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The influence of body size on dive duration of underyearling southern elephant seals (Mirounga leonina)

Published online by Cambridge University Press:  01 August 2000

Lyn G. Irvine
Affiliation:
Institute of Antarctic and Southern Ocean Studies, University of Tasmania, P.O. Box 252C, Hobart, Tasmania 7001, Australia Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia.
Mark A. Hindell
Affiliation:
Department of Zoology, University of Tasmania, P.O. Box 252C, Hobart, Tasmania 7001, Australia
John van den Hoff
Affiliation:
Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia.
Harry R. Burton
Affiliation:
Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia.
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Abstract

The dive duration of 16 underyearling (6–12 months old) southern elephant seals Mirounga leonina during their second trip to sea was investigated using geolocating time–depth recorders. Underyearling seals had a lesser diving ability, with respect to duration and depth, than adult southern elephant seals. Individual underyearlings dived for average durations of up to 20.3 min and depths up to 416 m compared to durations and depths of 36.9 min and 589 m, respectively for adults. Dive duration was positively related to their body mass at departure, indicating that smaller seals were limited to shorter dive durations, perhaps as a result of their lesser aerobic capacity. All seals often exceeded their theoretical aerobic dive limit (average of 22.1 ± 18.1%). The number of dives exceeding the theoretical aerobic dive limit was not related to mass, suggesting that factors other than mass, such as foraging location or prey availability, may have been responsible for differences in diving effort. Foraging ability, indicated by the ability of the seals to follow vertically moving prey, was positively related to seal mass, indicating that small mass restricted foraging ability. The shorter dive durations of the smaller seals inferred that they had shallower dive depths in which to search for prey, thus restricting foraging ability. Although foraging ability was restricted by size, foraging success was found to be inversely related to mass, the smaller seals gaining a higher proportion of blubber than larger seals during their foraging trips. Thus, despite smaller seals being restricted to shallower depths and shorter durations, their foraging success was not affected.

Type
Research Article
Copyright
© 2000 The Zoological Society of London

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