, Volume 158, Issue 10, pp 2209-2217
Date: 04 Jun 2011

Use of multiple tools to assess the feeding preference of coastal dolphins

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The feeding preferences of the coastal dolphins Pontoporia blainvillei and Sotalia guianensis in south-eastern Brazil (21º18′S–22º25′S) were assessed through the prey’s index of relative importance (IRI), total mercury concentration (Hgtot), and stable isotopic (δ15N and δ13C) to compare their efficiency in the discrimination of prey contribution to the predators’ diet. The IRI was the best tool to describe the dolphins’ preference, while Hgtot and δ15N seemed to be efficient as a trophic marker when the diet is made up of prey of varying sizes, as observed in S. guianensis. Both dolphins presented lighter δ15N than their prey species, which is an unusual pattern. However, as the sample size to isotope ratios analysis was small, especially to the dolphins, the results should be considered with caution, and further studies are necessary to corroborate these findings. The δ13C values characterized a typical coastal food chain, confirming the preferential area of these species.

Communicated by C. Harrod.