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Ontogenetic and sexual characterization of the feeding habits of franciscanas, Pontoporia blainvillei , based on tooth dentin carbon and nitrogen stable isotopes
Author(s) -
Troina Genyffer,
Botta Silvina,
Secchi Eduardo R.,
Dehairs Frank
Publication year - 2016
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/mms.12316
Subject(s) - δ15n , trophic level , stable isotope ratio , isotope analysis , isotopes of nitrogen , δ13c , biology , isotope , zoology , ecology , physics , quantum mechanics
We assessed the feeding habits of franciscanas ( Pontoporia blainvillei ) from southern Brazil through carbon and nitrogen stable isotopes measured in the tooth dentin of dolphins from different age classes. Generalized additive models were fitted to assess whether sex, age, and total body length explained changes in franciscanas isotope ratios. Bayesian isotope mixing models were applied to estimate the contributions of prey items, selected based on stomach content analysis ( SCA ), to franciscanas' diet. Different trophic enrichment factors ( TEF ) were applied and the results were compared using Bhattachayya's coefficient index to test for differences in model outputs and to define the best TEF for franciscanas. We found different relative importance of the main prey between the methods, and the contribution by squids could be lower than suggested by SCA . Because the dentin deposited during nursing seems to influence the isotopic ratios of juveniles, caution is recommended when interpreting dietary estimates based on whole tooth samples. This study is the first to characterize ontogenetic shifts in franciscanas' feeding habits using stable isotope analysis (SIA) and testing different TEF values. SIA and SCA complement each other in dietary studies, mitigating potential biases resulting from the use of each method separately.