Identifying foraging events in deep diving southern elephant seals, Mirounga leonina , using acceleration data loggers

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: Gallon, S, Bailleaul, F, Charrassin, JB, Guinet, C, Bost, CA, Handrich, Y, Hindell, MA
• Format: Article in Journal/Newspaper
• Language: English
• Published: Pergamon-Elsevier Science Ltd 2013
• Subjects: Biological Sciences; Ecology; Marine and Estuarine Ecology (incl. Marine Ichthyology); Elephant Seals; Mirounga leonina; Southern Elephant Seals
• Online Access: https://doi.org/10.1016/j.dsr2.2012.09.002; http://ecite.utas.edu.au/89051

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.