Behavioral differences in urban Sciurus carolinensis with varying human exposure as a model for synanthropic human-animal relationships

Synanthropic animals are considered a halfway point between wild and domestic animals that live in urban environments and depend on humans for their survival. Sciurus carolinensis, the eastern gray squirrel, symbolizes a distinctive coexistence between human and wildlife as they are commonly fed in parks and gardens. They are native to the eastern United States. Where they are invasive, they are found only in urban areas and not in rural or wildlife areas. This study examined how different levels of human exposure impact the behavior of S. carolinensis in its non-native range from two different perspectives by using flight initiation distance and feeding surveys. Flight initiation distance (FID) measures the distance at which S. carolinensis begins to flee from an approaching predator or threat and helps us better understand how prey organisms measure threats and assess the trade-offs of the conflicting demands for the need to forage and to avoid predation. Measuring how close S. carolinensis comes for food helps us better understand how they interpret the risk assessment involved with approaching us for food and their commensal relationships with humans. Surveys were conducted at 8 locations in Spokane County, Washington State. FID surveys were conducted on 47 squirrels and feeding surveys were conducted on 42 squirrels. The locations ranged from parks to campuses to represent an urban gradient based on relative number of people. FID increased with starting distance, and it decreased with an increase in human exposure. Locations with fewest humans had the highest measurements of FID. Locations with more humans had the shortest measurements of FID. Squirrels were more likely to take peanuts at locations with more humans and a lower tree density. This may be due to a shift in natural resources to anthropogenic food sources for urban squirrels. Squirrels seem to be more habituated with humans in areas that have more humans and are developing a commensal relationship with us where their natural food sources are declining