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Dietary variation within and between populations of northeast Atlantic killer whales, Orcinus orca, inferred from δ13C and δ15N analyses

Authors

  • Andrew D. Foote ,

    Corresponding author
    1. Institute of Biological and Environmental Sciences, University of Aberdeen, School of Biological Sciences, Tillydrone Avenue, Aberdeen, AB24 2TZ, United Kingdom, and Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, 1350 Copenhagen K, Denmark
      (e-mail: afoote@snm.ku.dk).
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  • Heike Vester ,

    1. Ocean Sounds, Hjellskaeret, 8312 Henningsvaer, Norway, and Cognitive Ethology Lab, German Primate Center, Kellnerweg 4, 37077 Göttingen, Germany, and Max Planck Institute for Dynamics and Self-Organization, Bunsenstraße 10, 37073 Göttingen, Germany
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  • Gísli A. Víkingsson ,

    1. Marine Research Institute, Program for Whale Research, PO Box 1390, 121 Reykjavík, Iceland
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  • Jason Newton

    1. NERC Life Sciences Mass Spectrometry Facility, SUERC, East Kilbride, G75 0QF, United Kingdom.
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(e-mail: afoote@snm.ku.dk).

Abstract

Epidermal skin samples from eastern North Atlantic killer whales, Orcinus orca, were analyzed for carbon and nitrogen stable isotope ratios. From those, comparisons within a data set of 17 samples collected from Tysfjord, Norway, in November suggested that diet is relatively specialized during this time period at this location. There were significant differences between a small set of samples from Iceland and those collected from Norway, which had all been assigned to the same population by a previous population genetics study. The results would be consistent with matrilines feeding on either the Norwegian or Icelandic stocks of Atlantic herring (Clupea harengus). There was no significant difference within Icelandic samples between those assigned to the population known to feed upon herring and those assigned to a population hypothesized to follow Atlantic mackerel (Scomber scombrus). The greatest differences were between the epidermal samples analyzed in this study and tooth and bone collagen samples from the North Sea that were analyzed previously, which also showed significantly more variation in isotopic ratios than found for skin samples. These differences could reflect differences in turnover rate, differences in diet-tissue fractionation and discrimination due to the amino acid composition of the different tissues, and/or greater competition promoting dietary variation between groups in the North Sea.

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