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Marine Biology

, 166:32 | Cite as

Individual foraging specialization and sexual niche segregation in South American fur seals

  • Renan C. de LimaEmail author
  • Valentina Franco-Trecu
  • Damián G. Vales
  • Pablo Inchausti
  • Eduardo R. Secchi
  • Silvina Botta
Original paper

Abstract

Individual variation in habitat and resource use has been reported for many top predators. This variation becomes important when comparing individuals taking into account sex, size, or age classes, since it can influence population dynamics and stability. We evaluated the individual variation and sexual/geographical isotopic niche overlap of the South American fur seal (SAFS) from the western South Atlantic. Whiskers of adult individuals from Brazil (n = 19), Uruguay (n = 29), and Argentina (n = 5) collected between 2005 and 2016 were serially sampled, resulting in 1001 samples, and their carbon and nitrogen isotopic ratios were analyzed longitudinally. According to its length, time integrated by whiskers ranged between 1.4 and 5.6 years. Males had δ13C (− 14.5 ± 0.6‰) and δ15N (18.9 ± 1.2‰) values significantly higher than females (δ13C = − 15.2 ± 0.5‰, δ15N = 17.8 ± 1.2‰). Females from Uruguay and Brazil were isotopically similar, displaying a large isotopic niche overlap (65.2–84%). Contrary, moderate isotopic niche overlaps were observed between males from Uruguay and Brazil (40.1–48.4%), and Uruguay and Patagonia (22.3–27.8%), indicating the use of different prey and/or feeding grounds. The WIC/TNW index of individual specialization pointed a significant specialization in males (0.38 for δ15N and 0.39 for δ13C). Females, on the other hand, are more generalists compared to males (0.53 and 0.71, for δ15N and δ13C, respectively). Differences in the ecological opportunity between sexes can account for these variations. Our study points out that trophic generalist populations of SAFS are composed of specialist and generalist individuals.

Notes

Acknowledgements

We would like to thank all researchers, students, and volunteers from Laboratório de Ecologia e Conservação da Megafauna Marinha/EcoMega-FURG who participated in data collection. Financial support was provided by ONG Yaqu Pacha and Comisión Sectorial Investigación Científica—UdelaR (Uruguay). National Council for Research and Technological Development (CNPq) provided a research fellowship to ERS (PQ 307846/2014-8). Our grateful thanks to Leandro Bugoni, Márcio Araújo, Danielle Monteiro, and the two anonymous reviewers for their helpful comments on the manuscript. Coordination for the Improvement of Higher Education Personnel (CAPES) provided a scholarship to RCL. This article is part of RC de Lima’s Master of Science Dissertation in Biological Oceanography (IO-FURG, RS, Brazil) under the supervision of SB and ERS, and is a contribution of the research group Ecologia e Conservação da Megafauna Marinha-EcoMega/CNPq.

Compliance with ethical standards

Conflict of interest

DINARA (National Council for Aquatic Resources, Ministry of Livestock, Agriculture and Fishing, Uruguay) allowed access to the field sites and facilities during 2009 and 2010 (permits 572/2008 and 1022/2010). The authors declare that they have no conflict of interest.

Supplementary material

227_2019_3480_MOESM1_ESM.pdf (1.3 mb)
Supplementary material 1 (PDF 1284 kb)

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Renan C. de Lima
    • 1
    • 2
    Email author
  • Valentina Franco-Trecu
    • 3
  • Damián G. Vales
    • 4
  • Pablo Inchausti
    • 5
  • Eduardo R. Secchi
    • 1
    • 2
  • Silvina Botta
    • 1
    • 2
  1. 1.Laboratório de Ecologia e Conservação da Megafauna Marinha, Instituto de OceanografiaUniversidade Federal do Rio GrandeRio GrandeBrazil
  2. 2.Programa de Pós-Graduação em Oceanografia BiológicaUniversidade Federal do Rio GrandeRio GrandeBrazil
  3. 3.Departamento de Ecología y Evolución, Facultad de CienciasUniversidad de la RepúblicaMontevideoUruguay
  4. 4.Laboratorio de Mamíferos MarinosCentro para el Estudio de Sistemas Marinos (CESIMAR, CONICET)Puerto MadrynArgentina
  5. 5.Centro Universitario Regional del EsteUniversidad de la RepúplicaMaldonadoUruguay

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