Depletion of deep marine food patches forces divers to give up early
Many optimal foraging models for diving animals examine strategies that maximize time spent in the foraging zone, assuming that prey acquisition increases linearly with search time. Other models have considered the effect of patch quality and predict a net energetic benefit if dives where no prey is...
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Online Access: | https://doi.org/10.1111/j.1365-2656.2012.02021.x http://www.ncbi.nlm.nih.gov/pubmed/22881702 http://ecite.utas.edu.au/89060 |
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ftunivtasecite:oai:ecite.utas.edu.au:89060 2023-05-15T16:05:24+02:00 Depletion of deep marine food patches forces divers to give up early Thums, M Bradshaw, CJA Sumner, MD Horsburgh, JM Hindell, MA 2013 https://doi.org/10.1111/j.1365-2656.2012.02021.x http://www.ncbi.nlm.nih.gov/pubmed/22881702 http://ecite.utas.edu.au/89060 en eng Blackwell Publishing Ltd http://dx.doi.org/10.1111/j.1365-2656.2012.02021.x http://purl.org/au-research/grants/arc/A00104696 Thums, M and Bradshaw, CJA and Sumner, MD and Horsburgh, JM and Hindell, MA, Depletion of deep marine food patches forces divers to give up early, Journal of Animal Ecology, 82, (1) pp. 72-83. ISSN 0021-8790 (2013) [Refereed Article] http://www.ncbi.nlm.nih.gov/pubmed/22881702 http://ecite.utas.edu.au/89060 Biological Sciences Ecology Marine and Estuarine Ecology (incl. Marine Ichthyology) Refereed Article PeerReviewed 2013 ftunivtasecite https://doi.org/10.1111/j.1365-2656.2012.02021.x 2019-12-13T21:52:37Z Many optimal foraging models for diving animals examine strategies that maximize time spent in the foraging zone, assuming that prey acquisition increases linearly with search time. Other models have considered the effect of patch quality and predict a net energetic benefit if dives where no prey is encountered early in the dive are abandoned. For deep divers, however, the energetic benefit of giving up is reduced owing to the elevated energy costs associated with descending to physiologically hostile depths, so patch residence time should be invariant. Others consider an asymptotic gain function where the decision to leave a patch is driven by patch-depletion effects - the marginal value theorem. As predator behaviour is increasingly being used as an index of marine resource density and distribution, it is important to understand the nature of this gain function. We investigated the dive behaviour of the world's deepest-diving seal, the southern elephant seal Mirounga leonina , in response to patch quality. Testing these models has largely been limited to controlled experiments on captive animals. By integrating in situ measurements of the seal's relative lipid content obtained from drift rate data (a measure of foraging success) with area-restricted search behaviour identified from first-passage time analysis, we identified regions of high- and low-quality patches. Dive durations and bottom times were not invariant and did not increase in regions of high quality; rather, both were longer when patches were of relatively low quality. This is consistent with the predictions of the marginal value theorem and provides support for a nonlinear relationship between search time and prey acquisition. We also found higher descent and ascent rates in high-quality patches suggesting that seals minimized travel time to the foraging patch when quality was high; however, this was not achieved by increasing speed or dive angle. Relative body lipid content was an important predictor of dive behaviour. Seals did not schedule their diving to maximize time spent in the foraging zone in higher-quality patches, challenging the widely held view that maximizing time in the foraging zone translates to greater foraging success. Article in Journal/Newspaper Elephant Seal Mirounga leonina Southern Elephant Seal eCite UTAS (University of Tasmania) Journal of Animal Ecology 82 1 72 83 |
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Open Polar |
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eCite UTAS (University of Tasmania) |
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ftunivtasecite |
language |
English |
topic |
Biological Sciences Ecology Marine and Estuarine Ecology (incl. Marine Ichthyology) |
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Biological Sciences Ecology Marine and Estuarine Ecology (incl. Marine Ichthyology) Thums, M Bradshaw, CJA Sumner, MD Horsburgh, JM Hindell, MA Depletion of deep marine food patches forces divers to give up early |
topic_facet |
Biological Sciences Ecology Marine and Estuarine Ecology (incl. Marine Ichthyology) |
description |
Many optimal foraging models for diving animals examine strategies that maximize time spent in the foraging zone, assuming that prey acquisition increases linearly with search time. Other models have considered the effect of patch quality and predict a net energetic benefit if dives where no prey is encountered early in the dive are abandoned. For deep divers, however, the energetic benefit of giving up is reduced owing to the elevated energy costs associated with descending to physiologically hostile depths, so patch residence time should be invariant. Others consider an asymptotic gain function where the decision to leave a patch is driven by patch-depletion effects - the marginal value theorem. As predator behaviour is increasingly being used as an index of marine resource density and distribution, it is important to understand the nature of this gain function. We investigated the dive behaviour of the world's deepest-diving seal, the southern elephant seal Mirounga leonina , in response to patch quality. Testing these models has largely been limited to controlled experiments on captive animals. By integrating in situ measurements of the seal's relative lipid content obtained from drift rate data (a measure of foraging success) with area-restricted search behaviour identified from first-passage time analysis, we identified regions of high- and low-quality patches. Dive durations and bottom times were not invariant and did not increase in regions of high quality; rather, both were longer when patches were of relatively low quality. This is consistent with the predictions of the marginal value theorem and provides support for a nonlinear relationship between search time and prey acquisition. We also found higher descent and ascent rates in high-quality patches suggesting that seals minimized travel time to the foraging patch when quality was high; however, this was not achieved by increasing speed or dive angle. Relative body lipid content was an important predictor of dive behaviour. Seals did not schedule their diving to maximize time spent in the foraging zone in higher-quality patches, challenging the widely held view that maximizing time in the foraging zone translates to greater foraging success. |
format |
Article in Journal/Newspaper |
author |
Thums, M Bradshaw, CJA Sumner, MD Horsburgh, JM Hindell, MA |
author_facet |
Thums, M Bradshaw, CJA Sumner, MD Horsburgh, JM Hindell, MA |
author_sort |
Thums, M |
title |
Depletion of deep marine food patches forces divers to give up early |
title_short |
Depletion of deep marine food patches forces divers to give up early |
title_full |
Depletion of deep marine food patches forces divers to give up early |
title_fullStr |
Depletion of deep marine food patches forces divers to give up early |
title_full_unstemmed |
Depletion of deep marine food patches forces divers to give up early |
title_sort |
depletion of deep marine food patches forces divers to give up early |
publisher |
Blackwell Publishing Ltd |
publishDate |
2013 |
url |
https://doi.org/10.1111/j.1365-2656.2012.02021.x http://www.ncbi.nlm.nih.gov/pubmed/22881702 http://ecite.utas.edu.au/89060 |
genre |
Elephant Seal Mirounga leonina Southern Elephant Seal |
genre_facet |
Elephant Seal Mirounga leonina Southern Elephant Seal |
op_relation |
http://dx.doi.org/10.1111/j.1365-2656.2012.02021.x http://purl.org/au-research/grants/arc/A00104696 Thums, M and Bradshaw, CJA and Sumner, MD and Horsburgh, JM and Hindell, MA, Depletion of deep marine food patches forces divers to give up early, Journal of Animal Ecology, 82, (1) pp. 72-83. ISSN 0021-8790 (2013) [Refereed Article] http://www.ncbi.nlm.nih.gov/pubmed/22881702 http://ecite.utas.edu.au/89060 |
op_doi |
https://doi.org/10.1111/j.1365-2656.2012.02021.x |
container_title |
Journal of Animal Ecology |
container_volume |
82 |
container_issue |
1 |
container_start_page |
72 |
op_container_end_page |
83 |
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1766401304013307904 |