title: Holocene changes in the trophic ecology of an apex marine predator in the South Atlantic Ocean.
abstract: Predators may modify their diets as a result of both anthropogenic and natural environmental changes. Stable isotope ratios of nitrogen and carbon in bone collagen have been used to reconstruct the foraging ecology of South American fur seals (Arctocephalus australis) in the southwestern South Atlantic Ocean since the Middle Holocene, a region inhabited by hunter-gatherers by millennia and modified by two centuries of whaling, sealing and fishing. Results suggest that the isotopic niche of fur seals from Patagonia has not changed over the last two millennia (average for the period: δ13C2200-0BP= -13.4 ± 0.5‰, δ15N2200-0BP= 20.6 ± 1.1‰). Conversely, Middle Holocene fur seals fed more pelagically than their modern conspecifics in the Río de la Plata region (δ13C7000BP= -15.9 ± 0.6‰ vs. δ13CPRESENT= -13.5 ± 0.8‰) and Tierra del Fuego (δ13C6400-4300BP= -15.4 ± 0.5‰ vs. δ13CPRESENT= -13.2 ± 0.7‰). In the latter region, Middle Holocene fur seals also fed at a higher trophic level than their modern counterparts (δ15N6400-4300BP= 20.5 ± 0.5‰ vs. δ15NPRESENT= 19.0 ± 1.6‰). Nevertheless, a major dietary shift was observed in fur seals from Tierra del Fuego during the nineteenth century (δ13C100BP= -17.2 ± 0.3‰, δ15N100BP= 18.6 ± 0.7‰), when marine primary productivity plummeted and the fur seal population was decimated by sealing. Disentangling the relative roles of natural and anthropogenic factors in explaining this dietary shift is difficult, but certainly the trophic position of fur seals has changed through the Holocene in some South Atlantic regions.
authors.affiliation: Laboratory of Marine Mammals, Centro para el Estudio de Sistemas Marinos (CESIMAR-CCT CONICET-CENPAT), Blvd. Brown 2915, 9120, Puerto Madryn, Argentina. vales@cenpat-conicet.gob.ar.
authors.forename: Damián G
authors.initials: DG
authors.lastname: Vales
authors.affiliation: IRBio and Department of Evolutionary Biology, Ecology and Environmental Science, Faculty of Biology, University of Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain.|IRBio, Faculty of Biology, University of Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Cardona
authors.affiliation: Centro Austral de Investigaciones Científicas (CADIC-CONICET), Bernardo Houssay 200, 9410, Ushuaia, Argentina.
authors.forename: Atilio F
authors.initials: AF
authors.lastname: Zangrando
authors.affiliation: Instituto de Investigaciones Arqueológicas y Paleontológicas del Cuaternario Pampeano (INCUAPA-CONICET), and Facultad de Ciencias Sociales, UNCPBA, Avenida del Valle 5737, B7400JWI, Olavarría, Argentina.
authors.forename: Florencia
authors.initials: F
authors.lastname: Borella
authors.affiliation: IRBio and Department of Evolutionary Biology, Ecology and Environmental Science, Faculty of Biology, University of Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain.|IRBio, Faculty of Biology, University of Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Saporiti
authors.affiliation: Centro Austral de Investigaciones Científicas (CADIC-CONICET), Bernardo Houssay 200, 9410, Ushuaia, Argentina.|Museo Acatushún de Aves y Mamíferos Marinos Australes, Sarmiento 44, 9410, Ushuaia, Argentina.
authors.forename: R Natalie P
authors.initials: RN
authors.lastname: Goodall
authors.affiliation: Laboratory of Mammal Ecology, Universidade do Vale do Rio dos Sinos (UNISINOS), Av. Unisinos 950, São Leopoldo, 93022-000, Brazil.|Study Group of Aquatic Mammals from Rio Grande do Sul (GEMARS), Av. Tramandaí 976, Imbé, 95625-000, Brazil.
authors.forename: Larissa Rosa
authors.initials: LR
authors.lastname: de Oliveira
authors.affiliation: Laboratory of Marine Mammals, Centro para el Estudio de Sistemas Marinos (CESIMAR-CCT CONICET-CENPAT), Blvd. Brown 2915, 9120, Puerto Madryn, Argentina.|Universidad Nacional de la Patagonia, Blvd. Brown 3600, 9120, Puerto Madryn, Argentina.
authors.forename: Enrique A
authors.initials: EA
authors.lastname: Crespo
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D004463:Ecology; D046069:Fur Seals; D009587:Nitrogen Isotopes; D009752:Nutritional Status
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes
keywords: Arctocephalus australis; Environmental changes; Fur seals; Historical ecology; Hunter-gatherers; Sealing; Stable isotopes