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Brault EK, Koch PL, Costa DP, McCarthy MD, Hückstädt LA, Goetz KT, McMahon KW, Goebel ME, Karlsson O, Teilmann J, Harkonen T, Harding KC
Trophic position and foraging ecology of Ross, Weddell, and crabeater seals revealed by compound-specific isotope analysis
Bulk stable isotope analysis has become a common tool to assess foraging ecology of pinnipeds. However, consumer bulk stable isotope values not only reflect trophic dynamics, but also variations in baseline isotope values. Brault et al. used compound specific isotope analysis of amino acids (CSI-AA) to separate isotopic effects of a shifting baseline versus trophic structure on the foraging ecology of Antarctic pinnipeds. They found that crabeater and Weddell seals forage within similar food webs closer to shore whereas Ross seals forage in a distinct open ocean food web. Additionally, their CSI-AA data indicated that Ross seals have a high trophic position equivalent to that of Weddell seals, which differs from conclusions of nitrogen isotope results on bulk tissues.