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绪论 虎鲸类型和种群（第2页）

Northernwaters

NorthPacific

ResearchoffthewestcoastofCanadaandtheUnitedStatesinthe1970sand1980sidentifiedthefollowingthreetypes:

Resident（fish-eating）orcas:Thecurveddorsalfinsaretypicalofresidentfemales.

Resident:ThesearethemostmonlysightedofthethreepopulationsinthecoastalwatersofthenortheastPacific.Residentsdietsconsistprimarilyoffishandsometimessquid，andtheyliveinplexandcohesivefamilygroupscalledpods.Femaleresidentscharacteristicallyhaveroundeddorsalfintipsthatterminateinasharpcorner.Theyvisitthesameareasconsistently.BritishColumbiaandWashingtonresidentpopulationsareamongstthemostintensivelystudiedmarinemammalsanywhereintheworld.Residentorcascanbedividedintoatleastthreedistinctmunities;northern，southernandsouthernAlaskan.SouthernAlaskanresidentorcasaredistributedfromsoutheasternAlaskatotheKodiakArchipelagoandnumberover700individuals.Thesewhalesconsistoftwointerbreedingclansdistinguishedbyacousticcallsandwhoserangesoverlap.ThenorthernresidentmunitylivesincoastalandinlandwatersfromsoutheasternAlaskatoVancouverIsland.Itconsistsofthreeclansand16podsandnumberover300orcastotal.ThesouthernresidentmunitygenerallyinhabitstheinlandwatersofsouthernBritishColumbiaandWashington，butcanbefoundintheouterwatersoffVancouverIsland，Washington，OregonandCalifornia.Theyconsistofoneclanandthreepods，andnumberlessthan80individualsandarelistedasendangered.

TransientorBiggs:Thedietsoftheseorcasconsistalmostexclusivelyofmarinemammals.Theyliveinthesameareasasresidents，butthetwoavoideachother.Transientsgenerallytravelinsmallgroups，usuallyoftwotosixanimals，andhavelesspersistentfamilybondsthanresidents.Transientsvocalizeinlessvariableandlessplexdialects.Femaletransientsarecharacterizedbymoretriangularandpointeddorsalfinsthanthoseofresidents.Thegreyorwhiteareaaroundthedorsalfin，knownasthe“saddlepatch“，oftencontainssomeblackcolouringinresidents.However，thesaddlepatchesoftransientsaresolidanduniformlygrey.Transientsroamwidelyalongthecoast;someindividualshavebeensightedinbothsouthernAlaskaandCalifornia.TransientsarealsoreferredtoasBiggsorcainhonourofcetologistMichaelBigg.Thetermhasbeeincreasinglymonandmayeventuallyreplacethetransientlabel.Thetransientecotypeisestimatedtohavediverged700，000yearsago.Thereareatleastthreedifferent“stocks“oftransientsoffNorthAmerica，theAT1stockwhichoccursfromPrinceWilliamSoundtoKenaiFjords，theGulfofAlaskaAleutianIslandsBeringSea（GOAAIBS）stockandthewestcoaststockwhichrangesfromsoutheastAlaskatoCalifornia.AT1isconsideredadepletedstock;itwasaffectedbytheExxonValdezoilspillanddeclinedfrom22individualstoeightbetween1989and2004.TheGOAAIBSstockmaynumberaround500whaleswhilethewestcoasttransientsnumberover320orcaswithover200alongsoutheastAlaska，BritishColumbiaandWashingtonandover100orcasoffCalifornia.Californiatransientsdonotappeartointerminglemuchwiththosefurthernorthandwestcoasttransientsmaybedividedintosub-munities.

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Offshore:AthirdpopulationoforcasinthenortheastPacificwasdiscoveredin1988，whenahumpbackwhaleresearcherobservedtheminopenwater.Astheirnamesuggests，theytravelfarfromshoreandfeedprimarilyonschoolingfish.However，becausetheyhavelarge，scarredandnickeddorsalfinsresemblingthoseofmammal-huntingtransients，itmaybethattheyalsoeatmammalsandsharks.TheyhavemostlybeenencounteredoffthewestcoastofVancouverIslandandnearHaidaGwaii.Offshorestypicallycongregateingroupsof20–75，withoccasionalsightingsoflargergroupsofupto200.Littleisknownabouttheirhabits，buttheyaregeneticallydistinctfromresidentsandtransients.Offshoresappeartobesmallerthantheothers，andfemalesarecharacterizedbydorsalfintipsthatarecontinuouslyrounded.

Separatefish-eatingandmammal-eatingorcamunitiesalsoexistoffthecoastoftheRussianFarEastandHokkaido，Japan.RussianorcasaremonlyseenaroundtheKamchatkaPeninsulaandCommanderIslands.Over2，000individualresident-likeorcasand130transient-likeorcashavebeenidentifiedoffRussia.Atleast195individualorcashavebeencatalogedintheeasterntropicalPacific，rangingfromBajaCaliforniaandtheGulfofCaliforniainthenorthtothenorthwestcoastofSouthAmericainthesouthandwesttowardsHawaii.OrcasappeartoregularlyoccurofftheGalápagosIslands.OrcassightedinHawaiianwatersmaybelongtoagreaterpopulationinthecentralPacific.

NorthAtlanticandadjacent

Orcatail-slappinginVestfjorden，Norway

Atleast15，000whalesareestimatedtoinhabittheNorthAtlantic.IntheNortheastAtlantic，twoorcaecotypeshavebeenproposed.Type1orcasconsistofsevenhaplotypesandincludeherring-eatingorcasofNorwayandIcelandandmackerel-eatingorcasoftheNorthSea，aswellasseal-eatingorcasoffNorway.Type2orcasconsistoftwohaplotypes，andmainlyfeedonbaleenwhales.

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IntheMediterraneanSea，orcasareconsidered“visitors“，likelyfromtheNorthAtlantic，andsightingsbeelessfrequentfurthereast.However，asmallyear-roundpopulationexistsintheStraitofGibraltar，whichnumberedaround39in2011.DistinctpopulationsmayalsoexistoffthewestcoastoftropicalAfrica，whichhavegeneralizeddiets.

ThenorthwestAtlanticpopulationisfoundyear-roundaroundLabradorandNewfoundland，whilesomeindividualsseasonallytraveltothewatersoftheeasternCanadianArcticwhentheicehasmelted.SightingsofthesewhaleshavebeendocumentedasfarsouthasCapeCodandLongIsland.ThispopulationispossiblycontinuouswithorcassightedoffGreenland.Orcasaresightedyear-roundintheCaribbeanSea，andanestimated267（asof2020）isdocumentedinthenorthernGulfofMexico.

NorthIndianOcean

Over50individualwhaleshavebeencatalogedinthenorthernIndianOcean，includingtwoindividualsthatweresightedinthePersianGulfin2008andoffSriLankain2015.

Southernwaters

OrcabeachingtocapturesealionatValdesPeninsula

AsmallpopulationoforcasseasonallyvisitsthenorthernpointoftheValdesPeninsulaontheeastcoastofArgentinaandhuntforsealionsandelephantsealsontheshore，temporarystrandingthemselves.OffSouthAfrica，adistinctive“flat-tooth“morphotypeexistsandpreysonsharks.Apairofmaleorcas，PortandStarboard，havebeewellknownforhuntinggreatwhitesandothersharksofftheSouthAfricancoast.

OrcasoccurthroughoutthewatersofAustralia，NewZealandandPapuaNewGuinea.TheyaresightedyearroundinNewZealandwaters，whileoffAustralia，theyareseasonallyconcentratedoffthenorthwest，intheinshorewatersofNingalooReef，andthesouthwest，attheBremerregion.GeneticevidenceshowsthattheorcasofNewZealand，andnorthwestandsouthwestAustraliaformthreedistinctpopulations.NewZealandorcasmainlypreyonsharksandrays.

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Antarctic

Around25，000orcasareestimatedaroundtheAntarctic，andfourtypeshavebeendocumented.Twodwarfspecies，namedOrcinusnanusandOrcinusglacialis，weredescribedduringthe1980sbySovietresearchers，butmostcetaceanresearchersareskepticalabouttheirstatus，andlinkingthesedirectlytothetypesdescribedbelowisdifficult.

Someexamplesofvariationsinorcas

TypeAorAntarcticorcaslooklikea“typical“orca，alarge，black-and-whiteformwithamedium-sizedwhiteeyepatch，livinginopenwaterandfeedingmostlyonminkewhales.

TypeB1orpackiceorcasaresmallerthantypeA.Ithasalargewhiteeyepatch.Mostofthedarkpartsofitsbodyaremediumgreyinsteadofblack，althoughithasadarkgreypatchcalleda“dorsalcape“stretchingbackfromitsforeheadtojustbehinditsdorsalfin.Thewhiteareasarestainedslightlyyellow.Itfeedsmostlyonseals.TypeB1orcaareabundantbetweenAdelaideIslandandthemainlandAntarcticpeninsula.

TypeB2orGerlacheorcasaremorphologicallysimilartoTypeB1，butsmaller.Thisecotypehasbeenrecordedfeedingonpenguinsandseals，andisoftenfoundintheGerlacheStrait.

TypeCorRossSeaorcasarethesmallestecotypeandliveinlargergroupsthantheothers.Itseyepatchisdistinctivelyslantedforwards，ratherthanparalleltothebodyaxis.LiketypeB，itisprimarilywhiteandmediumgrey，withadarkgreydorsalcapeandyellow-tingedpatches.ItsonlyobservedpreyistheAntarcticcod.

TypeDorSub-Antarcticorcaswerefirstidentifiedbasedonphotographsofa1955massstrandinginNewZealandandsixat-seasightingssince2004.Thefirstvideorecordofthistypewasmadein2014betweentheKerguelenandCrozetIslands，andagainin2017offthecoastofCapeHorn，Chile.Itisrecognizablebyitssmallwhiteeyepatch，narrowerandshorterthanusualdorsalfin，bulboushead（similartoapilotwhale），andsmallerteeth.Itsgeographicrangeappearstobecircumglobalinsub-Antarcticwatersbetweenlatitudes40°Sand60°S.Althoughitsdietisnotdetermined，itlikelyincludesfish，asdeterminedbyphotographsaroundlonglinevessels，whereTypeDorcasappearedtobepreyingonPatagoniantoothfish（Dissostichuseleginoides）.

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TypesBandCliveclosetotheice，anddiatomsinthesewatersmayberesponsiblefortheyellowishcolouringofbothtypes.MitochondrialDNAsequencessupportthetheorythatthesearerecentlydivergedseparatespecies.Morerecently，pletemitochondrialsequencingindicatesthetypesBandCberecognizedasdistinctspecies，asshouldtheNorthPacifictransients，leavingtheothersassubspeciespendingadditionaldata.AdvancedmethodsthatsequencedtheentiremitochondrialgenomerevealedsystematicdifferencesinDNAbetweendifferentpopulations.A2019studyofTypeDorcasalsofoundthemtobedistinctfromotherpopulationsandpossiblyevenauniquespecies.

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