Isotopic niche of the Neotropical otter, Lontra longicaudis (Carnivora, Mustelidae), in different coastal aquatic systems in southern Brazil

The Neotropical otter, Lontra longicaudis, is an opportunistic species usually found in freshwater habitats; however, it has also been recorded in environments with marine influence (e.g., islands and estuaries). Thus, we hypothesized that the isotopic niche of the Neotropical otter is wider in a coastal island (Santa Catarina Island—SC) and in a river basin composed of a series of lagoons and an estuary (Tramandaí River Basin—RS) than in a wetland (Taim Wetland—RS) due a greater occurrence of the species in the marine environment of the former areas. In order to test this hypothesis, the stable isotope ratios of carbon and nitrogen in otter samples from different regions were analyzed. Long-term isotopic niche of otters was wider in Santa Catarina Island, followed by Taim Wetland, and Lagunar System of Tramandaí. Therefore, we conclude that otters from Santa Catarina Island and Taim Wetland use both freshwater and marine environments as foraging areas. The sampled otters of the Lagunar System of Tramandaí, on the other hand, used predominantly freshwater environments to forage. The differences found among the otters from different regions are probably related to a variety of factors, such as landscape characteristics, sampling and prey availability.