Variations in behavior and condition of a Southern Ocean top predator in relation to in situ oceanographic conditions

*Natural Environment Research Council Sea Mammal Research Unit, Gatty Marine Laboratory, University of St. Andrews, St. Andrews, Fife KY16 8LB, United Kingdom;
^‡Centre d'Etudes Biologiques de Chizé, Centre National de la Recherche Scientifique, Villiers-en-Bois, F-79360 Beauvoir sur Niort, France;
^§Antarctic Wildlife Research Unit, School of Zoology, University of Tasmania, P.O. Box 252-05, Hobart, TAS 7001, Australia;
^¶Center for Ocean Health, Institute of Marine Sciences, Long Marine Laboratory, University of California, 100 Shaffer Road, Santa Cruz, CA 95060;
^‖Laboratoire d'Océanographie Physique Muséum National d'Histoire Naturelle, 43 Rue Cuvier, 75231 Paris Cedex 05, France;
**British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, United Kingdom;
^††Commonwealth Scientific and Industrial Research Organisation (CSIRO) Marine and Atmospheric Research and Antarctic Climate and Ecosystems Cooperative Research Centre, G.P.O. Box 1538, Hobart, TAS 7001, Australia;
^‡‡Antarctic Cooperative Research Centre, University of Tasmania, P.O. Box 252-80, Hobart, TAS 7001, Australia;
^§§Antarctic Ecosystem Research Division, National Oceanic and Atmospheric Administration, 8604 La Jolla Shores Drive, La Jolla, CA 92038; and
^¶¶Valeport Ltd., St. Peter's Quay, Totnes, Devon TQ9 5EW, United Kingdom

Edited by Mary E. Power, University of California, Berkeley, CA, and accepted by the Editorial Board June 18, 2007 (received for review February 8, 2007)

Abstract

Responses by marine top predators to environmental variability have previously been almost impossible to observe directly. By using animal-mounted instruments simultaneously recording movements, diving behavior, and in situ oceanographic properties, we studied the behavioral and physiological responses of southern elephant seals to spatial environmental variability throughout their circumpolar range. Improved body condition of seals in the Atlantic sector was associated with Circumpolar Deep Water upwelling regions within the Antarctic Circumpolar Current, whereas High-Salinity Shelf Waters or temperature/salinity gradients under winter pack ice were important in the Indian and Pacific sectors. Energetic consequences of these variations could help explain recently observed population trends, showing the usefulness of this approach in examining the sensitivity of top predators to global and regional-scale climate variability.

Footnotes

^†To whom correspondence should be sent at the present address:
Norwegian Polar Institute, Plarmiljøsenteret, 9296 Tromsø, Norway.
E-mail: martin.biuw{at}npolar.no
Author contributions: M.B., L.B., C.G., M.H., D. Costa, L.-B.C., F.R., M.M., S.T., Y.-H.P., S.R.R., N.B., M.G., D. Crocker, and M.A.F. designed research; M.B., C.G., J.-B.C., F.R., F.B., Y.T., B.M., M.G., and M.A.F. performed research; M.B. and L.B. analyzed data; M.B., L.B., and M.A.F. wrote the paper; P.L., J.N., F.M., and M.A.F. developed hardware and analytical tools; and S.T. was a key researcher on the United Kingdom component of Southern Elephant Seals as Oceanographic Samplers and provided extensive input into manuscript preparation.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission. M.E.P. is a guest editor invited by the Editorial Board.
This article contains supporting information online at www.pnas.org/cgi/content/full/0701121104/DC1.
Abbreviations:

SO,

Southern Ocean;

CTD-SRDL,

conductivity-temperature-depth satellite relay data logger;

ACC,

Antarctic Circumpolar Current;

SACCF,

Southern ACC Front;

SAF,

Subantarctic Front;

PF,

Polar Front;

AAIW,

Antarctic Intermediate Water;

θ,

potential temperature;

S,

salinity.