Dynamics of Large Herbivore Populations in Changing Environments: Towards Appropriate Models

210 Pages·2010·2.39 MB·English

Dynamics of Large Herbivore Populations
in Changing Environments
Dynamics of Large Herbivore Populations in Changing Environments: Towards Appropriate Models
Edited by Norman Owen-Smith
© 2010 Blackwell Publishing Ltd. ISBN: 978-1-405-19894-3
Dynamics of Large
Herbivore Populations in
Changing Environments:
Towards Appropriate
Models
Editedby
Norman Owen-Smith
A John Wiley & Sons, Ltd., Publication
Thiseditionfirstpublished2010,©2010byBlackwellPublishingLtd
BlackwellPublishingwasacquiredbyJohnWiley&SonsinFebruary2007.Blackwell’s
publishingprogramhasbeenmergedwithWiley’sglobalScientific,TechnicalandMedical
businesstoformWiley-Blackwell.
Registeredoffice:JohnWiley&SonsLtd,TheAtrium,SouthernGate,Chichester,WestSussex,
PO198SQ,UK
Editorialoffices:9600GarsingtonRoad,Oxford,OX42DQ,UK
TheAtrium,SouthernGate,Chichester,WestSussex,PO198SQ,UK
111RiverStreet,Hoboken,NJ07030-5774,USA
Fordetailsofourglobaleditorialoffices,forcustomerservicesandforinformationabouthowto
applyforpermissiontoreusethecopyrightmaterialinthisbookpleaseseeourwebsiteat
www.wiley.com/wiley-blackwell
Therightoftheauthortobeidentifiedastheauthorofthisworkhasbeenassertedinaccordance
withtheCopyright,DesignsandPatentsAct1988.
Allrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,or
transmitted,inanyformorbyanymeans,electronic,mechanical,photocopying,recordingor
otherwise,exceptaspermittedbytheUKCopyright,DesignsandPatentsAct1988,withoutthe
priorpermissionofthepublisher.
Wileyalsopublishesitsbooksinavarietyofelectronicformats.Somecontentthatappearsin
printmaynotbeavailableinelectronicbooks.
Designationsusedbycompaniestodistinguishtheirproductsareoftenclaimedastrademarks.All
brandnamesandproductnamesusedinthisbookaretradenames,servicemarks,trademarksor
registeredtrademarksoftheirrespectiveowners.Thepublisherisnotassociatedwithanyproduct
orvendormentionedinthisbook.Thispublicationisdesignedtoprovideaccurateand
authoritativeinformationinregardtothesubjectmattercovered.Itissoldontheunderstanding
thatthepublisherisnotengagedinrenderingprofessionalservices.Ifprofessionaladviceorother
expertassistanceisrequired,theservicesofacompetentprofessionalshouldbesought.
LibraryofCongressCataloging-in-PublicationData
Dynamicsoflargeherbivorepopulationsinchangingenvironments:towardsappropriate
models/editedbyNormanOwen-Smith.
p.cm.
‘‘ThisbookoriginatedfromaworkinggroupestablishedattheNationalCenterforEcological
AnalysisandSynthesis(NCEAS)attheUniversityofCalifornia,SantaBarbara’’–Pref.
ISBN978-1-4051-9894-3(hardback)–ISBN978-1-4051-9895-0(pbk.)
1.Ungulates–Ecology.2.Herbivores–Ecology.3.Mammalpopulations–Mathematicalmodels.
I.Owen-Smith,Norman.II.NationalCenterforEcologicalAnalysisandSynthesis
QL737.U4D962010
599.6(cid:2)17–dc22
2009038755
ISBN:9781405198943(hardback)and9781405198950(paperback)
AcataloguerecordforthisbookisavailablefromtheBritishLibrary.
Setin10.5/12.5PhotonMTbyLaserwordsPvtLtd,Chennai,India
PrintedinMalaysia
1 2010
Contents
Contributors ix
Preface xi
1 Definitivecasestudies 1
NormanOwen-SmithandJasonP.Marshal
1.1 ReddeeronRum 2
1.2 SoaysheeponHirta 5
1.3 RoedeerinFrance 8
1.4 BighornsheepinAlberta 10
1.5 KuduinKruger 13
1.6 WildebeestinSerengeti 15
1.7 MooseonIsleRoyale 18
1.8 ElkinNorthYellowstone 20
1.9 Overview 22
Acknowledgments 28
References 28
2 Thesuiteofpopulationmodels 34
NormanOwen-Smith
2.1 Modelsofdensitydependence 36
2.2 Autoregressivetime-seriesmodels 40
2.3 Age-orstage-structuredmodels 43
2.4 Trophicinteractionmodels 49
2.5 Physiologicalormetaphysiologicalmodels 52
2.6 Modelsaccommodatingspatialstructure 53
2.7 Individual-basedmodels 54
2.8 Overview 54
Acknowledgments 57
References 57
3 Climaticinfluences:temperate–tropicalcontrasts 63
NormanOwen-Smith
3.1 Temperateenvironments 65
3.2 Tropicalandsubtropicalenvironments 77
vi Contents
3.3 Effectsofpredationandhunting 86
3.4 Overallassessment 88
Acknowledgments 90
References 90
4 Demographicprocesses:lessonsfromlong-term,
individual-basedstudies 98
Jean-MichelGaillard,TimCoulsonandMarcoFesta-Bianchet
4.1 Lifehistoryoflargeherbivores:abriefreview 99
4.2 Differentialcontributionsofdemographicparameterstopopulation
growth 103
4.3 Climaticvariation,density-dependence,andindividualvariability 106
4.4 Conclusions:howcanfutureanalysesoflargeherbivoredemography
dealwithcomplexdemographicprocesses? 108
Acknowledgments 110
References 110
5 Irruptivedynamicsandvegetationinteractions 117
JohnE.Gross,IainJ.GordonandNormanOwen-Smith
5.1 Modelsofherbivore–vegetationinteractions 118
5.2 Examplesofirruptivedynamics 122
5.3 Effectsofirruptionsonvegetation 127
5.4 Changingperspectives 128
5.5 Synthesis 132
5.6 Implicationsforconservationandmanagement 133
Acknowledgments 135
References 135
6 Howdoeslandscapeheterogeneityshapedynamics
oflargeherbivorepopulations? 141
N.ThompsonHobbsandIainJ.Gordon
6.1 Whatisspatialheterogeneity? 143
6.2 How does spatial heterogeneity influence ungulate population
dynamics? 143
6.3 Mechanisms explaining the influence of spatial heterogeneity on
populationdynamics 148
6.4 Influencesfromhigh-qualityresources 151
6.5 Influencesfrombufferresources 154
6.6 Globalchangeandaccesstoheterogeneitybylargeherbivores 155
6.7 Conclusions:theimportanceofspatialcontextforpopulation
dynamics 157
Acknowledgments 158
References 158
Contents vii
7 Towardsanecologyofpopulationdynamics 165
NormanOwen-Smith
7.1 Phenomenologicaldescriptors 167
7.2 Timeserieselaborations 171
7.3 Environmentalstructure 174
7.4 Populationstructure 183
7.5 Adaptiveresponsesandenvironmentalcontexts 188
7.6 Summaryandconclusions 190
Acknowledgments 190
References 190
Index 197
Contributors
TimCoulson,DepartmentofLifeSciences,ImperialCollegeLondon,
Ascot,UK.Email:[email protected].
Marco Festa-Bianchet, Department of Biology, University of Sherbrooke,
Sherbrooke,Canada.Email:[email protected].
Jean-MichelGaillard,LaboratoiredeBiometrieetBiologieEvolutive,
UniversiteClaudeBernardLyon,VilleurbanneCedex,France.
Email:[email protected].
IainJ.Gordon,CSIRODaviesLaboratory,Aitkenvale,Queensland,
Australia.Email:[email protected].
John Gross, Inventory and Monitoring Program, National Park Service,
FortCollins,Colorado,USA.Email:[email protected].
JasonMarshal,SchoolofAnimal,PlantandEvironmentalSciences,
UniversityoftheWitwatersrand,Johannesburg,SouthAfrica.
Email:[email protected].
NormanOwen-Smith,SchoolofAnimal,PlantandEnvironmental
Sciences,UniversityoftheWitwatersrand,Johannesburg,SouthAfrica.
Email:[email protected].
N. Thompson Hobbs, Natural Resource Ecology Laboratory and Gradu-
ate Degree Program in Ecology, Colorado State University, Fort Collins,
Colorado,USA.Email:[email protected].
Preface
This book originated from a working group established at the National
CenterforEcologicalAnalysisandSynthesis(NCEAS)attheUniversityof
California, Santa Barbara. The problem confronted was the contrasting
dynamicsshownbypopulationsoflargemammalianherbivoresinrecent
decades. Some of these populations had declined abruptly in abundance,
most notably in certain protected areas in Africa. Others had become
so abundant as to threaten plant populations and forest regeneration,
especially in parts of Europe and North America. Conventional mod-
els emphasizing population regulation around some steady state seemed
inadequate to explain these divergent trends. Hence, the specific aims of
the group were to challenge the prevalent models using existing data
sets,anddevelopalternativemodelscapableofaccommodatingthecom-
plexity of environmental influences operating at different spatial and
temporalscales.
Thegroupmetannuallyover3years,2001–2003.Muchsharedunder-
standing was gained, and several joint-authored publications appeared
in journals. Numerous other papers have subsequently been published
relatingtothedynamicsoflargeungulatepopulations.Atthesametime,
populationecologyhasbeenundergoingaphaseoftheorymaturation,evi-
dencedbytheappearanceofseveralbooks(e.g.Lande,EngenandSaether
2003, Turchin 2003, Cuddington and Beisner 2005) as well as numer-
ouspapersinecologicaljournals.A‘‘balanceofnature’’perspectiveisno
longertheprevalentparadigm(Cooper2003),andnewapproachesprovide
greater recognition ofdisequilibrium processes, nonlinearresponses,and
theconsequencesofspatialstructure,enabledbyexpandedcomputational
capacitytoaccommodatethiscomplexity(Owen-Smith 2002,Ellnerand
Guckenheimer2006,Clark2007).
Studiesonlargeherbivoreshavebeenmakingasubstantialcontribution
to this theoretical reassessment. New insights have been provided by
the opportunities to follow changes in certain ungulate populations in
demographicorevenindividualdetail,revealingresponsemechanismsthat
xii Preface
generally remain cryptic for small mammal or insect populations. Being
directlydependentonvegetationasafoodresource,herbivorepopulations
respond sensitively to patterns of plant growth, and hence to changing
climatic and human influences on vegetation dynamics. Complications
arisefromtheadditionaleffectsofpredationandhuntingonsomeofthese
populations, as well as from fragmentation of the spatial context within
whichtheyexist.
Itistimetotakestockofthenewknowledgethathasbeengainedfrom
theselargeherbivorestudies.Inparticular,thereisaneedtoassesswhat
revision of theory, expressed through models of population dynamics, is
needed to represent and explain the causes of change, looking beyond
the expected density-dependent feedbacks that have apparently been
ineffectiveinsomecircumstances.
Accordingly,thisbookisaimedatfillingthisneedthrough(i)reconciling
theoreticalmodelswithempiricalfindingsonthepopulationdynamicsof
large mammalian herbivores, and (ii) developing appropriate models for
identifying thefactors andprocessescausingchangesin abundance.It is
structuredasfollows.
Chapter 1 summarizes findings from a set of long-term studies on her-
bivore populations that have been especially influential in revealing the
processes contributing to changes in abundance. Chapter 2 outlines the
suiteofmodelingapproachesrepresentingprevalenttheoryandconcepts.
The following chapters then explore particular aspects more compre-
hensively. Chapter 3 is concerned with identifying local and broad-scale
climatic influences on population dynamics, as well as the modifying
effects of predation and hunting, structured as a temperate–tropical
comparison. Chapter 4 considers the demographic processes that gen-
erate changes in abundance, as illuminated by individual-based studies.
Chapter5identifiescircumstancesthatmayleadtoirruptiveoscillationsin
abundance. Chapter 6 examines how spatial heterogeneity modifies the
influences of temporal variation in conditions on population processes.
Finally, Chapter 7 outlines an alternative paradigm for accommodating
theeffectsofspatialandtemporalvariabilityinresourcesandconditionson
populationdynamics.
All chapters were subject to outside review before being accepted for
publication, initially individually and then by the two reviewers of the
complete book. Chapters were revised and re-submitted in the light of
criticalcomments.WeareindebtedparticularlytoJohnFryxellforproviding
very incisivesuggestionsforfinalimprovementofallofthechapters.We
are also indebted to the various people, both members of the NCEAS
Preface xiii
group and others from outside this group, who gave some of their time
toassessparticularchapters.Mostfundamentally,theNationalCenterfor
EcologicalAnalysisandSynthesis,UniversityofCalifornia,SantaBarbara,
providedthefundingthatenabledtheworkinggroup‘‘Dynamicsoflarge
mammalian herbivores in changing environments: alternative modeling
approaches’’tomeetandshareourexperiencesandexpertise.
NormanOwen-Smith