Progress 04/01/11 to 06/30/12
Outputs
OUTPUTS: This project funded by the Skagit Valley Wildlife Research Grant Program of Seattle City Light provided funding for a final field season on the project, Western Gray Squirrel: Measure Distribution, Abundance, and Habitat Use in Lake Chelan National Recreation Area, Washington (WNZ-1285). The final report for the primary project is given below: Fieldwork on this project has concluded. A successful dissertation defense was accomplished in May 2012. Reports of work "in progress" for this project were given at several scientific meetings in previous years and for residents of Stehekin and the Methow Valley, Washington. Results of this study were also given at seminars and public presentations at the University of Washington. Papers for publication in scientific journals are in preparation. PARTICIPANTS: Collaborators at the University of Washington included: Dr. Gordon Bradley: UW faculty colleague and graduate committee member. Dr. Lorentz Hauser: UW faculty colleague and graduate committee member. Dr. Joseph Ammirati, project advisor. Dr. Loveday Conquest, statistical consulting. Kathryn D. Stuart, Ph.C. / Ph.D.: graduate student supported by the project. Collaborating individuals outside the University of Washington included: Dr. Mathew Vander Haegen, Washington Department of Fish & Wildlife: graduate committee member. Dr. Kurt Jenkins, USGS, graduate committee member. Robert Kuntz, National Park Service, project advisor. Vicki Gempko, National Park Service, logistical support and radiotelemetry. Dr. James Trappe, Oregon State University, project advisor. Cherrill Bowman, Washington Department of Fish and Wildlife, genetic tissue analysis. Kristin Mansfield and Charles Leathers, Washington Animal Disease Diagnostic Laboratory, Washington State University, necropsies and histology. Dave Volson, U.S. Forest Service, logistical support. John Rohrer. U.S. Forest Service, logistical support. Peter Morrison, Pacific Biodiversity Institute, GIS support. Collaborating organizations included: Washington Department of Fish & Wildlife. School of Environmental and Forest Sciences, University of Washington. School of Aquatic and Fishery Sciences, University of Washington. Department of Biology, University of Washington. Pacific Northwest Cooperative Ecosystem Studies Unit. National Park Service. U.S. Geological Survey. U.S. Forest Service, Wenatchee and Winthrop stations. The Wildlife Society, Washington Chapter. The Methow Conservancy. Pacific Biodiversity Institute. Seattle City Light. Washington Animal Disease Diagnostic Laboratory, Washington State University. TARGET AUDIENCES: Because this study dealt with a state-threatened species on National Park, National Forest, and private lands, its response to ongoing fire fuel reduction plans are of widespread interest. Studied populations were located at the northern periphery of the species range, and before this project were the focus of only one study, one that did not address fire fuel reduction impacts, winter ecology, diet, genetics, or alternative means of information transfer to the public. How these populations compared to others in the state and the northwest were of interest not only to wildlife conservationists and land managers, but the public as well. PROJECT MODIFICATIONS: In the spring of 2011 we expanded the initial study area around Stehekin eastward into the Methow Valley. This was done with financial assistance from the Skagit Valley Wildlife Research Grant Program of Seattle City Light. We expanded the study area to arrive at statistically adequate sample sizes and to extend the project's scope of inference more broadly to the northern population of the squirrel. Study approaches and methodologies were consistent throughout the study.
Impacts
The western gray squirrel (Sciurus griseus) was classified as a Washington State threatened species by the Washington Department of Fish and Wildlife in 1993 due to a decline in range and number. The North Cascades population is geographically and genetically isolated from others in Washington, Oregon, and California, and may be ecologically unique as it exists in a mixed-conifer forest habitat that lacks oak (Quercus spp.): a source of forage and maternal nests in most other portions of the range. The North Cascades are also distinguished by high average annual snowfall and cold temperatures, frequent wildfire and dynamic forest management. Land management agencies have initiated fire fuel reduction plans that may have potentially adverse effects on western gray squirrels. Local populations in Stehekin and the Methow Valley are likely small, making them susceptible to stochastic threats including genetic drift and inbreeding, which reduce evolutionary fitness and increase extinction risk. We studied distribution, life history, and response of squirrels to fire fuel treatments in the North Cascades from 2008-2011 using live trapping, radiotelemetry, and genetic and fecal sampling. Scientific communication between researchers and the general public was evaluated with interviews and an experimental study on the effectiveness of alternate communication methods. Squirrels used fire fuel treated areas disproportionately within their home ranges indicating that recent treatments and wildfires have not negatively affected western gray squirrel habitat at the home range scale. We also found no evidence that treatments and wildfire have negatively affected western gray squirrel diet. Areas used for nesting were characterized by large, tall trees, high levels of dwarf mistletoe infection, high canopy cover and connectivity; all characteristics that can decrease with fire fuel reduction treatments. Future treatments can focus on retaining patches of large trees with some mistletoe infection, and moderate levels of canopy cover and connectivity to conserve western gray squirrel nesting habitat in the North Cascades. Average home range size, degree of overlap, and effective population size indicate that the North Cascades may support a larger population of western gray squirrels than previously thought. Understanding and support for wildlife research increased significantly through science communication.
Publications
- Stuart, K.D. 2012. Ecology and conservation of the western gray squirrel in the North Cascades. Ph.D. Dissertation, University of Washington, Seattle. 239p.
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