Elephant Seals: Pushing the Limits on Land and at Sea

212 Pages·2021·18.418 MB·English

by  Bernard J. Le Boeuf

Elephant Seals
Pushing the Limits on Land and at Sea
How did the elephant seal survive being driven to the brink of extinction in the
nineteenth century? What variables determine the lifetime reproductive success of
individual seals? How have elephant seals adapted to tolerate remarkable physio-
logicalextremes ofnutrition, temperature, asphyxia, and pressure?
Answering these questions and many more, this book is the result of the author’s
50-yearstudyofelephantseals.Thechapterscoverabroadrangeoftopicsincluding
diving, feeding, migration, and reproductive behavior, yielding fundamental infor-
mation on general biological principles,the operation ofnatural selection, theevolu-
tion of social behavior, the formation of vocal dialects, colony development, and
population changes over time. The book will be a valuable resource for graduate
studentsandresearchers ofmarinemammal behaviorandreproductivelifehistoryas
well asfor amateur naturalists interested inthese fascinating animals.
Bernard J. Le Boeuf is Emeritus Professorof Biology atthe University of California,
Santa Cruz. He is considered one of the pioneers of the field of marine mammal
behavior, known particularly for his studies of seal social behavior, diving behavior,
divingphysiology,andmigration.Hehaspublishedwidelyontopicsinreproductive
behavior,ecology, and behavioral biology.

Elephant Seals
Pushing the Limits on Land and at Sea
BERNARD J. LE BOEUF
UniversityofCalifornia,SantaCruz
UniversityPrintingHouse,CambridgeCB28BS,UnitedKingdom
OneLibertyPlaza,20thFloor,NewYork,NY10006,USA
477WilliamstownRoad,PortMelbourne,VIC3207,Australia
314–321,3rdFloor,Plot3,SplendorForum,JasolaDistrictCentre,NewDelhi–110025,India
103PenangRoad,#05–06/07,VisioncrestCommercial,Singapore238467
CambridgeUniversityPressispartoftheUniversityofCambridge.
ItfurtherstheUniversity’smissionbydisseminatingknowledgeinthepursuitof
education,learning,andresearchatthehighestinternationallevelsofexcellence.
www.cambridge.org
Informationonthistitle:www.cambridge.org/9781316511541
DOI:10.1017/9781009052085
©BernardJ.LeBoeuf2021
Thispublicationisincopyright.Subjecttostatutoryexception
andtotheprovisionsofrelevantcollectivelicensingagreements,
noreproductionofanypartmaytakeplacewithoutthewritten
permissionofCambridgeUniversityPress.
Firstpublished2021
PrintedintheUnitedKingdombyTJBooksLimited,PadstowCornwall
AcataloguerecordforthispublicationisavailablefromtheBritishLibrary.
LibraryofCongressCataloging-in-PublicationData
Names:LeBoeuf,BernardJ.,author.
Title:Elephantseals:pushingthelimitsonlandandatsea/BernardJ.LeBoeuf,UniversityofCalifornia,
SantaCruz.
Description:Cambridge,UnitedKingdom;NewYork,NY:CambridgeUniversityPress,2021.|
Includesbibliographicalreferencesandindex.
Identifiers:LCCN2021017370(print)|LCCN2021017371(ebook)|ISBN9781316511541(hardback)|
ISBN9781009055031(paperback)|ISBN9781009052085(epub)
Subjects:LCSH:Elephantseals.|Elephantseals–Adaptation.
Classification:LCCQL737.P64L4252021(print)|LCCQL737.P64(ebook)|DDC599.79/4–dc23
LCrecordavailableathttps://lccn.loc.gov/2021017370
LCebookrecordavailableathttps://lccn.loc.gov/2021017371
ISBN978-1-316-51154-1Hardback
CambridgeUniversityPresshasnoresponsibilityforthepersistenceoraccuracy
ofURLsforexternalorthird-partyinternetwebsitesreferredtointhispublication
anddoesnotguaranteethatanycontentonsuchwebsitesis,orwillremain,
accurateorappropriate.
Contents
Preface page vii
Acknowledgments ix
1 Origins,Misnomers, and Bottleneck 1
2 Back from the Abyss,Population Recovery,and Genetic Aftermath 8
3 The Year of the Seal 17
4 Fieldwork 101: Getting There and Getting Started 28
5 Adapting toLifeatSea and onLand 44
6 The Cost ofLiving in aSeal Harem 55
7 Coito ergosum: Males Explained 62
8 Females: Designed toReproduce 80
9 Diving, Foraging, and Migration 99
10 Development 119
11 Sleep When You Can 129
12 What IsAll theNoiseAbout? 134
13 Comparisons, UnsolvedMysteries, and Conclusions 141
References 157
Index 181
Color plates can befound between pages 118and 119.
v

Preface
Theelephantsealisassociatedwithsuperlatives:thelargestsealwithmalesweighing
over two tons; extremely polygynous, with some males mating with hundreds of
females; and the most sexually dimorphic marine mammal, with males being 3–10
times larger than females. Females fast while lactating. Alpha males fast for over a
hundred days during the breeding season. They dive deeper and longer than other
sealsandsealions,andtheyspendmoretimeatseasubmergedthanmostwhales.No
other large mammal has come so close to extinction and made such a rapid and
successfulrecovery.Theseanimalsarefascinatingbecausetheystretchtheboundaries
of what can be done both on land and at sea. This book describes the essential
elements of the behavior and biology of northern elephant seals that have enabled
them to thrive andadapt on land and at sea.
We know a great deal about this animal because it has been studied thoroughly,
intensively, and continuously at the same site, Año Nuevo State Park, for over five
decades. More than 200 peer-reviewed research papers have been published on the
elephantsealsfromthisrookery.Tworeasonsaccountforthedurationandabundance
ofthestudies.First,thesesealsareexceptionallyamenabletolong-termstudybecause
individualscanbeidentifiedandfollowedforlife;theyarerobustagainstdisturbance
anddonotfleeinfear;theybreedintheopenairwheretheycanbeviewed;theycan
be tagged, weighed, measured, blood-sampled, and tissue-sampled; and they will
carry attached recording instruments for up to eight months at sea without harm and
effectsontheirsubsequentbehavior.Second,theyinhabitandbreedinnatureamere
25 minutes away from the University of California at Santa Cruz, where researchers
can sally forth with minimal effort and cost to conduct studies daily throughout the
year andcontinuouslyover the years.
The perspective here is my own. I describe studies by me and my students and
colleaguesconducted overfivedecadeson a wide variety ofresearch projects onthe
behavior,physiology,andbiologyoftheseanimalsinthefield.Mostofthesestudies
have been published in peer-reviewed scientific journals. Some of these studies are
longterm,involvingthetrackingofindividualsovertheirlifetimes.Firsthandexperi-
ence permits additional insights that enable presentation of personal stories and
reminiscences in the text (boxes) that didn’t fit in research articles or book chapters,
themainsourceofreportingforacademics.Ourresearchonnorthernelephantsealsis
compared with findings from several research teams studying the southern elephant
seals in thesouthernhemisphere.
vii
viii Preface
Forthesakeofmakingthestorymoreaccessibletoawideaudienceandforeaseof
reading, I’ve minimized the use of references, tables, and figures, and I’ve excluded
equations, statistical tests, and mathematical models altogether. These details can be
tracked down in the references cited. This book should be of interest to students of
animal behavior, marine mammalogists, and naturalists, and it should be especially
useful and informative to visitors to marine mammal parks and aquaria and the
thousands of tourists that view elephant seals in nature annually at mainland sites in
California and Argentina.
Forthosewhowanttoconsultoriginalsourcesorwantmoredetailthanisprovided
inthetext,consulttheReferences.Thelistincludespublishedpeer-reviewedresearch
articles, books, book chapters, and popular pieces, with a special emphasis on the
researchconducted at Año NuevoState Park.
The metric system is used throughout this book with length measurement in
meters (m) or kilometers (km) and temperature inCentigrade units ((cid:1)C).