Distribution of tree squirrels in California: A species distribution modeling approach to analyzing data
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.