are solitary predators who eat just about anything - mice, shrews, squirrels, ruffed grouse, songbirds, chipmunks, rabbits, muskrats and even porcupines. Curiously fish are not a common food item.
Fishers are excellent climbers and spend much of their time in trees. The regrowth and recovery of eastern forests since the 1920s has undoubtedly contributed to the fisher's rapid population expansion.
Today, fisher populations support modest trapping seasons in West Virginia, Maryland, northern Michigan, New York and New England. And the Pennsylvania Game Commission is currently engaged in a three-year study to better understand fisher biology and population size.
So when you're in the woods, be alert. If you see a dark, fox-sized mammal jumping from tree limb to tree limb, you may have seen a fisher. Chalk up another wildlife management success story.
Send questions and comments to Dr. Scott Shalaway, RD 5, Cameron, WV 26033 or via e-mail to firstname.lastname@example.org