Martes
pennanti
(Fisher)
Description:
Fishers are rare in Idaho, but
if you should observe one, it looks larger than a marten, almost the size of
a small fox, and it has no throat patch. Its longer fur is very dark, black
to dark brownish, and often with a grizzled appearance on the face, neck and
shoulders. Their legs and feet appear black. They appear stouter than a marten
or a weasel. Total length is 31 to 41 inches (790-1033 mm), tail length is 11
¾ to 16 5/8 inches (300-422 mm), and they weigh 3 to 18 pounds (1.4-8.2 kg).
Range:
They occur throughout much of Canada, and south through the Rockies, and in
the northern Great Lakes Region and New England. Fishers were extirpated from
Idaho, and re-introduced to three, north-central Idaho sites in the early 1960's.
They are rare in other parts of Idaho, but little is known about their distribution.
Habitat:
They are found in upland and lowland
mixed, deciduous, or coniferous forests, but they prefer
mixed or coniferous forests. In Idaho, they prefer mature or old-growth coniferous
forests with a dense canopy. They seem to favor forested riparian habitats in spring, summer,
and fall, and younger-aged forests in the winter.
Diet:
They mainly prey on other mammals such as small rodents, shrews, squirrels,
hares, muskrat, beaver, porcupine, and raccoons. They also feed on deer carrion, but will also eat birds
and fruits. They have a reputation of being predator specialists on porcupines.
Ecology:
Trapping and habitat loss due to logging extirpated them from their range
by the early 1900's. However, reintroduction has established their populations
in certain areas. They are active both day and night, but seem more nocturnal
in summer and diurnal in winter. In a study in Maine, they were mostly active
shortly before sunrise and after sunset; and activity was reduced in winter.
When inactive, they occupy dens in tree hollows, under logs, or rocky crevices,
or in warmer months they rest in branches of conifer trees. Their home range
has been estimated at 10 to 800 km2 by snow tracking, and 2 to 75 km2 by telemetry.
An Idaho study found their home range to vary from 6 to 120 km2. Generally,
the ranges of adults of same sex do not overlap. In Maine, home ranges of females
were stable between seasons and years, but males moved extensively in late winter
and early spring and their ranges shifted between years. population density in New England and the
Great Lakes area has been estimated at up to about 1 per 3 to 11 km2 in summer,
and 1 per 8 to 20 km2 in winter. Densities are lower in the western U.S. due
to lower habitat quality.
Reproduction:
They breeds from late February to April; the peak occurs in March. After
fertilization of the egg, the embryo becomes dormant for 10
to 11 months (delayed
implantation). Young are born from
March to early April. Litter size averages about 3
young. Young are weaned mid-May to early June,
and become independent probably by late August to early September when they
can kill on their own at about 4 months of age. They sexually mature in 1-2
yr; not all adult females breed in a given year. Apparently, breeding is promiscuous.
Conservation:
Status: | Protected nongame species |
Global Rank: | G5 |
State Rank: | S1 |
Important State References:
Jones,
J.L. 1991. Habitat use of fisher in north-central Idaho. M.S. Thesis, Univ.
Idaho, Moscow. 147pp.