Determining habitat suitability for the western gray squirrel and eastern gray squirrel in California: Predicting future ranges with Maxent and ArcGIS

The main goals of this study were to map the current distribution of the invasive eastern gray squirrel in California as of 2016, to project the potential future geographic range of the species, and to identify areas where the future range of the eastern gray squirrel is likely to overlap the range of the native western gray squirrel. Location data were obtained from museum specimens, wildlife rehabilitation centers, a roadkill database, and research-grade citizen observations. Ecological niche models were created with Maxent, while range and habitat suitability maps were produced with ArcGIS software. Populations of eastern gray squirrels are currently concentrated around Sacramento, the San Francisco Bay, Monterey, and Bellota. The highest priority areas for control and eradication are areas of western gray squirrel habitat near existing eastern gray squirrel populations, including both peninsulas of the San Francisco Bay, areas near Santa Cruz, Oakland, Santa Rosa, and the Monterey Peninsula