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Canyoutellagibbonbyitscall?Inter andIntragroupcomparisonofKlosssgibbon
(Hylobatesklossii)vocalisationsinprimaryrainforest
andpeatswampforesthabitatsonSiberutIsland,
Indonesia.
EmmaFenton
[wordcount:12,652]
ThesissubmittedforthedegreeofMScConservation,
DeptofGeography,
UCL(UniversityCollegeLondon)
August2010
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UNIVERSITY COLLEGE LONDON
MSc Conservation
Please complete the following declaration and hand this form in with your MSc Research
Project.
I, ............................Emma Fenton.......................................................................................................
hereby declare :
(a) that this MSc Project is my own original work and that all source material used isacknowledged therein;
(b) that it has been prepared specially for the MSc in Conservation of University CollegeLondon;
(c) that it does not contain any material previously submitted to the Examiners of this or anyother University, or any material previously submitted for any other examination.
Signed : ....................................................................................
Date : .....................................................................................
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Abstract
TheMentawai Islands are recognised as being global biodiversity hotspots. They
support the greatest density of endemic primates found on any island chain and
providehabitat foravastarrayof floraand fauna. Theyarealso currentlyunder
huge from habitat destruction through illegal logging, the palm oil industry and,
morerecently,thepaperindustry. AllfouroftheendemicprimatesoftheMentawai
IslandsincludingtheKlosssgibbonareratedasEndangeredorCriticallyEndangered
bytheIUCNandalthoughtradeoftheseanimals isprohibitedbynational lawsand
bytheinternationalCITEStreaty,huntingforbushmeatstillcontinuesatanalarming
rate.
The aimof this researchwas toanalyzeand compareKlosss gibbon vocalisations
withinandbetweentwodifferentlyforestedhabitatsonSiberutIsland,W.Sumatra:
Indonesia. The vocalisationsof thedifferent gibbon typeshave anecdotallybeen
reportedasdifferentand, ifthis isthecase,itcouldopenupspeculationaboutthe
abilityofthegibbonstoadapttheirbehaviouralecologytohabitattypeand,inturn,
enablediscussionontheabilityofthisspeciestorespondtodifferentpressuressuch
asclimatechange,habitatdestructionandhunting.
It ishoped that theability todiscriminatebetweendifferentgroupsor individuals
basedontheirvocalcharacteristicscouldopenthedoorformoreindepthstudieson
the behavioural ecology of the Klosss gibbon. Something previously thoughtimpossiblebecauseoftheidenticalmorphologyacrossallageandsexclasses.
Klosssgibbonswererecordedat5differentlocationsintheprimarylowlandtropical
rainforestbutwerenotencountered inthepeatswampecosystem.Analysisofthe
vocalisations from the primary rainforest shows that individual gibbons can be
identifiedanddistinguishedbasedonthevocalcharacteristicsoftheircalls; thelack
of gibbon observations in the swamp forest led to the proposal of theories that
might explain the apparent disappearance of the gibbons from this habitat, and
speculationabout
what
this
might
mean
for
the
species
in
the
future.
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Contents
Content PageNumber
ListofAcronyms 6
ListofTables 6
ListofFigures 7
Acknowledgements 8
Introduction
Chapter1Geography
1.1 TheMentawaiIslands 1.2 Siberut 1.3 TheforesthabitatsonSiberut
1.3a ThePeleonanForest
1.3b PungutFieldStation
1.3c ThePeatSwampForest
9
10
11
11
Chapter2TheprimatesofSiberut&Hylobatesklossii
2.1. Klosssgibbonconservationstatus 2.2 Klosssgibbonstrongholds
2.2a SiberutNationalPark
2.2b SiporaandthePagais
2.3 ThreatstoSiberuthabitatandprimates 2.4 Traditionalculture 2.5 CurrentconservationmanagementfortheKlosssgibbon
15
17
19
21
23
24
Chapter3LiteratureReview
3.1 Selectionofresearchfocalhabitats 3.2 Klosssgibbonvs.othersmallgibbons 3.3 Vocalisationstudies
3.3a Terms,definitions,andexpectationsforprimate
vocalisations
3.3b Vocalisationresearch
3.3c Expectationsforvocalisationsinatropicalrainforest
3.3d Klosssgibbonvocalisations
26
26
26
30
Chapter4
Research
rationale
37
Chapter5Methods
5.1Studysubjects 5.2FieldStudysites 5.3Vocalisationcapturetechniques
5.3a FieldworkPungutResearchstation
5.3b FieldworkSwampforestresearchsite
5.4Datacollection 5.5Methodadaptationsfortheswamp 5.6Equipment 5.7Songboutdigitisation 5.8Statisticalanalysis
38
38
38
39
42
43
44
44
46
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Chapter6Results 47
Chapter7Discussion 55
Chapter8TheFutureofKlosssGibbonresearch 61
Chapter9Autocritique 63
References 64
Appendices
1. ThedifferentforestsofSiberutandtheirstructuralecology2. GPSdatafortheresearchsitesandthelisteningposts3. Fulllistofequipmentandsoftwareusedforthisresearch4. TransectmapofPungutresearchstation
69
70
71
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ListofAcronyms
Acronym Description
CITES
Conventionon
International
Trade
in
Endangered
Species
CV CoefficientofVariation
DPZ DeutchesPrimatenzentrum[TheGermanPrimateCentre]
GPS GlobalPositioningSystem
IPB InstitutPertanianBogor[BogorUniversity]
IUCN InternationalUnionforConservationofNature
SCP SiberutConservationProject
SNP SiberutNationalPark
ListofTables
TableNumber Description
1.1 SummaryofecologicalfindingsfromQuinten(2008)
2.1 IUCNassessmentsoftheKlosssgibbon
3.1 SummaryofrelevantresearchontheKlosssgibbon
3.2 Termsanddefinitionsusedwhendescribinggibbonsongs
3.3 Principlesofsoundtransmissionthroughatropicalrainforest
3.4 CallingfrequenciesofdifferentspeciesintheKlossshabitat
3.5 DeconstructionofthemaleKlossssong
3.6 DeconstructionofthefemaleKlossssong
5.1 Variablesnotedforeachrecording
5.2 Vocalvariablesisolatedandanalysedfromthedataset
6.1 ResultsfromtheDiscriminantFunctionAnalysisshowingthe
percentageofindividualscorrectlyassignedtotheirrespective
groupsusingallvariables
6.2 ResultsfromtheDiscriminantFunctionAnalysisshowingthe
percentageofindividualscorrectlyassignedtotheirrespective
groupsusingallvariablesexcludingtheposttrillelements.
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ListofFigures
Figurenumber Description
1.1 MapshowingthelocationoftheMentawaiIslands
1.2 MapshowingtheextentofthePeleonanforestofnorthernSiberut
1.3 AerialviewofPungutresearchcamp
2.1 TheotherendemicprimatesofSiberut
2.2 TheKlosssgibbon
2.3 MapshowingthelocationofSNP&themanagementzoneswithinit
3.1 MapdetailingtheproposedradiationofhylobatidsinIndonesia
5.1 Mapshowingthelocationoftheresearchsites
5.2 MapshowingthelocationofthelisteningpostsatPungutresearchcamp
5.3 MapshowingtheextentofthePeatswampforestinthePeleonan
forest
5.4 MapshowingthepositionofthetransectinthePeatswampforest
5.5 StylizedsonogramsofthemaleKlossscall
6.1 Mapshowingthepositionofthegroupsandtheirpredicted
homeranges
6.2 Graphshowingthecoefficientsofvariation(CV)acrossallindividualsfor
allvariablesmeasured
6.3 GraphcomparingtheCVbetweengroupsforallvariablesmeasured
6.4 GraphcomparingCVbetweengroupsforallvariablesexcluding
frequencymodulationof1stposttrillnote
6.5 CanonicalDiscriminantfunctionsshowingtheclusteringofcallsaround
thegroupcentroidforallvariables
6.6 CanonicalDiscriminantfunctionsshowingtheclusteringofcallsaround
groupcentroidsforallvariablesexcludingposttrillelements
6.7 CanonicalDiscriminantfunctionsmappingallthegroupstogether
excludingposttrillvariables
7.1 MapshowingencroachmentintothePeleonanforestfrom1988tothe
present
7.2 MapshowingencroachmentwithrespecttothePeatswampforest
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Iwouldliketotakethisopportunitytothankallofthepeoplewhomadethis
researchpossible.
ThepeopleatDPZ,whofundedtheproject,trainedmetousetheequipment,and
keptmeorganised:ThomasZiegler,KeithHodges,KurtHammerschmidt,Ellen
Wiese,andespeciallyMarcelQuintenforhishelponceIwasoutofthefieldandthe
generousdonationofhisGISdata.
DrMuhammedAgil,PakLucky,andAminahatIPB,whomanagedtheadministration
ofmyVISAandofficialdocumentsandhelpedmeincountry.
ThestaffoftheSCPandtheotherresearcherswhoweremysurrogatefamilywhileI
wasawayandwereonhandwhenthingsweregoingwrong:Jess,Christin,Dodo,
Feri,Yohanna,Rose,PakTarsan,IbuNovi,IbuRippe,PakLucienandmanymore.
Myguidesandassistantwhohelpedmecollectthedata,findtheBilouandlivein
theforrest. Withoutthemmyprojectwouldneverhavegotstarted: Tue,Binson,
Bitcar,andTitan.
FinallyforJess,myfriendsand myfamilyonceIgothome,forhavingpatiencewhen
Iwaswritingandteachingmehowtocrossroadsagain.
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Introduction
Theaimof thisproject is tocharacterizeandcompareKlosssgibbonvocalisations
withinandbetweentwodifferentlyforestedhabitatsonSiberutIsland,Indonesia. If
differencesarefounditcouldallowspeculationontheabilityofthisspeciestoadapt
to pressures such as habitat destruction and climate change by evolution of
communicationwithinandbetweengroups.
TheKlosssgibboniscurrentlyassessedasEndangeredaccordingtoIUCNguidelines
(BrandonJones et al., 2004) and is under threat from habitat loss; through
encroachment from logging, construction of roads, population growth and
agriculturesuchascoffeeandrubberplantations,aswellassubsistenceagriculture;
and hunting for cultural use, and for trade as bushmeat or pets (Nijman, 2001;
Campbell et al., 2008; Cheyne et al., 2008; Fuentes, 1997; Geissmann, 2007;
Whittakeretal.,2003).
It is importantthatmore isknownaboutKlosssgibbonsastheyplayan important
role inthefunctionandhealthoftheecosystemsthattheyareapartof. Primates
areknowntohaveimportantrolesinforeststructureandregenerationthroughseed
dispersal (Chapman, 2005). They have also been used as potential indicators for
climate change (BrandonJones,1996). More specifically, it is crucial thatmore is
understood about the populations of Klosss gibbons that exist on Siberut as it
represents the largestpatchofundisturbed forest that formspartof this species
extentofoccurrenceanditisthoughtthatthemajorityofKlosssgibbonsremaining
in theMentawai IslandsexistonSiberut inandaround thenationalpark (Fuentes,
1997;Tenaza&Mitchell,1985;Whittaker,2005a;Whittaker,2005b).There isalso
nocurrentcaptivepopulationofKlosssgibbons,orabreedingprogramme forthis
species,andtherearenoplansforoneinthenearfuture(Fuentes,1997).
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1 Geography
1.1. TheMentawai Islands are situated 85135km off thewest coast of central
Sumatrabetween0o55Sand3
o20Sand98
o15Eand100
o40E (Fuentes,2002)
seeFigure1.1.
Figure1.1:Mapshowingthe locationoftheMentawai Islands,Indonesia. AdaptedfromQuinten
(2008;p.3).
TheMentawaiIslandswereformedapproximately200millionyearsagoduetothe
subduction of the Indian tectonic plate under the Sunda plate (Waller, 2005;
Whittaker 2005a), the ensuing upward shift caused a submergence that created
deep sea trenches approximately 1.8km to the west of Sumatra, further west it
caused an uplift that created the chain of islands that includes the Mentawais
(Waller, 2005). Despite the sea level rising and sinking by over 200m since the
Pleistocene, the deep sea trenches have kept the Mentawais separate from
mainlandSumatraforover500,000years(Whittaker,2005a;Waller,2005;Whitten,
1980)despitethefactthattherestofSundaland(Java,Borneo,Malayaandsouthern
Indochina)wasconnectedbylandbridgesasrecentlyas10,000yearsago.
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AsaresultofthisseparationtheMentawaisareconsideredanimportantPleistocene
refuge (BrandonJones,1998). Theyprovideuniquehabitattoavastarrayof flora
andfauna(Fuentes,2002),theyhavethehighestlevelofendemismofanychainof
islands,approximately65%ofnonvolantmammalsintheMentawaisareendemicat
genusorspecieslevel(Whittaker,2005a);inanareaequivalentto6550km2(orone
thirdoftheareaofWales)therearefourendemicprimates(Fuentes,2002;Tenaza
&Mitchell,1985;Whittaker,2005b;Whitten,1980). Asaresultofthisuniqueness,
the tropical rainforest on these islands containmany hundreds of potential food
species(Whitten,1984a).
1.2Siberut is thenorthernmostand largestoftheMentawai Islands. It isalso the
bestknownoftheMentawais,ithasthesparsesthumanpopulationat4personsper
km2,asopposedto9/km
2inSiporaandthePagais(Tenaza&Mitchell,1985). Ithas
been estimated that Siberut has been occupied by humans for at least the past
2,0003,000years(Fuentes,2002).
Siberutisvisitedbyabout2,000touristsperyear,mostlytoobservethelifestyleand
cultureof localpeople(Whittaker,2005a). SiberutdiffersfrommainlandIndonesia
andhenceotherwellstudiedgibbonhabitats, in that it receivesveryhigh rainfall
(+/ 4,200mmperannum)andhaslessfertilesoils(Whitten,1982a).
1.3 The Forest habitats on Siberut and theMentawai Islands are very similar to
those on the Malay Peninsula and Sumatra but they grow with extremely high
rainfallandon relativelypoorsoil (Whitten,1980). Themajor forest typeson the
Mentawai Islands are tropical primary lowland dipterocarp forest, primarymixed
forest, secondary forest, Barringtonia forest, peat swamp forest and palm
dominated swamp forest; other types present includemangrove, freshwater and
sagoswampsaswellaswestcoastbeachvegetation (Fuentes,2002;Waller,2005;
Whitten,1980). Appendix1details thedifferent forest types and their structural
ecology.
AlthoughthemajorityofforestonSiberutistropicallowlandevergreenforest,there
areinfactsixforestformationsthatarerecognizedontheMentawaiIslands:tropical
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lowland evergreen forest,brackishwater forest,mangrove forest, two freshwater
swamps (including thepeatswamp thatencompasses thesecond researchsite for
thisproject),andbeachforest(Whitten,1980).
The tropical lowland evergreen forest can be divided into two main categories:
Dipterocarpusdominated,andmixedforest(Whitten,1980).
The Dipterocarpus forest is generally restricted to the hills and higher ridges on
Siberut, theemergents in this forest typeexceed70mand thecontinuous canopy
occurs between 30m and 50m. Themixed forest on Siberut typically covers the
lowerlyingareasandhillsideswhere the tallest treesaregenerally less than50m
tall.
Thereisno
single
dominant
plant
family
but
common
ones
include
Dipterocarpacae, Euphorbiaceae, Myristicaceae, and among the smaller trees
Rubiaceae(Whitten,1980).
1.3a The Peleonan Forest of North Siberut, which forms the focus of this
dissertation, isrecognizedforthehighdensityofallfouroftheendemicMentawai
primate species (Whittaker, 2005a; Whittaker, 2005b). It is one of the last
remaining,relativelyundisturbedprimaryrainforestsonSiberut(Ziegleretal.,2004).
SeeFigure1.2forlocationofthePeleonanforest.
Figure1.2:MapshowingtheextentofthePeleonanforestonNorthernSiberutinyellow(Quinten,
2008;GoogleEarth,2010).
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The forest also has more accessible terrain both for tourism and research, so
although it is only 4,000ha, it is of particular importance with regards to the
conservationof theseprimate species. Itwasextensively loggedaround20years
ago and currently there are low levels of hunting within this region (Whittaker,
2005b).
ThereishigherfoodavailabilityinthePeleonanforestcomparedtothesurrounding
primaryDipterocarpforestbecausethereareahigherproportionoftreesthatbear
fleshyfruitsandthereforeitisunusuallyproductive(Whittaker,2005a,b).
1.3b
Pungut
Field
Station
Figure1.3: AerialviewofpartofPungutcamp,usedwithpermissionfromC.Richter.
ThePungut fieldstation is located7kmupstream from thevillageofPolitcioman,
along the SigepRiver. Itwas established in2003 and isbasedon a6000ha area
withinthePeleonanforest(Ziegleretal.,2004). Theareaisprotectedatpresentby
contractualagreementsbetweentheSCP,localclansandIndonesianofficials(Ziegler
etal.,2004).
The station itself consists of 7 traditionally constructed wooden buildings and is
locatedinthecentreofaradialtransectsystem. Thetransectsystemcomprises26
main (spoke) transectsofbetween1.52km length,whichare connectedby inter
transects that expandoutwards from the camp in concentric circles (See transect
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map inAppendix 4). Allof the transects are systematicallyGPSmapped and are
clearedonaregularbasis(Ziegleretal.,2004).
1.3c The peatswamp forest on the northernmost coast of Siberut is the
secondresearchsite forthisproject. It lieswithinthePeleonan forestofnorthern
Siberutandlinesthecoast. Thearealiesbetween056to058Southand9848to
9850East. ItisborderedbytheoceanintheNorthandtheriverSigeptotheEast
and gives way to the primary lowland rainforest typical of the Peleonan forest
around2.53.5kmfromtheshoreline. Theforest isveryflatincomparisontothe
otherresearch
site
and
does
not
exceed
10m
above
sea
level
at
any
point
(Quinten,
2008). Lowlying flatareasareconducive tobecomingpeatswampecosystemsas
thetopography,coupledwithrelativelyhighrainfall,can leadtopoordrainageand
permanent water logging; consequently, many peat swamp ecosystems are
borderedbyhillsandhillsidesthatformtheirnaturalboundaries.
Therehasonlybeenonepreviousresearcheratthisfieldsiteandassuchtheplant
taxonomyisnotextensivelyknown. Belowisatablesummarisingtheenvironmental
conditionsthatweredocumentedduringthepreviousstudyTable1.1summarised
fromQuinten(2008).
Table1.1: SummaryofecologicalfindingsfromQuinten(2008).
EcologicalFinding Description
Dominanttreefamilies Lauraceae, Myrtaceae, Elaeocarpaceae,
Euphorbiaceae,Myristicaceae
Numberoftreespecies(inplot) 43 (local people say there are between
6070speciesintotal)
Mostabundanttreespecies Syzygium almini (Myrtaceae), Knema
curtisii (Myristicaceae), Palaquium
sp.(Sapotaceae)
Meantreeheight 16.3m(76%oftreesbetween020m)
Treesdisplaymany adaptations to Peat
SwampEcosystem
stilt roots, buttress roots,
pneumatophores,sclerophyllousleaves
Peatlayeraveragedepth >2.3m
Canopy Open and patchy as a result of the
prevalenceofyoungtrees(~4.5m).
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In comparison to the Lowland tropical forest of the first research site, the Peat
SwampForest isrelativelyspeciespoor,andthecanopy is lowerandpatchyrather
thancontinuous.
2.0 ThePrimatesofSiberut
Figure2.1:Figure2.1: TheotherendemicprimatesofSiberutfromlefttoright:Presbytispotenziani
(TheMentawaiLeafEatingmonkey),Macacasiberu(TheSiberutMacaque),andSimiasconcolor(The
pigtailedlangur). FromQuinten(2008).
AllfouroftheendemicprimatesoftheMentawaisareassessedaseitherthreatened
orendangeredby IUCNguidelines (Fuentes,2002). Theyalldependon the forest
but can avoid competitionwithinhabitatsbyusingdifferent forest strata in their
rangingandforagingpatterns(Whittaker,2005a;Fuentes,2002). Thepopulationsof
the primates on Siberut were estimated by Tenaza & Mitchell (1985) at: 36,000
Klosss gibbons; 46,000 Mentawai langurs; 19,000 pigtailed langurs; and 39,000
Mentawaimacaques.
Hylobatesklossii(TheKlosssGibbon)
Figure2.2: Hylobatesklossii.FromQuinten(2008;p.9)
VernacularName: KlosssGibbon
LocalName: Bilou
IUCNStatus: Endangered(En)
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TheKlosssgibbon isthesolegibbonspeciesoftheMentawai Islands (Campbellet
al.,2008;Tenaza&Hamilton,1971); itwasdiscovered in1902duringacollecting
expedition to the islands (Whittaker,2005a). It is theonlyMentawaiprimate for
whichasubspecieshasnotbeendescribedthatisuniquetoSiberutdespitethefact
thatalloftheMentawaiprimateshavehadasharedbiogeographichistory(Waller,
2005;Whittakeretal.,2003;Whittaker,2005a). Nophenotypicvariationhasbeen
notedintheKlosssgibbonasthroughoutitsrange ithasacompletelyblackpelage
andnofacialmarkings(Waller,2005),althoughrecentresearchsuggeststhatthere
maybevariationinthedirectionofthehairontheforearm(Whittaker,2005a). This
isreflected
in
the
fact
that
the
local
name
for
the
Klosss
gibbon
remains
the
same
throughouttheMentawaiIslands(Whittaker,2005a).
The Klosss Gibbon belongs to the family Hylobatidae, within the superfamily
Hominoidea (Whittaker,2005a); it is thesolegibbonspecies thathasacompletely
black pelage for all of its age/sex classes (Whitten, 1980). Klosss Gibbons are
monogamous,small,territorial,andarborealapes(Haimoff&Tilson,1985;Nijman,
2001;Whittaker,2005a); theyarealsodiurnalandaremoreomnivorous thanany
other gibbon species (Tenaza, 1975a; Waller, 2005). Although predominantly
frugivorous (upto72%ofthediet isfruit),KlosssGibbonswillalsoconsumebuds,
leaves, insects and eggs (Waller, 2005; Whittaker, 2005a; Marshall & Leighton,
2006),thisissurprisingsincetheyhaveapproximatelythesamebioecologyasother
gibbonspeciesandwouldthereforebeexpectedtohaveasimilardiet,howeverthe
dietoftheKlosssgibboncontainsrelativelyfew(2%)treeleavesandinsteadamajor
constituent(upto25%)ofthedietisarthropodsorsmallanimalprey(Nijman,2001;
Whitten,1982a;Whittaker,2005a).
Theprimary formof locomotion forallgibbons, includingKlosss, isbrachiation,or
rapid swinging underneath the branches of trees (Waller, 2005;Whitten, 1980).
This ismadepossibleby theextremely long forearms inrelation tohindlimbs that
Klosss gibbons possess, even in relation to other gibbon species (Waller, 2005;
Whittaker,2005a;Whitten,1984b). Klosssgibbonspreferentiallyuse the lowland
primaryforestclassfoundonSiberut(Fuentes,2002).
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AllgibbonsareprotectedbyinternationallawbyCITESAppendixI,whichprecludes
allinternationaltradeofthisspecies,theyarealsoprotectedbynationallawsinthe
majorityofcountriesthatprovidehabitatforthem(Geissmann,2007).
Competition occasionally arises between Klosss Gibbons and Mentawai Langurs
because they share several behavioural traits, as described by Tenaza & Tilson
(1985):
1) botharemonogamous;2) bothprefertoliveinhilly,primaryforest;3) botharestrictlyarboreal;4) bothsleepinemergenttrees3455mtall;and5) bothadvertisetheirpresencewithloud,sexuallydimorphicvocalisations.
(Tenaza&Tilson,1985;p.299)
ThiscompetitionisovercomebecausetheLangursexistpredominantlyontheedges
ofthegibbonhomerangesandthereforeneveroccurwithinthecore/centralpartof
thegibbon
territory
(Tilson
&
Tenaza,
1982).
Where
interactions
do
occur
between
these species, the gibbonsgenerally supplant the Langurs (Tenaza& Tilson,1985;
Tilson&Tenaza,1982;Fuentes,2002).
ThevocalisationsofKlosssgibbonswillbediscussedinmoredetailintheLiterature
Review(p.26)inassociationwiththerelevantrelatedcasestudies.
2.1Klosssgibbonconservationstatus
86% of all gibbon taxa have been assigned a heightened threatened status over
recentyears,39%bytwoIUCNcategories(Geissmann,2007)andtheKlosssgibbon
isnoexception.
Recently, current Klosss gibbon population estimates have been shown to be
inaccurate, as the home range sizes used to create themwere particularly small,
thereforeallowingmoregroupsthanare likelytoexistonSiberut(Whitten,1982a;
Whittaker,2005a;Whittaker,2005b). Mostrecentestimatessuggestthatthereare
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approximately20,00025,000KlosssgibbonsintheMentawaiIslands,mostofwhich
existonSiberutandinparticular,SiberutNationalPark(13,19015,413)(Geissmann,
2007;Whittaker,2005a). Thisresearchhasledtotheproposalofamorethreatened
statusfortheKlosssgibbon,asthedataindicatetheremighthavebeenadecrease
in the population of gibbons of ~50% over the last 25 years (approximately 3
generations) (Whittaker, 2005a). This proposal is based on a decline in area of
occupancy, extent of occurrence, and/or quality of habitat, and levels of
exploitation(Whittaker,2005a).
TheKlosssgibbon iscurrentlyassessedasEndangeredby the IUCN,although this
has been the cause of some dispute since the 1980s. Table 2.1 summarises the
assessmentsmadeduringthecourseofresearchontheKlosss.
Table2.1: IUCNassessmentoftheKloss'sgibbonthroughouttheresearchhistory(IUCN,2008).
Year Assessment Researcher(Assessmentbody)
1986 Vulnerable IUCNConservationMonitoringCentre
1988 Endangered
1990 Endangered IUCN
1994 Endangered IUCN
1996 Vulnerable
2000 Vulnerable
2005 Endangered Whittaker,D.
2008 Endangered,A2cd Whittaker,D.;IUCN
The Justification for the current assessment is based on the work of Whittaker
(2005b):
Endangeredduetoapastandcontinuedpopulationdecline,estimated
atmorethan50%overthepast45years(approximately3generations)
duetohuntingandlossofhabitat(IUCN,2008).
Asa resultof the IUCNclassificationandcampaigningbydifferent research
groups all gibbonswere listedunderCITESAppendix1,whichprecludes all
internationalcommercialtrade inthe listedspecies. Gibbonspeciesarealso
protected intheirnativecountriesbynational legislation(Geissmann,2007).
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DespitetheselawstheKlosssgibbonstillfacesanumberofthreats;theseare
discussedinsection2.3p.21.
TheconservationactioncurrentlyrecommendedbyIUCNandtheresearchers
whohaveworkedwiththeKlosssgibbonsissummarizedonp.24.
2.2Klosssgibbonstrongholds
2.2aSiberutNationalPark is theonlyprotectedarea in theMentawai Islandsand
thus the only protected areawithin the range of the Klosss gibbon (Geissmann,
2007). At 1,926 km2it covers nearly half the island see Figure 1.2 (Whittaker,
2005b). It is divided into three different areas, which are managed distinctly:
sanctuary, traditional use, and park village zones (Whittaker, 2005a). Limited
traditionalhunting ispermitted in the traditionaluse zones;however it is strictly
prohibited in the sanctuary zones (Whittaker, 2005a). Commercial logging is not
allowed ineither thesanctuaryor the traditionalusezones. Thereare threepark
villagezonesandnorestrictionsareplacedonthelanduseinthesezones.
Figure 2.3:Map showing the locationof theSiberutNationalPark (LEFT), theonly formally
protected area on the Mentawai Islands (adapted from MFRI, 2008), and (RIGHT) the
distributionof
the
different
management
zones
within
the
park,
from
Whittaker
(2005a).
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The park has very rugged terrain and few of the 2,000 annual tourists visit the
nationalpark.Unfortunately,despitebeingaprotectedarea,SNPexperiencesvery
littlelawenforcement,whichresults inextractionofforestproducts,bothprimates
for the bushmeat and pet trade, and timber and other forest products for
constructionandtrade(Whittaker,2005b).
TheNationalPark istheonly formallyprotectedareathroughouttheentireKlosss
range.
2.2bSiporaandthePagais.
Tenaza(1991)foundthatlocalpeopleonthetwoPagaiislandswereconvertingthe
foresttoplantationsforcashcropsataratethatmeanttheprimateswerelikelyto
beexterminatedbyhabitatdestruction. MorerecentlyreportsfromSiporasuggest
that the forest there has been extensively logged and is becoming unsuitable as
primatehabitat (Brown,pers.comm.). Economicdevelopmentandencroachment
into the forest is a big problem on Sipora, particularly for oil palm plantations
(IGCMW,2008). Itisestimatedthatonly1015%oftheislandsforestcoverremains
(Fuentes,1997).
In 1991 Richard Tenaza proposed the creation of reserveson fourof the smaller
islands around the Pagais: Sinakak (6km2), Simalegu (2km
2), Simatapi (2.5km
2),
Tinopu (14km2), including themarine environments around these islands (Tenaza,
1991). Sinakak has populations of all 4 endemic primates, while Simalegu and
Simatapi have populations of the pigtailed langurs. Despite not having primate
populations,Tinopuwas included in the reserve in thehope that itmightprovide
suitable habitat for reintroduction and controlledbreeding programmes as these
havebeensuggestedascriticalprospectstoconsidertherebyensuringthelongevity
oftheMentawaiprimates(Tenaza,1991).
Asyet,theseproposedreserveshavenotreceivedformalprotectionand it is likely
thatthehabitatwillbecomeunsuitableordisappearbeforetheydoasthereisonly
an estimated 15% forest cover remaining on both of the Pagai islands (Fuentes,
1997). Fuentes (2002)predicts that thenumbersofMentawaiprimatesonSipora
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andthePagais, includingtheKlosssgibbon,couldbehalvedbeforetheendofthe
nextdecade. For thisreasonSiberuthasbeendescribedas the lastbesthope for
longtermconservationof theMentawaiprimates (Whittaker,2005a;Whittakeret
al.,2003;Fuentes,1997).
2.3ThreatstoSiberuthabitatsandprimates
ThemainthreattothehabitatsonSiberut,andbyextensionthespeciesthatoccur
within them, is fragmentation through logging; agriculture both subsistence
encroachment cultivation and commercial encroachment such as rubber, tea, oil
palm, and pine plantations; forest product extraction by local people; increase in
humanpopulationsand thereforespace required for them to live in;andcharcoal
burning (Cheyne et al., 2008; Fuentes, 2002; Fuentes, 2008; Whittaker, 2005a).
Thereare2 largecompaniesthatcontrol loggingconcessionsthatcover100,000ha
and400,000haareasofSiberut (mostly in theNorth). Theseconcessionareasare
validforthenext20yearsandareactivelybeinglogged)(IGCMW,2008). Only25%
ofthesouthernpartofSiberutstillexistsasforesthabitat,withtheresthavingbeen
extensively logged. However, it is not just commercial encroachment that is
threateningthesefragilehabitats,landtenureforusebylocalpeopleisatraditional
rightanddoesnotrequireapermit from Jakarta forencroachment into the forest
habitat (IGCMW, 2008). This habitat destruction has a twofold effect: firstly, it
reducesthesizeofthehabitatavailabletogibbonstherebyreducingthenumberof
groups that can coexistwithin this space; secondly, it forces gibbons into poor
quality or degraded habitats and therefore they become easier prey for hunters
(Fuentes,1997). Mackinnon (1984)notes that evenselectivelylogged forestsare
extremely suboptimal habitat for gibbons as they require continuous canopy for
theirbrachiationtypeoflocomotion,thusgibbonscanbesaidtobemoreaffected
bydeforestationandhabitatfragmentationthantheotherMentawaiprimates.
With the increase in human populations, particularly since 2003 when the
Indonesian government declared the State of Mentawai as somewhere for
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populationrelocationtooccur,theareaofforestconvertedforsubsistencefarming
andcashcropsisontheincrease(Fuentes,1997). Thishabitatfragmentationopens
uptheforestandallowsaccesstopreviously inaccessibleareas,thereby increasing
thelikelihoodofprimatesbecomingpreytohunting,disease,andcaptureforthepet
trade(Fuentes,2002).
Tenaza&Tilson (1985)state that theonly truepredatorsof theKlosssgibbonon
Siberut are humans and pythons as there are no wild felids on Siberut and the
raptorsthathuntwithinKlossgibbonterritorieshavenotbeenreportedtopreyon
them,however,morerecently,Klosssgibbonshavebeenreportedlypreyedonby
eagles(IGCMW,2008).
Klosssgibbonsarehuntedforanumberofreasons:
1) Forsubsistenceuse. Althoughtraditionallytaboo,huntingofKlosssgibbonshasbeenon the increasesince thearrivalofmissionariesonthe islandand
theincreasedavailabilityofairriflestohuntwithinsteadofbowsandarrows
(Tenaza&Mitchell,1985;Tenaza&Tilson,1985;Whittaker,2005a;Whitten,
1982b). TheKlosssgibbonistheonlyIndonesiangibbonspeciesthatisnow
extensively hunted for food (IGCMW, 2008). Traditional huntingmethods
anduses for theKlosssGibbonwillbeexplained further inSection2.4 (p.
23).
2) Theillegalwildlifetrade(Cheyneetal.,2008)3) Theuseofbodypartsinthemanufactureoftraditionalmedicines(Cheyneetal.,2008)
4) Poaching forsale tobarownersas touristattractionsoraspets (Cheyneetal.,2008;Campbellet
al.,2008;Whittaker,2005a)
5) Klosss gibbons are a common and appreciated gift among local people(Campbelletal.,2008)
6) For sale as bushmeat in markets both on Siberut and mainland Sumatra(Campbelletal.,2008;Cheyneetal.,2008)
Anothermajorproblem for the longterm conservation of Klosss gibbons is that
large populations, an estimated 3,960 4,680 individuals, of this species occur
outsideprotectedareas(Geissmann,2007;Whittaker,2005a)and lawenforcement
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within protected areas is minimal at best (Whittaker, 2005b). There is also no
captivebreedingprogrammecurrentlyinexistenceorevenproposedfortheKlosss
gibbon,thismakesprotectionofthepopulations inthewildallthemore important
(Fuentes,2002).
2.4TraditionalCulture
Traditionally, the social organisation of the Mentawai culture, consisted of small
villagegroupsofbetween3080people(collectivelycalledtheuma)whoinhabited
and defended small, isolated territories that were centred around a wooden
longhouse(alsocalledan uma)(Fuentes,2002). Although farmingprovidedsome
aspectsoftheirdiet,proteinwasprimarilyobtainedthroughhuntingprimatesand
secondarilyfromfishinginriversandthesea(Fuentes,2002).
All four speciesofSiberutprimatesare/werehuntedby localpeople, traditionally
withbowsandpoisonedarrows(Tenaza&Mitchell,1985;Whittaker,2005a). With
theadventofmechanisation,accesstotheforesthasbeendrastically improvedby
the construction of logging roads deep into the forest allowing access to parts
previously undisturbed. The traditional hunting techniques have also been
abandoned in favourofthemoreaccurate .177calibreairrifles (Whittaker,2005a;
Fuentes,2002;Tenaza&Mitchell,1985).
CatholicandProtestantmissionarieshavealsoplayed theirpart in the increase in
huntingonSiberut,particularly inthe last50years. Thetraditionalanimistreligion
oftheMentawaisprecludedthehuntingofKlosssGibbons,Whittaker(2005a)goes
somewaytoexplainingthis(squarebracketsaretheauthorsnotes):
AccordingtoSiberutcreationmyth,longagotherewerenohumansin
the Mentawais, but there were many Bilou [Klosss Gibbons]. The
treetopsbecameovercrowdedwithBilou, and theyhad ameeting to
decidewhattodoabout it. Aftermuchdiscussion itwasdecidedthat
half the Bilou should move down to the ground. They did, and
eventuallychangedintohumans(Whittaker,2005a:p.10).
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It is for thisreason thathuntingof theKlosssgibbonhas traditionallybeen taboo
althoughthereareexceptionsforspecialcircumstances(Whitten,1982c). Withthe
advent of the Catholic and Protestant advancement through Indonesia, and the
decisionofPresidentSukarnothatallIndonesiancitizensmustadheretooneoffive
accepted religions: Hinduism, Buddhism, Islam, Christianity (Protestantism) or
Catholicism (Ricklefs,1993); the traditional religionof theMentawaishasbeenall
butlost,alongwiththerelatedhuntingtaboos(Whittaker,2005a).
2.5CurrentconservationmanagementfortheKlosssgibbon
As there is only one formally protected area within the Klosss gibbon range of
extent, themanagement for theconservationof thisspecies is resultantly focused
onanareathatprovideshabitatforonlyhalfoftheestimatedgibbonpopulation. In
spiteofthis,theKlosssgibbonisCITESlistedandthereforeprotectedbyIndonesian
national law (IUCN, 2008). However, the enforcement in the National Park is
virtuallynonexistentandthereforeothermanagementstrategieswereproposedby
Whittaker(2005)andsubsequentlybytheIUCN(2008):
1) IncreasedprotectionfortheSiberutNationalPark,whichcurrently lacksenforcement.
2) Formal protection of the Peleonan forest of northern Siberut,which ishome to unusually high densities of all four endemic primates but is
unfortunatelymuchmoreaccessible.
3) ProtectionofareaswithinthePagaiIslandsbycooperatingwithaloggingcompanythathasbeenpractisingsustainableloggingtheresince1971.
4) Conservationeducation,especiallyregardinghunting.5) Developmentofalternativeeconomicmodelsforlocalpeopleinorderto
preventfurtherencroachmentforsubsistenceuseand,morecritically,to
preventthemfromsellingofftheirlandtologgingcompanies.
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Despite these suggestions being made very seriously for the past 5 years, both
nationallyand internationally,therehavebeennorealsignsof improvement inthe
rateofhabitat loss intheMentawaisandthe Indonesiangovernmenthasmadeno
movetocreateNationalParksoveranyotherpartsofthearchipelago.
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3.0LiteratureReview
Forthepurposesofthisproject,theliteraturereviewwillbesplitintothreesections:
section 3.1 addresses the reasons for selection of the two habitats intended for
research in this project; 3.2 will discuss previous research pertaining to gibbon
studies,withparticularfocusontheKlosssgibbon;section3.2willdefinetheterms
used in vocalisation research, list theexpectations forKlosss gibbon vocalisations
given the restraintsof calling ina tropical rainforest,and summarise the research
thathasbeendoneonprimate vocalisation studies, again focusingon the Klosss
gibbon.
3.1Selectionofresearchfocalhabitats
ThePungut researcharea, in theprimary lowland tropical rainforest,was selected
becauseKlosssgibbonshavebeenstudiedextensivelyinthisareabeforetherefore
itcouldbeconfidentlyassumedthattherewouldstillbegibbonsinthisareaduring
the course of this research. Secondarily, no vocalisation studies on the Klosss
gibbonhaveeverbeenachievedwithinthePeleonanforestofnorthernSiberutand
thereforeitisinterestingtodiscoverwhetherornotgroupswithinarelativelysmall
areacanbedistinguishedonthebasisoftheirvocalcharacteristics.
Thepeatswamphabitatwaschosenbecauseprevious researchhas indicated that
there are gibbons that use this habitat and, based on their location and their
extrapolatedhomerange,itispossiblethattherearegibbonsthatinhabitexclusively
swamphabitats. Thesegibbonswereanecdotallydescribedashavingdifferentcalls
fromthoseintheprimaryrainforest(Quinten,2008).
3.2 KlosssGibbonvs.othersmallgibbons
ThemostrecentphylogenyofthegibbonsintheHylobatesgenuswaspublishedby
Whittaker et al. in 2007. They disprove the longstanding belief that the Klosss
gibbonisaprimitivetaxon,insteadfindingittobethemostrecentlyderivedtaxon,
sharingcharacteristicswithH.moloch the JavanSilverygibbon (Whittakeretal.,
2007).
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ThegibbonsareproposedbyWhittakeretal.(2007)tohaveradiated inanorthto
southdirection,withthenorthernmosttaxonbeingthebasaloneH.pileatus. This
isshowninFigure3.1below.
Figure 3.4: Map showing the proposed radiation of gibbon species of the Hylobates genus in
Indonesia. TheKloss'sgibbonextentofoccurrenceiscircledinred. AdaptedfromWhittakeretal.(2007:p.626).
Themostdetailedcomparisonsofgibbonmorphologyandbioecologypertinentto
KlosssgibbonswerepublishedbyWhitten(1984)butonlyconsiderthecomparisons
betweenH.klossii,H.agilis(theagilegibbon),andH.lar(thelargibbon).
Morphologically the three species are extremely similar except that agile and lar
gibbonshaveahairdensity that is three timeshigher thanonKlosssgibbons,and
theKlosssgibbonwouldnotbeexpectedtohavevastlydifferentecologyfromthe
othertwospeciesbasedonsizealone(Whitten,1984b).
Whitten (1984b)made sevenobservationsabout thebehaviourofKlosssgibbons
comparedtoagileandlargibbons:
1) Itisactiveforlongereachday;2) spendslessoftheactivityperiodtravellingandfeeding;3) spendsmoreoftheactivityperiodresting;4) livesinasimilarsizedhomerangeandterritory;
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5) hasa longerday rangeand travels furtherand fasterat theendof theday;
6) spendsthesametimeeachdayeatingfruit,muchlesstimeeatingleavesandmoretimeeatingarthropods;
7) usessimilartypesofnighttrees(Whitten,1984b:p.225)
Someofthesedifferencescanbeexplainedintermsofthechoiceoflocomotionthat
Klosss gibbons employ. Brachiation is the primarymethod of locomotion for all
gibbonspecies, theKlosssgibbonhas the longest forearmsofanygibbonspecies,
therefore, foranygivenamountoftimespenttravelling, it is likelythattheKlosss
gibboncan
travel
further
than
the
other
gibbon
species
and
for
less
time
as
this
travelismoreefficient(Whitten,1984b). Thisexplainspoints2and3.
Point6canbeexplainedasH.klossiihasa lesserabilitytoprocessanddigesthard
foods such asplant fibre, since theyhave fewermolar shearing surfaces than the
other gibbon species (Whitten, 1984b). High numbers of shearing surfaces are
frequentlyassociatedwith folivory. It ispossiblethatthisstatistic isskewedbythe
fact that the forests on theMentawais, and in particular the Peleonan forest of
northern Siberut, have aboveaverage productivity and a higher percentage of
fruitingtreesthanmanyforestsintherestofIndonesia(Whittaker,2005a,b). There
is speculation that the reduced folivory of the Klosss gibbon is due to high
concentrationsoftoxicsecondarycompoundsintheleavesoftheMentawaiforests,
howeverthereislittleevidencetosupportthisassumption.
Points1and5canbeexplainedbythedietofKlosssgibbonscomparedtotheother
2species. Agileand largibbonspreferentiallyeat figsatthestartandendofeach
dayasthisfoodsourcecontainsmanyseeds,whichwillreleaseenergyslowlyovera
givenperiodoftime,Klosssgibbonshowever,prefertoeatfigsduringtheafternoon
andfleshyfruitsintheevening,thereforetheycantravelfurtherinthedayandfeed
for longer inorder tomaximise theenergyavailable to them throughout thenight
(Whitten,1984b). Thisisdue,inpart,tothescarcityoffigspeciesinKlosssgibbon
habitats. Therefore, the Klosssmay spendmore time restingduring the relative
safetyoftheday inordertomaximise itsactivityperiodsothat itcan ingestmore
fruitbeforefindingasleepingtreeforthenight.
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Table3.1belowsummarisestherelevantresearchthathasbeencompiledsofaron
theKlosssgibbon.
Table3.3:BriefsummaryofallrelevantresearchontheKloss'sgibbon.
Author
Year(s)
ResearchSummary
Miller,G.S. 1903 [Seventy new Malayan mammals] The original
descriptionoftheKlosssgibbon.
Chasen,F.N.,
Kloss,C.B.
1927 [Spolia Mentawiensa mammals] First
collections and descriptions of mammals from
SiporaandSiberut
Tilson,R.,Tenaza,
R.R.
19741975,
19801981
[Monogamy,TerritoryandsongamongstKlosss
gibbons]FirstestimateofKlosssgibbonhome
range sizes and the number of territories that
couldpotentiallyexist in theMentawais. Night
treepreference.Chivers,D.J. 1977 [The LesserApes]The firstattempt toassess
thenumberofKlosssgibbons in theMentawai
Islands.
Whitten,A.J. 19801984 [TheKlossGibbon inSiberutRainForest]PhD
thesison thebehaviouralecologyoftheKlosss
gibbon,firststudytohabituategibbongroups.
Paciulli,L.M. 2004 [Theeffectsof logging,hunting,andvegetation
on the densities of primates in the Mentawai
Islands] Klosss gibbon population estimates,
laterproven tobe too conservativebecauseofinappropriatesurveymethodsused.
Waller,M.S. 2005 [Vocal diversity of the Klosss gibbon]
ComparisonsofH.klossiibetweentheMentawai
islandsandonlocationsonthesouthofSiberut.
Whittaker,D.J. 2005 [Evolutionary Genetics of Klosss Gibbons]
PhylogeneticanalysisofKlosssgibbondiversity
usingfaecalsamplescollectedacrosstheislands.
Marshall,A.J.,
Leighton,M.
2006 [Food availability and gibbon density]
Estimatinggibbonabundancewithavailabilityof
differentfoodspecies.Cheyneetal., 2008 [Densityandpopulationestimatesforgibbonsin
Indonesia]Mostrecentaccurateassessmentof
Klosss gibbon population numbers throughout
theMentawaiIslands.
Quinten,M. 2008 [Survey of the Primate Community of Peat
Swamp Forest on Siberut, Mentawai Islands:
Indonesia MSc thesis] Estimating primate
densityintheareausedforthesecondresearch
site.
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3.3Vocalisationstudies
a)Terms,definitions,andexpectationsforprimatevocalisations.
Waller (2005) states that the accepted definition of a song is a series of notes,
generallyofmore thanone type,uttered insuccessionandsorelatesas to forma
recognisablesequenceorpatter intime. Thisdefinitionwas firstusedtodescribe
birdsongbuthasnowbeenexpandedtoothertaxa. This isconsideredappropriate
for tworeasons:the loudcallsofgibbonshaveallof the featuresofbirdsong;and
they are generally complex and long, and can take place without any external
stimulus(Whitten,1980).
Table
3.2below
outlines
terms
that
are
used
to
describe
various
aspects
of
gibbon
songsandtheirdefinitions. Thesedefinitionsare inaccordancewiththoseusedby
Whitten(1980:p.245,258;1982d:p.44,48)
Table3.2:Termsanddefinitionsusedwhendescribinggibbonsongs.
Term Definition
Note/element A continuous sound of even or variable pitch with a
characteristicstructure
Phrase/call Asinglenoteorcollectionofnoteswhich formadistinctunit
withinasong
Series Similarphrasesrepeatedoneaftertheother,formingadistinctsectionwithinasong
Songbout Theperiodbetween the firstand lastnotesofacollectionof
two or more phrases, within which no two phrases are
separatedbymorethantwominutes
Openingsequence Fromthe firstnoteofthefemalesongtothebeginningofthe
firstgreatcall
Greatcall From the first steeplyrisingnoteof theascent, to the lastof
the following lowpitcheddescendingnotes,whetherornota
trillisincluded
Greatcallseries Fromthestartofthefirstgreatcalltotheendofthefinalgreatcall
Femalesong fromthefirstnoteoftheopeningsequencetothe lastnoteof
thefinalgreatcall
Theextenttowhichgibboncallsmaybetransmittedthroughaforestisgovernedby
certain principles, identified by previous studies, which are unchanged and
unchangeable. These have been identified by Whitten (1982a) and are detailed
below.
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b)Vocalisationresearch.
Singing is relatively rareamongprimatesand is restricted toonly fourgenera: the
indri (Indri), titi monkey (Callicebus), gibbon (Hylobates) and tarsier (Tarsius),
although the vocalisations of some great apes (Orangutans, Gorillas, and
chimpanzees) show similarities to gibbon vocalisations in: acceleration of note
rhythm,locomotordisplays,andvolume(Waller,2005).
Previousvocalisationstudieshaveshownthatindividualsongsarerecognisedtovary
in relation tochangingexternalstimulisuchas foodabundance,orsocialcontexts
(Waller,2005).
The function of gibbon songs has only recently begun to be understood but
traditionallytheyaresaidtobemaintenanceofspatialorganisationwithinafamily
groupandamongstneighbouringones,andtoserveasterritorialadvertisementto
individualsoutsideof the familygroup inorder todiscourage them from intruding
into occupied territories (Haimoff & Tilson, 1985). More recently it has been
proposed that gibbon songs also transmit other relevant information about the
callingindividual(Haimoff&Tilson,1985).
Gibbonsongsarespeciesandsexspecificandhavebeenshowntobeperfecttools
for analysing phylogenetic relationships between taxa, this is possible because
certainaspectsofsongsareconsideredtobe inherited,ratherthan learnt through
group interaction (Waller, 2005). Male gibbons are recognized asmaking use of
vocalisations for mate attraction, territorial advertisement, and defence of their
homerange(typicallybetween2040hectares)(Waller,2005).
c)Expectationsforvocalisationsinatropicalrainforest.
Transmissionofsoundsthroughatropicalrainforest isacomplexissue. Inorderto
achievesuccessfultransmissionofvocalisations,gibbonsneedtotake intoaccount
severaldifferent factorssuchas foliage,temperaturegradients,groundeffectsand
airturbulence(Whitten,1982). This ismadeallthemoredifficultbythemultitude
ofbirds,mammalsandinsectsthatcompetefordifferentsoundfrequenciesinorder
to communicate with other individuals of the same species. Table 3.3 lists the
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principles that apply to sound transmission through a heterogeneous, complex
mediumsuchasatropicalrainforest.
Table3.4:Principlesofsoundtransmissionthroughatropicalrainforest. AdaptedfromWhitten
(1980;1982).
Principle Source
Soundswithwavelengthsshorterthanobjects inthesound
pathwillbereflected,whereaslongerwavelengthswillnot.
Stephens & Bate
(1966)
Lowerfrequencysoundsareabsorbedlessrapidlybyhumid
airthanhighfrequencysounds.
Evans & Bass (1972)
IN Waser & Waser
(1977)
Vocalisations from sitesabove the rangeofgroundeffects
andat
times
of
minimum
acoustical
interference
increase
transmissiondistance.
Waser & Waser
(1977)
Complex structural properties of forests produce sound
windows, and at these frequencies sound attenuation is
lessthanforlowerorhigherfrequencies.
Morton(1975)
Haimoff & Tilson
(1985)
Temperature gradients, such as those through the forest
strata in which temperature increases with height, will
refract sound downwards, causing it to be trapped and
attenuatedwithintheforest.
Waser & Waser
(1977)
It is reasonable to expect that, given the limitations that gibbons face when
producingvocalisationsandthelimitationsoftheirownlaryngealmorphology,they
have evolved suitable adaptations thatminimise the attenuation of their calls in
ordertoguaranteemaximumtransmissiondistance(Whitten,1980).
Therefore,accordingtotheseprinciples,gibbonsshouldproducevocalisationswith
thefollowingproperties:
Relativelylowfrequencynotes fromsongsiteshighabovetheground at timeswhen thedifference in temperaturebetween the ground and the
canopy is least and when fewest other animals are calling in the same
frequencyrange(i.e.inthefewhoursbeforedawn)
Schneideretal.(2008)statethat,becauseofthescatteringandreverberationeffects
ofthedifferentforestmediaandbackgroundnoise,Klosssgibbonloudcallsshould
below
pitched
and
whistle
like
with
low
frequency
modulation.
Interestingly,
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Klosss gibbonswere theonlyprimateon Siberut that fulfilled thepredictions for
vocalisationsbothstructurallyandintheirutilisation(Schneideretal.,2008).
As Klosss gibbons generally inhabitat dense forest habitat, they have evolved a
narrow frequency range for their vocalisations that is perfectly adapted for long
rangecommunicationwithinthishabitatinordertomaximisethetransmissionover
largedistances(Haimoff&Tilson,1985).
Table 3.4 lists other organisms that compete for frequencies in Klosss gibbon
habitatandthefrequenciesthattheycallat.
Table3.5:CallingfrequenciesofcompetitororganismswithinKloss'sgibbonhabitat. Adaptedfrom
Whitten(1980).
Organism Frequency(kHz)
cicadas&orthopterans
exceptPompomiadecen 3.05.4 2Majorityofbirdswithloudsongs
except hill mynahs & asian fairybluebirds(butonlybriefly)
greater coucal (low frequencynotessungrepeatedly)
1.84.5
0.60.8 0.3
Siberutmonkeys 0.31.4
d)Klosssgibbonvocalisations.
Gibbon vocalisations are affected by many factors, including weather, ambient
temperature,topographyofthearea,andhumandisturbance(Cheyneetal.,2008).
Waller (2005) found that temperatureshad to reachaminimumof21.5oC, in the
hour before dawn (Whitten, 1980) with little or no rain during the night before
Klosss
gibbons
will
sing.
Whitten (1980: p.271) divides Klosss gibbon vocalisations into 4major classes of
songbout:
1. Predawnmalesongs;2. Postdawnmalesongs(beforefemalesongsoriffemalesongsdidnotoccur);3. Femalesongs;and4. Postdawnmalesongs(afterfemalesongs).
The order of gibbon vocalisations seems to be predetermined, by other gibbons
withinthe familygroup,othergibbongroups,andexternalstimulisuchasweather
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and ambient temperature. Despite these restrictions,Whitten (1980) found that
bothmale and female gibbonshave a tendency to singmost frequently at about
08:30.
Malecalls
MaleKlosssgibbonssing,onaverage,onceevery2.5daysbeforedawn,afterdawn
onceevery9.8days,andoverallonceevery1.7days(Tenaza,1975b;Waller,2005;
Whitten,1980). Themalevocalisationsoccurpredominantly in the sleeping trees
during the few hours that precede dawn (79%) (Haimoff& Tilson, 1985; Tenaza,
1975b;Whitten,1980;Whitten,1982d). This isbecausethesleepingtreestendto
be emergents i.e. tall trees that stand above the canopy, that therefore allow
maximum transmission of vocalisations (Whitten, 1980). Male vocalisations also
occurinthe5hoursafterdawn(19%)andcanalsooccurinthemidmorningandat
otherhoursalthoughthisislesscommon(2%)(Tenaza,1975b). Songboutscanlast
upto2hours,whichcomprisesalmost20%ofthegibbonsactivityperiod(Whitten,
1980).
Thedistance fromwhichamalecallcanbeheard isdisputed in literature,ranging
from 500700m, as reported by Tenaza& Tilson (1977) to 1.5km, as reported by
Whitten(1980). MaleKlosssgibbonsfrequentlysingatthesametimeasgibbonsin
adjoining territories, this countersinging is considered a form of competition
between the males (Waller, 2005). Male gibbons countersing while they are
separatedbydistancesof150500m(Tenaza,1975a). Thedifferencesbetweentheir
songs allow them to exchange informationwithout coming close to one another
(Haimoff&Tilson,1985).
Themalesonghasbeendescribed indetailbyWhitten(1980:p.248),thedifferent
phrasesarelistedanddescribedinTable3.5below.
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Table3.6: DeconstructionofthemaleKloss'sgibbonsong. AdaptedfromWhitten(1908:p.248).
Phrase Description
First Single pipes are given, which can be heard from about 250m away.
Phrases of double, triple or quadruple pipes develop, and intervals
betweenthemvaryfromabout4minutesattheoutset,to10secondsasthesongprogresses.
Second The pipes are followed by descending whoos, reminiscent of the first
notesofthetawnyowl,whicheventuallysupersedethepipes. Inthelater
stages,thesinglewhoo is followedbyoneortwoslightlyshorterwhoos
withanarrowfrequencyrange.
Third Thewhoos giveway towhoops.Whoopsareoftenprecededbywhoos
initially,but later thewhoosaresupersededbyhighpipes thatstart the
phrase. Thesewhoopsincreaseinnumberuptoaboutsevenconsecutive
notes, and each phrase generally finishes with one or two shallowdescendingwhoos.
Fourth Thetrilldevelops,precededbyanumberofwhoops,andusuallyfollowed
byoneortwoshallowwhoos.
Femalecalls
FemaleKlosss gibbons sing,on average,onceevery45days (Tenaza,1975b), all
femalevocalisationsoccur in the4hoursaftersunrise,once thegibbonshave left
thesleepingtreefortheday(Tenaza,1975b;Haimoff&Tilson,1985;Waller,2005).
The female vocalisations are predominantly given after dawn, generally after the
firstmalecalloftheday(Whitten,1980).
The female call or Great call of the Klosss gibbon was first structurally
deconstructed tentativelybyWhitten (1980), itwas this research that established
that each great call had specific quantifiable physical features that could be
statisticallytestedinordertoproveordisprove individuality inthecalls(Haimoff&
Tilson,1985). Throughthecourseofthisresearchand laterstudies,thegreatcalls
came to beused as indicatorsof thepresenceof gibbon groupsbecause loneor
floatingfemalesnevercall,whereasfloatingmaleshavebeenrecorded,therefore
afemalecallislikelytobeanindicationofgrouppresence(Whittaker,2005a).
Table3.6describesthedeconstructed femaleKlosssvocalisations,asdescribedby
Whitten(1980)andWaller(2005).
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Table3.7: DescriptionofthedifferentphrasesfromthefemaleKloss's'greatcall'. Adaptedfrom
Whitten(1980:p.258)andWaller(2005:p.7).
Phrase Description
First Theinitialnotesoftheopeningsequencearelikequietcoughs,theseare
singlepitchedhoots(~0.7kHz),butthemainnotessoonbegin.Second Afteraboutthreeminutesofthemainnotes,alongerrisingnoteisgiven
thatdenotesthe initiationofthegreatcallseries(0.61.0kHz)withfast
bubblingnotes (1.01.2kHz). Eachgreatcall lasts forapproximately30
seconds.
Third The lastphraseofagreatcall is the interlude,with slower fallingnotes
(1.0 0.4kHz). The great calls are separated by an interval of
approximately30 seconds. During these intervals,whoopsaregivenby
thefemales.
Fourth Greatcallseriescanlastforupto20minutes,individualgreatcallslacking
thetrillaregivenmostfrequentlyatthestartofaseries.
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4.0 Researchrationale
The aim of this study is to characterize and compare Klosss gibbon vocalisations
withinand
between
two
differently
forested
habitats
on
Siberut
Island,
Indonesia
Primarytropical lowland forest,andpeatswamp forest. Thestudywillbeusedto
describethevocalflexibilityofKlosssgibbonsongsandwilldeterminetheextentto
whichthegibbonsusethepeatswamp foresthabitat. Asrecentlyas20yearsago
research states thatH.klossiiwas rare in the swamp forestsonSiberut (Whitten,
1980). With no evidence to indicate that these studies were incorrect when
published, it must be assumed that Klosss gibbons have moved to inhabit the
swamp forests relatively recently in the last 20 years. This is likelydue to the
devastatingeffectsof loggingandother threats thatwereoutlined in section2.3.
Thesupposedability for thegibbons tomove intoandcolonisenewhabitats is, in
theory,apromisingglimpseoftheirabilitytosurviveasaspecies. However,allof
theswampforestonSiberutliesoutsidetheboundariesofwhatlittleprotectedarea
exists in the Klosss gibbon home range. Furthermore, the swamp forests are
predominantlycoastal,andsubsequentlyat risk frombeingsubmergeddue to the
changingsea levelsthathavebeenpredictedwiththeonsetofacceleratedclimate
change (Meehl et al., 2005). Furthermore, the Peleonan forest itself, which
encompassesbothfieldsites,hasbeenrecognisedasbeingofparticularimportance
to all of the Mentawai primates, not just the Klosss gibbon and so a better
understanding of the gibbons and other primates within this area could lead to
internationalpressuretopreservethisuniquehabitat.
Ifthegibbonshave indeedcolonisedanewhabitatthen it is importantto findout
howthisimpactsontheirbehaviouralecology,ifthetruismsofpastresearcharestill
applicable,andhowcurrentconservationimperativesneedtobeadaptedinorderto
accountforthisnewbehaviour. Iftheyarenolongertobefoundintheswampthen
itmust be investigated because it could imply a reduction in the fitness of the
Klosssgibbonasaspeciesandadecrease intheabilityofthegibbonstoadaptto
habitatpressures.
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5.0Methods
TheaimofthisresearchistocharacterizeandcompareKlosssgibbonvocalisations
within and between two differently forested areas in the Peleonan forest of
northernSiberut,Indonesia.
Vocalisationstudiescanbebroadlyseparated into2differentcategoriesaccording
to thepurposeof the research:1) thoseused forcensus techniques,and2) those
usedtocharacterizespecificvocalisationcharacteristics.
Where the research looked simply at the presence of groups i.e. primate census
research, generally each vocalisation incident is regarded as indicative of the
presence of a group anything from a lone floatingmale to a complex group
comprisingmany
males
and
females.
In
the
case
of
Klosss
gibbon,
itisthe
female
greatcall that isused to indicate thepresenceofagroupasno individual females
hadbeenrecordedforthisspecies(Whittaker,2005a).
Wheretheaimoftheresearchwastospecificallycharacterizethevocalisations,the
methodology generally involves the use of listening posts that offer the best
opportunityfortheresearchertorecordthecallswiththeminimumofobstruction
andthereforedistortionofthecall(Waller,2005;Keith,2005).
5.1Studysubjects
The subjects of this study were wild populations of Kloss gibbons. 5 groups(individuals)wererecordedandatotalof154callswereofsufficientquality tobe
usedforstatisticalanalysis.
5.2FieldStudysites
Gibbonsongswererecordedfromtwolocations,asshowninFigure5.1. GPSpoints
for the research sitesand the listeningpointsare listed inAppendix2alongwith
topographical data. These study siteswere chosen as Klosss gibbons have been
observedorstudiedatbothofthesitespreviously.
Pungut researchcamp is located inprimary lowland tropical rainforest, thearea is
notformallyprotectedandhasbeenrecordedashavingunusuallyhighdensitiesof
thefourendemicMentawaiPrimates. Thecampwasestablishedin2004bySCPand
hasbeenusedforpreviousresearchonKlosssgibbons.
TheEcolodge(PaleLeukLeu) is locatedonthenortherncoastofSiberut. Thebeach
giveswaytoaswampandthenapeatswampforest,which isthesecondresearch
focussiteforthisproject. Thestructureoftheforesthereisverydifferentfromthat
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at Pungut camp and so comparison between the two sites should elucidate the
abilityofgibbonstoadapttheircallsaccordingtohabitat.
Figure5.5:Mapshowingthelocationofthe2researchsitesonSiberut,Indonesia.
5.3
Vocalisation
capture
techniques
5.3aFieldworkPungutResearchStation
The fieldwork for this research was undertaken using the 'listening post'
methodologywherebytheresearcherwaitsandrecordsfromone location inorder
toobtainvocalisationdatafromindividualgroups,thenthelisteningpostischanged
inorder tomaximise the likelihood thatdifferentgroupscanbe recorded (Waller,
2005:Keith,2005). ThelisteningpostsatPungutwerenotchosenwhollyrandomly,
but instead were chosen according to where it would be most likely to obtain
successful recordings. Factors taken intoconsideration included:LikelypositionofKloss'sgibbonsleeping(andthereforesinging)trees,topography,'soundwindow'.
Previous researchhasestablished thatKloss'sgibbon sleeping trees tend tobe:a)
emergenti.e.Talltrees,thecrownofwhichisseveralmetresabovethecanopyof
therainforest;b)inthecentreoftheirhomerangesoftenonhilltopsasvalleyscan
demarcate theboundariesbetweendifferentgibbon territories,and;c)reasonably
staticwithin thehomerange (Whitten,1981). Themale gibbons,when they sing,
sing from the sleeping tree until sunrise when the group / individual will begin
foraging(pers.Obs.).
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The topography of the forest plays a big part in the ability of the calls to be
transmittedandaffectsthedistanceoverwhichtheycanbeheard. Forthisreasonit
wasdecided thathilltopswouldpresent thebestopportunity forobtaininggibbon
vocalisations for two reasons: 1) The calls canbeheardover greaterdistances astherearefewerobstructionsbetweenthecallingindividualandtheresearcher,2)if
onahilltoptherewouldbeagreaterpossibilityofbeingclosertoacallingindividual
atthestartofthecallsequence.
The'soundwindow'wasdefinedbyHaimoff&Tilson(1985)asbeingthefrequency
atwhichthecomplexstructuralpropertiesofarainforestleastattenuatethesound
thatisbeingisolated. Forthisreason,thesamplingfrequencyfortherecordingswas
chosenas44KHzinordertominimisetheeffectsofinsectnoiseontherecordings.
ThelocationoftherecordingsitesisshownbelowinFigure5.2.
Figure5.2:MapshowingthelocationofthelisteningpostsinrelationtothePungutresearchcamp.
5.3bFieldworkswampforestresearchsite
Figure5.3showstheestimatedextentoftheswampforestonSiberut,inrelationto
theboundariesof thePeleonan forestarea. It isborderedon twosidesbywater:
the sea in theNorthand theRiver Sigep in theEast, thenon thewesternborder
thereisthetownofSikapogna,whichisexpandingandencroachingontheforest.
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Figure 5.3: The extent of the swamp forestwithin the Peleonan forest area. The yellow area
denotestheboundariesofthePeleonanForest;theredareadenotestheestimatedboundariesof
thePeatSwampForestecosystem.
Asthepeatswampforestispredominantlyflat,withlittleelevationmorethan10m
above sea level,adifferentapproachhad tobe taken inorder to tryand find the
gibbons.
A central transectwas cut roughlydueSouth from thePaleLeukLeuon thebeach
trying, where possible, to follow the main transect cut by Quinten (2008). The
rationale behind this decision was twofold: 1) the transect would be marginally
easiertocutastherehadbeenonetherepreviously;2)Itwouldmaketheresultsof
thisstudydirectlycomparablewiththoseofQuinten(2008)thereforegivingagood
indicationofthepopulationdynamicsofthegibbonsinhabitingtheswampareas.
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Oncethecentraltransecthadbeenestablished,secondarytransectswouldbecutat
intervals from the main transect, similar to Quinten (2008) in order to enable
locationidentificationofdifferentgroups.
Figure5.4showstheoriginaltransectsystemcutbyQuinten(2008)andthetransect
systemcutbytheresearcherforthepurposeofthisstudy.
Figure5.4: Mapshowing thepositionof the transect in thepeatswamp forest. Thepurple line
denotesthetransectcutbythepreviousresearcher(Quinten,2008),theblueflagsmarkwaypoints
alongthetransectcutduringthisresearch.
5.4DataCollection
TheequipmentwasprovidedbytheGermanPrimateCentre(DPZ)andaweeklong
trainingperiodwascompletedpriortotraveltotheresearchsiteinordertoensure
thatthetechniquesbeingused inthestudywereperfected. Thevocalisationsthat
wererecordedweredonesousingthemethoddetailedinthissectionoftheproject
andusingthesameequipment.
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Theresearchwasconductedwiththehelpof3experiencedMentawaivillagers,Tue
Salamanang, Binson Salamanang, Bitcar Salamanang1. Their local expertisewas
crucial for estimating the distances to calling individuals, cutting transects in the
swamp forest, and finding appropriate locations to record from. All three hadworked for the SCP in some capacity for years, and Tue had experienceworking
alongsideresearchersstudyingtheKlosssgibbon.
Itwasacceptedthatonlyonemalesongboutwouldberecordedeachdayspentin
thefieldasitwouldnotbepossibletoobtaingoodqualityrecordingsformorethan
onegroupasthatwouldnecessitatemovingfromonegrouptoanotherorbeingat
an intermediate point between the two calling groups and compromising on
recordingquality. Thefemalesongswererecordedadlibitumastherewasnoway
ofpredictingwherethegroupwouldbeifandwhenthefemalescalled.
Thelisteningpostswerevisitedfrom04:30hruntil06:30hr(sunrise),whenthemale
Klossscalled,unlesstherewasrain. Iftherewasraintheteamremained incamp
untilitstoppedfor3reasons:1)theKlosssdonottendtocallduringrain,2)therain
could potentially damage the equipment and therefore the risk of damage
outweighedthepotentialbenefitofachievingrecordings,3)thequalityofrecordings
during therain,even ifclose (
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obtainrecordings fromtheswampasthegibbonswereneverheardwithin4kmof
thecoast,incontrasttothefindingsofQuinten(2008). Thereasonforthisapparent
disappearance of the gibbons from the peat swamp habitatwill be addressed in
detailinthediscussion.
5.6Equipment
ThecallswererecordedonaMarantzSolidStateRecorder(modelPMD661)usinga
SennheiserME66shotgununidirectionalrecorderwithaK6powermodule. Inorder
tominimisethedisturbancescausedbywindorrainandtoprotectthemicrophone
from the humidity at the field site a rubberfoamMZW 66 prowindscreenwind
guardwasused.
Thisequipmenthasalreadybeenusedinordertocompiledataonthevocalisations
of Mentawai primates and was therefore deemed appropriate for this study
(Schneideretal.,2008).
NavigationaldataandlisteningpointlocationsweretakenwithaGarmin60CSXGPS.
Thiswas chosenbecauseof itsdurability, robustness andproven recordofbeing
abletotakeGPSwaypointsevenunderdensetropicalrainforestcanopy. Afulllistof
equipmentandsoftwareusedcanbefoundinAppendix3.
5.7Song
bout
digitisation
ThedatawasdigitisedusingAvisoftSASLabProbioacousticsoftware. Inorder to
maketheresultsofthisresearchcomparabletothoseofothervocalisationstudiesa
standardsetofvariableswillbemeasuredandanalyzed. Theseare listed inTable
5.2below.
Table5.9:Vocalvariablesanalyzedfromthedataset.
Variable Description
Durationofcall Timefromstarttoendofphrase(seconds)
Numberofelementsinthecall Countofthetotalnotesinthecall
Maximumfrequencyinthecall MeasuredinHertz
Numberofpretrillelementsinthe
call
The total number of notes that occur before
thetrillinthecall
Durationofpretrillnotes Thetimefromthestartofthefirstnotetothe
finalnotebeforethetrillphrase(seconds)
Maximum frequency of pretrill
notes
MeasuredinHertz
Numberofnotesinthetrill Numberofnotesthatoccurinthetrillphrase
Durationofthetrill Time from the start to the end of the trill
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phrase(seconds)
Minimumfrequencyofthetrill MeasuredinHertz
Maximumfrequencyofthetrill MeasuredinHertz
Frequency modulation of the 1st
posttrillnote
Differenceinfrequencyfromthestartofthe1st
posttrill note to the end of the 1st posttrill
note. MeasuredinHertz
Numberofposttrillnotes Countof thetotalnumberofnotes thatoccur
afterthetrillphrase
Durationofposttrillnotes Timefromthestartofthe1stposttrillnoteto
theendofthefinalnoteinthecall(seconds)
Maximum frequency of post trill
notes
MeasuredinHertz
Eachmale great call has three elements: pretrill, trill, and posttrill as shown in
Figure5.5.
Figure5.6: Stylizedsonogramsshowingthethreeelementsineachcall. A=pretrillelement,B=
trillelement,C=posttrillelement.
The callswere digitised using a 16bit sampling size and 44.1 kHz sampling rate.
Avisoftwaschosenbecauseoftheeasewithwhichsoundscanbeeditedefficiently
withoutrequiringspecialisedtraining.
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Onlycallswithallthreeelementsweredigitised,fragmentswereleftout. Fragments
includedaborted callsandalso the whoos thatare sung in the initial stagesofa
songboutbeforethemorecomplexcallsstart.
5.8StatisticalAnalysis
ThedatageneratedfromAvisoftwerethenanalysedusingSPSS14.0forWindowsby
DiscriminantFunctionAnalysis(DFA). DFAisusedtodeterminewhichvariablescan
beusedtodiscriminatebetweennaturallyoccurringgroups.
DFAworkswithdatathathasalreadybeenclassified inordertoestablishrules for
futureclassificationofadditionaldata. ByusingDFA, it ishopedthat thedifferent
groups within and between habitat types on Siberut can be isolated and
differentiatedinastatisticallysignificantmanner.
AfunctionthatisselectedbytheDFAiseitheroneofthevariablesisolatedfromthe
data, or a combination of variables that can represent themselves and other
variablesasaresultof linearcorrelations. Thevariablesthatwerechosenforthe
functionswereacceptedorrejectedaccordingtoWilks test. The coefficient is
defined as the proportion of the total variance in the discriminant scores not
explainedbythedifferencesamongthegroups(Landau&Everitt,2004). Itteststhe
differences between themeans of several groups using a combination of several
variables.
Thepriorprobabilitiestheprobabilitythatasamplewillbeassignedtothecorrect
groupby chancewere adjusted according to the group size automaticallyusing
SPSS.
Tablesshowingwhetherornotacallhadbeencorrectlyassignedtoagroupbyusing
thefunctionswerecrossvalidatedusingtheleaveoneoutmethodology;thisgives
amoreconservativeestimateofcorrectpredictedassignment.
Canonicaldiscriminantfunctionsareusedtovisuallyshow:a)howtightlythevalues
clustertothecentrepoint(centroid)inthefunctionsforagroupasawhole,andb)
how closely clustered the group centroids are, thereby showing how distinct the
differentKlosssgibbongroupsare.
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6.0Results
TheworkatthesecondresearchsiteattheEcolodgedidnotyieldanyresultsasthe
gibbonswerenotencounteredinthepeatswampforest. Hypothesesastowhythis
apparent disappearance might have occurred are suggested in the Discussion
section. Assuch,acomparisonbetweenthepopulationsintherainforestandthose
inhabiting theswamp forest isnotpossible. The resultschapter therefore focuses
onthedatacollectedfromthePungutresearchsite.
The basic descriptive statistics will be discussed concurrently with the results
presentedhere;theresultsoftheDiscriminantFunctionAnalysiswillbeoutlined in
thischapterandthenexaminedinthediscussionchapter.
FieldTime
Iwasabletocomplete34daysoffieldworkandaccrue289hoursoffieldtime,the
majorityofthistimewasonsubsequentdays. Unfortunatelythereweredayswhere
fieldworkwasnotpossiblebecauseof theweather, thishappenedon7occasions,
andIwasunabletoworkontheweekendsbecausethelocalvillagerswhoactedas
guideshadtoattendchurch.
Groupdistributionwithintheresearchsite
Figure6.1showsthedistributionofgroupsinthestudyarea.
Figure 6.7: Map showing the position of the listening posts/sleeping trees with visual
representationof
estimated
gibbon
home
range
sizes.
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TheestimatedhomerangefortheKlosssgibbonis2040hectares;thisisdisplayed
onFigure6.1asconcentriccircles. Itisimportanttonoteherethathomerangesare
unlikely to be perfect circles but these represent the most widelyused visual
representationforprimatehomeranges.
The home ranges are visually depicted as buffer zones extending out from the
positionof thesleeping/calling tree. The rationalebehind this is that thesleeping
treestendtobechoseninthemiddleoftheKlossshomerange,ashasbeenfound
inpreviousresearch(Whitten,1980;Tenaza,1975b).
The light green circledenotes theboundaryof ahypotheticalhome range at the
inner limitoftheestimatefrompreviousresearch,thedarkgreencirclerepresents
the same boundary at the outer limit of previous estimates, and the blue circle
showsanintermediatestate.
Whittaker (2005a) foundthatKlosssgibbonstend to inhabitareasmoresimilar to
the lower endof thehome range size, in addition, thehigherproductivityof the
Peleonan foresthas led tosuggestions that thegibbons in thishabitatmighthave
home ranges as small as 67ha (Tenaza, 1975b) as a results of reduced need for
extensive foraging between food sources. With these suggestions inmind I can
concludethat,giventheminimaloverlappingbetweenmyprojectedhomeranges,it
islikelythatthegroupsIhaveidentifiedareseparate. Theonlypossibleexceptionis
Group4andGroup2, it couldbeargued that these are the same groupbecausethereisadegreeofoverlapbetweentheprojectedhomeranges. Iamconfidentthis
isnotthecasefor2reasons:
1) Sleeping trees tend tobe in the centreofKlossshome rangesanddonotmovealargedistancewithinthatarea(Whitten,1980;Tenaza,1975b).
2) The boundaries between Klosss home ranges are generally dictated bytopography,thecentreofthehomerangesisgenerallyfoundonahilltopand
theboundariesnormally followvalley floors (Tenaza,1975b). The sleeping
trees forbothGroup4andGroup2areonhilltopsandareseparatedbya
valley.
For these reason I can conclude that Group 2 and Group 4 are in fact separate
groups. AllfurtherstatisticalobservationsarebasedontheassumptionthatIhave5
distinctgroupsorindividuals.
Intraindividualdiversity
Coefficientsof variation (CV)were calculated for eachof the variables across the
entire
sample.
This
shows
the
degree
of
variation
within
a
measure
with
respect
to
themean.
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Thesearedetailed inFigure6.2. AscanbeseenfromFigure6.2,thecoefficientof
varianceformostofthevariableisrelativelylow;howeverthisisnottrueforthree
of thevariables: 1)Frequencymodulationof the1stposttrillnote,2)Numberof
posttrillnotes,3)Durationofposttrillnotes.
Figure6.2: Graphshowingthecoefficientofvariationforallthevariablesstudied.
Thelargevarianceforthefrequencymodulationcanbeexplainedbecause,forsome
ofthecalls,theposttrillnoteisadescendingwhooooandthereforethefrequency
attheendofthenoteislowerthanthatatthestartofthenoteproducinganegative
frequencymodulation,and forother calls, the firstposttrillnote is similar to the
ascending notes of the pretrill phrases producing a large positive frequency
modulationandhencethevarianceacrossthesampleisverylarge.
Thelargevaluesforthenumberofposttrillnotesanddurationofposttrillnotesis
simplydue toa large rangeofvalues for thisvariable,hencea largecoefficientof
variation.
Intragroupdiversity
Figure 6.3 compares the coefficients of variation between the groups across the
wholesetofvariables. ThegreatestvaluesfallwithintheFrequencymodulationof
1stposttrillnotecategory. Asthislargevaluehasbeenexplainedbythereasoning
above, the results for this variable are omitted so that the values for the othervariablescanbeexamined. ThisisshowninFigure6.4.
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50
0
100
200
300
400
500
600
700
800
900
1000
Duration
of call
actual
no.
max.
freq. ofcall
no. of
pre-trillnotes
Duration
of pre-trill notes
Max.
freq. ofpre-trill
notes
No.
notes intrill
Duration
of trill
Min.
freq. oftrill
Max.
freq. oftrill
no. of
post-trillnotes
Duration
of post-trill notes
Max.
freq. ofpost trill
notes
Freq.
mod. Of1st post-
trill noteVariable
Coefficientofvariation(
%)
Group 1
Group 2
Group 3
Group 4
Group 5
Bar chart showing the coefficient of variation between the groups for all variables
Figure6.3: Graphcomparingthecoefficientsofvariationacrossthegroupsforallvariables.
AscanbeseeninFigure6.4,thecoefficientofvariationformostofthevariables is
reasonably low;theexceptionsareforthosevariables thatmeasureaspectsofthe
posttrillelementofthecalls. Thisimplies,withtheexceptionofthosevariablesjust
mentioned, that the range of figures for each of the remaining variables stays
relatively stable and can therefore be considered an accurate reflection of the
variablesthathavebeenmeasured.
HoweveritmustbementionedthatalowC.V.valuecanalsobeindicativeofasmall
samplesizesotheseresultsmustbeviewedwiththatinmind.
Bar chart showing coefficient of variation for all variables excluding frequency
modulation of 1st post-trill note.
0
10
20
30
40
50
60
70
80
90
100
Duration
of call
actual no. max.
freq. of
call
no. of
pre-trill
notes
Duration
of pre-trill
notes
Max.
freq. of
pre-trill
notes
No. notes
in trill
Duration
of trill
Min. freq.
of trill
Max.
freq. of
trill
no. of
post-trill
notes
Duration
of post-
trill notes
Max.
freq. of
post trill
notes
Variable
Coefficientofvaria
tion(%)
Group 1
Group 2
Group 3
Group 4
Group 5
Figure 6.4: Graph comparing the coefficients of variation between the groups for differentvariables.
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