Stable isotopes document seasonal changes in trophic niches and winter foraging individual specialization in diving predators from the Southern Ocean

• Published in: Journal of Animal Ecology
• Main Authors: Cherel, Yves, Hobson, Keith, A, Guinet, Christophe, Vanpé, Cécile
• Other Authors: Centre d'Études Biologiques de Chizé (CEBC), Centre National de la Recherche Scientifique (CNRS), Environment Canada, National Wildlife Research Centre, The present work was supported financially and logistically by the ANR Biodiversité REMIGE, the Institut Polaire Français Paul Emile Victor (IPEV, programme no. 109), the Terres Australes et Antarctiques Françaises, and the Canadian Wildlife Service of Environment Canada.
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: fur seal; nonbreeding period; penguin; resource partitioning; trophic level; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Antarctic; Southern Ocean; Antarc*; Antarctic Fur Seals; Antarctica; Crozet Islands; King Penguins
• Online Access: https://ofb.hal.science/hal-04241126; https://ofb.hal.science/hal-04241126/document; https://ofb.hal.science/hal-04241126/file/Cherel%20et%20al.%202007%20Journal%20of%20Animal%20Ecology.pdf; https://doi.org/10.1111/j.1365-2656.2007.01238.x

Climatic variation outside the breeding season affects fluctuations in population numbers of seabirds and marine mammals. A challenge in identifying the underlying biological mechanisms is the lack of information on their foraging strategies during winter, when individuals migrate far from their breeding grounds.We investigated the temporal variability in resource partitioning within the guild of five sympatric Subantarctic penguins and fur seals from Crozet Islands. The stable isotopic ratios of carbon (δ13C) and nitrogen (δ15N) for whole blood were measured for penguins and fur seals, as were the isotopic ratios for penguin nails and food. Animals were sampled at two periods, during breeding in summer and at their arrival in the colonies in spring (hereafter winter, since the temporal integration of blood amounting to several months).In summer, δ13C and δ15N for blood samples defined three foraging areas and two trophic levels, respectively, characterizing four nonoverlapping trophic niches. King penguins and female Antarctic and Subantarctic fur seals are myctophid eaters foraging in distinct water masses, while both macaroni and rockhopper penguins had identical isotopic signatures indicating feeding on crustaceans near the archipelago.Isotopic ratios were almost identical in summer and winter suggesting no major changes in the species niches, and hence, in the trophic structure of the guild during the nonbreeding period. A seasonal difference, however, was the larger variances in δ13C (and also to a lesser extent in δ15N) values in winter, thus verifying our hypothesis that trophic niches widen when individuals are no longer central place foragers.Winter isotopic ratios of macaroni penguins and male Antarctic fur seals had large variances, indicating individual foraging specializations. The range of δ13C and δ15N values of male fur seals showed, respectively, that they dispersed over a wide latitudinal gradient (from Antarctica to north of the archipelago) and fed on different prey (crustaceans and fish).By ...