Eastern Gray Squirrel Ecology and Interactions with Western Gray Squirrels

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Eastern Gray Squirrel Ecology and Interactions
with Western Gray Squirrels
Photo Rod Gilbert
Photo Mary Linders
Aaron Johnston School of Forest Resources
University of Washington
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Eastern Gray Squirrel
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Western Gray Squirrel
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Current Distribution of Western Gray Squirrels
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Objective Investigate competition

• Are they competing?
• Test for competitive effects
• How are they competing?
• Describe and compare components of the niche

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Niche
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Resource Partitioning
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Competitive Exclusion Principle
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Competition
Interference
Exploitation
Photo David J. Slater
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Ideal Free Distribution
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Equilibrium
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Density Dependent Habitat Selection
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Methods
Photo Danielle Reese
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Utilization Distributions
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Measuring Spatial Overlap
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t15 5.36, P 0.0001
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Utilization Distributions
F3,30 2.89, P 0.052
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Habitat Analysis
H0 There is no difference between eastern and
western gray squirrels in their selection of
habitat.
Habitat Plots
GIS Layers
Nest Plots
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Methods Habitat measurements
COMPOSITION
STRUCTURE
DIVERSITY
OVERSTORY
UNDERSTORY
Habitat Plot
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F7,152 8.6, P lt 0.001
ebh enh enl ebl wnl wbh wbl wnh
2.64 2.58 1.97 1.77 1.25 1.13 1.04 0.98
     
         
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Methods Removal Experiment

• Randomized block design
• Site Experimental unit
• Removal treatment assigned randomly to a set of
  sites in 2009 and another set in 2010

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t16 0.133, P 0.896
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Hmmm
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Acknowledgements
WDFW Gene Orth, Matt Vander Haegen, Caitlin
McIntyre, AnnMarie Prince, Mary Linders Fort
Lewis Todd Zuchowski, Dave Clouse Nature
Conservancy Cheryl Fimbel, Sanders
Freed Volunteers Danielle Reese, Val Filer,
Sara Gregory, Amy Stratton, Scotty Hardwick,
Cindi Perez, Tadd Wheeler, Rachel Lipsky, Jesse
McCarty Committee Steve West, Matt Vander
Haegen, John Marzluff, Josh Lawler, Jim Kenagy
Photo Danielle Reese
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Photo Danielle Reese