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Individual Highlight

Fisher Survival and Response to Marijuana Plantations and Fuel Treatments in the Sierra Nevada

Photo of Male fisher in ponderosa pine tree. Jordan Latter, U.S. Department of Agriculture Forest Service.Male fisher in ponderosa pine tree. Jordan Latter, U.S. Department of Agriculture Forest Service.Snapshot : Research shows that pesticide poisoning related to illegal marijuana cultivation may be affecting the ability of fisher populations to expand. Fishers show short-term avoidance of forest stands treated for fuel reduction, but the size and configuration of treatments applied were important.

Research Location : Sierra National Forest, Calif.
Research Station : Pacific Southwest Research Station (PSW)
Year : 2016
Highlight ID : 1149

Summary

In 2016, Forest Service researchers summarized results of fisher survival, limiting factors, population growth and occupancy following fuel-reduction activities. The data suggest that predation is the highest source of mortality, though current predation rates may be inflated as a result of illegal marijuana cultivation on public lands. Direct poisoning accounted for 10 percent of fisher mortality rates statewide, a 57 percent increase in the last three years. In particular, adult female survival rates may be too low to support population expansion. The estimated population growth rate is currently 0.96, though because the associated confidence interval overlapped with 1.0, there is no evidence the population is declining. Instead, evidence indicates a stable population unable to expand. Occupancy analyses indicate that fishers do avoid post-treatment landscape; however, this is likely a temporary behavior. Telemetry monitoring indicated that animals remained in the area and moved around treated areas as long as the treatment area was small relative to overall home range size and corridors for movement were maintained.

Forest Service Partners

External Partners

 
  • ??Richard Sweitzer, Great Basin Institute
  • Benjamin Sacks, University of California Davis, Mammalian Ecology and Conservation unit, Veterinary Genetics Laboratory
  • Bret Furnas, California Department of Fish and Wildlife
  • Deana Clifford, California Department of Fish and Wildlife
  • Greta Wengert, Integral Ecology Research Center
  • J. Mark Higley, Hoopa Tribal Forestry
  • Janet Foley, University of California Davis School of Veterinary Medicine
  • Leslie Woods, California Animal and Food Safety Laboratory, University of California Davis
  • Megan Jones, University of California Davis, Department of Pathology, Microbiology, and Immunology
  • Mourad Gabriel, Integral Ecology Research Center
  • Nicole Stephenson, University of California Davis School of Veterinary Medicine
  • Patricia Gaffney, University of California Davis, Department of Pathology, Microbiology, and Immunology
  • Reginal Barrett, University of California Berkeley
  • Richard Brown, Humboldt State University
  • Robert Poppenga, California Animal and Food Safety Laboratory, University of California Davis
  • Sean Matthews, Oregon State University
  • Stefan Keller, University of California Davis, Department of Pathology, Microbiology, and Immunology
  • Viorel Popescu, Simon Fraser University