fenton 2010 kloss s gibbon vocal is at ions in primary rain- and peat swamp forest habitats on...

8/3/2019 Fenton 2010 Kloss s Gibbon Vocal is at Ions in Primary Rain- And Peat Swamp Forest Habitats on Siberut

1/72

1

Canyoutellagibbonbyitscall?Inter andIntragroupcomparisonofKlosssgibbon

(Hylobatesklossii)vocalisationsinprimaryrainforest

andpeatswampforesthabitatsonSiberutIsland,

Indonesia.

EmmaFenton

[wordcount:12,652]

ThesissubmittedforthedegreeofMScConservation,

DeptofGeography,

UCL(UniversityCollegeLondon)

August2010


2/72

2

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 : .....................................................................................


3/72

3

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.


4/72

4

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


5/72

5

Chapter6Results 47

Chapter7Discussion 55

Chapter8TheFutureofKlosssGibbonresearch 61

Chapter9Autocritique 63

References 64

Appendices

1. ThedifferentforestsofSiberutandtheirstructuralecology2. GPSdatafortheresearchsitesandthelisteningposts3. Fulllistofequipmentandsoftwareusedforthisresearch4. TransectmapofPungutresearchstation

69

70

71

72


6/72

6

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.


7/72

7

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


8/72

8

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.


9/72

9

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).


10/72

10

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.


11/72

11

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


12/72

12

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).


13/72

13

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


14/72

14

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).


15/72

15

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)


16/72

16

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).


17/72

17

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


18/72

18

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).


19/72

19

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).


20/72

20

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


21/72

21

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


22/72

22

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


23/72

23

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).


24/72

24

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.


25/72

25

Despite these suggestions being made very seriously for the past 5 years, both

nationallyand internationally,therehavebeennorealsignsof improvement inthe

rateofhabitat loss intheMentawaisandthe Indonesiangovernmenthasmadeno

movetocreateNationalParksoveranyotherpartsofthearchipelago.


26/72

26

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).


27/72

27

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;


28/72

28

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.


29/72

29

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.


30/72

30

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.


31/72

31

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


32/72

32

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,


33/72

33

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


34/72

34

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.


35/72

35

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).


36/72

36

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.


37/72

37

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.


38/72

38

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


39/72

39

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.).


40/72

40

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.


41/72

41

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.


42/72

42

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.


43/72

43

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 (


44/72

44

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


45/72

45

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.


46/72

46

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.


47/72

47

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.


48/72

48

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.


49/72

49

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.


50/72

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.

8/3/2019 Fenton 2010 Kloss s Gibbo

fenton 2010 kloss s gibbon vocal is at ions in primary rain- and peat swamp forest habitats on...

Documents