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SHORTCOMMUNICATIONLong-distancedispersalinredfoxesVulpesvulpesrevealedbyGPStrackingZeaWalton1&GustafSamelius2&MortenOdden1&TomasWillebrand1Received:22January2018/Revised:26September2018/Accepted:3October2018/Publishedonline:11October2018#TheAuthor(s)2018AbstractDispersalisafundamentalprocessthatfacilitatespopulationandrangeexpansionbyprovidingamechanismforcolonizationandmetapopulationlinkages.
Yetquantifyingthedispersalprocess,particularlylong-distancedispersalevents,hasbeeninherentlydifficultduetotechnologicalandobservationallimitations.
Additionally,dispersaldistancecalculatedasthestraight-linedistancebetweeninitiationandsettlementfailstoaccountfortheactualmovementpathoftheanimalduringdispersal.
Here,wehighlightsixlong-distancedispersalevents,representingsomeofthelongestdispersaldistancesrecordedforredfoxes.
Cumulativedispersalmovementsrangedfrom132to1036kmandoccurredwithinbothsexes(1female,5males).
Withoneexception,dispersaleventsrangedfrom7to22daysandtendedtobedirectednorth-northwest.
Importantly,cumulativemovementswereuptofivetimeslongerthanstraight-linedistances,withtwofoxestravelinganadditional114and256kmbeforereturningto,andsettlingin,areaspreviouslyencounteredduringdispersal.
Thissuggestsaroleofhabitatassessmentandhomingbehaviorduringdispersalandindicatesthatthecapacityandpotentialfordispersalarenotlimitingfactorstoeithersexinaredfoxpopulation.
Dispersalcapacityshouldthusbeconsideredregardingtransboundarymanagementanddiseasecontrolofredfoxpopulations.
KeywordsCanid.
Dispersal.
Long-rangemovements.
Meso-carnivore.
Scandinavia.
Transboundarymanagement.
Rangeexpansion.
Diseasetransmission.
Redfox.
Norway.
Sweden.
Globalpositioningsystem(GPS)IntroductionDispersalisafundamentalprocessinecologyprovidingthemechanismbehindpopulationandrangeexpansion(Sutherlandetal.
2000;Lambinetal.
2001).
Yetquantifyingthedispersalprocess,particularlylong-distancedispersalmovements,hasbeeninherentlydifficultduetotechnologicalandobservationallimitations(Nathanetal.
2003;Nathan2005;WhitmeeandOrme2013).
Thisalsocontributestodif-ficultiesdefiningwhatrepresentsalong-distancedispersalmovementfordifferentspecies.
Long-distancedispersalhasbeenalternatelydefinedasanabsolutedispersaldistance,or,asthoseindividualsthatdispersesubstantiallyfurtherthantherestofthepopulation(Nathan2005).
Here,wefollowthelatter,defininglong-distancedispersalasindividualsthatrep-resentoutliersonthespectrumofdispersaldistancesrecordedforaparticularspecies.
Far-rangingindividualsandtherolethattheyplayinrangeexpansion,colonization,andmetapopulationlinkagesareofgreatinteresttoresearchers(ShigesadaandKawasaki2002;Wabakkenetal.
2007;Ciuccietal.
2009).
Long-distancedis-persaleventsbycanidshavebeenpreviouslyrecognized(wolvesCanislupus(Wabakkenetal.
2007);coyotesCanislatrans(Harrison1992;KolbeandSquires2004);redfoxesVulpesvulpes(AllenandSargeant1993;Colsonetal.
2017)).
However,dataarescarceandsucheventsarebelievedtobenotablebutuncommon(Sutherlandetal.
2000;Nathanetal.
2003).
Thus,quantifyingsuchmovementshaslargelyremainedelusive.
Muchofthepreviousknowledgeregardingdispersalhasreliedoncapture-mark-recapturestudiesorveryhighfrequen-cy(VHF)radiotrackingtechnology,wheredispersalisoftenquantifiedasthestraight-linedistancebetweeninitiationandsettlement.
However,thisfailstoaccountfortheactual*ZeaWaltonzea.
walton@inn.
no1FacultyofAppliedEcology,AgricultureSciencesandBiotechnology,DepartmentofForestryandWildlifeManagement,InlandNorwayUniversityofAppliedSciences,Evenstad,2480Koppang,Norway2SnowLeopardTrust,4649SunnysideAvenueNorth,Suite325,Seattle,WA98103,USAEuropeanJournalofWildlifeResearch(2018)64:64https://doi.
org/10.
1007/s10344-018-1223-9movementpathoftheanimalduringdispersal(Stormetal.
1976;HarrisandTrewhella1988;AllenandSargeant1993;Gosselinketal.
2010).
Further,dispersaldatamaybeofcoarsetemporalresolutionormayfailtorecordanimalsdispersinglongdistances,potentiallybeyondstudyareaorcountryboundaries.
Thisoversimplificationofdispersalcanhaveim-plicationsregardingtheextentofdispersaleventsandtheunderstandingofthedispersalprocess(Nathanetal.
2003;WhitmeeandOrme2013).
Theredfox,ahighlyadaptableandflexiblegeneralistmesopredator,hassuccessfullycolonizedmostofthenorthernhemisphere,leadingtooneofthelargestgeographicrangesofanyterrestrialmammal(LarivièreandPasitschniak-Arts1996).
Thebehavioralplasticityofredfoxesandtheirabilitytorespondtolandscapeproductivitychangesandhumansub-sidieshasallowedthemtoexpandintoincreasinglynorthernlatitudes,whichhasdirectimplicationsfortheseecosystems(Colsonetal.
2017;Elmhagenetal.
2015,2017).
Dispersalisaprerequisiteforrangeexpansion(Clobertetal.
2001)butourunderstandingofhowlong-distancedispersaleventsmaycon-tributetorangeexpansionremainslargelyunknown.
WithadvancesinGPSandsatellitetrackingtechnology,itisnowpossibletocapturedispersaleventsintheirentirety,withhighspatialandtemporalresolution(Nathan2005;Cagnaccietal.
2010).
Thisgreatlyfacilitatesamorecomprehensivequanti-ficationofindividualdispersalpatternsanddistancestraveledthanpreviouslyattainable.
Here,weexaminesixindividuallong-distancedispersaleventsbyredfoxesfromthreedifferentpopulationsinNorwayandSwedenusingGPStelemetry.
Withthesedata,weaimtoimproveunderstandingofthecharacteristicsoflong-distancedispersaleventsofredfoxes.
Specifically,wequantifybothstraight-lineandcumulativedistancestraveled,aswellasthetiming,duration,anddirectionalityoftheselong-distancedispersalevents.
Further,weexplorewhetherlong-distancemovementsoccurasamultistageprocessorassingleeventsanddiscusstheirpotentialimplicationsfornorthernrangeexpansionsanddiseasetransmission.
MethodsBetween2011and2017,wecaptured101redfoxeswithinfourdifferentstudyareasinSwedenandNorway,aspartofalong-termresearchproject(seeWaltonetal.
2017fordetails).
Thefourstudyareasrepresentagradientoflandscapeproductivityandhumanlanduse.
Thesouthernmoststudyarea,Kolmrden(58N),Sweden,consistsofboreonemoralforests,agriculturallands,andscatteredhumansettlements,whilenorthernborealforestsandalpinetundraoflowdiversityandproductivitychar-acterizethenorthernmoststudyareainHedmarkCounty(62N),Norway.
Norwayspruce(Piceaabies)andScotspine(Pinussylvestris)dominatetheforestsinallareas,butbirch(BetulapubescensandB.
verrucosa)andotherdeciduoustreespeciesareincreasinglypresenttothesouth.
Allcapturedfoxes>5kgwerefittedwithGPSradiocollars(TellusUltralight,210g,Televilt,Inc.
Lindesberg,Sweden).
Wefurthersexed,measured,weighed,andagedallcapturedfoxes.
Agewasdefinedassub-adult(1year)basedontheamountoftoothwearandtoothcoloration.
Additionally,weassumedabirthdateofApril1foryoungoftheyear(HarrisandTrewhella1988)toapproximateageinmonthsattimeofdispersal.
Foradditionaldescriptionofstudyareasandcapturemethod-ologyseeWaltonetal.
(2017).
GPScollarsvariedinpositionschedules,withcollarsdeployedbeforeOctober2015programmedtotakethreepositionsperdaywithadrop-offafter270days(9months),andcollarsdeployedafterOctober2015programmedtotakesixpositionsperdaywithadrop-offafter180days(6months).
Weadditionallyhadseveralfoxescapturedafter2015withpositiondatacollectedat10-minintervalsforupto3-weekperiodswithintheirstandardsixpositionsperdayprogramming.
Wedeterminedfoxesengagingindispersalusingnetsquareddisplacement(NSD)(BrgerandFryxell2012;Gurarieetal.
2017),andvisualinspectionofmovementdatainQGIS2.
18.
0(QuantumGISDevelopmentTeam2017).
Individualsthatdispersedstraight-linedistancesgreaterthan60kmrepresentedoutliersonthespectrumofdispersaldis-tancesrecorded,andwe,thus,definedtheseindividuals(n=6)aslong-distancedispersersfollowingNathan(2005).
Toallowcomparisonofdispersaldistancesamongthesefoxes,westandardizedpositionintervaltothreepositionsperday(thelowestmaximumnumberofpositionsperdayrecorded).
Intotal,6629GPSpositionswereavailableforfurtheranaly-sis.
TheGPSfixsuccessratewas98.
1%withameanhori-zontaldilutionofprecision(HDOP)of1.
06±0.
8SD(range=0–25.
5).
LowerHDOPvaluesareconsideredtobemorepre-cise(D'EonandDelparte2005)and99.
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