Feeding ecology of two wild sympatric canids in protected areas of northeastern Argentina

The role of mesocarnivores in wildlife communities tends to be overlooked, which has led to a large gap in natural history knowledge. In northeastern Argentina, two mesocarnivore foxes, Cerdocyon thous and Lycalopex gymnocercus, live in sympatry in noncompetitive coexistence. Their feeding habits have been studied in many occasions; however, the studies related to trophic variability in a wider spatial scale remain scarce. In this study, we aimed to analyze how the diet of these foxes varies in three protected areas in Argentina: the Mburucuyá National Park (MNP), the “San Nicolás Portal” (SN), and the Natural Reserve Rincón de Santa María (RSM). We collected fecal samples in each area, identified them using thin layer chromatography at species level, and classified the found feeding items to obtained two parameters: occurrence and relative frequency. Furthermore, we compared the diet of the two species in each site and between sites using chi-square and estimated trophic niche breadth and overlap between the species. We found that both species consumed different food categories, with variable frequencies across study sites. We observed that in each area, the foxes differed in diet composition. However, we found no differences between the diet compositions of C. thous and L. gymnocercus, showing high niche overlap in each site. Here, we show the plasticity of both fox species in changing their diets even with small geographical variation. Both species can coexist even with a high diet overlap, possibly explained by their noncompetitive coexistence which may occur due to the current changes in the ecosystem interactions, or partitioning may exist but on a smaller niche level.