Identifying foraging events in deep diving southern elephant seals, Mirounga leonina , using acceleration data loggers
Southernelephantseals(Miroungaleonina) rangewidelythroughouttheSouthernOceanandareassociatedwithimportanthabitats(e.g., iceedges,shelf)wheretheyaccumulateenergytofueltheirreproductiveeffortsonland.Knowledgeofthefinescaleforagingbehaviourusedtogarnerthisenergy,however,islimited.Forthefirsttime,accele...
Published in: | Deep Sea Research Part II: Topical Studies in Oceanography |
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Main Authors: | , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Pergamon-Elsevier Science Ltd
2013
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Subjects: | |
Online Access: | https://doi.org/10.1016/j.dsr2.2012.09.002 http://ecite.utas.edu.au/89051 |
Summary: | Southernelephantseals(Miroungaleonina) rangewidelythroughouttheSouthernOceanandareassociatedwithimportanthabitats(e.g., iceedges,shelf)wheretheyaccumulateenergytofueltheirreproductiveeffortsonland.Knowledgeofthefinescaleforagingbehaviourusedtogarnerthisenergy,however,islimited.Forthefirsttime,accelerationloggersweredeployedonthreeadultsouthernelephantsealsduringatranslocationstudyatKerguelenIsland.Theaimsofthestudywereto(1) identifypreycaptureattemptsusing2-Daccelerometertagsdeployedontheheadofsouthernelephantseals,(2)comparethenumberofforagingdivesidentifiedbysimpledivedepthprofilesandaccelerometerprofilesand(3)comparedivecharacteristicsbetweenpreyencounterandnon-preyencounterdives.The2-Dloggersrecordeddeptheverysecond,surgeandheaveaccelerationsat8or16 Hzandwerecarriedforperiodsbetween23and121h.Rapidheadmovementswereinterpretedtobe associatedwithpreyencounterevents.Accelerationdatadetectedpossiblepreyencountereventsin3952%ofdiveswhilst6780%ofdiveswereclassifiedasforagingdiveswhenusingdivedepthprofilesalone. Preyencountersoccurredinsuccessivedivesduringdaysandnightsandlastedbetweententhsof asecondand7.6min.Binomiallinearmixedeffectmodelsshowedthatsealsweredivingsignificantlydeeperandincreasedbothdescentrateandbottomdurationwhenencounteringprey.Dive duration,however,didnotsignificantlyincreaseduringdiveswithpreyencounters.Theseresultsare inaccordancewithoptimalforagingtheory,whichpredictsthatdeepdiversshouldincreaseboththeir transitratesandthetimespentatdepthwhenaprofitablepreypatchisencountered.Thesefindings indicatethatthistechniqueispromisingasitmoreaccuratelydetectspossiblepreyencountereventscomparedwithdivedepthprofilesaloneandthusprovidesabetterunderstandingofsealforagingstrategies. |
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