PS 60-210
Distribution of tree squirrels in California: A species distribution modeling approach to analyzing data
Wednesday, August 12, 2015
Exhibit Hall, Baltimore Convention Center
Rosemary B. Garcia, Department of Geosciences and Environment, California State University, Los Angeles, Los Angeles, CA
Alan Muchlinski, Department of Biological Sciences, California State University, Los Angeles, Los Angeles, CA
Hong-Lie Qiu, Department of Geosciences and Environment, California State University, Los Angeles, Los Angeles, CA
Frasier M. Shilling, Department of Environmental Science and Policy, University of California, Davis, Davis, CA
Kate Tiedeman, Department of Environmental Science and Policy, University of California, Davis, Davis, CA
Background/Question/Methods: Providing an accurate and detailed description of the distribution of a species within a defined geographic area is challenging. Past distribution maps have been dependent on museum specimens and are not frequently revised. Also, invasive species tend to be underrepresented in museum collections. In this study, we describe a new method for establishing the current and historical range of a native and introduced species of tree squirrel in California using species habitat modeling software (MaxEnt). The method involves the collection of location data from wildlife rehabilitation facilities, museum collections, a personalized smartphone application, and other citizen reported records. We provide geographic range for the Eastern Fox Squirrel (
Sciurus niger) and the Western Gray Squirrel (
Sciurus griseus) in California. Large sample sizes over a specified geographic area allow for detailed mapping of the distribution of each species. In addition, assessments related to habitat use and future range expansion were made using GIS software (ArcGIS).
Results/Conclusions: Current data show three large populations of S. niger within California. The first population extends north, south, and east of San Francisco, the second population extends north, south, and east of Los Angeles and a third major population extends in all directions from Sacramento. Other isolated populations also exist within the state. Sciurus griseus has been displaced from areas now dominated by S. niger. Preliminary data analysis of the distributions show a high correlation with land cover type and impervious surfaces. Preliminary analysis also suggests that the population from the San Francisco area will join with the population from Sacramento to form one large metapopulation. The model suggests paths that S. niger may use to eventually connect the Northern and Southern Populations, along with suitable paths that may connect other smaller currently established but isolated populations. The distribution map for S. griseus shows that there are populations in the paths of range expansion for S. niger. This suggests additional populations of S. griseus will be displaced over time.
