College squirrels gone wild? Using Sciurus carolinensis behavior to assess the ecosystem value of urban green spaces

Predicted rapid increases in urbanization in the face of accelerating biodiversity loss underscores the need for urban development that promotes, rather than displaces, native plants and animals. One approach for increasing urban biodiversity is through the development of “green infrastructure”. Although research has explored urban-rural gradients and the overall value of urban green infrastructure, few studies have investigated the habitat value for wildlife of different types of urban greenspace. Here, we use a well-established metric in ecology, giving up-densities (GUDs), to compare foraging costs for a common urban wildlife species, the eastern gray squirrel ( Sciurus carolinensis ), among three green infrastructure categories: municipal parks, college campuses, and residential yards. We found that GUDs for gray squirrels did not differ significantly among location categories after controlling for proximity to roads, but proximity to roads was associated with significantly higher GUDs in all locations. In an explicit test, we also found that both proximity to roads and traffic volume were associated with higher GUDs. We also found that maximum distance from roads was significantly higher for campuses and parks than for residential yards, indicating a greater proportion of the area of campuses and parks is “away from roads” compared to residential yards. Our results indicate that vehicle traffic may contribute significantly to an “urban landscape of fear” for gray squirrels and suggest that campus and park configurations that reduce road effects could improve habitat quality for squirrels and possibly other animals.