why survey for amphibians?fwf.ag.utk.edu/mgray/wfs493/lectures/graeter.pdf · 2017-04-06 ·...
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TechniquesforInventory&MonitoringofAmphibians
Gabrie l le Graeter
Wi ld l i fe Divers i ty B io log ist
NCWi ld l i fe Resources Commiss ion
SEPARCSteer ing Committee
Outline- Whysurveyamphibians?
- Definingyourgoal
- Beforeselectingatechnique
- Techniques◦ Active◦ EasyPassive◦ IntensivePassive
- LimitationsandTips
- Resources
WhysurveyforAmphibians?
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Whysurveyforamphibians?•Amphibiansaredeclining.Abetterunderstandingofaspecies’status=betterabilitytoconservethespeciesandtheirhabitat
•Needmoreinformationaboutdistributionofmanyspecies
•Tolearnmoreaboutthelifehistory(e.g.,breedingtimes,growthcurves,movement,clutchsize)
•Toanswerimportantresearchquestions
DefiningyourGoal
DefiningtheGoalWhatistheQuestion?◦ Identifyingthespeciesthatinhabitadefinedareaorhabitat?Therefore,thereisaneedforpresence orabsencedata.
◦ Determiningthegeographicdistributionofaspeciesorgroupofspecies?Eitheramonghabitattypesoracrossadefinedregion(s)
◦ SoundslikeINVENTORY
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DefiningtheGoalWhatistheQuestion?◦ Determinethestatusofaspeciesatagivensiteorhabitat?Therefore,thereisaneedforabundanceordensitydata.
◦ Determinepopulationchangesinsinglespeciesorspeciesassemblagesovertime.Eitheratagivenhabitat,amonghabitattypes,oracrossadefinedregion(s)
◦ SoundslikeMONITORING
Inventoryvs.Monitoring
• Theyarenotthesame(andprobablyshouldnotbediscussedinthesamesentence)
• However,someofthetechniqueshaveoverlappinguses
InventoryComesBeforeMonitoringFirstconductaninventory
Basedontheresultsdiscoveredduringtheinventoryprocess,furtherdecisionsaremadetomonitorparticularspecies
Examplesofspeciesmaywanttomonitor:thoseendangered,suspectedindecline,vulnerabletolandmanagementmanipulations
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ValueofLong-TermMonitoringJustastheresultsofanInventory willelucidatetheneedsandgoalsofaMonitoring program,
RepeatedMonitoringmaymorphintoaResearchstudy
PointstoconsiderbeforeselectingTechniques
BeforeSelectingTechniques
• Knowbiology&lifehistoryofthespecies
• Knowthehabitats
• Considernaturalenvironmentalfluctuations
• Considertime,funds,andpersonnelavailable
• Accountforinfluenceofdetectability
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Speciesandlifestagesaresometimesdifficulttodistinguish
Itisimportanttofindalllifestagessotherearenomisidentifications
Findinglarvaisimportantbecauseyouknowtheyarebreeding
Speciesandlifestagesaresometimesdifficulttodistinguish
Somespeciesareboomorbustbreeders◦ Itisnotuncommonforaspeciestonotbreedformultipleyears,andthen.........
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Knowthehabitats•Knowthehabitattypesthespeciesuses
•Complexityofthehabitat
•Learnabouthowthespeciesusesthehabitat• Microhabitatselected?Woodydebris,leaflitter,etc.• Above/belowground?
•Mapthehabitattohelpwithplanning
•Sizeoftheareatobestudied
HabitatMapping•Thefirstbasicstepindesigninganinventoryormonitoringplanismappingoutyourhabitattypes
•Willhelpyouidentifythetypesofhabitatpresent
•IfyouhaveGISresourcesutilizethem,ifnot,canuseGoogleEarth
•Oftenverysmallhabitatfeaturescontainadisproportionateamountofamphibianandreptilediversity• Seeps• Streams• Wetlands• Rockoutcrops• Etc.
NaturalEnvironmentalFluctuations
• Activity&reproductionofaspeciesvarieswithnaturalenvironmentalfluctuations
• Fluctuationsoccuratsmallscales(localthunderstorms)andatlargerseasonalandannualscales
• Examples:precipitation,temperature,humidity,drought,hurricanes
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SeasonalityAffectsSamplingImmigration
Callingbyadults
Eggdeposition
LarvalperiodMetamorphosis
Emigration
Seasonal wetlands hydrology
summer
winter
DryBay– Summer1993
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DryBay- Summerof2002
Berealistic•Howmuchtimedoyouhavetodevotetothis?•Isfundingalimitation?Whatisthebudget?
•Howmanypersonnelareavailable?
Detectability – theprobabilityoffindingaspeciesgivensomeunitofsearcheffort.
◦ Alotofherpshaveaverylowdetectability,sotohaveanychanceoffindingsomerarespeciesyoumusthavealotofeffort(sometimesyears)beforeyoucanconfidentlysayitisnotpresent
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Detectabilityisinfluencedby...• Unpredictableseasonalevents– droughts,coldwinters,heatwave,heavyrains,etc.• Reproductivecycles- somespeciesmayonlybedetectedduringtheirbriefbreedingseason• Landscapeandhabitat– complexity,won’tfindaspeciesifhabitatnotpresent• Currentweather:relativehumidity,barometricpressure,cloudcover• Air,water&substratetemperature• Soilmoisture&rainfall• Moonbrightness• Diurnalv.nocturnalactivity
Techniques
Samplingtechniques
3broadcategoriesoftechniques◦ Activesampling◦ Easypassivesampling◦ Intensivepassivesampling
Formoststudiesitislikelyyouwouldneedtocombinetechniquesforbestresults◦ Youcanalmostneverdocumentallofthediversityinanareausingasinglecategoryofsamplingtechniques
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Designcomponent
TimeconstrainedTimeconstrained- Apredeterminedtimeischosen
#ofobserversXtimesampled;forcatchorvisualencounter◦ Youcanalsopredetermineifyouarelookingfornotonlyacertainspeciesbutforaspecificlifestage,sex,size,orcharacteristic
Whatthistellsyou◦ Presence◦ Lifehistoryinfo- e.g.wheneggsaredeposited◦ Specieshabitatinfo◦ Aroughestimateofpopulationsize(notactualsize,butforcomparison)
AreaconstrainedAreaconstrained- adefinedamountofhabitatisselectedforsampling◦ Randomlyselectedplots◦ Certainhabitattypes- ponds,caveentrances,etc
Samestrengthsandweaknessesoftimeconstrainedbutyoucanalsogetaverycrudeestimateofdensity
Mustbewaryofdifferentsizedhabitatsifyougothehabitattyperoute
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TransectSurveysTransects- asurveylinelengthisselectedandcombinedwithadetectionmethod
Veryversatile- forexample,herearesomedetectionmethodsthatcanbeused◦ Visualencounter◦ Flippingcoverobjectswithin1m oftransect◦ Countingeggmassesinapond◦ Etc.
ActiveSampling
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ActiveSamplingActivesamplingiseasytouse◦ Veryeffectiveforspeciesthatareeasilyseenorthatleavetracesoftheirpresence(eggmasses,burrows,etc.)◦ Noteffectiveforsomespecies,especiallyifstaffarenotexperienced
Themostbasicformispresence-absencesearches◦ Searchahabitatandifyoufindaspeciesyouknowit’sthere(obviously)◦ Presence/Absencetellsyouverylittleaboutpopulationsizesandotherpopulationparameters(e.g.growth,decline,etc.)
◦ Agoodtooltogetpeopleinvolvedinyourprogram(e.g.BioBlitz)butnotgoodastheonlytool
Activesamplingincludes:- Handcollecting
- Signandtracking
- Visualencountersurveys
- Dipnetting andsweepsamples
- Kicksampling
- Eggmasscounts
- Snorkelingsurveys
- Electroshocking
- Auditorysurveys- Roadcruising
Handcollecting&SignandTracking
•HandCollecting– captureviahandortools(snakehooks,long-handleddipnets).Mayinvolvelookingthroughleaflitter,underlogs,orbehindbark.• Importanttoleavesearchedhabitatsasundisturbedaspossible– putrocksandlogsback
•Sign&Tracking– maylocatethembyfollowingdistinctivefootprints,locatingrecentlyusedburrows,hibernacula,ornestsandbyidentificationofscat• Moreusefulwithreptilesthanamphibians
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VisualEncounterSurveys•VESisatime-constrainedmethod:observerssampleapre-definedarea
• Timeand#ofobserversmustberecorded• DiffersfromTransectsurveyinthatdoesnothavetobelinear
•3VESSamplingDesigns:• Randomizedwalk– useaseriesofcompassdirections,distance.• Quadrat– systematicallysurveybywalkingparallelordiagonalpathways• Transect– lineartransectsareestablishedandwalkedbyobservers.
Dipnetting•Definition:Anetissweptthroughanaquatichabitat
• Meshsizeisimportant
•Mostuseful:• Insmallshallowaquatichabitats(smallerareameansgreaterchanceallspeciespresentwillbecaptured)
• Whensearchingforevidenceofreproduction
•WhendoingInventory,mustsearchasmanymicrohabitatsaspossible
•Timing:shouldcoincidewithwhenspeciesaremostlikelyfoundinaquatichabitats(breeding,larvalseasons,etc.)
SweepsamplesSweepsamples- sweepingalargedipnetthroughthewatercolumnorsubmergeddetritustocapturesubmergedindividuals◦ Usuallyamphibianlarvaeandbreedingadults
Total#ofsweepsperareaand#ofindividualscapturedarerecorded
Example- 5dipnetsweepsontheedgeofapondevery15meters
Whatthistellsus◦ Larvalspeciespresentatthattime◦ Lifehistorytraitssuchaswheneggsaredepositedandwhenlarvadevelop◦ Habitatinfo◦ Microhabitatpreferences◦ Density
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KickSampling•Definition:Liftingandremovingallloosecobblefromstreambottomandhandrakingorkickingloosepebblesintoanetorseriesofnets.• CandoAreaorTime-constrained
•Netsused:• D-framenetsmostcommonlyused• Seinenetscanbeusedtocapturemissedindividuals
•Remember:• Alwaysreplaceanylargehabitatitems(≥200mmcobble,woodydebris)• Timing– whenspeciespresent,whenwaterflow/depthissuitable
•Candetermineoccupancyandabundance
EggMassCounts•Searchingapond/wetland/streamforglobularmassesorstringsofeggs
•Usefultohavemorethanoneobservertohelpwithdetection
•KeepinmindthatoneeggmassmaycontaineggsfrommorethanonefemaleANDthatonefemalemaydepositmorethanoneeggmassinabreedingpond
•Someamphibianslayeggsondryground(e.g.,marbledsalamanders,Ambystoma opacum)
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EggMassCounts
Spottedsalamander
Woodfrog
Americantoad
Snorkeling•Usefulinaquaticenvironmentswithclearwaterconditions
• Maybedoneatnightorday(dependingonactivityoftargetspecies)• E.g.,Hellbendersalamanders
•Sampling:• Canhaveapermanentlyestablishedtransectline- formonitoring• Indeepwater,SCUBAmaybeneeded
•Insomecases,substratemaybemoved,butthiscanbedetrimentaltohabitatandshouldbeavoidedforlong-termstudiesorwithaspeciesofconservationconcern.
•Safety:• Canbedangerousifstrongcurrents,verycoldwater,orslipperyrocks• Mustnotbedonealone
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Electro-shocking•Usehighcurrentsofelectricitytotemporarilystunaquaticanimals
•Primarilyusedforfish,butalsoaquaticamphibians,mostlysalamanders
•Current– AC,DCorDCpulsed• UseofDCpulsehaslesslethaleffectonamphibians• DCpulsemosteffectivefordrawinghidinganimalsout
•Mosteffective:• Inwaternotexceeding1mdepth• Usedsuccessfullytosurvey:hellbenders,sirens,mudpuppies
•Utility:• Pros:Canfindhard-to-findspecies,quick,lesshabitatdisturbance• Cons:Physiologicalimpacttoanimals,expensive,potentiallydangerous
•Tips:• Donotuseduringeggdepositionandnesting(Sept-Nov)especiallywhenspeciesofconcernarepresent(hellbenders)
• Goodforinventory.Donotuseformonitoring.
Auditorysurveys•Callsurveys- somespeciesoffrogsareonlyeasilydetectablebyhearingtheircall
•Aretrainingprogramsonline:NAAMP
•Provideinfoon◦ Inventoryofspeciescomposition◦ Breedingtimes◦ Maleabundance◦ Climaticconditionsthatleadtobreeding◦ Locationofbreedingponds
Roadcruising•WithAmphibians,mostusefulinareaswheretheroadbisectsorisperipheraltoabodyofwaterwithspeciesthataremovingbetweenbreedingand/orforaginglocations.
•Timingisimportant– heavyprecipitationandwarmweather
•Arebiasesassociatedwithmethod(e.g.,roadsaffectpopulations,somespecieswillavoidroads)soshouldpairwithothertechniques
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RoadCruisingGetapositiveI.D.
Pickinguproad-killedspecimensScientificuseofotherwisewastedindividual
ConstrainingEffortConstrainingeffortcanhelpmakeactivesamplingmoreuseful◦ Timeconstrained(resultsarereportedas#ofspecies/individualsperpersonperhour)
◦ Areaconstrained- adefinedamountofhabitatisselectedforsampling◦ Randomlyselectedplots◦ Samestrengthsandweaknessesoftimeconstrainedbutyoucanalsogetaverycrudeestimate
ofdensity
◦ Example:Sweepnetsampling(#ofsweepsperpersonperspecies)
EasyPassiveSampling
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EasyPassiveSamplingEasypassivesamplingrequiresnoobservereffortandcausesnoharmtoanimals
Basicallyitisputtingouthabitat-likecontraptionsthatmightattractamphibians,butwon’ttrapthem.◦ Coverboards◦ Leaflitterbags
EasyPassivesurveysincludes:
- Artificialcover
- PVCPipesurveys
- Leaflitterbagsurveys
- Automatedrecordingsystems
ArtificialCover– “coverboards”TargetSpecies
AdvantagesandDisadvantages
UsefulforMonitoring
Tinvs.Wood(plywoodvsparticleboard)PlacementofArrays
Flagging
Numbering
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CoverboardsPROSSuitableforvarietyofspecies
Excellentforsalamandersandsmallaquaticsnakes
Donotrestrictanimalmovements- don’thavetobecheckeddaily
CONSTimetoinstall
Unsightlyappearance?
Catchraterelativelylow
Capturesuccesssubjecttoimmediateweatherconditions
Pickingthearraypatternbestsuitedforyourhabitat
Four-toedsalamanderHemidactyliumscutatum
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COVERBOARDMATERIALS
Considerthepros&cons
PaperbyGrantetal.1992
204ftx4ftplywoodboards@25mintervals=400m
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SamplingArborealSpecies
Theywon’tstayinthebucket!
Barkingtreefrog (Hyla gratiosa)
PVCPipesCancreatePVCpipehabitatfortreefrogs◦ Canbeattachedtotrees,stakes,orstuckdirectlyintheground
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LeafLitterbagsurveys•Plasticnettingwith1.9cmmesh,smallrocksplacedonthenettingandcoveredwithleavesandcabletiesbindittogether– manyvariations
•Canbeusedtosampleforstream-dwellingsalamanders• Especiallyusefulfordetectingpresenceofmorerareandelusivespecies• Larvalsalamanders(bagmustbesubmergedcompletely)
•Bagsplacedinstreamatregularintervals– weighedorstakeddownsocan’tfloataway
•Afteracclimationperiod,eachbagischeckedforsalamanders(detailsinGraeteretal.2013)
AutomatedRecordingSystems:“Frogloggers”
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• Explosive breeders that are missed with other surveys
• Good for remote or inaccessible sites
• Vouchers
• May reveal novel behaviors
Frogloggers -- Pros:
• Somewhat expensive
• Time consuming and tedious to listen to recordings
• May be more involved than necessary for inventory
Frogloggers -- Cons:
IntensivePassiveSampling
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IntensivePassiveSamplingCreatingtrapsthatamphibiansandreptilescannotgetoutofwithoutassistance
Onlyfortheverydedicated◦ Labor,time,andfinanciallyexpensive◦ Trapsmustbecheckedregularlytoavoidharmtotheanimalscaptured◦ Youmustbepreparedtogetthingsoutoftrapsthatyoumightnothaveintendedtocatch
IntensivePassiveincludes:- Aquaticandterrestrialfunneltrapping
- Terrestrialdriftfencesandpitfalltraps
FunnelTrapping•Labor,time,andfinanciallyexpensive
•Trapsmustbecheckeddailytoavoidharmtotheanimalscaptured
•Traptypes:• AquaticFunneltraps:minnowtraps,trashcantraps,hooptraps• Terrestrial:wirehardwareclothcylinderorwoodenboxtraps
•Inventoryvs.Monitoring:• Goodforinventory,butmustusealotoftraps,sampleallhabitattypes,andtrapinmultipleseasons
• Monitoring– muststandardizeschemesocanrepeatitandallowcomparisonofcaptureratesovertime.
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FunnelTraps
DriftFencesEssentiallyawallthattheindividualwalksuptoandthenalong.Thewallleadsthemtooneofavarietyoftraps
DRIFTFENCES
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Possibledriftfence,pitfall&funneltrapconfigurations
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DriftFenceConcernsToomuchrain
Toohot
FireAnts
Personneltocheck- holidays,weekendsRaccoons
Toomanycapturestodealwith!
Monitoringcancost$$
Limitations&Tips
TechniqueshaveLimitations• Eachtechniquehasunderlyingassumptions,biasesandlimitations.
• Unlikelythatonetechniquecanbeusedtosampleanentirecommunity
• Therearehumanbasedconstraints(money,people,time)-- bepractical
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Tips:1. Useseveralmethods
2. Knowthespecies– identification,naturalhistory
3. Considertimingandseasonality
4. Habitatandmicrohabitatiskey5. Consultwithexperts
6. Gethands-ontraining
Resources
PARCProductsAllavailableonAmazon!
TechniquesTable– veryusefulwhendecidingwhichtechniquestouse
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OtherResources:
AcknowledgementsNCWildlifeResourcesCommission
USFWSStateWildlifeGrantprogram
PARCandSEPARC
KurtBuhlmann,SavannahRiverEcologyLab/UniversityofGeorgia
JJApodaca,WarrenWilsonCollege
ManyothersthatcontributedtothePARCInventoryandMonitoringbook
Questions?
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