Early-life sexual segregation: ontogeny of isotopic niche differentiation in the Antarctic fur seal.
Investigating the ontogeny of niche differentiation enables to determine at which life-stages sexual segregation arises, providing insights into the main factors driving resource partitioning. We investigated the ontogeny of foraging ecology in Antarctic fur seals (Arctocephalus gazella), a highly dimorphic species with contrasting breeding strategies between sexes. Sequential δ(13)C and δ(15)N values of whiskers provided a longitudinal proxy of the foraging niche throughout the whole life of seals, from weaning, when size dimorphism is minimal to the age of 5. Females exhibited an early-life ontogenetic shift, from a total segregation during their first year at-sea, to a similar isotopic niche as breeding females as early as age 2. In contrast, males showed a progressive change in isotopic niche throughout their development such that 5-year-old males did not share the same niche as territorial bulls. Interestingly, males and females segregated straight after weaning with males appearing to feed in more southerly habitats than females. This spatial segregation was of similar amplitude as observed in breeding adults and was maintained throughout development. Such early-life niche differentiation is an unusual pattern and indicates size dimorphism and breeding constraints do not directly drive sexual segregation contrary to what has been assumed in otariid seals.
Deakin University, Geelong, Australia School of Life and Environmental Sciences (Burwood Campus).|Centre d'Etudes Biologiques de Chizé, UMR 7372 du CNRS-Université de La Rochelle, 79360, Villiers-en-Bois, France.
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Kernaléguen
Deakin University, Geelong, Australia School of Life and Environmental Sciences (Burwood Campus).
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Arnould
Centre d'Etudes Biologiques de Chizé, UMR 7372 du CNRS-Université de La Rochelle, 79360, Villiers-en-Bois, France.
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Guinet
Eco-Evolutionary Mathematics, IBENS, Ecole Normale Supérieure, Paris, France.|UMMISCO, Université Pierre and Marie Curie et Institut de Recherche pour le Développement, Bondy, France.
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Cazelles
Littoral Environnement et Sociétés (LIENSs), UMR 7266 du CNRS-Université de la Rochelle, 2 rue Olympe de Gouges, 17000 La Rochelle, France.
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Richard
Centre d'Etudes Biologiques de Chizé, UMR 7372 du CNRS-Université de La Rochelle, 79360, Villiers-en-Bois, France.
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Cherel
D000367:Age Factors; D000818:Animals; D000864:Antarctic Regions; D002247:Carbon Isotopes / Q000378:metabolism; D017753:Ecosystem; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D046069:Fur Seals / Q000502:physiology*; D008297:Male; D009587:Nitrogen Isotopes / Q000378:metabolism; D012621:Seasons; D012737:Sex Factors; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013997:Time Factors; D014738:Vibrissae / Q000378:metabolism
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes