title: Patterns of Natural and Human-Caused Mortality Factors of a Rare Forest Carnivore, the Fisher (Pekania pennanti) in California.
abstract: Wildlife populations of conservation concern are limited in distribution, population size and persistence by various factors, including mortality. The fisher (Pekania pennanti), a North American mid-sized carnivore whose range in the western Pacific United States has retracted considerably in the past century, was proposed for threatened status protection in late 2014 under the United States Endangered Species Act by the United States Fish and Wildlife Service in its West Coast Distinct Population Segment. We investigated mortality in 167 fishers from two genetically and geographically distinct sub-populations in California within this West Coast Distinct Population Segment using a combination of gross necropsy, histology, toxicology and molecular methods. Overall, predation (70%), natural disease (16%), toxicant poisoning (10%) and, less commonly, vehicular strike (2%) and other anthropogenic causes (2%) were causes of mortality observed. We documented both an increase in mortality to (57% increase) and exposure (6%) from pesticides in fishers in just the past three years, highlighting further that toxicants from marijuana cultivation still pose a threat. Additionally, exposure to multiple rodenticides significantly increased the likelihood of mortality from rodenticide poisoning. Poisoning was significantly more common in male than female fishers and was 7 times more likely than disease to kill males. Based on necropsy findings, suspected causes of mortality based on field evidence alone tended to underestimate the frequency of disease-related mortalities. This study is the first comprehensive investigation of mortality causes of fishers and provides essential information to assist in the conservation of this species.
authors.affiliation: Integral Ecology Research Center, Blue Lake, California, United States of America.|Mammalian Ecology and Conservation Unit, Veterinary Genetics Laboratory, University of California Davis, Davis, California, United States of America.
authors.forename: Mourad W
authors.initials: MW
authors.lastname: Gabriel
authors.affiliation: California Animal Health and Food Safety Laboratory System, University of California Davis, California, United States of America.
authors.forename: Leslie W
authors.initials: LW
authors.lastname: Woods
authors.affiliation: Integral Ecology Research Center, Blue Lake, California, United States of America.
authors.forename: Greta M
authors.initials: GM
authors.lastname: Wengert
authors.affiliation: University of California Davis, School Veterinary Medicine, Davis, CA, United States of America.
authors.forename: Nicole
authors.initials: N
authors.lastname: Stephenson
authors.affiliation: Wildlife Department, Hoopa Tribal Forestry, Hoopa, California, United States of America.
authors.forename: J Mark
authors.initials: JM
authors.lastname: Higley
authors.affiliation: Pacific Southwest Research Station-Sierra Nevada Research Center, United States Forest Service, Fresno, California, United States of America.
authors.forename: Craig
authors.initials: C
authors.lastname: Thompson
authors.affiliation: Wildlife Conservation Society, Hoopa, California, United States of America.
authors.forename: Sean M
authors.initials: SM
authors.lastname: Matthews
authors.affiliation: Sierra Nevada Adaptive Management Project, University of California, Berkeley, California, United States of America.
authors.forename: Rick A
authors.initials: RA
authors.lastname: Sweitzer
authors.affiliation: Pacific Southwest Research Station-Sierra Nevada Research Center, United States Forest Service, Fresno, California, United States of America.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Purcell
authors.affiliation: Sierra Nevada Adaptive Management Project, University of California, Berkeley, California, United States of America.
authors.forename: Reginald H
authors.initials: RH
authors.lastname: Barrett
authors.affiliation: Department of Pathology, Microbiology and Immunology, University of California Davis, Davis, California, United States of America.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Keller
authors.affiliation: Department of Pathology, Microbiology and Immunology, University of California Davis, Davis, California, United States of America.
authors.forename: Patricia
authors.initials: P
authors.lastname: Gaffney
authors.affiliation: Department of Pathology, Microbiology and Immunology, University of California Davis, Davis, California, United States of America.
authors.forename: Megan
authors.initials: M
authors.lastname: Jones
authors.affiliation: California Animal Health and Food Safety Laboratory System, University of California Davis, California, United States of America.
authors.forename: Robert
authors.initials: R
authors.lastname: Poppenga
authors.affiliation: University of California Davis, School Veterinary Medicine, Davis, CA, United States of America.
authors.forename: Janet E
authors.initials: JE
authors.lastname: Foley
authors.affiliation: Department of Wildlife, Humboldt State University, Arcata, California, United States of America.
authors.forename: Richard N
authors.initials: RN
authors.lastname: Brown
authors.affiliation: Wildlife Investigations Laboratory, California Department of Fish and Wildlife, Rancho Cordova, California, United States of America.
authors.forename: Deana L
authors.initials: DL
authors.lastname: Clifford
authors.affiliation: Mammalian Ecology and Conservation Unit, Veterinary Genetics Laboratory, University of California Davis, Davis, California, United States of America.|Department of Population Health and Reproduction, University of California Davis, Davis, California, United States of America.
authors.forename: Benjamin N
authors.initials: BN
authors.lastname: Sacks
mesh_terms: D000818:Animals; D002140:California; D003247:Conservation of Natural Resources; D004785:Environmental Pollutants / Q000506:poisoning*; D004787:Environmental Pollution / Q000009:adverse effects*; D005260:Female; D020387:Food Chain; D006801:Humans; D008297:Male; D045969:Mustelidae; D011156:Population Density
chemical_list: D004785:Environmental Pollutants