Fisher (Martes pennanti)
Habitat
The
fisher prefers dense forest environments, with thick, high overhead canopies.
Fishers avoid open spaces with no overhead cover. Although fishers spend
most of their time on the ground, they are quite capable of climbing trees,
with the ability of jumping from one tree to another.
Length
Head and body: Up to 25 inches (63 cm)
Tail: Up to 17 inches (43 cm)
Weight
Males: 5.7-12.1 pounds (2.6-5.5 kg); females 2.9-7 pounds (1.3-3.2 kg)
Life
Span
About 10 years in the wild; longer in zoos.
Diet
In the wild: Small
to medium sized birds and mammals and carrion. At times they may
feed on fruits and nuts.
At
the zoo:Canine
diet, carrots, kibble, apples, dog biscuit, fruit, day-old chicks
and treats.
Reproduction
Fishers reach sexual maturity from 1-2 years
of age. Both sexes are predominantly solitary except during the breeding
season, which occurs in the beginning of March. Gestation lasts about
51 weeks. The gestation period is long because the fertilized egg is
delayed several months before implanting on the uterine wall. An average
size litter of three young are born from late February through April
in dens situated high in hollow trees. Females mate almost immediately
after giving birth, and are therefore pregnant most of the time.
Life Cycle
Young are born blind and helpless, but after four weeks are able to
eat meat. At about 7 weeks their eyes open, and they begin to walk
at approximately 9 weeks. The female may move her young several times
to alternate dens. By 17 to 18 weeks, they are weaned and ready to
leave the den. Except for raising young, fishers normally do not have
a permanent den. Instead, they seek temporary shelter in hollow trees
and logs, stumps, holes in the ground, or wherever they can find seclusion.
The fishers home range appears to encompass one to four square miles
(2.6-10.4 sq km). Home ranges of males seldom overlap, and males are
not tolerant of one another. There is wide overlapping of territories
between males and females. Territories are identified through scent
marking.
Opportunistic
Hunters
The fisher is largely an opportunist when hunting. Most of its hunting consists
of the chance investigation of sites where small mammals are likely to be found.
Fishers kill all prey, except porcupines, by biting them through the back of
the head. The fisher is one of the few predators that eats porcupines. The
hunting of a porcupine is hard work and a successful kill may take half an
hour. The arrangement of quills on a porcupine protects it from an attack to
the back of the neck. To counter this pointy defense, the fisher circles the
porcupine and bites at its face until the porcupine suffers shock or is unable
to protect itself. The fisher then overturns the porcupine and begins to feed
on its belly. As would be expected, fishers may sustain some injury from the
quills of their victims, but even though quills sometimes penetrate a fisher's
intestines, they seldom appear to cause serious damage to the animal. Porcupines
are not an essential part of the fisher's diet because fishers live in areas
not inhabited by this prey species.
Bigger and Stronger
The fisher is a close relative of the marten. Similar in structure
and body proportions, the fisher is nearly twice as large as a
marten, and four times as heavy. Their coats also differ. The fisher's
coat is very dark brown to blackish brown with gold to silver hoariness
on the head and shoulders. Fishers have strong, moderately large
feet with hairy soles. Each foot has five toes that terminate in
sharply curved, partially retractable claws. The legs and tail
are black. The chest has a variable cream-colored patch.
Location
at the Zoo
Woodland Park Zoo no longer exhibits fishers. Other
animals that can be seen along the Northern Trail are gray wolves,
brown bear, mountain goat, porcupine, bald eagle and Roosevelt elk.
Conservation
Connection
During the late 19th century through the 1920s, fishers
were extensively trapped for their pelts. Loss of required forest
habitat due to extensive logging also contributed greatly to their
population decline during this century. By the 1930s, the fisher
was essentially eliminated in the United States. The demise of the
fisher had a positive effect on porcupine populations. With the removal
of their primary predator, porcupine populations expanded. This in
turn led to the extensive damage to forests, caused by the porcupines
debarking and killing of trees. With the realization that fishers
are important for controlling porcupine populations, fishers were
reintroduced to certain areas during the 1950s and 1960s. Legal trapping
of the fisher for the fur market continues today in areas of the
United States and Canada.
How You Can Help!
The effort to save endangered species requires
cooperation and support at the international, national, regional and
individual levels. You can help in this cause. Join and become active
in Woodland Park Zoo and other conservation organizations of your choice.
Let your elected representatives know your views about protecting endangered
species and wild habitats.
Contact Woodland Park Zoo at webkeeper@zoo.org to find
out about ways you can support conservation efforts at the zoo. Learn
other ways you can help conserve wildlife and the habitats they require
for survival by visiting our How You Can Help page.
Sources and Suggested
Reading
Chapman, Joseph A. and George A. Feldhamer,
ed. 1982. Wild Mammals of North America: Biology, Management, Economics.
The Johns Hopkins University Press, Baltimore, MD. 1147 p.
Nowak, Ronald M. ed. 1991. Walker's Mammals of the
World. 5th Edition. The Johns Hopkins University Press, Baltimore
and London. 1629 p.