Foraging behavior of free-ranging Weddell seals (Leptonychotes weddelli) in the Antarctic fast-ice environment


Foraging behavior of free-ranging Weddell seals (Leptonychotes weddelli) in the Antarctic fast-ice environment

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dc.contributor.advisor Fuiman, Lee A.
dc.creator Madden, Kiersten Marie, 1980- 2008-08-29T00:07:56Z 2008-08-29T00:07:56Z 2007-12 2008-08-29T00:07:56Z
dc.description.abstract Detailed information on diet and foraging behavior is necessary for understanding predator-prey interactions and food-web dynamics. The primary objective of this dissertation was to gain a more complete understanding of the natural foraging behavior of Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarctica using a video data recorder to document the seal's three-dimensional movements and encounters with prey. Seals exhibited a variety of dive types that could be sorted into five groups based on 18 dive descriptors. Three of these groups (deep aerobic, deep anaerobic, and shallow aerobic) were identified as foraging dives, the frequency of which varied with bathymetry. Deep aerobic foraging dives were similar in depth and duration to foraging dives in previous studies and were more common at offshore breathing holes. However, differences occurred between offshore free-ranging and isolated-hole dives in the behaviors involving descent and the frequency of certain behavioral transitions. These differences were responses by the seals to variations in prey abundance, rather than responses to a change in breathing hole availability. Even with an apparently homogenous sample of seals, there was significant individual variability in foraging success, behavior, diet, and foraging tactics. Dive depth, duration, distance, and energetic cost were important for explaining foraging success when seals dove in shallow areas where Antarctic silverfish (Pleuragramma antarcticum) were more difficult to reach and less abundant. However, the relationship between those variables was not the same for all individuals. Diet and foraging tactics also varied significantly among individuals diving near the coastline. Two coastal seals specialized on silverfish, while two others consumed silverfish and benthic prey. Although benthic prey were more accessible along the coastline than offshore, silverfish, which have a high lipid content, required less handling to consume. Thus, it may be energy-efficient for seals to specialize on silverfish at coastal locations despite the additional time and energy required to travel to depths where silverfish are located. These results helped us understand variability within Weddell seal populations and the basis upon which foraging decisions are made in response to changes in bathymetry, access to breathing holes, and prey abundance and availability.
dc.format.medium electronic
dc.language.iso eng
dc.rights Copyright © is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.
dc.subject.lcsh Weddell seal--Food--Antarctica--McMurdo Sound
dc.subject.lcsh Weddell seal--Locomotion--Antarctica--McMurdo Sound
dc.title Foraging behavior of free-ranging Weddell seals (Leptonychotes weddelli) in the Antarctic fast-ice environment
dc.description.department Marine Science Institute
dc.identifier.oclc 212627917
dc.identifier.recnum b69734768
dc.type.genre Thesis
dc.type.material text Marine Science Institute Marine Science The University of Texas at Austin Doctoral Doctor of Philosophy

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