TROPHIC NICHE AND HABITAT USE OF TWO SYMPATRIC ENDEMIC DOLPHIN SPECIES FROM PATAGONIA, ARGENTINA.

DURANTE CRISTIAN ALBERTO; LOIZAGA DE CASTRO ROCIO; CRESPO ENRIQUE ALBERTO

Viña del Mar

Congreso; 11th International Conference on the Applications of Stable Isotope Techniques to Ecological Studies (IsoEcol 2018); 2018

Dolphin species that lives in sympatry frequently requires some degree of resources partitioning, differing in diet and habitat use patterns as a strategy for coexistence. In the southwestern Atlantic Ocean, Commerson?s and Peale?s dolphins use different habitats both inshore and offshore, such as open ocean, rivers mouths, deep bays and kelp forests. Stomach content analysis suggests that both species feed mainly on pelagic and demersal fish and cephalopods. While most preys are shared they differ in the principal prey items. In order to understand the trophic relationships between these species, the aim of this study is to determinate the trophic niche and habitat use of two endemic dolphins that lives in sympatry along the Argentine Sea. Stable carbon and nitrogen isotope ratios were analysed of 14 and 23 skin biopsies of Commerson?s and Peale?s dolphins, respectively, sampled in December 2007 to 2009 in southern Chubut, Argentina (45º 04? 34.5??S, 65º 38? 37.2??W). Significant differences in both δ15N and δ13C were found between species. In particular, Peale´s dolphins showed two ecotypes segregated in habitat. δ13C difference suggested the spatial partitioning in depth or distance from shore inter and intraspecific, being the Commerson´s dolphins and Peale´s dolphins ecotype1 more pelagic/offshore and the Peale´s dolphin ecotype2 more benthic/inshore. Isotopic niche width varied between species and ecotypes. Commerson´s dolphins presented lower inter-individual variation (SEAc=0.28?2), following by ecotype1 (SEAc=0.39?2) and ecotype2 (SEAc=1,31?2) of Peale´s dolphins. The results indicated a partitioned use of resources between these two small cetacean species living in sympatry. Moreover, the Peale´s dolphins seem to have two different foraging strategies in a small area promoting the coexistence and reducing intra/inter specific competition. To our knowledge, this is the first study characterizing the trophic niche and habitat use of Peale´s and Commerson´s dolphins living in sympatry along the Patagonia, Argentina.