Stable isotopes (δ15N, δ13C, δ34S) in skin reveal diverse food sources used by Southern right whales Eubalaena australis

Abstract

Skin samples collected from living Southern right whales (SRWs) off Península Valdés, Argentina, show a wide range of stable isotope values (δ15N, δ13C, δ34S). These were compared to the isotopic signatures of euphausiids and copepods from different areas across the Southwestern South Atlantic and the Atlantic sector of the Southern Ocean. Our results suggest that that this population of SRWs uses at least 3 distinct food sources. Each food source May represent a single feeding ground or a combination of feeding grounds with different prey species distributions. Individual whales pursue foraging strategies that vary substantially in the amounts of time they spend in different feeding grounds along their migratory paths. The 3 grounds that appear to contribute most to the diets of Península Valdés SRWs correspond to areas previously documented in the log books of whaling ships: the Patagonian Shelf, South Georgia and the waters of the Polar Front. It is possible that additional feeding areas are also currently being used in the South Atlantic. Age and sex classes differ isotopically, but these differences could be caused by biomechanical or physiological characteristics rather than by age- and sex-specific specialization in different feeding areas.