Stable isotopes point to anthropogenic subsidies in northern raccoons at the urban-wild interface
2022
Nicholson, Molly | Cove, Michael V.
Increasing availability of anthropogenic food affects biological communities and can alter food webs at the urban interface. Although northern raccoons (Procyon lotor) are known to associate with anthropogenic environments, little research has been conducted examining the differences in raccoon diets across urban-wild gradients. The Florida Keys present a unique study system because they vary in levels of urbanization interspersed with wildlife refuges and natural habitats. We collected hair samples from the tails of road killed raccoons in undeveloped natural areas in Key Largo, highly developed areas in Big Pine Key, and from individuals caught in a trapping array from natural areas on Big Pine Key for analyses of carbon and nitrogen stable isotope ratios. We observed limited variation in δ¹⁵N ratios across the three different raccoon groups, but we did note slightly higher δ¹⁵N in raccoons from natural areas on Big Pine Key, suggesting more predatory behavior. However, we observed marked differences in the δ¹³C ratios of raccoons from natural areas in Key Largo and Big Pine Key as compared to individuals occurring in highly developed parts of Big Pine Key. These enriched carbon signatures correspond with human foods derived from corn (C4 plants) in the urban raccoons. Our results reveal that raccoons in developed areas benefit from the consumption of human-derived subsidies, but it might further put them at risk from conflict and vehicular strikes.
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