As we have often discussed, the Eastern Fisher continues to grow more robust and expand its Northeastern range(New England down through NJ and Pennslvania over the last few years), the Western Fisher is in trouble and absent from more and more of its historical range........I do not subscribe to the bobcat or coyote predation theory put forth below regarding Fisher decline in California.............Coyotes and Bobcats are very established in the East(bobcats a bit slower to grow, but holding their own) and one would think they would be adversely impacting Eastern Fishers.............but they are not!!!!!.........Is Logging and habitat alteration the problem for the Fisher decline out West?

Fisher Decline Documented in California

The Hoopa Valley Tribe, in cooperation with the Wildlife Conservation Society and the University of Massachusetts, reported a 73-percent decline in the density of fishers -- a house-cat sized member of the weasel family and candidate for endangered species listing -- on the Hoopa Valley Indian Reservation in northwestern California between 1998 and 2005.

The scientists speculate that changes in prey habitat, disease, and increases in predation -- especially by bobcat -- may be responsible for the population decline observed on the reservation. However, additional efforts are needed to determine trends in fisher populations and expand monitoring to other regions.

The study appears in the June edition of the online journal The Wildlife Society Bulletin. Co-authors on the study include Sean M. Matthews of WCS, J. Mark Higley and J. Scott Yaeger of the Wildlife Department of Hoopa Tribal Forestry, and Todd K. Fuller of the University of Massachusetts Department of Environmental Conservation.

Study data were collected using a mark-resight method, where fishers were captured, ear-tagged to identify individuals, and subsequently photographed at remote camera stations. Study authors also report that different methods currently used by scientists to evaluate populations of fishers can produce different results and lead managers to ill-informed conclusions about population status. Mark-resight methods have long been held as the gold standard of wildlife population monitoring, yet are costly and labor-intensive.

WCS Conservation Biologist Sean Matthews said, "It is critical to understand the status of a population when making decisions about species conservation. Our study further demonstrates the importance in monitoring populations of imperiled species and the limitations of some methods in detecting large changes in population size."

Mark Higley, the Hoopa Tribe's wildlife biologist, said, "For the study of at-risk or sensitive populations, defensible, large-scale occupancy estimation or mark-recapture methods should be used to monitor changes in populations and to determine trends. Snapshots in time such as the two presented in the paper, give us some important insights, but do not tell the whole story. Long term demographic and occupancy monitoring studies may allow for modeling cause and effect factors such as changes in habitat, climate change, disease exposure, and increases in larger predators. These data are a cornerstone in evaluating extinction risk, identifying population-level threats, and determining the success of conservation measures."
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Local Species Information - Fisher (Martes pennanti)

General Information

	Status:	Federally listed as a Candidate (western United States Distinct Population Segment)
	Date Listed:	Listed on April 8, 2004
	Species Assessment:	Species Assessment current as of April 2008

 

Natural History

Background   

A resident of coniferous and mixed coniferous forests, the fisher once occurred throughout much of Canada, the northern United States, and the western United States.  Fisher populations have declined primarily due to loss of habitat from timber harvest activities and trapping.  Populations of fishers have declined in all Canadian provinces and states except the Yukon and in the extreme northeastern United States (Maine, New Hampshire, and Vermont).  In the western United States and Canadian Provinces, the number of fishers has been greatly reduced and their populations fragmented.  Fishers are no longer believed to occupy the lower mainland of British Columbia and the area west of Okanogan extending down to Washington.  

Identifying Characteristics

Adult fisher with radio collar.  Photo Credit: J. Mark Higley,

Hoopa Valley Tribal Forestry

Markings: The fisher is light brown to dark blackish-brown, with the face, neck, and shoulders sometimes being slightly gray.  The chest and underside often has irregular white patches.  The fisher has a long body with short legs and a long bushy tail.  At 6.6 to 13.2 pounds, male fishers   weigh about twice as much as females (3.3 to 5.5 pounds).  Males range in length from 35 to 47 inches while females range from 29 to 37 inches in length.  Fishers from the Pacific States may weigh less than fishers in the eastern United States.

Look-a-like Mammals  

 American Marten

American martens (Martes americana) have similar body shapes to fisher, but are smaller and usually lighter in color than fishers.  The fur on the throat of martens is a buff or orange color; legs and tails are typically darker than the rest of the body.  Female martens range from 18 to 22 inches in length and weigh 1.5 to 1.8 pounds.   Male martens range from 20 to 25 inches in length and weigh 1.6 to 2.8 pounds. 

American marten.  Photo Credit: Eugene Wier

American Mink

The American mink (Mustela vison) also has a similar body shape to fisher, but are smaller and usually darker in color than fishers.  Their fur is deep, rich brown, with or without white spots on the stomach.  American mink have webbing at the base of their toes, and their ears barely stick out above their fur.  Females range from 18 to 22 inches in length and weigh 1.2 to 1.7 pounds.  Males are slightly larger than females, ranging from 19 to 28 inches in length and 1.9 to 2.8 pounds.

American mink.  © 2004 Ron E. VanNimwegen

Geographic Range

The West Coast Distinct Population Segment includes the states of Washington, Oregon, and California.  Fishers are known to occur in Oregon and California; fishers were re-introduced into the Olympic Peninsula of Washington in January and March of 2008.  For more information on the re-introduction, please follow these links to Olympic National Park and Washington Department of Fish and Wildlife web pages.

Map showing the current and historic range of fisher

in the western United States.  Image obtained

from the fisher Species Assessment.

  

Habitat

Fishers use late-successional habitats with dense canopy closure, large diameter trees (conifers and hardwoods) and snags with cavities and other deformities, large diameter down wood, multiple canopy layers.  Late-successional coniferous or mixed forests that contain key habitat and structural components provide the most suitable fisher habitat because they provide abundant potential den sites and preferred prey species.  The physical structure of the forest and prey associated with forest structures are thought to be the critical features that explain fisher habitat use, rather than specific forest types.  The West Coast population of the fisher inhabits forested areas from sea level along the California Oregon Coast to approximately 1,970 to 8,530 ft in the Sierra Nevada.

Prey

Fishers have a diverse diet that includes birds, squirrels, mice, shrews, voles, reptiles, insects, plants, fruit, and dead animals.  Small and mid-sized mammals are the most common prey items eaten by fishers in the Pacific States.  Fishers search for prey in forested stands, avoiding openings.

Reproduction

Except during the breeding season, fishers are solitary animals.  The breeding season for the fisher is generally from late February to the end of April.  Female fishers raise 1 to 3 kits, which are weaned by 10 weeks old.  When they are 1 year of age, kits have established their own home ranges and are no longer dependent upon adults.

Fisher kits.  Photo Credit: Cathy Raley,