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Ontogenetic changes in feeding habits of northern elephant seals revealed by δ15N and δ13C analysis of growth layers in teeth

Abstract:

Stable isotope analysis is useful for examining the feeding strategies of mammals. Isotopes in the annual deposition growth layers of dentine in teeth permit assessment of ontogenetic dietary shifts in individuals, because this metabolically inert tissue is not resorbed after deposition. Profiles of stable isotope ratios of nitrogen (δ 15 N) and carbon (δ 13 C) from the teeth of northern elephant seals Mirounga angustirostris, aged between 1 and 11 yr, were described from stranded individuals in San Benito and Magdalena Islands, Mexico, between 2000 and 2009. δ 13 C and δ 15 N values differed with age in each sex indicating shifts in feeding habits throughout life, as well as in their physiological condition. Although steady δ 13 C values within each individual suggest fidelity to feeding grounds, differences in δ 13 C values between males and females were likely a reflection of sexual segregation on the feeding areas …