rodent responses to the lunar phases among different...

Rodentresponsestothelunarphasesamongdifferenthabitatstructure.StephanieCampbell&CharlesW.GunnelsIV

FloridaGulfCoastUniversity,DepartmentofMarineandEcologicalSciences

INTRODUCTIONNocturnalanimalsexperiencehighdegreesoflightvariaFonassociatedwiththephasesofthelunarcyclesaswellasthedegreeofcanopystructure.Thererecentlyhasbeenasurgeofexcitementconcerningrodentresponsetolunarphases&canopystructurestemmingfromthehighdegreeofvariaFonamongdifferentspecies.Peromyscusgossypinus&Sigmodonhispidusco‐occurinsouthwestFlorida,yeteachspeciesexemplifiesuniquelifehistorytraitsandbehavioraldifferences.Experimentwillhelpdeterminehowthesetwoco‐occurring,uniquespecieswillrespondtolunarphasesandcanopystructurewithinthesameenvironment.

HYPOTHESISBothspeciesshouldshowdecreasedacFvityduringfullmoonsandincreasedacFvityduringnewmoons.RodentswillchangetheiracFvityduringnightsoffirst‐quarterandthird‐quartermoonsbecausechangesintheamountoflight.BecauseS.hispidusisbothdiurnal&nocturnal,weexpectlunarphasetohavelesseffectonits’acFvitythantheexclusivelynocturnalP.gossypinus.

RESULTS

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ACKNOWLEDGEMENTSWewouldliketothankJimGoodwinandtheSouthFloridaWaterManagementDistrict,BrendaBrooks,andBrendaThomasforallowingmetoconductmyresearchatCREW.WewouldliketothankPaigeMarFnforteachingmeskillsetsneededtoconductmystudyandmyhusbandStevenRogersforassisFngmeinfieldresearch.

CONCLUSIONBothPeromyscusgossypinusandSigmodonhispidusavoidedlunarlightandpreferredclosedcanopies.PeromyscusgossypinuswasmoreacFveduringnewmoons.UnlikeS.hispidus,P.gossypinuswasfoundinopenhabitats,whichissurprisingbecausethiswasthebrightestenvironment.OpenhabitatswereuFlizedbyP.gossypinusduringthedarkestlunarlightstages,hencesuchhighacFvityduringnewanddarkmoons.ThispacerncouldbeexplainedbythefactthatforagingopportuniFes,suchasnewgrassesorseeds,areonlyavailableinopencanopies.ThisalsomayexplainwhyP.gossypinusadventureoutintoopencanopiesduringperiodsoflicletonolunarlight.PeromyscusgossypinusmayavoidtheseareasduringperiodsofhighlunarlightintensitybecauseofahighpredaFonrisk.Eventhoughbothspecieslivewithinthesameenvironments,theybothresponduniquelytolunarphaseandcanopystructure.

ABSTRACTMoonlightaffectsmammalianresponsestovariablehabitatsthatmayresultfromdifferentpredaFonrisks.StudyingthenocturnalacFviFesofrodentspromotesunderstandingofhowtheseanimalsreactintheirenvironmentduringdifferentlunarphases.RodentsshowahighdegreeofvariaFoninresponsetolunarcycleandvariableenvironments.WeexaminetheresponseofPeromyscusgossypinusandSigmodonhispidustolunarphasesandcanopystructure.Weexaminedthesespeciesbecausetheyaresympatricandshowlifehistorydifferencesthatshouldinfluencetheirresponses.Wetrappedrodentsonnightsconcurrentwiththelunarcyclesinthreehabitats:open,parFal,andclosedcanopies.Trappingtwiceanightatmidnightandmorningallowedusdeterminehowrodentsrespondtolunarphase,lunarlight,andcanopystructure.Bothspeciespreferclosedcanopy.Peromyscusgossypinusrespondedtolunarphases;theyweremostacFveatthenewmoon.PeromyscusgossypinususedopenhabitatsmorethanS.hispidus.Peromyscusgossypinus,whichisexclusivelynocturnal,avoidedlight,whileS.hispidus,whichisbothdirunallyandnocturnallyacFve,wasmoretolerantoflight.

METHODS• ExamineddistribuFonPeromyscusgossypinus&Sigmodonhispidusin3habitattypes(open,parFal,closedcanopies)

• Small‐mammalmark‐recapture(April‐November2009)

• DistribuFonobservedacross4lunarphases(new,1stQuarter,full,3rdQuarter)

• Rodentstrapped2xpernight(midnight&dawn)

• 3replicateseachhabitatsite9sites

• Sitespecifics:1transect,7trapsevery8meters

• Trappingpressure:63trapspersession;126trapspernight

• Provisions:food(bait),nesFngfluff,foliagecover

• UseMann‐WhitneyU‐test&Kurskal‐Wallistocomparegroups

Rodentsdidnotrespondtolunarphases(K=3.86,df=3,p=0.277).

WewereequallylikelytocaptureP.gossypinusandS.hispidusindarkorlightcondiFons(U=261.5,nlight=21,ndark=34,p=0.091).

Surprisingly,P.gossypinusmadeuseoftheopenhabitat,whichS.hispidusavoided(K=20.61,df=2,p<0.001).

MorePeromyscusgossypinuswerefoundduringthenewmoon(K=7.65,df=3,p=0.05).

Rodentsappearedtoavoidlunarlight(U=773.0,nlight=44,ndark=46,p=0.045).

Rodentsavoidedtheopencanopyandfavortheclosedcanopy(K=33.79,df=2,p<0.001).

Peromyscusgossypinusrepresented46%ofcapturedanimalsandSigmodonhispiduswerecollected54%oftheFme(t=0.67,df=54,p=0.51,Homean=0.5).