Diversity and Distributions. 2019;25:129–141. wileyonlinelibrary.com/journal/ddi  | 129© 2018 John Wiley & Sons Ltd

Received:15January2018  |  Revised:20July2018  |  Accepted:3August2018DOI:10.1111/ddi.12839

B I O D I V E R S I T Y R E S E A R C H

Assessing niche overlap between domestic and threatened wild sheep to identify conservation priority areas

Benjamin Bleyhl1  | Marine Arakelyan2 | Elshad Askerov3,4 | Hendrik Bluhm1 |  Alexander Gavashelishvili5 | Mamikon Ghasabian6 | Arash Ghoddousi1 |  Aurel Heidelberg7 | Igor Khorozyan8 | Alexander Malkhasyan9 | Karen Manvelyan9 |  Mohammadreza Masoud10 | Ehsan M. Moqanaki11  | Volker C. Radeloff12  |  Mahmood Soofi8 | Paul Weinberg13 | Nugzar Zazanashvili14,15 | Tobias Kuemmerle1,16

1GeographyDepartment,Humboldt-UniversityBerlin,Berlin,Germany2DepartmentofZoology,YerevanStateUniversity,Yerevan,Armenia3WWF-Azerbaijan,Baku,Azerbaijan4InstituteofZoologyofAzerbaijanAcademyofSciences,Baku,Azerbaijan5CenterofBiodiversityStudies,InstituteofEcology,IliaStateUniversity,Tbilisi,Georgia6ScientificCenterofZoologyandHydroecology,NASRA,Yerevan,Armenia7WWF-Germany,Berlin,Germany8WorkgrouponEndangeredSpecies,J.F.BlumenbachInstituteofZoologyandAnthropology,UniversityofGöttingen,Göttingen,Germany9WWF-Armenia,Yerevan,Armenia10IranianDepartmentofEnvironment,EastAzerbaijanProvincialOffice,Tabriz,Iran11IranianCheetahSociety(ICS),Tehran,Iran12SILVISLab,DepartmentofForestandWildlifeEcology,UniversityofWisconsin-Madison,Madison,Wisconsin,U.S.A.13NorthOssetianNatureReserve,Alagir,RSO-Alania,Russia14WWFCaucasusProgrammeOffice,Tbilisi,Georgia15InstituteofEcology,IliaStateUniversity,Tbilisi,Georgia16IntegrativeResearchInstituteonTransformationsofHuman-EnvironmentSystems(IRITHESys),Humboldt-UniversitätzuBerlin,Berlin,Germany

CorrespondenceBenjaminBleyhl,GeographyDepartment,Humboldt-UniversityBerlin,Berlin,Germany.Email:benjamin.bleyhl@geo.hu-berlin.de

AbstractAim:Populationsoflargeungulatesaredwindlingworldwide.Thisisespeciallysoforwildsheep,whichcompetewithlivestockforforage,aredisturbedbyshepherdsandtheirdogs,andareexposedtodiseasetransmissionsfromlivestock.Ouraimwastoassessspatialpatternsinrealizednicheoverlapbetweenwildanddomesticsheeptobetterunderstandwherepotentialcompetitionmightarise,andthustoidentifypri-orityareasforwildsheeprecovery.Location:SouthernCaucasus(220,000km2).Methods:WestudiedGmelin’smouflon(Ovis orientalis gmelinii),anancestorofdo-mesticsheep,to investigateseasonalhabitatuseandnicheoverlapwithdomesticsheep.Tomaphabitat,weanalysedmouflonoccurrences collectedduring2006–2016,anddomesticsheepoccurrencesfromshepherdcamplocationsdigitizedonhigh-resolution satellite imagery. We mapped areas of potential competition be-tweenmouflonanddomesticsheepandassessedpotentialhabitatdisplacement.Results:Mouflonanddomesticsheepnichesoverlappedsubstantially(overlapindexI=0.89,where1meansperfectoverlap)butwerenotidentical.Mouflonhabitatwaslesswidespreadthandomesticsheephabitat(14,000vs.40,270km2)andtendedtobelocatedinmoreruggedareaswithlessvegetationcover.Weidentified51prioritypatches as reintroduction candidates if grazing pressure and poaching werereduced.Main conclusions:Ourresultssuggestthatcompetitionwithdomesticsheepmighthavepushedmouflonintomarginalhabitat.Thus,conservationeffortsfocusingoncurrentmouflonhabitatmightmiss suitable reintroductionsites.Wedemonstratethat a combined habitatmodel forwild and domestic sheep can identify generalsheephabitat,whichmightbemoreuseful for conservationplanning thanunder-standing currentmouflon habitat selection.Our results highlight that consideringcompetition with livestock is important for large ungulate conservation, both intermsofreactive(e.g., lesseninglivestockpressureinprimehabitat)andproactivestrategies(e.g.,reintroductioninareaswithlowcontemporaryoverlap).

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1  | INTRODUC TION

Largeungulatesarethreatenedthroughouttheworldandtheirnum-bershavedeclinedprecipitouslyduring recentdecades (DiMarcoetal.,2014;Rippleetal.,2015).Thisisworrisomeaslargeungulatesplayimportantrolesforecosystemfunctioning,forexampleaseco-systemengineers(Pringle,Young,Rubenstein,&McCauley,2007)oraspreyforlargecarnivoresandscavengers(Margalida,Colomer,&Sanuy,2011;Wolf&Ripple,2016).Therefore,understandingthreatstolargeungulatesandensuringthattheirpopulationsareviableisanimportantconservationgoal(Rippleetal.,2016).

A key factor contributing to large ungulate declines is conflictwithpeople,oftenthroughcompetitionwithlivestock.MorethanaquarteroftheEarth’slandsurfaceisusedforgrazing,withlivestockoutnumberingwildungulatesbyseveralordersofmagnitude(Berger,Buuveibaatar,&Mishra,2013;Robinsonetal.,2014).Livestockgraz-ingaffects largeungulatepopulations inmanyways, includingthedegradationoffoodresources,displacementofungulatesfromsuit-ablehabitats,diseasetransmissionanddirectmortalityfromshep-herdsandtheirdogs(Chirichella,Ciuti,&Apollonio,2013;Krishna,Kumar,& Isvaran, 2016;Namgail, Fox,&Bhatnagar, 2006).Whilecertainpastoralsystemsallowforcoexistenceandmaintainopen-land habitats for wild grazers, more commonly, competition withlivestock threatens largeungulates,particularly in resource-scarceregionssuchasdrylandsormountainousareas(Ekernasetal.,2017;Mishra,VanWieren,Ketner,Heitkonig,&Prins,2004;Riginosetal.,2012).

Generally, competitionbetweenspeciesoccurswhen theyde-pend on the same limiting resources, which is likely the case fordomestic livestock and their wild ancestors (Madhusudan, 2004).Withmore thanonebilliondomestic sheepworldwide (Ovis aries; FAOSTAT,2017),mostofwhicharepastured,wildsheeparelikelyparticularly negatively affected by competition with livestock(Mishra,VanWieren,Heitkönig,&Prins,2002;Owen-Smith,2002;Shackleton, 1997).Wild sheep also often occur in areaswith lowproductivityandmaythereforebeparticularlypronetocompetitionand conflictswith shepherds and their dogs (Ekernas etal., 2017;Schieltz&Rubenstein,2016;Shackleton,1997).Conservationplan-ningtoprotectandrestorewildsheeppopulationsthusrequiresun-derstandingwhereandtowhatextentdomesticandwildsheepmaycompete.

Speciesdistributionmodelshelptounderstandnichecharacter-isticsandtoidentifyhabitatpatterns(Franklin,2009).Thesemod-elscombineoccurrencedataandenvironmentalfactorstodescribe

species’niches inenvironmental space.Analysingmultiple speciesallowstoassessthedegreeofrealizednicheoverlapbetweenthem(Warren,Glor,&Turelli, 2010).However,while thereareanalysesusingspeciesdistributionmodellingtoquantifynicheoverlapamongdifferent wild species (e.g., Blair, Sterling, Dusch, Raxworthy, &Pearson,2013;Wordley,Sankaran,Mudappa,&Altringham,2015),toourknowledge,thishasnotyetbeendonebetweenlivestockandwild ungulates. Broad-scale studies might benefit especially fromsuch an approach, because detailed information on grazing pres-sureorthelocationofdomesticanimalsisoftennotavailableacrosslargergeographicareas,which is limitingtheiruseaspredictors inwildlifehabitatmodels.

Given the high ecological and biological similarity of domesticandwild sheep, their fundamental niches shouldoverlap substan-tially(Gordon,2009).Ifrealizednicheoverlapislow,however,thenthismayindicatenichepartitioningandpossiblythatwildsheepareaso-calledrefugeespeciesthatisconfinedtomarginalhabitat(i.e.,habitatwherefitnessmightbedecreaseddueto,forexample,lowerresource availability or higher mortality; Caughley, 1994; Kerley,Kowalczyk, & Cromsigt, 2012). This marginalization would havelikelyoccurredoverlongtimeperiods,resultinginshiftingbaselinesthat might lead conservationists to regard the current habitat ofthis species as optimal,whichwould lead tomisguided conserva-tion effort (Cromsigt,Kerley,&Kowalczyk, 2012; Soga&Gaston,2018). Similarly, mapping suitable habitat based on current habi-tatusemightbeerroneousforspeciespushed intomarginalhabi-tat(Braunisch,Bollmann,Graf,&Hirzel,2008;Kerleyetal.,2012).Assumingsimilarhabitatusebydomesticandwildsheep(Hofmann,1989),quantifyingrealizednicheoverlapwouldbeawaytotestforapossiblerefugeestatusofwildsheep.Jointlyassessingpotentialhabitatforwildanddomesticsheepcouldthenprovideabetteras-sessmentofoptimalwildsheephabitat.

TheCaucasusMountains at the crossroadsof Europe,CentralAsiaandtheMiddleEastareaglobalbiodiversityhotspotandhometomanyiconiclargeungulates,includingEuropeanbison(Bison bona-sus),bezoargoat(Capra aegagrus),andGmelin’sorArmenianmouflon(Ovis orientalis gmelinii)(Mittermeieretal.,2004).TheCaucasus,par-ticularlyitssouthernpart,hasalonghistoryoflivestockhusbandry,datingback toaround9,000BC (Kalandadze&Nebieridze,1989).Today,poachingandovergrazingarethemainthreatstolargeungu-latesinthesouthernCaucasus(Williams,Zazanashvili,Sanadiradze,&Kandaurov, 2006).Mostwild ungulate populations experienceddrastic population declines due to poaching after and during theIranian 1979 Revolution and the breakdown of the Soviet Union

K E Y W O R D S

Armenianmouflon,Caucasus,Gmelin’smouflon,human–wildlifeconflict,livestock,nicheoverlap

Funding informationFederalStateofBerlin,Germany;WorldLandTrustthroughtheIranianCheetahSociety

Editor:JoernFischer

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andare indireneedofbroad-scaleconservationplanningandac-tion (Bragina etal., 2015;Ghoddousi etal., 2017). Thismakes theCaucasusaninterestingandrelevantregiontoexplorepotentialef-fects of coexistence and competition betweenwild and domesticsheep.

The southern Caucasus is a stronghold for Gmelin’s mou-flon. This species, one of the seven subspecies of Asiatic mou-flon, the ancestor of domestic sheep, is listed as vulnerable inthe IUCN Red List of Threatened Species (Alberto etal., 2018;Rezaeietal.,2010;Valdez,2008).Gmelin’smouflononlypersistsin very small populations of a few hundred individuals each inArmenia andAzerbaijan, and around1,200–1,400 in the IranianpartoftheCaucasus(Baskin&Danell,2003;IranianDepartmentof Environment, unpubl. data; Mallon, Weinberg, & Kopaliani,2007). These populations are severely threatened by livestockgrazingandoftenoccur close to internationalborderswithhighmilitarypresence,fragmentingtheirrangeandincreasingpoach-ing risk (Khorozyan, Weinberg, & Malkhasyan, 2009; Talibov,Weinberg,Mammadov,Mammadov,&Talibov,2009). Identifyingareas to establish new and expand existing populations, ideallysothatkeyhabitatpatchesareconnected,isthereforeimportant(Zazanashvili,Garforth,Jungius,&Gamkrelidze,2012).

Ourgoalwastoassessrealizednicheoverlapbetweendomes-tic sheep andGmelin’smouflon in the southernCaucasus to bet-ter understandwhere potential competitionmight arise, and thusto identify suitable habitat formouflon recovery. Specifically, ourobjectiveswere(a)tomapmouflonsummerandwinterhabitat;(b)toassessnicheoverlapinenvironmentalandgeographicspacewith

domesticsheepinsummer;and(c)tousethisinformationtoidentifymouflonconservationpriorityareas.

2  | METHODS

2.1 | Study area

Our study area covers large parts of the southern Caucasus andstretches over Armenia and parts of Azerbaijan, Georgia, Iranand Turkey (Figure1). It is limited in the north by the Rioni RiverLowlands(Georgianblacksearegion)andtheKurariver,andinthesouth(inTurkeyandIran)bytheCaucasusEcoregionasdelineatedby the Ecoregion Conservation Plan for the Caucasus (Williamsetal.,2006).Mostpartsofthestudyareaaremountainousinclud-ingtheentireLesserCaucasusandthesouthernCaucasusvolcanicuplandswithMt.Araratasthehighestpeak(5,137m).Thevegeta-tionischaracterizedbyopenjuniperwoodlands,steppes,mountainsteppes, subalpine and alpine grasslands, andbroadleaved forestswithsomemixedandconiferousforests inmorehumidareas.Theareasthatmouflonoccupyincludegrasslandsandopenshrubcom-munitiesofrollingsteppesandofthesubalpineandalpinezones.

Livestock husbandry is widespread in the southern Caucasus.After the breakdown of the Soviet Union, domestic sheep num-bersdeclinedsubstantiallyandin2017werestillatlowerlevelsinGeorgiaandArmenia than in theearly1990s (FAOSTAT,2017). Incontrast, livestock numbers in Azerbaijanwere almost twofold in2017comparedtotheearly1990s,partlyduetoincentivesthrough

F IGURE  1 StudyareaandmouflonoccurrencelocationsinthesouthernCaucasus[Colourfigurecanbeviewedatwileyonlinelibrary.com]

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privatization and agricultural reforms (FAOSTAT, 2017; Kosayev&Guliev, 2006). In Iran, sheepnumbers almost doubled after the1979 Revolution until the early 2000s, but have been decreasingsincethen(FAOSTAT,2017).Nevertheless,sheepproductionintheIranianCaucasusisamongthehighestintheregionwithover6mil-lionheads (StatisticalCenterof Iran,2017).Thepastoral livestocksysteminthestudyareaismostlybasedontranshumance,utilizingsummerpasturesinthemountainsandwinterpasturesinthesteppelowlands(Williamsetal.,2006).Onaverage,onetothreeshepherdsaccompany herds of several hundred sheep, and almost all herdshavedogs(normallybetweenoneandfourdogsper100sheep).

2.2 | Mouflon ecology and occurrence data

While the exact historic range of mouflons is somewhat unclear,the species was widespread in the region and occurred in largernumbers.Today,itisrestrictedtosmallherdsinsouthernArmenia,Nakhchivan(autonomousexclaveofAzerbaijan)andnorth-westernIran(Baskin&Danell,2003;Dinnik,1910).IntheCaucasus,moufloninhabitmountaingrasslandsandshrublandsondryandmainlyopenslopeswithapreferenceforslightlyruggedterrain(Gavashelishvili,2009; Khorozyan etal., 2009; Zazanashvili etal., 2012). In ourstudy,werefertohabitatasencompassingalltypesinwhichmou-flonoccurandsurvive.Mouflonfeedmainlyongrassesandshrubsbut sometimes also on grain (Valdez, 2008). In summer, mouflonusuallymigrate towards higher elevations for fresh and nutritiousfodder. Socially,mouflon live in groupswith adultmales separatefromadult femalesand theyoung (Karami,Ghadirian,&Faizolahi,2016). However, during the rut (i.e.,mating season;November toDecember), dominantmalesestablishgroupswith several femalesanddefendthemfromothermales(Karamietal.,2016).

We analysed 211 mouflon occurrence locations from pop-ulations in Armenia, Azerbaijan and Iran, collected in the fieldduring2006–2016.Mouflonoccurrencelocationswerecollectedbywalking transects and through point counts and opportunis-tic direct observations. We split the data into summer (May–September)andwinter(October–April)sightings.Further,weusedonlylocationswithaminimumdistanceof500mbetweenthemtoreducespatialautocorrelationthatcouldleadtoinflatedaccuracymeasuresorbiasedparameterestimations(Dormannetal.,2007;Veloz,2009),resultingin91summerand97winterlocations(46ofwhichwererepeatedsightingsfrombothseasonsandfromthesamelocation).

2.3 | Mouflon habitat mapping

Wemappedsuitablemouflonsummerandwinterhabitatwithmaxi-mum entropy modelling (Maxent; Phillips, Anderson, & Schapire,2006),aspeciesdistributionmodellingalgorithmthatiswell-suitedfor presence-only data and outperforms concurrent algorithms(Elithetal.,2006).Weranthemodelswithamaximumof2,500it-erations,quadraticandhingefeaturesonly,anddefaultsettingsforconvergencethresholdsandregularization(Phillips&Dudik,2008).

Because sampling background data from too broad areas can re-sultinoverlysimplisticmodels,wesampled10,000pointsasback-groundina30-kmbufferaroundallmouflonlocations(VanDerWal,Shoo,Graham,&Williams,2009).Wevalidatedourmodelswitha10-foldcross-validationandthemeanareaunderthecurve(AUC)ofthereceiveroperatingcharacteristic(ROC)curve.Toassessvariableimportance,weusedthepercentgaincontributionofeachvariableanda jackknife testmeasuringtheAUCforsinglevariablemodelsandmodelswithout thisvariable (Phillipsetal.,2006).Wefurthercompared differences in model predictions with and without theclamping function, which avoids extrapolation by restricting fea-turestorangebetweenvaluescoveredbythetrainingdata.

Tocharacterizehabitatsuitability,weusedsevenpredictorsre-lated to topography, landscape composition, resource availabilityandhumandisturbance(seeSupportingInformationAppendixS1fora-priorihypothesesontheirrelationstohabitatsuitability).Forto-pography,wederivedaspect(flat,north,east,south,andwest),localterrainruggedness (usinga90-mneighbourhoodrule;Sappington,Longshore, & Thompson, 2007) and landscape ruggedness (meanslopewithin2km)basedonShuttleRadarTopographyMissiondata(SRTM;NASAJPL,2013).Wedefinedlocalruggednesstocharacter-izethedirectsurroundingsofacell(i.e.,atpixellevel)andlandscaperuggednesstocharacterizethegeneraltopographicsettinginwhichacellwasembedded(i.e.,a2-kmwindowsurroundingthecell).Wetestedotherneighbourhoods(30and210mforlocal,and0.3,1and3kmforlandscaperuggedness),whichresultedinmodelswithverysimilar,butlowerAUCvalues(resultsnotshown).Tocaptureland-scapecomposition,weusedarecent,high-resolutionlandcovermapwiththeclassesconiferousforest,broadleavedforest,mixedforest,rangeland, cropland, built-up, ice and permanent snow, andwater(Bleyhletal.,2017).Additionally,weacquiredVegetationContinuousFieldsdata(VCF,MOD44B,years2000–2010)fromtheModerateResolution ImagingSpectroradiometer (MODIS) to calculatemeanfractional woody vegetation cover. We measured human distur-bance as the Euclidean distances to roads and settlements, usingdata from Open Street Map (OSM; http://www.openstreetmap.org/)andtheWorldWideFundforNature’sCaucasusProgrammeOffice(WWFCauPO).Distanceswerelimitedtoamaximumof8kmforroadsand6kmforsettlementsbecauseinitialmodelspredictedlesssuitablehabitatforhigherdistances.Weconsidereddecreasinghabitatsuitabilityathigherdistancestobeanartefactofourpres-encedatabecausemouflonarecurrentlynotcolonizingallavailableremoteandsuitableareasandbecauseveryremoteareasmightnothave been surveyed equally intensively as more accessible areas(Bleyhl etal., 2015). We further tested climatic variables (annualmeantemperature,minimumtemperatureofthecoldestmonth,an-nualprecipitationandprecipitationofcoldestquarter;WorldClim2;Fick&Hijmans,2017)butthesedidnotimprovemodelperformanceandwerethereforedroppedinourfinalmodels.Weresampledallpredictorvariablestoa100-mresolutionandreprojectedthemtotheAlbersEqualAreaprojection.Correlationamongourpredictorvariables was generally low (r<0.65; see Supporting InformationAppendixS1).

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2.4 | Quantifying niche overlap between domestic sheep and mouflon

Because domestic sheep and mouflon are closely related, funda-mentalnicheoverlap (aswellasfunctionalsimilarity) is likelyhigh,butrealizednicheoverlapmayormaynotbehigh.Ontheonehand,realizednicheoverlapmightbehigh,becausethespeciesrelyonthesameresources.Ontheotherhand,becausedomesticsheephavebeen reared in the Caucasus formillennia (Akhalkatsi, Ekhvaia, &Asanidze,2012),mouflonmighthaveadaptedthroughresourcepar-titioning(Schoener,1974;Voeten&Prins,1999).Competitionwithlivestockmighthavepushedmouflonintomarginalhabitat,possiblyrendering thema refugeespecies (Fritz,DeGarine-Wichatitsky,&Letessier,1996;Kerleyetal.,2012).Bothscenarioswouldresultinaloweroverlapofrealizednichesthantheclosephylogeneticrela-tionshipofthetwospeciessuggests.Wetestedthehypothesisthatrealized niche overlap betweenmouflon and domestic sheepwaslowerthanexpected,eitherbecausethespeciesadaptedtocoexist-encethroughadaptingtheirnicheorbecausemouflonisarefugeespecies.

Toassessthehabitatuseofdomesticsheepinthesamewayasthemouflon’sniche,wecapturedthesummerdistributionofdo-mesticsheepbymappingallshepherdcampswithin30kmofourmouflonoccurrences.Campsappearedashomogeneousopen-soilpatcheswithinotherwiseheterogeneously texturedgrassland inhigh-resolution imagery in GoogleEarth and BingMaps. Often,these camps had tent-like structures making the identificationeasy.We digitized 977 shepherd camps and excluded locationswith an elevation<1,500mbecause these are likely not relatedtosummershepherdingthatmostlytakesplaceathighelevations(werepeatedournicheoverlapanalysiswithallshepherdcampsanddidnotfindsubstantialdifferences;resultsnotshown).Tore-duce spatial autocorrelation, we applied a minimum distance of500mbetweencamps,resultingin586locations.Totestwhethernicheoverlapchangeswhenusinglikelydomesticsheeplocations(rather thancamp locations),wealsoassessedoverlapbasedonrandomly sampled (i.e., simulated) sheep occurrenceswithin setdistancesaroundthecamps(100,200,500,1,000and2,000m).Becausedomesticsheeparekeptonwintergrazingsitesatlowerelevations,sometimesseveralhundredkilometresawayfromthesummercampsandpredominantlyoutsidecurrentmouflonareas,wedidnotexpectwinternichestooverlapandmappedonlysum-merhabitatfordomesticsheep.

First,tomapthespatialoverlapoftherealizednichesofsheepandmouflon,weoverlaidsuitablemouflonandsheepsummerhab-itat.Wedelineatedhabitatusing themaximumtrainingsensitivityplusspecificitythreshold(Liu,White,&Newell,2013).Wealsocal-culatedEuclideandistancesofallmouflonsummerlocationstotheclosestshepherdcamp.Second, toquantify realizednicheoverlapbetweenmouflonanddomesticsheep,weusedthesimilaritysta-tisticI(vanderVaart,1998)calculatedbyENMTools(Warrenetal.,2010).Thissimilaritystatisticrangesfrom0(nooverlap)to1(com-pleteoverlap).WeranMaxentmodelswiththesamesettingsand

predictorvariables fordomesticsheepandcomparedthemtoourmouflonsummermodelusingthe30-kmbufferareatoprojectthemodels as abasis for the comparison.To testwhether anoverlapexisted between domestic sheep summer habitat and mouflonwinterhabitat,wealsoquantifiedthesimilarityusingourmouflonwintermodel.Additionally,wealsocalculatednicheoverlapbasedonmodels thatusedonlyenvironmentalpredictors (i.e., excludinghumandisturbancepredictors).Finally, to testourhypothesis thatwildanddomesticsheephaveidenticalrealizedniches,weusedtheidentitytestinENMTools(Warrenetal.,2010).Forthistest,wede-rivedadistributionoftheoverlapindexfrom100replicatesbasedonrandompartitioningofapooleddatasetofoccurrencelocations(i.e.,treatingthedataasifmouflonanddomesticsheepoccurrenceswere from the same species). Subsequently, we tested the actualoverlapindexscoreagainstthisdistributionunderthenullhypothe-sisofnicheidentitytoassesswhetherthescoreissignificantlylower(attheα=0.05level;Warrenetal.,2010).

2.5 | Priority habitat patches for mouflon

Weidentifiedfourtypesofpriorityhabitatpatchesbasedonhabitatsuitabilityusingthetrainingsensitivityplusspecificitythreshold(Liuetal.,2013)andaminimumarearule(Figure2).First,weidentifiedsuitableareasbasedoncurrentlyoccupiedmouflonhabitat(i.e.,ourmouflon summermodel), that were larger than 300km2 (mouflon habitat patches). A patch of 300km2 could harbour approximately3,600–4,800 individuals, assuming a density of 12–16 individualsperkm2(basedonstudiesofOvis vignei,acloselyrelatedwildsheepinIran;Farhadinia,Moqanaki,&Hosseini-Zavarei,2014;Ghoddousietal., 2016). Second,we identified areaswith suitable habitat forbothmouflonordomesticsheep(potential mouflon habitat patches),becausemouflonmightusesuboptimalhabitatduetocompetitionwithdomesticsheepandacombinationofbothhabitatareaspoten-tiallybetterdescribessuitablehabitat.Third,we identifiedhabitatpatcheswherecompetitionpotentialwithdomesticsheep is likelylowest(low-risk patches),byselectingsuitablemouflonhabitatthatdoes not entail suitable domestic sheep habitat. Finally, to assesswhichnewareascouldbestfosterconnectivityamongcurrentmou-flon habitat patches,wehighlightedpotential mouflon patcheslocatedwithin a corridor connectingmouflon habitat patches (connectivity patches). We identified these corridors with a least-cost analysisusingoursummerhabitatsuitabilitymapasacostsurface(highestsuitability=lowest cost to travel through a cell; resistance valuesbetween 1 and 11) and roads as partial barriers (resistance value100;Bleyhletal.,2017).Weusedsummerhabitatbecausewewereinterestedindispersalcorridorsandnotinmigrationcorridorsfromsummertowinterhabitat,whichwouldrequireamorefine-scaleas-sessment.Wederivedleast-costcorridorsusingtheLinkageMapperToolkit(McRae&Kavanagh,2011).Forallprioritypatches,wecal-culatedtheareathatiscurrentlyprotectedbasedonprotectedarealayersfromWWFCauPO(wwfcaucasus.net),theshareofsuitablewinterhabitatbasedonthemaximumtrainingsensitivityplusspeci-ficitythreshold(Liuetal.,2013),andthedistancesfromeachpatch

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to internationalborders (whichmightberelatedtopoachingpres-surefromborderpatrols;Khorozyanetal.,2009).

3  | RESULTS

3.1 | Mouflon habitat modelling

Ourmouflonmodelpredictedwidespreadareasofsuitablebutcur-rentlyunoccupiedhabitatacrossthesouthernCaucasus,mainly intheborderregionofArmenia,AzerbaijanandIran.Suitablemouflonsummerhabitatgenerallyoverlappedwith suitablewinterhabitat,but winter habitat was more widespread (Figure3). Our MaxentmodelshadhighAUCvaluesof0.89forsummerand0.83forwin-ter.Variableimportancewassimilarforbothseasons.Mouflonhab-itat occurred far away fromhuman settlements and roads, and inmedium-ruggedterrainwithlowwoodyvegetationcover.Rangelandwas the land cover class with highest suitability in both seasons.Aspect had only a minor influence on summer habitat suitability(leastimportantvariable),butsouthfacingslopeswereimportantinwinter.Further,restrictingfeaturestorangescoveredbythetrain-ingdatashowedthatourresultswerenotaffectedbyextrapolation.

3.2 | Niche overlap between domestic sheep and mouflon

Mouflon occurrence locations differed markedly from shepherdcamp locations in geographic space and regarding some of our

predictor variables. Mouflon locations were far from shepherdcampsinbothseasons(distancesrangedfrom0.4to22km,median:5km,standarddeviation:4km).Further,mouflonhabitatwasmorerugged and characterized by higher distances to settlements andbyhighersharesofsparsevegetation (seeSupporting InformationAppendixS1).

We found substantial overlap between the realized niches ofdomesticsheepandmouflonduringsummer,particularlybasedonmodels without the human disturbance predictors (I=0.89). Theniche overlap did not change markedly for winter mouflon loca-tions (I=0.88).Overlap indexvalues increasedslightlywithbufferdistancearoundshepherdcampsthatweusedtosampledomesticsheeplocations(Table1).However,thetworealizednicheswerenotidenticalaccordingtothenicheidentitytest(i.e.,ourempiricalsim-ilarityindicesweresignificantlylowerthanindicesfromthepooledmodel).

Despite the differences in location and niche characteris-tics,wefoundthatthemajorityofsuitablemouflonhabitatwasalso suitable for domestic sheep (77%; Figure3). In general,domesticsheephabitatwasmuchmorewidespreadthanmou-flonhabitat(40,270km2comparedto14,000km2formouflon)andonlya fewareas thatwere suitable formouflonwerenotsuitable for domestic sheep (3,280km2 or 23%of all suitablemouflon habitat). The combination of both mouflon and do-mestic sheep habitat revealedwidespread areas (43,560km2)potentiallysuitableasgeneralOvishabitatacrossthesouthernCaucasus(Figure3).

F IGURE  2 Flowchartofouranalysestoidentifypriorityhabitatpatches.Dashedlineisonlydashedtodistinguishitfromothercrossinglines

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3.3 | Priority habitat patches

Weidentifiedfourtypesofprioritypatchesformouflonconserva-tion:(a)mouflon habitat patchesarethemostsuitablepatchesbasedon current mouflon habitat use only; (b) potential mouflon habitat patchesarebasedontheassumptionthatmoufloncouldalsothriveinareas suitable fordomestic sheep; (c) low-risk patches are thosepatcheswith leastpotential for competitionwithdomestic sheep;and(d)connectivity patchesarepotentialmouflonpatchesthatwouldfosterconnectivityamongmouflonhabitatpatches(i.e.,amongcat-egory(a)patches).

We found eleven mouflon habitat patches with high habitatsuitability and an area exceeding 300km2 (Figure4). All of thesepatches had at least 73% suitable winter habitat. In total, thesehabitatpatchescovered6,830km2(meanpatchsize:620km2).Wefoundmouflon habitat patches in all countriesexceptGeorgia, and

themajorityofthemwas in Iran (sixareas, intotal3,000km2).Ofthetotalareacoveredbysuchpatches,18%wasprotected(9%inreserves with IUCN category I or II; see Supporting InformationAppendix S2 for an overview of all priority patches). Six of theeleven patches were close to international borders (<10km) andthreeextendedacrossborders.Further,77%ofthetotalareawasalsosuitablefordomesticsheep.Thecombinationofmouflonanddomesticsheephabitat,thatispotentialmouflonhabitat,resultedinmarkedlymoreandlargerprioritypatches.Intotal,wefound51po-tential mouflon habitat patches>300km2distributedacrossallcoun-triesandcoveringanareaof40,400km2(meanpatchsize:790km2).However,someofthemdidnothavemuchwinterhabitatinside(fivepatcheshadlessthan10%suitablewinterhabitat),andonly14%ofthe total areawas protected.Additionally,we only identified twolow-risk patches larger than300km2, one in theborder triangleofArmenia,Nakhchivan,andIran,andoneinIran,togethercoveringan

F IGURE  3  (a)Mouflonsummerandwinterhabitatsuitabilityand(b)areaswithsuitablemouflonanddomesticsheephabitat,aswellasareaswherebothhabitatsoverlap[Colourfigurecanbeviewedatwileyonlinelibrary.com]

136  |     BLEYHL Et aL.

areaof740km2(Figure4).Bothofthesepatcheshadalsosuitablewinterhabitat(96%oftheirarea),butonlythenorthernpatchatthebordertrianglewaspartlyprotected(87%ofitsarea).

We identified 25 connectivity patches that were >300km2 and locatedwithin the corridors linkingmouflon habitat patches (Figure5).Corridorlengthrangedfrom8to320km.Allcorridorscrossed at least one major road, and five corridors crossed in-ternational borders.Resistance along the least-cost path rangedbetween7.1and12.1(mean:9.5,standarddeviation:1.5),whichis high given that our resistance values ranged between 1 and11 (with 100 only used for partial barriers). We found at leastone connectivity patch in each corridor.On average, connectivity

patcheswerelarge(meanpatchsize:980km2)andcoveredatotalareaof24,000km2.

4  | DISCUSSION

Largeungulatesandparticularlywildsheeparethreatenedbycom-petitionwithlivestock.Competitioncanleadtothedisplacementofwildlifetomarginalhabitats,whichmightcompromiseconservationeffortsbasedonassessingcurrenthabitat.Inourstudy,weanalysedGmelin’smouflonhabitat,andinvestigatedseasonalhabitatpatternsand thepotential for competitionwithdomestic sheepusing spe-ciesdistributionmodellingandanicheoverlapanalysis.Weidenti-fiedwidespreadhabitatthatiscurrentlyunoccupied.However,ournicheoverlapassessmentalsorevealedthatdespiteaconsiderableoverlap, realized niches of mouflon and domestic sheep differedandmouflonhabitatwasassociatedwithlessproductiveareas.Ourstudyis,toourknowledge,thefirstthatusesnichemodellingtospa-tiallyassessthenicheoverlapbetweenawildungulateanditsdo-mesticrelative,therebyhighlightingopportunitiesforrestoringwildungulatepopulationsinlandscapessharedwithlivestock.

Wefoundwidespreadsuitablemouflonsummerandwinterhab-itatacrossthesouthernCaucasus.Muchofthishabitatiscurrentlynot occupied bymouflon, potentially providing space for reintro-duction andherd expansions. Suitablehabitatwasmostly locatedinmountainousareas,whichweexpected,giventhespecies’pref-erence formediumruggednessandareasafar fromhumansettle-ments (Gavashelishvili, 2009). The spatial distribution of summer

TABLE  1 Nicheoverlapindicesbetweenmouflonsummerhabitatanddomesticsheephabitatacrossarangeofbufferareasusedtoderivethedomesticsheepoccurrences

Domestic sheep locations

Overlap index I

Without human disturbance

With human disturbance

Camp 0.89 0.82

100-mbuffer 0.89 0.82

200-mbuffer 0.89 0.83

500-mbuffer 0.90 0.83

1,000-mbuffer 0.90 0.83

2,000-mbuffer 0.90 0.82

F IGURE  4 Distributionofmouflonhabitatpatches(basedonthemouflonsummermodel),potentialmouflonhabitatpatches(basedonthecombinationofmouflonanddomesticsheephabitat),andpatcheswithlowriskforcompetitionwithlivestock[Colourfigurecanbeviewedatwileyonlinelibrary.com]

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andwinterhabitatwasverysimilar,suggestingthatseasonalhabitatpreferencesdonotdiffersubstantially.Itmightbethattheresolu-tionofourpredictorvariableswasnotfineenoughtocapturefine-scaleseasonalmigrationsalongtheelevationgradient.However,inthe past, mouflon occasionally migrated over longer distances tolowerelevationsinwinter,forexamplefromArmeniatoNakhchivanandtoIran(Baskin&Danell,2003;Khorozyanetal.,2009).Borderpatrols that limitmigrationsandovergrazingofmouflonwinteringareasbydomesticsheepmayhavestoppedthesemigrations(Linnelletal.,2016;Talibovetal.,2009).

Ournicheoverlapassessmentrevealedthatmostsuitablemou-flonhabitatwasalsosuitablefordomesticsheep.Ahighnicheover-lapisnotsurprisinggiventhatthespeciesarecloselyrelated(Gordon,2009;Madhusudan,2004),buthighlightstheneedtolimitnegativeeffects of sheep onmouflon populations (Khorozyan etal., 2009;Talibovetal.,2009).Nicheoverlapwashigher formodelswithouthumandisturbance,whichindicatesthatmouflonutilizeareasclosetohumaninfrastructure,whereshepherdcampsareoftenlocated,lessthandomesticsheep.

Ingeneral,ouranalysesprovidemoresupportfordifferencesinmouflonanddomesticsheeprealizednichesduetoeitheradis-placementofmouflontomarginalhabitatsortonichepartitioning(whichinturncouldalsoleadtodivergingfundamentalnichesovertime).First,despitehighoverlap, realizednichesdifferedsignifi-cantly.Second,mouflonoccurrencesdifferedfromshepherdcamplocationsregardingseveralofourpredictorvariables.Differencesin habitat use might arise from niche partitioning as a strategyto coexist.Domestic sheep are herded in the area formillennia

(Akhalkatsietal.,2017),andmoufloncouldhaveadaptedtoavoidcompetition.Mouflonwere found in terrain that ismore ruggedandwithonlysparsevegetation,bothofwhicharegenerallyasso-ciatedwithdecreasedforageavailability(Chirichellaetal.,2013).Similar habitat-use patterns have been found for otherwild un-gulatesthatcompetewithlivestockandhavebeendisplacedintomarginalhabitat.Forexample,whenlivestockwaspresent,Argalisheep(Ovis ammon)werepushedtosteeperslopeswithlessveg-etationcover(Namgailetal.,2006)andibex(Capra pyrenaica)andchamois (Rupicapra rupicapra) to areas with decreased resourceavailability (Acevedo, Cassinello, & Gortazar, 2007; Chirichellaetal.,2013).Likewise,adisplacementofmouflonfrommiddletohigherelevationswithlessresourcesduetolivestockgrazinghasoccurredinNakhchivan(Talibovetal.,2009).Suchadisplacementtoareaswithlessresourceavailabilitymightinturnindicatethatmouflonarearefugeespecies(Kerleyetal.,2012).

Basedonourhabitat suitability analysis and thenicheoverlapassessment, we identified mouflon conservation priority patches.Usingcurrentmouflonlocations,weidentifiedelevenmouflon hab-itat patches.Yet,only18%oftheirareawasprotected.Additionally,themajority of the patcheswas also highly suitable for domesticsheep (77%) or located within 10km from international borders,whichmight be inaccessible to shepherds and provide havens formouflon, but sometimesmight also entail high poaching pressurefromborderpatrols(Khorozyanetal.,2009).Whencombiningmou-flon and domestic sheep habitat, we identified 51 potential mou-flon habitat patches that cover a substantially larger area than themouflon patches.Asournicheoverlapanalysissuggestedashiftto

F IGURE  5 Least-costcorridorsamongmouflonhabitatpatches(i.e.,patchesbasedoncurrenthabitatpatterns)andconnectivitypatchesthatwouldfosterconnectivityifnewherdswereestablished[Colourfigurecanbeviewedatwileyonlinelibrary.com]

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marginal habitat for mouflon, these 51 patches may include bet-ter habitat. Yet, due to their high suitability for domestic sheep,wewould expect strong potential for competitionwith livestock.Indeed,wefoundonlytwoareasthatwere>300km2andhadalowriskforcompetitionwithlivestock,underliningtheneedforconser-vationeffortsthatlimitnegativeeffectsofgrazinginthesouthernCaucasus(Shackleton,1997;Soofietal.,2018).

Connectivityamongmouflon habitat patcheswaslow.Wefoundat leastonehigh-level road crossingeachof theeleven corridors,fivecorridorscrossinginternationalborders,andhighaveragecostalongtheleast-costpaths.Toincreaseconnectivity,wehighlightedthosepotential mouflon habitat patchesthatwerelocatedwithincor-ridors.Allcorridorshadconnectivity patches.However,someofthecorridorswerevery long (upto320km),suggestingthatanactivedispersalmanagementincludingtranslocationsmightbeneededtoavoid the lossofgeneticdiversity (Bouzatetal.,2009;Ptaketal.,2002). Additionally, the exact historic distribution of mouflon isunclear, and therefore, patches in northernArmenia,Georgia andTurkeymightbeoutsidetheformermouflonrangeandneverbeenfunctionallyconnected.

Wesuccessfullygainedmoreknowledgeonpotentialnicheover-lap,consequencesofcompetition,andspatialhabitatpatternsofathreatenedlargeungulateandlivestock.Nevertheless,afewdraw-backsremained.First,tomodelthedomesticsheepniche,weusedlocationsfromshepherdcampsthatwederivedfromhigh-resolutionsatellite imagery instead of actual sheep locations. Further, areaswheredomesticsheepgrazearetoa largedegreedrivenbyshep-herds’ decisions instead of the animals themselves. However,nicheoverlap indiceswere similar for random locations inbuffersaroundthecamps,whicharemorelikelytheareasthesheepgraze.Wemighthavemissedsomecamps,butthisshouldnotaffectourmodelsunless therewas a systematicomissionbias. Second,highnicheoverlapamongspeciestranslatesintocompetitiononlywhenshared resources become limited,whichwe did not test (deBoer&Prins,1990;Putman,1996).Yet,highmountainregionsaregen-erallyresourcescarce,whichiswhyweassumedthatat leasthighstockingratesdodepleteresourcesformouflon.Additionally,phys-icaldisturbancebyherdersanddogsisakeyfactorofcompetitionand displacement (Chirichella etal., 2013; Young, Olson, Reading,Amgalanbaatar,&Berger, 2011) andmaybemoredetrimental formouflon than forage competition (Talibovetal., 2009). Finally,wedidnotassessiflivestockgrazinginsomeareascouldbebeneficialformouflonbykeepingformerlyforestedareasopen.It isunlikelythoughthatsuchhighgrazingpressurewouldleavesubstantialre-sourcesformouflon.

5  | CONCLUSIONS

Competition with livestock is a major threat to wild sheep(Shackleton,1997)necessitatingnewapproachestoidentifywheretorestorewildsheeppopulationsinhuman-dominatedlandscapes.Ourstudymakesprogresstowardsthatintwomainpoints.First,our

approachisapplicabletoassesscompetitionpotentialanddisplace-mentfromoptimalhabitats.Second,wehighlighthowpotentialbiasin current occurrence data due to competitionwith livestock andassociateddisplacementcanbeovercomewhenidentifyingpriorityconservationareas.Wesuggestthatconservationplanningshouldconsidercompetitionwithlivestockbothreactively(lesseninglive-stockpressureinsuitableungulatehabitat)andproactively(reintro-ductioninareaswithlowcompetitionpotential).

For mouflon conservation, our results point out that largeareasofsuitablehabitatexistinthesouthernCaucasuswherethemouflonpopulationcouldbeenlarged.Thisisurgentlyneededtosafeguardthespecies intheCaucasus(Zazanashvilietal.,2012).However, competition with livestock is very likely in most oftheseareasandconnectivityamongthemislow.Further,poach-ingmightbeaseverethreat toexistingandnewpopulations,aswell as to dispersing animals. Thus, conservation efforts shouldfocus on (a) lessening conflictwith livestock, particularly in keymouflon patches; and (b) improving connectivity among priorityhabitatpatchesandbetweenseasonalhabitatthroughprotectionof stepping stones and/or translocations. Promoting private orcommunity-basedreserveswithsmall-scale livestockproductionmayhelpestablishmouflonpopulationswithlocallandownerspo-tentiallyco-benefitingfromwildlife(e.g.,tourism,trophyhuntingoncepopulationsareviable)whilereducingpoachingriskformou-flon(Allanetal.,2017).

ACKNOWLEDG EMENTS

B. Bleyhl gratefully acknowledges funding through an Elsa-NeumannScholarship fromtheFederalStateofBerlin,Germany.We thank D. Frantz andM. Baumann for support in processingthedata.WealsothankWWF-Armenia,WWF-Azerbaijan,WWFCaucasusProgrammeOfficeGeorgia,andWWF-Germanyfor lo-gisticsupportduringfieldtrips.E.M.MoqanakiwassupportedbyaresearchgrantfromWorldLandTrustthroughtheIranianCheetahSociety.Wearegrateful for thehelpandconstructivecommentsoftworeviewers.

DATA ACCE SSIBILIT Y

WewillmakehabitatmapsavailableviaHumboldtUniversityBerlin’scloudstoragesystem(HU-Box).

ORCID

Benjamin Bleyhl http://orcid.org/0000-0002-4858-950X

Ehsan M. Moqanaki http://orcid.org/0000-0001-7968-0210

Volker C. Radeloff http://orcid.org/0000-0001-9004-221X

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BIOSKE TCH

Benjamin Bleyhl is a PhD student in the ConservationBiogeographygroupattheGeographyDepartmentofHumboldt-UniversityBerlin.He is interested in questions regarding largemammal habitat distribution that can inform conservationplanning.

Authors’contributions:B.B.,H.B.,T.K.andV.C.R.conceivedtheideas; B.B.,M.A., E.A., H.B., A.G.,M.G., A.G., A.H., I.K., A.M.,K.M.,M.M.,E.M.M.,M.S.,P.W.andN.Z.gatheredandanalysedthedata;B.B.andT.K.ledthewriting;andallauthorsapprovedandeditedthemanuscript.

SUPPORTING INFORMATION

Additional supporting information may be found online in theSupportingInformationsectionattheendofthearticle.

How to cite this article:BleyhlB,ArakelyanM,AskerovE,etal.Assessingnicheoverlapbetweendomesticandthreatenedwildsheeptoidentifyconservationpriorityareas.Divers Distrib. 2019;25:129–141. https://doi.org/10.1111/ddi.12839