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Depletion of deep marine food patches forces divers to give up early

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dc.contributor S Australian Res & Dev Inst
dc.contributor Univ Tasmania
dc.contributor Sch Earth & Environm Sci
dc.contributor Marine Predator Unit
dc.contributor University Of Western Australia
dc.contributor Sch Environm Syst Engn
dc.contributor University Of Adelaide
dc.contributor University Of Tasmania
dc.contributor Australian Inst Marine Sci
dc.contributor Univ Western Australia
dc.contributor Univ Adelaide
dc.contributor Inst Environm
dc.contributor Inst Marine & Antarctic Studies
dc.contributor Uwa Oceans Inst
dc.contributor Australian Institute Of Marine Science HINDELL, MARK A. THUMS, MICHELE BRADSHAW, COREY J. A. SUMNER, MICHAEL D. HORSBURGH, JUDY M. 2014-09-24T01:42:40Z 2017-03-21T01:08:54Z 2017-03-21T01:08:54Z 2019-07-08T02:24:07Z 2017-03-21T01:08:54Z 2014-09-24T01:42:40Z 2014-09-24T01:42:40Z 2019-07-08T02:24:07Z 2013-01-01
dc.identifier.citation Thums M, Bradshaw CJA, Sumner MD, Horsburgh JM, Hindell MA (2013) Depletion of deep marine food patches forces divers to give up early. Journal of Animal Ecology 82(1): 72-83 en_US
dc.identifier.issn 0021-8790
dc.description.abstract 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.
dc.description.sponsorship Funded by the Australian Research Council (DP0770901), the Natural Sciences and Engineering Research Council of Canada, Sea World Research and Rescue Foundation Inc. and the Australian Antarctic Division, with additional support from P. Rowsthorn and the University of Tasmania. M. Thums supported by an Australian Postgraduate Award.
dc.description.uri en_US
dc.language English
dc.language.iso en en_US
dc.publisher Wiley en_US
dc.relation.ispartof Null
dc.subject Mirounga-leonina
dc.subject Functional Response
dc.subject Swim Speed
dc.subject Ecology
dc.subject Aerobic Dive Limit
dc.subject Rate Maximizing
dc.subject Buoyancy
dc.subject Environmental Sciences & Ecology
dc.subject Weddell Seals
dc.subject Patterns
dc.subject Zoology
dc.subject Northern Elephant Seals
dc.subject Patch Model
dc.subject Diving Behavior
dc.subject Prey
dc.subject Stomach Temperature
dc.subject Foraging Behavior
dc.title Depletion of deep marine food patches forces divers to give up early
dc.type journal article en_US
dc.identifier.doi 10.1111/j.1365-2656.2012.02021.x
dc.identifier.wos WOS:000313752300009

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