Shift in foraging ground and diet broadening during ontogeny in southern elephant seals from Kerguelen islands

• Published in: Marine Biology
• Main Authors: Chaigne, Adrien, Authier, Matthieu, Richard, Pierre, Cherel, Yves, Guinet, Christophe
• Other Authors: Centre d'études biologiques de Chizé (CEBC), Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: geo; envir; Antarctic; Kerguelen; Kerguelen Islands; Antarc*; Elephant Seals; Mirounga leonina; Southern Elephant Seals
• Online Access: https://doi.org/10.1007/s00227-012-2149-5; https://hal.archives-ouvertes.fr/hal-00624915

International audience Highly dimorphic species like southern elephant seals (Mirounga leonina, SES hereafter) frequently exhibit resource partitioning according to sex and/or age classes. We measured carbon and nitrogen stable isotopes (δ13C and δ15N) of 404 blood samples (136 males and 268 females from Kerguelen Islands, 49°21′S, 70°18′E) from 2004 to 2011. Assuming that the distribution of carbon isotopes (δ13C value) reflects the two main foraging grounds (Polar Frontal and Antarctic Zones), we quantified the proportion of SES foraging within each zone in relation with size, a proxy for their age. We found a clear shift from Polar Frontal to Antarctic waters as male SES aged, but no relation as far as females is concerned. We also observed a widening range of nitrogen isotopic (δ15N) values, suggesting that both males and females expanded their diet spectra with age. Whereas males increased their trophic level, females remained constant on average, with some adult females feeding both at lower and at higher trophic levels than juveniles.