Food subsidies of raccoons (Procyon lotor) in anthropogenic landscapes

Abstract

Food subsidies from human sources are often exploited by free-ranging vertebrates living in human-dominated landscapes. To explore the importance and attempt to estimate the reliance of raccoons (Procyon lotor (Linnaeus, 1758)) — common synanthropes in North America — on such food subsidies, we analyzed hair samples from 122 raccoons collected across four states in the Midwestern United States (Wisconsin, Minnesota, Iowa, and Illinois), including 9 raccoons that were livetrapped and sampled in Madison (Wisconsin). We found that raccoons inhabiting areas with more agriculture had higher δ13C values, indicating a diet enriched with anthropogenic food from C4 photosynthetic plants, like corn (Zea mays L.). Surprisingly, raccoons inhabiting increasingly urban areas showed lower δ13C values, suggesting a diet with less anthropogenic food. Regardless, raccoons in urban areas enriched in 13C possessed high indices of body condition, suggesting that anthropogenic food subsidies are contributing to their overall nutritional condition. Our findings reveal that the degree to which synanthropes rely upon human foods differs by land-cover type and that the use of these calorically rich subsidies has important implications on individual health.