Isotopic variation in delphinids from the subtropical western South Atlantic

A dual stable isotope approach (delta C-13 and delta N-15) was used to investigate inter-and intra-specific variations in feeding ecology and habitat use of 7 delphinids from coastal/estuarine, continental shelf and offshore marine environments from southern Brazil: Tursiops sp., Orcinus orca, Stenella frontalis, Steno bredanensis, Delphinus delphis, Pseudorca crassidens and Lagenodelphis hosei. Teeth from 50 specimens acquired from stranded animals were analysed in this study. Tursiops sp. and O. orca are the most coastal species, and had the highest delta C-13 values followed by the continental shelf species S. frontalis, S. bredanensis and D. delphis. Lagenodelphis hosei showed the lowest delta C-13 value, demonstrating its typical offshore habitat. One group of P. crassidens had the lowest delta N-15 values, indicating their low trophic level feeding habit while two specimens of the same species showed the highest mean nitrogen isotope value. This first study on stable isotope values of delphinids from southern Brazil provides substantial new information about the trophic ecology, habitat use and feeding environments of these animals.