Trophic niche and habitat use of two sympatric endemic dolphin species from Patagonia, Argentina.

LOIZAGA DE CASTRO, R.; CRESPO, E.A.; DURANTE, C. A.

Viña del Mar

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

Dolphin species that lives in sympatry frequently requires some degree of resourcespartitioning, di􀃗ering in diet and habitat use patterns as a strategy for coexistence. In thesouthwestern Atlantic Ocean, Commerson?s and Peale?s dolphins use di􀃗erent habitats bothinshore and o􀃗shore, such as open ocean, rivers mouths, deep bays and kelp forests. Stomachcontent analysis suggests that both species feed mainly on pelagic and demersal _sh andcephalopods. While most preys are shared they di􀃗er in the principal prey items. In order tounderstand the trophic relationships between these species, the aim of this study is todeterminate the trophic niche and habitat use of two endemic dolphins that lives in sympatryalong the Argentine Sea. Stable carbon and nitrogen isotope ratios were analysed of 14 and 23skin biopsies of Commerson?s and Peale?s dolphins, respectively, sampled in December 2007 to2009 in southern Chubut, Argentina (45º 04? 34.5??S, 65º 38? 37.2??W). Signi_cant di􀃗erences inboth δ15N and δ13C were found between species. In particular, Peale?s dolphins showed twoecotypes segregated in habitat. δ13C di􀃗erence suggested the spatial partitioning in depth ordistance from shore inter and intraspeci_c, being the Commerson?s dolphins and Peale?sdolphins ecotype1 more pelagic/o􀃗shore and the Peale´s dolphin ecotype2 morebenthic/inshore. Isotopic niche width varied between species and ecotypes. Commerson?sdolphins 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 apartitioned use of resources between these two small cetacean species living in sympatry.Moreover, the Peale?s dolphins seem to have two di􀃗erent foraging strategies in a small areapromoting the coexistence and reducing intra/inter speci_c competition. To our knowledge,this is the _rst study characterizing the trophic niche and habitat use of Peale?s andCommerson?s dolphins living in sympatry along the Patagonia, Argentina.