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Fisher
THE SPECIES: Martes pennanti
Zigzagging though the forest, a lone fisher forages for prey. It climbs up and down a tree, sniffs a porcupine den, then roots through a windfall in the hopes of capturing a meal. When a snowshoe hare bounds away, the fisher captures it in a short rush. Wrapping itself around its prey with all four feet, it quickly delivers a fatal neck bite.
The fisher, a rare mammal in the Yukon, is the least known member of the weasel family.
DISTRIBUTION
The fisher is present in low numbers across much of southern and central Canada. In the Yukon, it is found mainly in the southeastern corner. Sightings and tracks have been recorded across the southern Yukon, but most often occur in Watson Lake area. Its present distribution suggests that the fisher may be a recent post-glacial immigrant to the territory. Some biologists believe that the fisher is still expanding its range northward today.
Dense spruce forest with a continuous canopy is the preferred habitat of the fisher. It will cross open areas such as frozen lakes, bogs, or burns, but will not forage under the snow cover in these regions.
CHARACTERISTICS
The fisher is uniquely adapted to preying on the porcupine. Unlike longer-legged animals that can only strike this quill-covered creature from above, fishers are the same height as porcupines and can fight face to face. Quickness, agility and effective biting help this weasel-shaped animal to avoid a porcupine's back and tail and concentrate on rapidly striking the unprotected face and belly.
A fisher climbing up a tree can swivel around and descend head first, just like a squirrel. Unsheathed claws enable it to grasp the tree trunk. Its extremely mobile hind limbs are able to rotate 180 degrees. If a porcupine under attack puts his face against a tree trunk in defence, a fisher can climb onto the tree and force the porcupine away. Fishers rarely suffer from quill wounds.
Normally, a fisher travels with the bounding gait typical of weasels. The forelimbs move together and the hind limbs land squarely in the same tracks of the forefeet. In deep snow or on thin crusts, fishers walk flat-footed to evenly distribute their weight over the snow, but they still use more energy. It is thought that deep snow may be one factor that limits the distribution of fishers.
Male fishers are nearly twice the size of female fishers, ranging from 2-6 kg in weight.
LIFE HISTORY
The life cycle of the fisher begins every spring when kits are born and adults mate. In March or April, a female will give birth in a protected nursery den. Such a nest may be high in a hollow tree with a woodpecker hole or low in a crevice between rocks. Litter sizes vary from one to five kits.
After four months, the kits are weaned and begin to hunt on their own. In autumn, the family breaks up and each member begins its solitary life.
The only time these solitary animals meet up with others is during the mating season. This time is approximately two weeks after mature females have given birth. However, the fertilized egg remains in "storage" in the female's uterus for 10-11 months. With increasing day length in the following spring, the egg implants in the uterine wall and begins to develop. Pregnancy lasts approximately 30 days. With this method of reproduction, female fishers are always in a state of pregnancy. While "delayed implantation" is not rare among mammals, the fisher has the longest period.
Fishers can travel long distances in short periods of time. They have been known to move up to 160 km in a single summer, but the normal home range for an adult male is 20 square kilometers. With its scent glands, the fisher marks its territory.
Fishers use a variety of sites for sleeping. These sites include hollow trees, logs, stumps, brush piles, rock falls, abandoned beaver lodges and tree nests. During severe winter weather, fishers may den up for a few days.
In addition to porcupines, the fisher lives on small mammals such as snowshoe hares, squirrels, chipmunks, mice and voles. These are killed with a swift bite to the neck and, depending on their size, may be swallowed whole. The fisher will also feed on small birds, carrion, berries and lichens.
Contrary to popular belief, fishers do not hunt or eat fish. It is thought that early Dutch settlers named this large member of the weasel family after the European polecat known as "fitch" or "fitchet."
FISHERS AND PEOPLE
Since the fisher is rare in the Yukon, it is not an important species for the trapping industry. Fewer than five fishers are trapped in the southeast Yukon each year.
VIEWING OPPORTUNITIES
Fishers are rarely seen in the Yukon, or for that matter, anywhere else. Remember that they are present only in the southeast Yukon and they prefer dense, valley-bottom, spruce forests. By chance you may observe a large weasel-like animal darting after a snowshoe hare or facing off with a prickly porcupine. Consider yourself lucky if you ever see one of these elusive mammals in the Yukon.