PARENT SESSION
Poster Session #69: Animal Ecology.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Are city slickers nuts? Diet selection and food cacheability in urban versus natural squirrel populations.

Burke, Anna^*,1, van der Merwe, Marius¹, Brown, Joel¹, ¹ University of Illinois at Chicago, Chicago, IL

ABSTRACT- We measured the foraging responses of urban and natural populations of fox squirrels, Sciurus niger, to microhabitat (near and away from trees), and on a cacheable vs. non-cacheable food (hazelnuts with and without shells, respectively). Urban squirrels seem to win twice over their natural counterparts; they have more food and experience less predation. And indeed, urban populations achieve much higher densities than natural populations. Natural squirrel populations have lower densities and encounter higher levels of predation. Therefore, urban squirrels should be more food-limited than natural squirrel populations. To test this hypothesis, we measured the giving-up densities (GUDs) of fox squirrels on hazelnuts in Oak Park, IL (urban) and the Morton Arboretum, Lisle, IL (natural). We predicted the urban squirrels would have lower overall GUDs, show less of a distinction between safe and risky microhabitat, and have a higher preference for cacheable relative to non-cacheable hazelnuts. "Urban" squirrels had 12% lower GUDs than "natural" squirrels. Overall, squirrels preferred safe microhabitats over the risky. Contrary to predictions there was no interaction between microhabitat and location. Squirrels at both locations showed a strong preference for cacheable nuts (cacheable hazelnut GUDs were 14% lower than non-cacheable GUDs), but there was no interaction between cacheability and location. The differences in foraging behavior of the urban squirrels relative to the natural population suggests that they perceive their environment to consistently have a lower supply of food.

KEY WORDS: Sciurus niger, foraging, GUDs