Anthropogenic food use and diet overlap between red foxes (Vulpes vulpes) and arctic foxes (Vulpes lagopus) in Prudhoe Bay, Alaska

Red foxes (Vulpes vulpes (L., 1758)) recently expanded into the oil fields at Prudhoe Bay, Alaska, USA, and we hypothesized that the availability of anthropogenic foods may contribute to their success and persistence there. This study assessed the importance of anthropogenic foods to the diets of red foxes and arctic foxes (Vulpes lagopus (L., 1758)), and competition for food resources between the two species in Prudhoe Bay. We used stable isotope analysis of fox tissues to infer diet during summer and winter for both red and arctic foxes, and lifetime diet for red fox. While the contribution of anthropogenic foods in late summer for both species' diets was low (similar to 10% to 15%), the contribution in late winter was higher and varied between species (red foxes = 49%; arctic foxes = 39%). Estimates of lifetime diet in red foxes suggest consistent use of anthropogenic foods. We found moderate overlap of fox diets, although red foxes appeared to be more specialized on lemmings, whereas arctic foxes had a more diverse diet. Availability and consumption of anthropogenic foods by red foxes, particularly in winter, may partially explain their year-round presence in Prudhoe Bay.