Ecology and conservation of the Anastasia Island beach mouse (Peromyscus polionotus phasma)

119 Pages·1996·3.4 MB·English

by  Frank, Philip A.

ECOLOGYANDCONSERVATIONOFTHEANASTASIAISLAND
BEACHMOUSE(PEROMYSCUSPOLIONOTUSPHASMA)
By
PHILIPA.FRANK
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOLOFTHEUNIVERSITY
OFFLORIDAINPARTIALFULFILLMENTOFTHEREQUIREMENTSFORTHEDEGREE
OFDOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
1996
ACKNOWLEDGMENTS
Firstandforemost,IthankSteveHumphreyforhiscreativeideas,stimulating
discussions,andprofessionalleadership. JohnEisenberg,MelSunquist,KenPortier,
andGeorgeTanneralsodeservethanksforservingonmydoctoralcommittee.
IamgratefultotheFloridaGameandFreshWaterFishCommissionforfunding
thisproject. ThanksalsogototheU.S.FishandWildlifeService,U.S.NationalPark
Service,andFloridaDepartmentofEnvironmentalProtectionfortheirhelpinassisting
allaspectsofthisproject.
VolunteerfieldassistancewasgenerouslyprovidedbyBertCharest,AliceBaird,
KarenLips,KevinFrank,MyronFrank,andWeazietheWonderDog. RebeccaHenson
deservesspecialrecognitionforassistanceintrappingandvegetationsamplingduring
longhoursofshadelesssummerheat. FellowgraduatestudentsBradStith,Miriam
Marmontel,KarlMiller,CarrieSekarak,BobGodshalk,MelissaFoster,JohnPolisar,
BethForys,RonEdwards,DaveLambert,andWendyTownsendprovidedthe
camaraderieessentialforsurvival. Myparents,MyronandMatty,andmybrotherKevin
deservespecialthanksfortheirmoralsupportandunderstandingofadecadeofmice.
Finally,Ithankthe2,244beachmicecapturedduringthestudyfortheir
cooperation,andapologizeformyperiodicintrusionsintotheirlives.
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1
TABLEOFCONTENTS
cage
ACKNOWLEDGMENTS
ii
ABSTRACT
y
CHAPTERS
1 INTRODUCTION 1
TheBeachMouse j
StudyArea 2
DissertationGoalsandStructure 6
2 POPULATIONBIOLOGY iq
Introduction 10
Methods
1
Results J5
PopulationDynamics 15
Survival 15
SexRatio 17
AgeStructure 17
Reproduction Ig
BodyMass 19
InteractionswithDomesticCatsandHouseMice 19
Discussion 20
PopulationLevels 20
PopulationEstimation 22
Survival 23
InteractionswithHouseCats 24
InteractionswithHouseMice 26
3 DISTRIBUTIONANDHABITAT 43
Introduction 43
Methods 44
Results 4g
iii
Island-wideDistributionofRodentSpecies 4
HabitatUsebyRodentSpecies 4
Discussion 5
BeachMouseHabitatUse 51
HabitatUsebyExoticSpecies 52
4 RE-ESTABLISHMENT 64
Introduction 64
Methods 65
Results 68
Distribution 68
PopulationMonitoring 69
ComparisonwithAnastasiaIslandPopulation .70
Discussion 70
PopulationVulnerability 70
HabitatUse 7.1
DifferencesbetweenAnastasiaIslandandGRSP 72
5 POPULATIONVIABILITYANALYSIS 77
Introduction 77
Methods 79
Results 33
Discussion 85
6 MANAGEMENTRECOMMENDATIONS 94
ManagementPhilosophyandGoals 98
ProposedManagementActions 99
PopulationMonitoring 99
HabitatManagement 101
DomesticCatControl 102
Range-wideManagement 103
CatastrophePlanning 103
REFERENCES
IO5
BIOGRAPHICALSKETCH HI
iv
AbstractofDissertationPresentedtotheGraduateSchoolofthe
UniversityofFloridainPartialFulfillmentoftheRequirements
fortheDegreeofDoctorofPhilosophy
ECOLOGYANDCONSERVATIONOFTHEANASTASIAISLAND
BEACHMOUSErPEROMYSCUSPOLIONOTUSPHASMA)
By
PhilipA.Frank
December,1996
Chairman:StephenR.Humphrey
MajorDepartment:WildlifeEcologyandConservation
TheAnastasiaIslandbeachmouse(Peromyscuspolionotusphasma)isan
endangeredrodentendemictonortheasternFlorida. Coastaldevelopmenthasreduced
boththequantityandqualityoftheremaininghabitat. Asaresult,populationsofthe
AnastasiaIslandbeachmousearereduced,fragmented,andatrisktoextinction. Atwo-
yearstudywasconductedtodocumentbeachmousepopulationecology,effectsofexotic
housemice(Musmusculus)anddomesticcats(Feliscattus),habitatrequirements,and
threatstotheircontinuedpersistence.
Live-trappingwasconductedquarterlyonseven1-hagridsfromJanuary,1989
throughOctober,1991. Atotalof23,200trapnightswereaccumulated,andatotalof
1,668beachmicewerecapturedon4,230individualoccasions. Beachmouse
populationsfluctuatedbetweenapproximately10to100perhaatasinglelocation.
Housemicedidnotnegativelyaffectbeachmousepopulations,butoccupiedsimilar
V
habitat. Housecatspreyeduponbeachmiceandmaynegativelyaffectbeachmouse
populations.
HabitatrequirementsofrodentsonAnastasiaIslandwerestudiedonlivetrapping
transects. Specificpatternsofhabitatusevariedbyspecies:beachmiceandhousemice
preferredprimarydunes;cottonrats("Sigmodonhispidus)preferreddense,grassyareas
andstabledunes;andblackrats(Rattusrattus)preferredstabledunes. Primarydune
habitatsadjacenttodevelopmentsupportedbeachmousedensitiestypicallyone-halfthat
ofundevelopedhabitats.
BeachmicehistoricallyoccupiedbothAnastasiaIslandandtheun-namedbarrier
islandimmediatelytothenorth,butweresubsequentlyextirpatedfromthenorthern
island. Arelocationof55adultbeachmicewasconductedtopublicly-ownedproperty
duringOctober,1992. Thepopulationrapidlybeacmeestablishedandexpandedovera
6.5-kmbeacharea. Post-releasemonitoringdocumentedthepersistenceofthis
populationthroughOctober1994.
Asimplemodelofbeachmousepopulationdynamicswasdevelopedtoexamine
theeffectsofcatastrophicstormsonpopulationpersistence. Frequentbutlesssevere
hurricanessuchasCategoryIandIIposeamuchgreaterthreatthandoextremelyrare
catastrophicCategoryVstorms. Recommendationsforbeachmousemanagement
includeregularmonitoringofpopulations,maintenanceofoptimalhabitatconditions,
andtheestablishmentofadditionalprotectedpopulationsincaptivity.
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CHAPTER
1
INTRODUCTION
TheBeachMouse
Theoldfieldmouse(Peromyscuspolionotuslisasmallnocturnalrodentthat
rangesthroughoutthesoutheasternUnitedStatesincludingportionsofAlabama,
Georgia,SouthCarolina,andFlorida(Hall1981). Subspeciesoftheoldfieldmousethat
occuroncoastalbeachdunesofportionsofAlabamaandFloridaaregenerallypalerthan
inlandformsandarecollectivelyreferredtoasbeachmice. Becauseofextensive
developmentofcoastalareas,beachmicehaveexperiencedextensivelossoftheir
preferreddunehabitats. Consequently,oftheeightrecognizedsubspeciesofbeachmice,
sixarelistedaseitherthreatenedorendangeredbytheU.S.FishandWildlifeService
andFloridaGameandFreshWaterFishCommission,andthepallidbeachmouse(R
decoloratus)isextinct(Ehrhart1978,HumphreyandBarbour1981,U.S.Fishand
WildlifeService1987).
ThesituationfacedbytheAnastasiaIslandbeachmouse(R phasma)typifies
theplightofbeachmicethroughouttheirrange Thesubspecieshasarestrictedrange,
occurringononlytwobarrierislandsin St.JohnsCounty,Florida. Priortotheinitiation
ofthisproject,therangeincludedonlyasingleisland(HumphreyandFrank1992)but
wasexpandedtoincludeanislandwheretheAnastasiaIslandbeachmousewasrecently
extirpated(Chapter3,Ivey1949,1959). TheAnastasiaIslandbeachmouseisahabitat
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2
specialist,occupyingthenarrowstripofdunesontheAtlanticcoastoftheisland
(PournelleandBarrington1955). Theavailabilityofthisnaturallylimitedhabitathas
beenseverelyreduced,degradedandfragmentedbycoastaldevelopment. Exotichouse
mice(Musmusculus)anddomesticcats(Felissvlvestris)havecolonizedthedune
habitatspreferredbytheAnastasiaIslandbeachmouseandmayposeaseriousthreatto
theremainingpopulation(Blair1951,Bowen1968,HumphreyandBarbour1981,Frank
1992). Finally,hurricanesarearegularalbeitunpredictablefeatureofbeachmouse
habitatonAnastasiaIslandandelsewhere. Theseseverestormscandestroylarge
amountsofbeachmousehabitat,posingaseriousandunpredictablethreattobeach
mousepopulations.
StudyArea
AnastasiaIslandisabarrierislandlocatedinnortheasternFlorida,inSt.Johns
County,andisthesouthernmostislandinaseriesofsouthernseaislandssharingsimilar
naturalandculturehistories(JohnsonandBarbour1990,Figure1.1). Theislandisa
long,thinformationextending22.2kmnorth-to-southandrangingfromapproximately
0.5to3.0kminwidtheast-to-west. ItisseparatedfrommainlandFloridabyextensive
saltmarshesandtheMatanzasRiver,tothenorthbytheSt.AugustineInlet,andtothe
southbytheMatanzasInlet. TheseawardsideoftheislandisboundedbytheAtlantic
Oceanandiscomposedoffinequartzsandsthatformthebeachesanddunes. Awide
beachbermslopesgentlyupwardfromtheshorelinetotheouterdunes,whichforma
continuousridgeparallelingtheocean.
.
3
ThedunevegetationonAnastasiaIslandcanbeclassifiedintogeneralzones:
foredunes,transitionaldunes,andstabledunes(JohnsonandBarbour1990,Figure1.2).
Thesedistinctzonesvaryintopographicandvegetativestructure,distancefi-omthehigh
waterlevel,elevation,stability,andplantspeciescomposition. Detaileddescriptionsof
plantcommunitiestypicalofthisregioncanbefoundinJohnsonandBarbour(1990),
LassieandMonk(1961),andKurz(1942)
Thezonenearesttheshorelineistheupperbeachandforedune(Johnsonand
Barbour1990),asparselyvegetated,low-elevationzonesubjecttocontinualdisturbance
fromwindandwaveerosion. Theheightofforedunesrangesbetween<1.0mto4-5m.
Vegetationontheforedunesisgenerallysparse,consistingofsalt-tolerantpioneering
speciesadaptedtotheharshconditions. Seaoats(Uniolapaniculata)isthemost
abundantandimportantdune-formingspecies,trappingsandandstabilizingthedunes.
Railroadvine(Ipomeabrasiliensis)andbeachmorningglory(Lstolonifera)arealso
commonpioneerspeciesplayinganimportantroleinearlyduneformation. Other
speciesfi-equentlyencounteredontheforedunesincludebeachelder(IvaimbricataV
pennywort(Hvdrocotvlebonarenensislsandspur(Cenchrusspp),beachpanicgrass
(Panicumaniarum),andeveningprimrose(Oenotheriahumifiisa).
Behindtheforedunesisthetransitionalzoneorbackdune,whichbeginsatthe
foreduneandcontinuesinlanduntiladistinctplantcommunityisrecognized(Johnson
andBarbour1990),usuallyscrub,hammock,orsaltmarshonAnastasiaIsland. The
widthofthiszoneisvariable,rangingfi-omlessthat10mto100mormore. Vegetation
inthetransitionzoneishighlyvariableandusuallyincludesspeciesfoundonthe
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foredunesaswellasplantsfrominlandcommunities.Thetransitionalvegetationon
AnastasiaIslandisgenerallysparseandlowcomparedtomoresouthernbarrierislands,
althoughdense,grassyswalescomposedofbeachcordgrass(Spartinapatens)andpurple
muhlygrass(Muhlenbergiacapillaris)arepresentinafewlocations.
Herbaceousspeciescommoninthetransitionzoneincludemanyfoundon
foredunesaswellascamphorweed(Heterothecasubauxillaris").firewheel(Gaillardia
pulchellalbeachcroton(Crotonpunctatus),pricklypear(Qpuntiahumifusa)anddevils
jointcactus(apusilla).greenbriar(Smilaxauriculata),plusavarietyofgrassesand
forbs. Shrubsandtreesthatmayoccurinthetransitionzoneincludewaxmyrtle(Myrica
cerifera),Atlanticcedar("JuniperussiliciolaVscruboak(QuercusvirginianaVsaw
palmetto(Serenoarepens),andredbay(PerseaborboniaVBecausewindandsalt-spray
retardsgrowthoftreesandprunesdistalendsofshootsinthetransitionzone,most
specimensencounteredare2.0morlessinheight. Coastalscrubwaspreviously
widespreadonAnastasiaIsland,butdevelopmenthasreducedittoafewsmallpatches.
Stabledunesaremostinterior,highestinelevation,oldest,andmoststable
(JohnsonandBarbour1990). ElevationsofstabledunesonAnastasiaIslandreachas
highas10-12m,buttheseformationsareabsentinmanyareasonAnastasiaIslandasa
resultofdevelopment. Theprinciplevegetationtypeonstablebackdunesisoakforestor
hammock. Theprimaryspeciesintheoakforestisliveoak(Q,virginianaVforminga
closedcanopyinmostplaces,withthecrownsoftensculptedbywindandsaltspraytoa
uniformlevel.Otherspeciescapableofreachingcanopyheightincludeslashpine(Pinus
elliottii),southernmagnolia(Magnoliagrandiflora),redbay,Atlanticcedar,andcabbage