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Stable isotope profiles in sperm whale teeth: variations between areas and sexes

Published online by Cambridge University Press:  04 April 2007

Sónia Mendes
Affiliation:
School of Biological Sciences (Zoology), University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
Jason Newton
Affiliation:
NERC Life Sciences Mass Spectrometry Facility, SUERC, East Kilbride, G75 0QF, UK
Robert J. Reid
Affiliation:
Wildlife Unit, SAC Veterinary Services, Drummondhill, Stratherrick Road, Inverness, IV2 4JZ, UK
Alexandros Frantzis
Affiliation:
Pelagos Cetacean Research Institute, Terpsichoris 21, 16671 Vouliagmeni, Greece
Graham J. Pierce
Affiliation:
School of Biological Sciences (Zoology), University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK

Abstract

Sperm whale (Physeter macrocephalus) teeth were used to investigate whether variation in the chronological profiles of carbon and nitrogen stable isotope ratios along dentine growth layers could reflect differences in ontogenetic movements and/or dietary shifts in animals from different regions and sexes, as well as to show the differences in the isotopic environments experienced by these animals. Absolute isotopic ratios ranged from -14.1 to -11.0‰ for carbon and 10.8 to 18.1‰ for nitrogen, with the whale from the Indian Ocean, the two from the Mediterranean Sea and the female from the Azores presenting the most different median isotopic ratios. The Icelandic and the Indian Ocean males showed the expected decrease in δ13C around the age of ten, denoting male segregation from natal groups. For the latter, this was larger by almost twofold compared to other teeth, probably due to the much stronger latitudinal gradient in planktonic δ13C in the southern hemisphere. The Mediterranean Sea whales exhibited the lowest median δ15N values, probably reflecting the oligotrophy of this sea, while the male showed a marked change in isotopes around the age of 20 that could indicate a move to the eastern basin or a temporal change in basal isotopic signatures. The Atlantic females did not show a marked change in δ13C as expected since they stay in low latitudes throughout their lives. Stable isotope profiles in whale teeth can be used to investigate differences in the timings of ontogenetic movements and dietary history between individuals and sexes, and the biogeochemistry of different regions inhabited, and have the potential to allow inferences to be made about population substructure.

Type
Research Article
Copyright
2007 Marine Biological Association of the United Kingdom

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