Sacramento Fish & Wildlife Office
Species Account
FISHER
(Martes pennanti)
Photo Courtesy Mark Higley
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About usThere is a special fisher species account for 4th, 5th and 6th grade students.
CLASSIFICATION: Federal Candidate Species (Federal Register 69:18769 pdf; April 7, 2004)
On December 5, 2000, we received a petition to list a distinct population segment of the fisher (including portions of California, Oregon, and Washington) as endangered pursuant to the Act, and to concurrently designate critical habitat.
After review of all available scientific and commercial information, we found that the petitioned action was warranted, but precluded by higher priority listing actions. The species is currently on our candidate species list. We will develop a proposed rule to list this population according to our listing priority system.
CRITICAL HABITAT: Need for critical habitat designation will be addressed in our proposed rule.
RECOVERY PLAN: None
DESCRIPTION:
The fisher (Martes pennanti) belongs to the weasel family (Mustelidae). Some researchers have recognized three subspecies of fisher: Martes pennanti pennanti in the east and central regions of North America, M. p. columbiana in central and northwestern regions and M. p. pacifica ("Pacific fisher") in the western region of North America. The Service does not recognize this distinction.
Fishers are similar to the much smaller weasels. They have a long body with short legs. Adults range in length from 90 to 120 centimeters (about 2.5 to 4 feet). Males weigh 3 to 6 kilograms (about 7 to 13 pounds), females 1.5 to 2.5 kilograms (about 3 to 5.5 pounds).
The fisher's head is broad and flat with a sharp, pronounced muzzle. Its eyes face forward and ears are broad, rounded and low. Fur length ranges from 30 millimeters (about 1 inches) on the stomach and chest to 70 millimeters (about 2.75 inches) on the back. The tail is long and bushy.
Fur color varies from light brown to dark blackish brown, typically being darkest on lower back, legs and tail. The face, neck and shoulders may have a lighter grizzled gray appearance. Often there are irregular white patches on the chest and underside.
Fishers have five toes on all four feet and retractable claws. Their feet are large with a pad on each toe and a group of four central pads.
Fishers can rotate their hind paws almost 180 degrees, allowing them to come down trees head first like a squirrel and grasp limbs. On the hind paws, the central pads have circular patches of coarse hair that are associated with plantar glands which produce a distinctive odor believed to be used for communication during reproduction.
Fishers are opportunistic predators with a diverse diet that includes birds, porcupines, snowshoe hare, squirrels, mice, shrews, voles, reptiles, insects, deer carrion, vegetation and fruit. The name "fisher" is misleading. Fishers do not actually catch fish!
The breeding season for the fisher begins in late February and lasts until mid-April. Implantation of the blastocyst phase of the embryo is delayed approximately ten months. Following implantation, gestation lasts for around 30 days. Birth thus occurs nearly one year later, just prior to mating. Litter sizes generally range from one to four, but can be as high as five or six in rare cases. Not all fishers produce young every year. Some research indicates that fisher reproductive rates fluctuate widely.
DISTRIBUTION:
Fishers, found only in North America, occur in the northern coniferous and mixed forests of Canada and northern United States, from the mountainous areas in the southern Yukon and Labrador Provinces in Canada southward to central California and Wyoming, the Great Lakes and Appalachian regions and New England.
In California, the fisher historically ranged throughout the Sierra Nevada from Greenhorn Mountain in northern Kern County to the southern Cascades at Mount Shasta. From there, they ranged west into the North Coast Ranges and Klamath Mountains from Lake and Marin Counties north to the State line.
Recent surveys indicate that the fisher occupies less than half of the range in California that it did in the early 1900s, and that the population is divided into two remnants. One is in the southern Sierra and the other in the northwest corner of the state. These populations are separated by about 250 miles, almost four times the species' maximum dispersal distance.
Failure to detect fishers in the central and northern Sierra Nevada suggests that they may be extirpated or occur at very low densities. This effectively isolates fishers in the southern Sierra Nevada from ones in northern California.
THREATS:
The primary threat mentioned in the December 5, 2002 petition is the loss and fragmentation of fisher habitat, which the petitioners state is due to timber harvest, roads, urban development, recreation, and stand-replacing fire.
The petitioners believe that past timber harvest in Washington, Oregon, and California has resulted in the loss of key components of fisher habitat over large portions of the landscape, and that the cumulative effects of continued timber harvest and fuels reduction projects on public and private lands would have dramatic effects on the fisher.
Other factors cited include poaching and incidental capture and injury, predation, mortality by vehicle collision, limited population size, and isolation of populations.
REFERENCES FOR ADDITIONAL INFORMATION: (Disclaimer)
Fisher Clearinghouse [Internet]. Bozeman (MT): Predator Conservation Alliance; c2002 [cited 2003 Apr 25].
U.S. Fish and Wildlife Service. 1996. Endangered and threatened wildlife and plants; 90-day finding for a petition to list the fisher in the western United States as threatened (pdf). Federal Register 61:8016-8018.
U.S. Fish and Wildlife Service. 2003. Endangered and Threatened Wildlife and Plants; 90-day Finding for a Petition To List a Distinct Population Segment of the Fisher in Its West Coast Range as Endangered and To Designate Critical Habitat (pdf). Federal Register 68:41169-41174. Literature Cited in Finding (pdf)
U.S. Fish and Wildlife Service. 2004.
12-month Finding for a Petition to
List the West Coast Distinct Population Segment of the Fisher (Martes pennanti) (pdf).
Portland, Oregon.
Note: This includes all the references cited in the finding.
U.S. Fish and Wildlife Service. 2004. Endangered and Threatened Wildlife and Plants; 12-month Finding for a Petition to List the West Coast Distinct Population Segment of the Fisher (Martes pennanti). Portland, Oregon. Federal Register 69:18769. This is the Federal Register notice of the finding.
Zielinski, W. J., T. E. Kucera, and R. H. Barret. 1995. Current distribution of the fisher, Martes pennanti, in California. California Fish and Game, 81(3), 104-112.
Photo Credit: Fisher photo by Mark Higley, Hoopa Tribal Forestry
