Distribution of Tree Squirrels in California: A Species Distribution Modeling Approach to Analyzing Data

R. Garcia1 , A. Muchlinski2 , F. Shilling3 , H.L. Qiu1 , K. Tiedeman3

1Department of Geosciences and Environment, California State University Los Angeles, CA 2Department of Biological Sciences, California State University, CA 3Department of Environmental Science and Policy, University of California Davis, CA Key Players

Western Gray Squirrel, Eastern Fox Squirrel, Sciurus griseus Sciurus niger rufiventer Western Gray Squirrel (Sciurus griseus) • Found along the forested eastern slopes of the mountains from Washington to California, then westward (except for the California Central Valley) through the coast ranges. Eastern Fox Squirrel (Sciurus(Sciurus niger nigerrufiventer) ) • Found in much of the eastern and central United States extending northward into the southern prairie provinces of Canada. Distribution of Tree Squirrels Wait…. The Eastern Fox Squirrel is here! What is the big issue? • It has been shown that the non-native species replaces (completely) the native species when the two come into contact. Red Squirrel • The American Eastern Gray Squirrel has taken over most of Europe and has mostly replaced the European Red Squirrel.

Hypothesis

• The non-native Eastern Fox Squirrel will have an increasing negative effect on the native Western Gray Squirrel in California. Main Take-Home Points

• The Eastern Fox Squirrel will continue to expand its geographic range in CA • There are populations of the Western Gray Squirrel “in the way” of continued expansion of the Eastern Fox Squirrel • GIS & Remote Sensing are valuable tools to understand future “conflict” between Eastern Fox Squirrels and Western Gray Squirrels in CA Goals for My Study

1: Gather data on the all-time distribution of the non-native and native species within the US 2: Map the distribution of each species in CA 3: Construct and Compare Ecological Niche Models for Each Species Goal 1: Gathering Data, Achieved!

So Far: ~37,000 records, ~29,000 locations Goal 2: Mapping Distribution, Achieved!

• Google Fusion Tables

Western Gray Squirrel

Eastern Fox Squirrel Goal 3: Construct and Compare Ecological Niche Models for Each Species • Use MaxEnt (Maximum Entropy Species Distribution Software) to find suitable habitat • Use ESRI ArcMap to classify the habitat Goal 3: Construct and Compare Ecological Niche Models for Each Species

Landcover gradient

Altitude gradient

Habitat model based on suitable Current Observation landcover and altitude zones in combination with current observations. Goal 3: Construct and Compare Ecological Niche Models for Each Species BIOCLIM data • Altitude • Mean Annual Temperature • Annual Precipitation • Land Cover Type* • Imperviousness* • Tree Canopy* Eastern Fox Squirrel

California Sightings National Sightings Eastern Fox Squirrel to Binary Ecological Niche Model

Apply Binary Threshold S. griseus Model to Binary Ecological Niche Model

Apply Binary Threshold Goal 3: Compare the Ecological Niche Models of the two species.

Eastern Fox Squirrel Western Gray Squirrel Overlap of Both Species

Unsuitable for Both Suitable for Both Suitable for S. niger only Suitable for S. griseus only S. griseus will lose over 99% of its projected niche area

Validation with New Range Maps Validation with New Range Maps Future Work

• Analyzing the importance of certain biotic features that would aid in determining future range (Land Cover Type, Imperviousness, Tree Canopy, NDVI). • Looking at how the model changes due to different time frames. • Determining specific migration areas and rates over time. Hypothesis – Supported!

• The non-native Eastern Fox Squirrel will have an increasing negative effect on the native Western Gray Squirrel in California. Conclusions – Take-Home Points

• The Eastern Fox Squirrel will continue to expand its geographic range in CA • There are populations of the Western Gray Squirrel “in the way” of continued expansion of the Eastern Fox Squirrel • GIS & Remote Sensing are valuable tools to understand future “conflict” between Eastern Fox Squirrels and Western Gray Squirrels in CA Acknowledgements

• Dr. Alan Muchlinski, Dr. Qiu, Dr. Aguilar, Carly Creley, Ruby Alvidrez • Sources of Data: Arctos, CDPH, California Living Museum, California Wildlife Center, Critter Creek, Gold Country Wildlife Rescue, Lindsey Wildlife, Orange County Vector Control, Peninsula Humane Society, SPCA Monterey County, Shasta Rehab, Sonoma County, Squirrelmender, Stanislaus Wildlife Rehab, Suisun Wildlife, Sulphur Creek Nature Center, Tehama Wildcare, Wetlands & Wildlife Care Center, WildCare, Wildlife Center Silicon Valley • Individuals: Fraser Shilling, Janel Ortiz, Julie King, Sheila Byrnes, and private citizens. Questions?

facebook.com/californiatreesquirrels Sciurus niger rufiventer Nationwide Population