Mantani, Kara (2010)
An ecological survey of the displacement of Western Gray Squirrels (Sciurus griseus) by Eastern Fox Squirrels (Sciurus niger) in the Claremont, California area.
Bachelor of Arts, Claremont McKenna College, Biology.
Advisor: Dan Guthrie.
The eastern fox squirrel (Sciurus niger) is a non-native tree squirrel species that has bred successfully across the West Coast. In the past few decades, S. niger has proven especially detrimental as an invasive species in Southern California, drastically affecting populations of the native western gray squirrel (Sciurus griseus). The aim of this study was to track the populations of S. niger and S. griseus at multiple study sites in and around Claremont, California. Coexistent and replacement sites were observed from June 2010 through October 2010. The coexistent sites were previously determined to support stable populations of both S. niger and S. griseus. These sites were mapped to validate that they continued to support stable populations of both species. Both species were mapped at the replacement sites, and the rate of expansion of S. niger was measured. At Evey Canyon, which showed the most expansion in four months, S. niger moved 351.13 meters in 121 days, or a rate of 1058.8 meters per year. This study allows us to see where conservation efforts must be focused before total replacement of S. griseus takes place. It also provides detailed maps that will enable continued research of S. niger’s expansion in the Claremont area.