Elephant Seals Population Ecology, Behavior, and Physiology

425 Pages·1994·23.1 MB·English

by  Burney J. Le Boeuf

Population Ecology,
Behavior,
and Physiology
ELEPHANT SEALS
Population Ecology, Behavior, and
Physiology
Edited by BurneyJ. Le Boeuf
and Richard M. Laws
Elephantseals, weighing upto2000
kilograms, are notonlythe largestseals
butamongthe mostimpressiveofall
marine mammals. Broughttothe brinkof
extinction bynineteenth-century hunters,
the northernspecies hasachieveda re-
coverythat isunmatched byanyother
marinevertebrate. Elephantsealsare
capableoftolerating remarkable
physiological extremesof nutrition,
temperature, and pressure.Theyspend
moretime underwaterthan mostwhales
and divedeeperand longerthan any
othermarinemammal. Lactating females
andthe largestbreeding malesduringthe
matingseasoncan lose uptoforty
percentoftheirbodyweightthrough
prolongedfasting.
Fortheseandotherreasons,theele-
phantseal hasbeenthesubjectofinten-
sivestudy inthe northern andthesouth-
ern hemispheres. ElephantSeals,thefirst
book-length discussionofthespecies,
gatherstogetherthe researchfindingsof
scientistsworking alongthe NorthAmer-
ican coastfrom CaliforniatoAlaska and
inthecircumpolarwatersoftheAntarc-
tic. Itdocumentsforthefirsttimethe
worldwidestatusofelephantseals,
noting boththeremarkableresurgenceof
the northernspeciesandthetroubling
declineofcertain populations inthe
south, which someattributetohuman
factorssuch asfishing and global
warming.
Amongthestudiesdiscussed bythe
authorsarethose involvingcutting-edge
researchontheseals'diving patterns.
Elephant Seals
FXWS-XTY-KU3Y
Elephant
Seals:
Population Ecology,
Behavior, and
Physiology
£DIT£DBY
Burney Le Boeufand Richard M. Laws
J.
UNIVERSITY OF CALIFORNIAPRESS
Berkeley LosAngeles London
Copyrightedmatsrial
UniversityoTCaliforniaPress
BerkeleyandLosAngeles,California
Universityot(ialiforniaPrcsS
London,England
Gopyrif^tO1994byTheRegentsoftheUniversityofGalifemia
LibraryofCongressCataloging-in-PublicationData
Elephantseals:populationecology,behavior,andphysiology/edited
byBumeyJ.LeBoeufandRichardM.Laws,
p. cm.
Includesbibliographicalreferencesandindex.
ISBN0-520-08364-4fcloth)
1. Elephantseals. I. LeBocuf,BurncyJ. II. Laws,RichardM.
QL737.P64E44 1994
599.74'8~dc20 93-38142
CIP
PrintedintheUnitedStatesofAmerica
123456789
Thepaperusedinthispublication meets the minimumrequirementsofAmericanNational
StandardforInformationSciences-PermanenceofPaperforPrintedLibraryMaterials,ANSI
239.48-1984^
Copyrightedmaterial
Tothosewhoprovidedfundsfortheconference:
GordonRtetzendWilliamLangofMineralsManagementSerme,
JdmTwissandRobertHofmanoftheMarineMammalCommission,end
GeorgeA.MaUochviatheGerenaMacgowan Trust
CopyrightedmatBrial
CONTENTS
PREFACE xi
CONTRIBUTORS / XD
1. ElephantSeals:AnIntroductiontotheGenus , /
BumeyJ.LeBoeufandRichardM.Laws
PARTI * POPULATIONECOT.QGY
2. HistoryandPresentStatusoftheNorthernElephantSealPopulation / 29
BrentS.Stewart,PamelaK. Yochem,HarrietR.Huber,RobertL.DeLons,
RonaldJ.Jameson,HHlUamJ.Sydeman,SarahG.Allen,andBumeyJ.LeBoeuf
3. HistoryandPresentStatusofSouthernElephantSealPopulations / 49
RichardM.Ijam
4. PossibleCausesoftheDeclineofSouthernElephantSealPopulationsinthe
SouthernPacificandSouthern IndianOceans / 66
MarkA.Hindell,DavidJ.Slip,andHornR.Burton
5. PopulationEcologyofSouthernElephantSealsatMarionIsland / S5
MaiihanA.UesUiandIan.V. WdkuLwn
6. BiomassandEnergyConsumptionoftheSouthGeorgiaPopulationofSouthern
ElephantSeals / 98
IanL.Boyd, TomA.Ambom,andMichaelA.Fedak
PARTII * BEHAVIORANDLIFEHISTORY
7.JuvenileSurvivorshipofNorthernElephantSeals / 121
BumeyJ.LeBoeuf,PatriciaMorris,andJoanruReiter
ott
mi CONTENTS
8. LifeHistoryStrategiesofFemaleNorthernElephantSeals / 137
WilliamJ.SydemanandNadavNur
9. SexualSelectionandGrowthinMaleNorthernElephantSeals / 154
WnlUrI. Clintnn
10. Sex-andAge-RelatedVariationinReproductiveEffortofNorthernElephant
Seals / 169
Charles}.Deutsch,DanielE.Crocker,DanielP. Costa,andBumeyJ.LeBoeuf
11. DietoftheNorthernElephantSeal / 211
GeorgeA.Antonelis,MarkS.Lowry,CliffordH.Fiscus,BrentS.Stewart,and
RobertL.DeLong
PARTIII « DIVINGANDFORAOTNO
12. TheoryofGeolocationbyLightLevels / 227
RogerD.Hill
13. VariationintheDivingPatternofNorthernElephantSealswithAge,Mass,
Sex,andReproductiveCondition / 237
BumeyJ.LeBoeuf
14. DivingBehaviorofSouthernElephantSealsfromMacquarieIsland:
AnOverview / 253
DavidJ.Slip,MarkA.Hindell.andHarryR.Burton
15. DevelopmentalAspectsofDivinginNorthernElephantSealPups / 271
PhilipH,ThorsonandBumeyJ.LeBoeuf
16. PostbrcedingForagingMigrationsofNorthernElephantSeals / 290
BrentS.StewartandRobertL.DeLong
17. FunctionalAnalysisofDiveTyp»esofFemaleNorthernElephantSeals / 310
TumohiroAsaga,YasuhikoNaito,BumeyJ.LeBoeuf,andHarmSakurai
18. SwimSpeedandDiveFunctioninaFemaleNorthernElephantSeal / 328
DanielE. Crocker,Bumeyf-LeBoeuf, YasuhikoNaito,TomohiroAsaga,and
DanielP. Costa
PARTIV • PHYSIOLOGICALECOLOGY
19. ApneaToleranceintheElephantSealduringSleepingandDiving:
PhysiologicalMechanismsandCorrelations / 343
MichaelA Cn\tellini
20. Expenditure,Investment,andAcquisitionofEnergyinSouthern
ElephantSeals / 354
MichaelA.Fedak,TomA.Ambom,B.J.McConnell,C. Chambers,IanL.Boyd,
J.Hanvood,andT.S.McCann
Copyri
CONTENTS
21. HormonesandFuelRegulationinFastingElephantSeals / 374
VickyLeeKirbyandC.LeoOrtiz
22. EndocrineChangesinNewbornSouthernElephantSeals / 387
MichaelM.Bryden
INDEX / 399
CopyrI
PREFACE
*'If you like superlatives, you will love this animal," a pitchman for
elephantseals mightsay.Thelistislongand&r-ranging. Itisthelargest
seal and one ofthe most sexually dimorphic marine mammals. It is ex-
tremely polygynous by comparison with any other large vertebrate.
Femalesfestwhilelactating, and thelargest breeding malesfastformore
than one hundred days during the breeding season. Elephant seals dive
deeperandlongerthananyotherpinniped,andtheyspendmoredmesub-
mergedduringtheirlong aquaticwanderings thanmostwhales. Noother
largevertebrate has come so dose to extinction as the northern elephant
sealdidonehundredyearsagoandmadesucharapidrecovery.
Although these superlatives make the two elephantseal species in the
genusMiromigaidealsubjectsforavarietyofscientificstudies,someoftheir
moremtmdaneattributesareresponsibleformuchoftheattentionbysci-
entists. Elephantseak breedonopenbeacheswheretheyareplainlyvisi-
ble.Theyareunafiraidofhumansanddonotfleewhenapproachedordis-
turbed.Consequendy, whensleeping, theycanbeeasilymarkedortagged
individually.Taggingatweaning,onemonthafterbirth,yieldsacohortof
known-age animak bysex. This is critical for long-term behaviorstudies
andstudiesofgrowth,aging,andsurvivalanddefinestheageandmatura-
tionvariablesinphysiologicalstudiesinthelaboratory.Toputthisinper-
spective, a biologistcanidentify, sex, and age moreelephantsealsinone
afternoonthanastudentofkillerwhalesmightaccomplishinamonth,ifat
all. Arrivals anddeparturesonrookeriesforbreedingandmoltingarepre-
dictable, which has facilitatedinstrumentationofindividualsforthestudy
(^divingandat-seabehavior.
Owinginlargeparttotheirease study,therudimentsofelephantseal
naturalhistory,thebasisforagoodmonograph,wereprovidedbythefirst
xi
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