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What the sources say

FisherPekania pennanti

Every figure, record and mechanism on the Fisher profile was written from a source, and this is the working table behind it: 51 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

Profile updated

Source
01

Animal Diversity Web

Martes pennanti. Animal Diversity Web.

The page saysclimbs trees
The source saysFishers are agile and speedy tree climbersNote: tagline
The page sayshunts porcupines
The source saysFishers hunt porcupinesNote: tagline
The page sayswhose females spend almost all of their adult lives pregnant or nursing
The source saysSo females essentially spend almost all of their adult life in a state of pregnancy or lactation.Note: tagline; pregnant or nursing = pregnancy or lactation
The page saysConiferous forests, also mixed and deciduous ones, from the Sierra Nevada of California to the Appalachians
The source saysFishers prefer coniferous forests, but they are also found in mixed and deciduous forests.Note: stats.habitat
The page saysfrom the Sierra Nevada of California to the Appalachians
The source saysfrom the Sierra Nevada of California to the Appalachians of West Virginia and VirginiaNote: stats.habitat
The page saysMice, porcupines, squirrels, snowshoe hares, birds and shrews, plus some fruit
The source saysFishers eat mice , porcupines , squirrels , snowshoe hares , birds , and shrewsNote: stats.diet
The page saysplus some fruit
The source saysThey may also feed on fruits and berries, such as beechnuts and apples.Note: stats.diet
The page saysIts embryos pause for 10 to 11 months and a mother mates again soon after giving birth, so a female is pregnant or nursing for almost all of her adult life
The source saysthe embryos sit in suspended development for 10 to 11 monthsNote: stats.superpower
The page saysa mother mates again soon after giving birth
The source saysShortly after giving birth, females experience a postpartum estrus and mate again.Note: stats.superpower; ADW's 'So' follows this sentence and annual breeding, not the pause alone
The page saysa female is pregnant or nursing for almost all of her adult life
The source saysSo females essentially spend almost all of their adult life in a state of pregnancy or lactation.Note: stats.superpower
The page saysThe fisher belongs to the weasel family
The source saysMustelidae badgers, otters, weasels, and relativesNote: Family line of the ADW classification table; the quote spans the table's rank and gloss.
The page saysIt has five toes on each foot and retractable claws.
The source saysFishers have five toes on their feet, and their claws are retractable.
The page saysIt is an agile, speedy tree climber, although it usually travels on the ground.
The source saysFishers are agile and speedy tree climbers, but they usually move on the ground.
The page saysOn average, males are the larger sex, with a body length of 900 to 1200 mm and a weight of 3.5 to 5 kg.
The source saysMales fishers are, on average, larger than females, with a body length of 900 to 1200 mm and a body weight of 3500 to 5000 grams.Note: 3500 to 5000 g = 3.5 to 5 kg
The page saysFemales measure 750 to 950 mm and weigh 2 to 2.5 kg.
The source saysFemales range from 750 to 950 mm in length and 2000 to 2500 grams in weight.Note: 2000 to 2500 g = 2 to 2.5 kg
The page saysOnly the fisher and the American marten are medium-sized predators that can climb well and also stretch their bodies out to follow prey into holes in the ground, hollow trees and other tight spaces.
The source saysFishers and American martens are the only medium-sized predators agile in trees that also possess the ability to elongate themselves to seek prey in holes in the ground, hollow trees and other small areas.
The page saysFishers are solitary hunters that look for prey their own size or smaller, though they can take bigger animals.
The source saysFishers are solitary hunters, and seek prey that is their own size or smaller, although they are capable of taking on prey larger than themselves.
The page saysThe menu includes mice, squirrels, snowshoe hares, birds and shrews, and they may also eat fruit and berries.
The source saysFishers eat mice , porcupines , squirrels , snowshoe hares , birds , and shrews
The page saysthey may also eat fruit and berries
The source saysThey may also feed on fruits and berries, such as beechnuts and apples.
The page saysThey also hunt porcupines, and Animal Diversity Web notes that this can help control porcupines, which damage timber by stripping bark and killing trees.
The source saysFishers hunt porcupines , and can effectively control porcupine populations (porcupines are known to damage timber crops by debarking and killing trees).
The page saysOnce a female's eggs are fertilized, the embryos stop growing for 10 to 11 months.
The source saysAfter fertilization, the embryos sit in suspended development for 10 to 11 months
The page saysCounting that pause, her pregnancy runs 11 to 12 months.
The source saysOverall, gestation lasts almost a full year, 11 to 12 months.
The page saysdelayed implantation
The source saysdelayed implantationNote: ADW reproductive-features term; definition from ADW glossary: a fertilized egg reaches the uterus but delays its implantation in the uterine lining
The page saysthe fertilized egg reaches the womb but delays attaching to its lining
The source saysa fertilized egg reaches the uterus but delays its implantation in the uterine lining, sometimes for several months
The page saysThe female then gives birth, to an average of 3 young, and soon afterward mates again.
The source saysThe average number of young in a litter is 3, ranging from 1 to 6. Shortly after giving birth, females experience a postpartum estrus and mate again.
The page saysSo a female spends almost all of her adult life pregnant or nursing.
The source saysSo females essentially spend almost all of their adult life in a state of pregnancy or lactation.
The page saysNewborns are blind, nearly naked and weigh about 40 grams.
The source saysYoung fishers are born blind and nearly naked. Each weighs about 40 grams at birth.
The page saysTheir eyes open after about 53 days.
The source saysThe eyes open after about 53 days.
The page saysBy four months old they can hunt for themselves.
The source saysBy the time they are four months old, the young are able to hunt for themselves
The page saysThe fisher is found nowhere but North America. Its range reaches south along California's Sierra Nevada and down the Appalachian chain, as far as West Virginia and Virginia, and it is absent from the prairies and the southern United States.
The source saysFishers are found only in North America, from the Sierra Nevada of California to the Appalachians of West Virginia and Virginia. They range along the Sierra Nevada to their southernmost extent and south along the Appalachian mountain chain. They do not occur in the prairie or southern regions of the United States.
The page saysThey prefer coniferous forest with plenty of hollow trees for dens.
The source saysFishers prefer coniferous forests ... They also prefer habitats with many hollow trees for dens.
The page saysEach fisher keeps a home range of 15 to 35 square kilometers, averaging about 25.
The source saysHome range size varies from 15 to 35 square kilometers in area, averaging about 25 square kilometers.
The page saysTrapping for pelts once had a significant effect on their numbers
The source saysFishers are trapped and killed for their pelts. Trapping, in the past, had a significant effect on fisher populationsNote: text split below
The page sayslogging destroys the near-continuous conifer forest they prefer
The source saysLogging of forests greatly impacts fishers and fisher populations by destroying their preferred habitat--continuous or nearly continuous coniferous forests
The page saysIn 2003 Animal Diversity Web reported that numbers seemed to have rebounded in parts of North America, including Michigan, Ontario, New York and some of New England.
The source saysIn some areas of North America, such as Michigan, Ontario, New York, and some areas of New England, fisher populations seem to have rebounded in recent years.Note: ADW account last updated 2003-05-22 (To cite this page: Rhines, C. 2003)
The page saysA male runs 90 to 120 centimeters long and weighs 3.5 to 5 kilograms. A female is smaller on average, at 75 to 95 centimeters and 2 to 2.5 kilograms.
The source saysMales fishers are, on average, larger than females, with a body length of 900 to 1200 mm and a body weight of 3500 to 5000 grams. Females range from 750 to 950 mm in length and 2000 to 2500 grams in weight.Note: converted units
The page saysIt belongs to Mustelidae, the family Animal Diversity Web describes as badgers, otters, weasels and their relatives.
The source saysMustelidae badgers, otters, weasels, and relatives
The page saysAlmost a full year: 11 to 12 months in all. For 10 to 11 of those months the embryo is on hold, picking up again late in the winter after mating.
The source saysthe embryos sit in suspended development for 10 to 11 months, and resume developing late in the winter following mating. Overall, gestation lasts almost a full year, 11 to 12 months.
The page saysOnce a female fisher's eggs are fertilized, the embryos stop growing for 10 to 11 months
The source saysAfter fertilization, the embryos sit in suspended development for 10 to 11 monthsNote: vibe.reason
The page saysdangerLevel: Medium
The source saysWhen startled, fishers may react aggressively to the perceived threat.Note: task #1246; Medium: can injure, but rarely seriously. ADW lists "injures humans: bites or stings" under negative impacts; pine marten stays Low (no such report).
The page saystags: climber
The source saysFishers are agile and speedy tree climbersNote: task #1246; Climber tag definition: scaling tree trunks with hooked claws; ADW states the behaviour.

Source
02

Human Ageing Genomic Resources, AnAge

AnAge entry for Martes pennanti. Human Ageing Genomic Resources, AnAge.

The page saysIn captivity, one fisher lived 14.3 years.
The source saysOne specimen lived 14.3 years in captivity
The page saysIn the wild, fishers may live up to 10 years.
The source saysIn the wild, fishers may live up to 10 years
The page saysOne fisher in AnAge's database lived 14.3 years in captivity.
The source saysOne specimen lived 14.3 years in captivity
The page saysweightKg: 3.175
The source saysAdult weight 3,175 gNote: task #1246; AnAge adult weight; ADW females 2 to 2.5 kg, males 3.5 to 5 kg, all Light. Name guess would have been Medium.

Source
03

Virginia Department of Wildlife Resources

Fisher. Virginia Department of Wildlife Resources.

The page saysA fox-sized relative of weasels that climbs trees, hunts porcupines and whose females spend almost all of their adult lives pregnant or nursing.
The source saysThis species is the largest of the genus with a long fox-sized body
The page saysfox-sized, with short legs, a long body, small rounded ears and a long, bushy tail
The source saysa long fox-sized body, short legs, and ears that are small and rounded. The tail is long and bushy
The page saysVirginia lost its fishers by the late 1800s to habitat destruction, heavy trapping and shooting
The source saysfishers were extirpated from the state by the late 1800’s (habitat destruction, excessive trapping and shooting)
The page saysbut in the past 20 years more have been sighted there, with evidence of breeding
The source saysIn the past 20 years, more fishers have been sighted in Virginia, predominantly in the northern and western counties, including evidence of reproductive populations.Note: page last updated April 16, 2026

Source
04

Helgen & Reid 2018

Helgen & Reid (2018). Martes pennanti. The IUCN Red List of Threatened Species 2018: e.T41651A125236220.

The page saysThe IUCN Red List rates the species Least Concern, filed under its older name, Martes pennanti.
The source saysLeast ConcernNote: hand check: verify:quotes cannot read this category (GBIF species endpoint answers NE for taxon 41651); GBIF's distribution record for taxon 176684433 gives threatStatus LEAST_CONCERN citing this DOI. Title of the assessment is 'Martes pennanti'. Also stated by adw-fisher: 'IUCN Red List Least Concern'.
The page saysLeast Concern
The source saysLeast ConcernNote: conservationStatus; hand check, see above

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.