瀕危的印度巴拉地區(qū)西藏盤羊的安全隱患

反射性動物，無論是2008年的還是，前墨，1985年；《承認與分散》的糧食價格審查（卓沃，1982；alados，1985；舒爾特，1989；伊皮埃和香韋爾，1994；本拉赫，1994；香韋爾和卡科伊爾，1994；香韋爾和科查，1994；香韋爾和科查，1994；香韋爾和科查?？埔曰貞賳T的職能，季度性制度的逐步形式（quire，1990）。對于促進學習，食物消費階段第一階段的食物（洋務和茶，1981；transport，2000）。Thevigilancelevelofananimalinresponsetopredatorsdecreaseswithincreaseingroupsize(seereviewsbyBarnardandThompson,1985;LimaandDill,1990).Italsodecreaseswithdecreaseindistancetoescapeterrain(RisenhooverandBailey,1985;seereviewbyElgar,1989).Theinverserelationshipbetweengroupsizeandvigilanceisrelatedtothebenefitofgrouping,asthevigilanceofanimalsinagroupincreasestheprobabilityofdetectingapredator(‘manyeyeseffect’;Powell,1974)oradecreaseinpredationrisk(‘dilutioneffect’;Quenette,1990).Ontheotherhand,thepositiverelationshipbetweenthevigilanceanddistancetoescapeterrainisexplainedbythehighersecurityoftheanimalasitgetsclosertoescapecover(Frid,1997).Inthisstudy,IlookedatthevigilancebehavioroftheendangeredTibetanargaliOvisammonhodgsoniinrelationtoitsgroupsizeandescapeterrainintheproposedGya-MiruWildlifeSancturay,Ladakh,India.ThismountainsheepisconfinedtotheTibetanPlateauanditsmarginalmountains,andisofglobalconservationimportance(Schaller,1998).Argalifeedinawiderangeofgroupsizes(Schaller,1998);ithasacursorialstrategyofout-runningpredators,andinhabitsopenareasawayfromcliffs(Namgailetal.,2004).TheTibetanwolfCanislupus(courser)isthemainpredatorfollowedbythesnowleopardUnciauncia(stalker)thatpreyonargaliinthearea(Namgailetal.,2006).Therefore,ifvigilanceisanimportantanti-predatorbehavior,itslevelshoulddecreasewitha)increaseingroupsizeandb)increaseindistancetocliff.1杏仁杏仁1.1“l(fā)atch”的定義ThestudywascarriedoutintheTsabracatchmentoftheproposedGya-MiruWildlifeSanctuary(GMWS),Ladakh,India.Itencompassesc.60km2,andislocatedat65kmsouthwestofLeh,theprincipaltownofLadakh.Thisprospectivereservehasauniqueassemblageoffloraandfauna.Theelevationinthearearangesbetween4200to5400m.Themonsooncloudshardlyreachthearea,whichlikerestoftheTrans-Himalayaissituatedintherain-shadowoftheGreaterHimalaya.Thusthemagnitudeofprecipitationislowanderratic,mostlyintheformofsnowinwinter,whichisassociatedwiththeextra-tropicaldisturbancesofmid-latitudesknownas“WesternDisturbances”(DharandMulye,1987).Thetemperatureduringthestudyperiodrangedbetween-10℃to-27℃(Namgail,2003).Thevegetationischaracterisedbydryalpinesteppe(RawatandAdhikari,2005),andthemostcommonvegetationincludeCaraganaspp.,Artemisiaspp.andEurotiasp.BesidesTibetanargali,thereisasmallpopulationofbluesheepPseudoisnayaurinthestudycatchment,butIdidnotobserveanyinteractionbetweenthetwoduringthestudyperiod,asthelatteralwaysgrazedclosertothecliffs(Namgailetal.1,alsoseeNamgailetal.,2004).Thereisnootherungulateinthearea,exceptfordomesticsheep-goatandoccasionallyfewhorsesaccompanyingtheherders.Theareaisearmarkedforwintergrazingbydomesticsheep-goat,andc.2000oftheselivestockaretakenintothecatchmentinthelatterpartofJanuaryeachyearfor2-3months.Apartfromthesnowleopardandwolf,therearemyriadsmallermammalianpredatorssuchastheEurasianlynxLynxl.isabellinaandredfoxVulpesv.montana,whicharethreatstothegrowinglambs.AvianpredatorsincludetheubiquitousgoldeneagleAquilachrysaetos,whichoccasionallyliftslambs(Namgail,2005).1.2其他社會activictivictivictivictspca和kraft和iphenractiviciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciphing/sregaciviwellofficiciviciviciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciphing/stvigittspDataonargali’sbehaviorwerecollectedbetweenJan.-March2003.Suitabletrailsandridgelineswerewalkedtolocateargaliherds.Theslopeswerescannedwith4×80binoculars.Onceagrouplocated,itssizeandthedistancetoclifffromitslocationwererecorded.Agroupisdefinedasacollectionofanimalswithin30mfromoneanotherandengagedinsimilaractivitiesonaslopeboundedbythesamecliffs,whileacliffisdefinedasaverysteepslope(>45°)onanareamorethan20mdiameterwithverticaldropsofmorethan5meters.Focalsamplingwasusedtoobservetheanimal’svigilanceandotherbehaviorsuchasfeeding,movingandothers(allothersocialactivities).Onanaverage,Iobservedthefocalanimalfrom250m.Anactive(non-lying)animalwaspickeduprandomlyfromthegroupandobservedthroughaspottingscopefor20minutesonastretch,usingastopwatch.Foreachobservation,groupsize,distancetocliffandsex/agecompositionwererecorded.Individualswerenotmarkedduringthepresentinvestigation,andtoavoidobservingindividualsmorethanonce(Machlisetal.,1985),Iobserveddifferentgroupsofargaliondifferentdays,andtoavoidresamplingofthesameindividual,Isystematicallyshiftedmyfocustodifferentindividuals(thenumberofindividualsobservedinafocalgrouprangedbetween1-5).Behaviorofthefocalanimalwasobservedandcalledoutbyonepersonandrecordedbyanother.Ananimalwasscoredforagingwhenitforagedonaplantspeciesormovedwithitsheadorientedtowardsit.Whenitstoodstillwithitsheadaboveshoulder,itwasconsideredtobevigilant,andwhenitmovedwithitsheaduprightaboveshoulder,itwasdeemedtobemoving.Allotheractivitiessuchassniffing,fightingetc.wereplacedinasinglecategory:‘others’.Iaggregatedthesetoffocalobservationsandcalculatedthepercenttimeallocatedbyargalitodifferentbehaviouralactivities.Datawerearcsinetransformedbeforeanalysistomeettheassumptionsofnormality.Iregressedgroupsizeanddistancetocliffagainstvigilanceandfittedlinearmodelstoevaluatetherelationshipbetweenvigilanceandtheaforementionedpredictors.FollowingCoteetal.(1997),Iusedprincipalcomponentanalysis(PCA)toevaluatethedifferencesintimebudgetsofdifferentage-sexclasses:male,femaleandyearling.Thisstatisticaltechniqueisusefulinanalyzingnon-independentdatasuchastimebudget.Subsequently,Itestedforsignificantdifferencesbetweenage-sexdifferencesonthefactorscoresofthefirsttwoaxeswithaone-wayANOVAfollowedbyposthocFisher’sLSDtest.2vigimance網(wǎng)絡vigimanrexIobserved152focalargaliindividualsduringthestudyperiod,butonlythoseobservedpriortothelivestockarrival(n=83)wereusedintheanalysisoftheeffectofgroupsizeanddistancetocliffonargali’svigilancelevel,whilealltheobservationswereusedforevaluatingtheage-sexdifferencesintimebudget.Therewereabout50argalisintheTsabracatchmentduringthestudyperiod,andoutofthe48individualscounted,15(31%)weremales,20(42%)females,4(8%)yearlingsand9(19%)lambs.Argali’sgroupsizerangedbetween1and25,andthemean(±SD)groupsizewas12.7(±5.9).Theeffectofgroupsizeontheargali’svigilancelevelwasexplainedbyalinearmodel.Vigilancedecreasedwithincreaseingroupsize(F1,81=36.05,P<0.001).Thirtypercentofthevariationinvigilancewasexplainedbythispredictor(R2=0.31;Fig.1a).Therewashowevernoeffectofdistancetocliffonthevigilancebehaviorofargali(R2=0.03,F1,81=2.69,P=0.10;Fig.1b).Therewasnorelationshipbetweenthetwopredictors:groupsizeanddistancetocliff(R=0.12).Mostofthevariation(73.3%)inthetimebudgetofargaliage-sexclasseswasexplainedbythefirsttwoaxesofPCA.Thefirstaxisexplained40.1%andthesecondoneexplained33.6%ofthevariability.Theformerdistinguishedforagingfrommovement,whilethelatterseparatedvigilancefromotherbehaviours,asindicatedbytheeigenvectors(Table1).Thereweresignificantdifferencesbetweenage-sexgroups:male,femaleandyearlingintheirtimeallocationtodifferentbehavioralactivities(F2,149=3.35,P<0.05,Fig.2).TheposthocFisher’sLSDtestsrevealedthatfemales,comparedtomalesandyearlings,spendmoretimebeingvigilant.Femalesalsoforagedmoreandmovedlessthanmales(Fig.3).3vigimaningvigimanamesingvigiman/athitch3ingvigimansitchingvigiman整體擬合第20eTherewasaninverserelationshipbetweenargalivigilancelevelandgroupsize.Sucharelationshipcouldberelatedtotheincreasedpredatordetection(manyeyeseffect).Anindividualargaliinagroupmaybetakingadvantageofthevigilanceofgroupmemberstoreduceitsownvigilancelevel,therebyallocatingmoretimetoothervitalactivitiessuchasforaging.Nevertheless,thereareotherbenefitsofgrouplivingingregariousanimals(Roberts,1996).Forexample,thepredationriskdecreaseswiththeincreaseingroupsize,astheprobabilityofanindividualbeingkilledinagroupoftwoishalfthatofbeingalone(dilutioneffect,Quenette,1990).Ifvigilancelevelofanindividualdependsonpredationrisk(probabilityofbeingkilled,incasethegroupisattacked),andifthatriskdeclineswithincreasinggroupsize,vigilanceshouldalsodeclinewithincreasinggroupsize(seereviewbyRoberts,1996).Thus,theobservednegativerelationshipbetweenargalivigilancelevelandgroupsizecouldalsoberelatedtoareducedpredationrisk(dilutioneffect).Therearehoweverseveralotherconfoundingfactorsthatmightaffecttherelationshipbetweenvigilancelevelofindividualanimalsandthegroupsize.Forexample,theperceivedlevelofpredationriskmaydeclinewithtimeataparticularsitewhilegroupmaybuildupthroughthattime(seeRoberts,1995,1996).Thishoweverisofconcerninspeciesinwhichindividualschangemembershipwithinaday.Theargalisarelessfluidvis-à-vistheirgroupsizeinthestudyarea(Namgailetal.,2007)aswellasinotherpartsofLadakh(Namgailetal.,2004).Forinstance,duringthestudyperiod,somegroupsremainedstaticforuptotendays.Therefore,thedecreaseinargali’svigilancelevelwithincreaseingroupsizecouldlargelybeattributedtothedecreasedriskofpredationinlargergroups.Furthermore,foragingconstraintsalsoleadtoadeclineinherbivorevigilancewithincreasinggroupsizeduetodensitydependenteffectsonsparetime(thetimeavailableforvigilancewhilechewingfood),whichtendtohaveanegativerelationshipwiththenumberofherbivoresinafoodpatch(Fortinetal.,2004b).Although,predationriskisthoughttobethemostimportantfactorinfluencingthevigilancelevelinherbivores,thereareotherpotentialfactorsthatcaninfluencetheirscanningrates.Forexample,Fortinetal.(2004b)haveshownthatanindividual’svigilancelevelincreasesinmoreproductivepatches,wherefoodintakeisconstrainedbyforageprocessingratherthanbyforageencounterrate.Thisislargelybecausetheanimalscanbevigilantwhileprocessingtheirfood(chewing)inpatcheswithhighvegetationbiomass.However,thespatialpatterninforagebiomasscouldnothaveinfluencedthebehavioralpatternsobservedinthepresentstudy,astheplants(smallherbsandshrubs)weresparselyandevenlydistributedacrossthestudyarea(Namgailetal.2).Contrarytomyexpectation,argali’svigilanceleveldidnotincreasewiththedecreaseindistancetocliff.Thiscouldberelatedtolesspredationpressurefromcliff-basedpredatorssuchasthesnowleopard,whichstalksattheedgeofthecliffs(JacksonandAhlborn,1989).Duringthethree-monthstudyperiod,Isightedwolfalmosteveryweek,whilstIdidnotseeanysnowleopard,althoughIfoundthecat’ssignssuchasscraps,butonlyattwolocations.Thus,sincewolfisthemajorpredator,whichhuntsintheopen,heighteningvigilancelevelnearcliffsisperhapslessbeneficial,especiallywhentheviewsareobstructedbythecliffs(seeArenzandLeger,1999).Contrastingly,thecliffsmaypreventanargalifrombeingdetectedbywolf,therebyleadingtoalowerlevelofperceivedthreatinhabitatsclosetocliffs.SuchobservationsweremadeintheAfricansavannas,whereungulatespeciesbecamelessvigilantinareaswithmorevisualobstructions(Scheel,1993).Duringthepresentinvestigation,thetimebudgetoffemalesdifferedsignificantlyfromthoseofmalesaswellasyearlings,astheformerspentmoretimebein