Idaho point-headed grasshopper survey and inventory : Idaho Falls District Bureau of Land Management : final report

2010·3.2 MB·English

by  Waterbury, Beth

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Final Report
December2010
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ABSTRACT
The Idahopoint-headed grasshopper (Acrolophitus pulchellus)(IPG)is arare Idahoendemic
knowntooccurinxericshrublands of Idaho’s BirchCreek andBigLost Riverdrainages. The
species is knownfrom only17records datingfrom 1883to1993. Surveys conductedin2002-
2003failedtodetect IPGs,leadingtospeculationthat thespecies was extinct. Duetothelackof
essential informationon distributionandstatus, the IPGis designatedas an IdahoSpecies of
Greatest ConservationNeedand aBureauof LandManagement Type2SensitiveSpecies. The
purposeofourproject was tosurveypubliclands withintheknownrangeofthis species to
demonstrate,ifpossible, its extant status, evaluatehabitat compositionandconditionat historical
sites ofcollection,andassess its general conservationstatus.
Wesurveyed7historiccollectionsites and22additional sites from 21Julyto20August 2010.
Wedetected55 IPGs in 11of29surveysites. Werecorded amajorityof detections intheBirch
CreekValleyofClarkCounty(n =41)onpublic lands managedbytheUpperSnake BLM Field
Office andtheDubois RangerDistrict ofCaribou-TargheeNational Forest. Werecorded IPGin
CusterCounty(n=14)intheBigLost Riverdrainageonpubliclands managedbytheChallis
BLM FieldOffice. Wedidnot detect IPGin Lemhi orButtecounties, inthe Little Lost River
Valley,oronpubliclands managedbytheSalmonBLM FieldOffice. Fiveof7historic
collectionsites were foundoccupiedbyIPG. Of 22additional sites surveyed,welocated IPGat
6newlocalities inClark County. Occupiedsites werelocatedonoutwash fans, alluvial fan and
stream terraces, andfoothills at elevationrange1572m to2082m. Soilswere well drained and
gravellytogravelly-loamywithunconsolidatedsurface gravels andcobbles. Sites werebarrento
sparselyvegetatedwithlow-growingxericshrubs,grasses, forbs, vagrant lichens, andmoss/
lichenbiological soil crusts.
Wediscoveredpreviouslyunreported aspects of IPGappearance,lifehistory, andbehaviors. We
documentedsexual dimorphism in IPGsizeandcolorandobserved IPGforagingon stemless
mockgoldenweed (Stenotis acaulis). Reproductivebehaviors were documentedat communal
“lek”sites wherebothsexes exhibitedstridulation(callingsongs produced byrubbingofthe
femuragainst theforewing) andcrepitation(visual/ acoustical communicationinvolvingrapid
flexingorsnappingofthehindwings inflight).
Oursurveyindicatedwidespreadbut lowmagnitudeimpacts tooccupied IPGhabitat from
noxious weeds andinvasiveplants, off-highwayvehicle(OHV)use, conversionofnativehabitat
toagricultural use,andlivestockgrazing. Management actions that: refrainfrom pesticideuse
inareas the IPGis knownorpredictedtooccur; prevent thespreadofnoxious weeds and exotic
invasiveplants; restrict OHVtravel todesignatedroutes; utilizenativespecies for rangeland
restorationprojects; andcloselymonitorlivestock grazingimpacts inknownbreedingsites
shouldbenefit this rare endemicgrasshopper.
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TABLE OFCONTENTS
ABSTRACT....................................................................................................................................ii
INTRODUCTION..........................................................................................................................1
STUDYAREA...............................................................................................................................1
METHODS.....................................................................................................................................2
RESULTS.......................................................................................................................................3
DISCUSSION.................................................................................................................................6
MANAGEMENTRECOMMENDATIONS..................................................................................8
ACKNOWLEDGEMENTS............................................................................................................9
LITERATURECITED.................................................................................................................10
APPENDIXA.PVTs at sites occupiedbyIdahopoint-headed grasshoppers.............................22
APPENDIXB.NWGAP ecological systems at sites occupiedbyIdahopoint-headed
grasshoppers..................................................................................................................................29
APPENDIXC.Descriptions ofsurveysites occupiedbyIdahopoint-headedgrasshoppers......33
APPENDIXD. IdahoSGCNgrasshoppers potentiallyoccurringinthestudyarea....................46
LIST OFTABLES
Table1. Records of Idaho point-headed grasshopper(Acropholitus pulchellus)........................12
Table2. Locations of Idahopoint-headed grasshopper(Acrolophitus puchellus)detections inthe
IdahoFalls BLM District andCaribou-Targhee National Forest,2010. Locations are
Decimal Degrees, WGS 84....................................................................................................13
Table3. PVTat sites occupiedbyIdahopoint-headed grasshopper(Acrolophitus pulchellus),
2010.......................................................................................................................................14
Table4.Summaryofthe environmental features at sites occupiedbyIdaho point-headed
grasshopper (Acrolophitus pulchellus),2010........................................................................15
Table5. Covariates influencingthedetectabilityof Idahopoint-headed grasshoppers
(Acrolophitus pulchellus)duringsurveys, 2010....................................................................16
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LIST OFFIGURES
Figure1. Locationofthe IdahoFalls BLM District studyareaandhistoric collectionsites of
Idahopoint-headed grasshoppers (Acropholitus pulchellus)................................................17
Figure2. MapofstudyareashowingIdahopoint-headed grasshopper (Acropholitus pulchellus)
surveysites andresults..........................................................................................................18
Figure3. An adult female Idahopoint-headed grasshopper(Acrolophitus pulchellus)exhibiting
its distinctivecolorpattern,acutelyslantedheadprofile,anddensepubescence.................19
Figure4. An adult male Idahopoint-headed grasshopper(Acrolophitus pulchellus)showingtan
andrufous coloration.............................................................................................................19
Figure5.Examples ofcrypticanddisruptive colorationofthe Idahopoint-headed grasshopper
(Acrolophitus pulchellus)onstemless mockgoldenweed(Stenotis acaulis)........................20
Figure6. MatingIdaho point-headed grasshopper(Acrolophitus pulchellus)female (below) and
male(above)showingsexual dimorphisminsizeandcoloration.The forb supportingthe
pairis stemless mockgoldenweed (Stenotis acaulis)............................................................20
Figure7. An Idahopoint-headed grasshopper(Acrolophitus pulchellus)feedingonstemless
mockgoldenweed (Stenotis acaulis). Theforbwas past peakfloweringbut retained green
foliagewell intomid-August 2010........................................................................................21
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INTRODUCTION
The Idahopoint-headed grasshopper (Acrolophitus pulchellus)(IPG)is arare Idahoendemic
knowntooccurinxericshrublands of Idaho’s BirchCreek andBigLost Riverdrainages. The
species is designated as an IdahoSpecies ofGreatest ConservationNeed (SGCN)duetolackof
essential informationon distributionandpopulationstatus (IdahoDepartment ofFish andGame
[IDFG] 2005). The IdahoStateOfficeofBureau of LandManagement (BLM)lists the IPGas a
Type2SensitiveSpecies,indicatingthat populations areimperiled rangewide,extinctionrisk is
high,andlikelihoodofbeinglistedundertheEndangeredSpecies Act intheforeseeablefutureis
also high. Priortothis survey,no IPGhadbeenobservedfor17 years, raisingtheprospect that
thespecies was extinct (Baker2003).
Fewerthan20records exist forthe IPG (Table1). Themost recent collections werein1972,
when5specimens werecollectedin3excursions toBirchCreekValley(Scoggan and Bresven
1972),andin1993,when 2specimens werecollectedin7days ofsurveyin theBirchCreek
Valley(Kell et al.1993). During2002-2003,Baker(2003)surveyedhistorical sites ofcollection
andotherpotentiallysuitablesites, but foundno IPG. Hespeculated that extremedrought had
suppressedpopulations,resultinginlowdensityor possiblyextinction.
Consideringthelackofinformationregardingecologyand current status, recommended actions
inthe IdahoComprehensiveWildlifeConservationStrategy(CWCS)call foradditional attempts
tolocatethe IPG(IDFG 2005). Theobjectives of this project wereto:
1. Surveypubliclands withintheknownrangeof IPGtodemonstrate,ifpossible,its extant
status.
2. Evaluatehabitat compositionandconditionat all historical sites ofcollection.
3. Report all IPGoccurrences, includinglocations, habitat compositionandcondition,current
landuses, andpotential threats.
4. Assess theconservationstatus ofthe IPGandmakeanynecessaryrecommendations
regardingconservationmanagement.
STUDYAREA
Thestudyareaencompassedportions oftheChallis, Salmon,andUpperSnakeFieldOffices of
the Idaho Falls District ofBLM; Dubois Ranger District ofCaribou-TargheeNational Forest;
andUpperSnakeandSalmon IDFG administrativeregions. The corestudyarea was locatedin
theBigLost River, Little Lost River,and BirchCreekfault-blockvalleys of east-central Idaho
withintheBeaverheadMountains Ecological Section(Figs.1,2). These3 drainages form part of
theSinks Drainages that originateinthemountains ofsoutheastern Idahoandflowsouthward
wheretheypercolateinto theSnakeRiverPlainaquifer(IDFG2007).
TheBigLost Riveris the largest oftheSinkDrainages, originatinginthePioneer, Boulder, Lost
River,andWhiteKnobmountainranges ofeast-central Idaho. Topographyis variedand
dramatic,withelevations rangingfrom 1460m at theBigLost RiverSinks to3859m at Borah
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Peaksummit. Valleys aredominatedbyhugealluvial fans comprisedof gravellyloam radiating
from thesteep,ruggedmountains. Valleyclimate is seasonallyinfluenced bymoist Pacific
Ocean airmasses anddry,coldcontinental fronts from Canada. Resultingprecipitationis
relativelyuniform throughout the year. Meanannual precipitationat Mackay(periodof record
1954-2005)was 25 cm andtemperatures rangedfrom -36to40°C (IDEQ 2004). Valleyand
foothill landcoveris predominantlyInter-mountainBasins BigSagebrush Steppeand Inter-
mountainBasins MontaneSagebrush Steppe (Appendix B).
The Little Lost Riverdrainageis ahigh elevation valleyrimmedbytheBig Lost RiverRangeto
thewest andthe Lemhi Rangetothe east. Elevations rangefrom 1463m at the Little Lost River
Sinks to3000-3600m peaks intheBigLost River and Lemhi ranges. Mountaintributaries are
short andflowsteeplyfrom theflankingmountains producingaseries ofcoalescingalluvial fans
extendingmorethanhalfwayacross thevalleyin places. Numerous springs contributetovalley
hydrology,makingthis valleymoreresistant todrought thanthe BigLost RiverValleytothe
west (IDEQ2000). Meanannual precipitationwas ≤25cm andtemperatures ranged from -36to
40°C (periodofrecord1954-2005). Inter-mountainBasins BigSagebrush Steppe, Inter-
mountainBasins MontaneSagebrush Steppe, and NorthernRockyMountain LowerMontane,
Foothill andValleyGrasslandaretheprimarylandcovertypes inthevalleyand foothills.
BirchCreekis alargeintermontanevalleybetweenthe Lemhi Rangetothe west,andthe
BeaverheadMountains totheeast. Elevations range from 1458m at the BirchCreekSinks to
3500m at DiamondPeak inthe Lemhi Range. BirchCreekValleyis dominatedbyalluvial fan
systems comprisedofcarbonatebedrocksediments (Moseley1992).Most drainages inthe
borderingmountains havenopermanent streams. Thosethat do,sinkintothealluvium as
groundwater. Mean annual temperatures as measuredat the IdahoNational Laboratory(period
ofrecordfrom 1954-2005)ranged from -44to41°C (Moseley1992). Landcoverin Birch
CreekValleyis representedbyInter-mountain Basins BigSagebrush Steppeand Inter-mountain
Basins MontaneSagebrush Steppe,whichpredominateonthebroad alluvial fans.
METHODS
Wesurveyedall historical collectionsites usingmappedcollectionrecords managedbythe
IdahoNatural HeritageProgram. Eachrecordinthis dataset is characterizedbyhow accurately
thereported collectionsitecouldbemapped. For records withfairtopoor locationaccuracies
(i.e.,mappedlocationexpectedtobewithin1to5 km oftheactual collectionsite),wesearched
a1km2 areacenteredon themappedpoint usingGlobal PositioningSystems (GPS)units to
locateandnavigatethesites. Forthoserecords withgeneral locationaccuracies (vagueor
problematicdata; 9of17 records),wesurveyedthenearest probableorsuitablelocations and
recordedperimetercoordinates withGPS units. Nearest probableorsuitablelocations were
chosenonthebasis ofplant community,elevation,landform,soils, andproximitytohistorically
occupiedhabitat (ScogganandBrusven1972,Kell et al.1993,Baker2003). Arecordwhich
mappedhighinthe Lemhi Range was determined inaccurateandomittedas asurveysite. In
addition,wesurveyed areas ofpotentiallysuitablehabitat unaffiliatedwithhistoricrecords.
Theseareas wereselectedtosamplespatial gaps betweenhistoric collectionsites.
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Weconductedsurveys from 21Julyto20August,expectingthat IPGwouldbeintheadult stage
andpresumablymoredetectable(Kell et al.1993). All sites weresurveyed at least once. We
conductedsecondsurveys at minimum 10-dayintervals at historiccollectionsites where IPG
was not detectedduringthefirst survey. Forall surveysites, ateam of2observers conducted
searches walkinginbelt transects approximately20m apart. Wevisuallyinspectedthe ground
surfaceandvegetation(grasses, forbs, shrubs)whilemakingintermittent sweeps withinsect nets
tocaptureand/orflush grasshoppers. Beatingsheets wereinitiallyused,but abandoneddueto
greatercaptureefficiencywithsweepnets. Wesurveyedat temperatures ≥15˚C,andsurveys
typicallylasted60to90 minutes. Date,time,fieldidentificationnumber, coordinates, and
collectorwererecordedinfieldnotebooks foreachgrasshopper collected. In addition,observers
recordedthesubstrateon whichgrasshoppers werecollected (i.e.,vegetation,ground),surface
soil characteristics, topography, general plant associations, andgrasshopper behaviors and
physical descriptions. Wecollected arepresentativesampleof grasshoppers from eachsurvey
site. At sites occupiedbyIPG,wecollectedupto2individuals persiteandphotographedall
IPGnot collected. All collected grasshoppers wereeuthanizedinkill jars primedwithethyl
acetate99%,thenpinned,labeled,andstoredinSchmidt boxes equippedwithVaportape II™
insecticidal strips todeterdermestidbeetledamage. TheW.F. BarrEntomologyMuseum at the
Universityof Idaho,Moscow,was theprinciplerepositoryforthe grasshoppercollection.
Wemappedall IPGlocations withArcMapVersion9.3overlaidwithdigital landcoverandsoils
layers toexaminehabitat characteristics. Weused 2landcoverlayers consistent withrespective
habitat classificationsystems usedbyBLM and IDFG. Thestandard BLM system is Potential
VegetationType (PVT), modeledfrom Natural ResourceConservationService(NRCS)
ecological sitedescriptions (ESD)(NRCS 2010b). Themodel usedbyIDFGis theNorthwest
GapAnalysis Program (NWGAP)landcoverlayer. NWGAP is basedon ecological systems as
definedbyNatureServe’s “International Ecological Standard: Terrestrial Ecological
Classifications (UnitedStates GeologicSurvey2008,NatureServe2010).” Weused theNRCS
Soil SurveyGeographic(SSURGO)databasefor soils coverage. Soil surveyinformationwas
availablefortheentirestudyarea (Hippleet al.2006,NRCS 2010b).
RESULTS
Surveys
Wesurveyed7historiccollectionsites and22additional sites from 21Julyto20August 2010.
Wedetected55 IPGs in 11of29surveysites (40%)(Table2,Fig.2,Appendix C). Werecorded
amajorityofdetections intheBirchCreekValleyofClarkCounty(n =41) onpubliclands
managedbytheUpperSnakeBLM FieldOffice andDubois RangerDistrict ofCaribou-Targhee
National Forest. Werecorded IPGinCusterCounty(n =14)intheBigLost Riverdrainageon
publiclands managedbytheChallis BLM FieldOffice. Wedidnot detect IPGin Lemhi or
Buttecounties, inthe Little Lost RiverValley,oronpubliclands managedbytheSalmonBLM
FieldOffice. All IPGdetections werelocated withinlatitudinal parallels 43°58’Nto44°16’N,
andlongitudinal meridians 112°32’W and113°44’W,anareaapproximately98km wide(E-
W)and33km long(N-S)(Fig.2).
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Fiveof7(71%)historic collectionsites were foundoccupiedbyIPG. We detected IPGon first
surveys ofthe BlueDome,PeteCreek, andUpper CedarCreeksites, andonsecondsurveys of
theBirchCreek andMyers/Grousesites. The2historicsites where IPGs werenot detectedwere
theHoweandSkull Canyonsites. The Howesite,whichwas basedonan undated IPGrecordof
fairlocationaccuracy, correspondedto aparcel of fallowprivateland. Becausethis portionof
thelower Little Lost RiverValleyhas beenunder cultivationformorethan acentury,we
assumedthis was aninaccuratelocationforthis record. TheSkull Canyon site,where IPG was
collectedin1993,was denselycoveredbyexoticweedyspecies, includingcheatgrass (Bromus
tectorum)andkochia(Kochiascoparia),indicatingpoor ecological condition.
Of22additional sites surveyed,welocated IPG at 6newlocalities inClark County. Non-
detectionof IPGat theother15surveysites mayhavebeenduetovariable detectability,plant
phenology, orotherbioticand/orabioticfactors. Elevationmayhave accountedfornon-
detectionat 8ofthe additional surveysites inupperBirchCreek ValleynearGilmoreSummit
(SalmonFO). Elevations inupperBirchCreek ranged from 2073m to2246m. Soils and
landform features weresimilartoother IPGoccupiedsites, but plant associations andstunted
structureindicatedharsherclimaticconditions. Elevations at positivedetectionsites across the
studyarearanged from 1572m to2082m (x=1859 m,SD=130).
HabitatAssociations
Surveysites occupiedbyIPGsharedseveral coarse-scaleenvironmental features. Surveysites
werelocatedin2of5basins (Birch, BigLost)of theSinks Drainages insoutheast Idaho. Both
basins containhigh elevationvalleys rimmedbymountain“island”land masses. Soil mapunit
characteristics forfoothills andvalleys showaverage annual precipitationintherangeof23to
25cm (NRCS 2010b). Topographyat surveysites includedwindswept,flat togentlyrolling
outwash fans, alluvial fanterraces,stream terraces, fanremnants, andfoothills between 1572m
to2082m. Soil properties weretypicallywell drained,and gravellytogravelly-loamywith
unconsolidatedsurface gravels and cobbles. Surveysites were oftensparselyvegetatedwith
matrices oflow-growingxericshrubs,grasses, forbs, andvagrant lichens, andevidenceofa
moss/lichenbiological soil crust.
PVT Analysis —Detections were associatedwith8ESDs invarious combinations (Table3,
Appendix A). Themost commonESDs at sites occupiedbyIPGwereGravellyLoam 8-12”
ARTRW8/PSSPS andShallowGravellyLoam 8-12”ARAR8/PSSPS-ACHY. Thesedatadid
not statisticallycompare habitat useandavailability,thus, results arepreliminaryandshouldnot
beinterpretedas IPGhabitat preferences
NWGAP Analysis.—NWGAP predictedland covertypes associatedwith IPGdetections (n=
55)comprised5ecological systems (Table4,Appendix B): IntermountainBasins Montane
Sagebrush Steppe(n =26), Intermountain Basins BigSagebrush Steppe (n =16),Northern
RockyMountains Lower Montane,Foothill,and ValleyGrassland(n=7), OpenSpace (n=4),
and Intermountain Basins Curl-leafMountainMahoganyWoodlandandShrubland(n=1).
Mappedecological systems at most occupiedsites correctlyclassifiedvegetationcovertypewith
theexceptionof4locations at theBlueDomesite,whichwereerroneouslydesignatedas Open
Space(Appendix B). Thesesites werewithin30m of IdahoStateHighway28,andspectral
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characteristics ofthesite were evidentlyinfluencedbytheroadsurface. As withPVT,theseare
preliminarylandcoverdataandshouldnot beinterpretedas IPGhabitat preferences.
FloristicAssociations—Sites occupiedbyIPG sharedseveral floristiccharacteristics. Shrub
layers wereopen-canopied(estimated≤5percent cover)withlowstature. Shrubcomposition
was typicallyamix ofWyomingbigsagebrush (Artemisiatridentataspp.wyomingensis),black
sagebrush (A.nova),and/orlowsage(A.arbusculassp.arbuscula),withminorcomponents of
greenrabbitbrush (Chrysothamnes viscidiflorus)and/orshadscalesaltbush (Atriplex
confertifolia). Sites hadasparsetoabundant herbaceous layerof cool-seasonperennial bunch
grasses and forbs (estimated≥10to25percent cover). Important graminoids includedbluebunch
wheatgrass (Pseudoroegneriaspicata),Sandberg’s bluegrass (Poasecunda), Idahofescue
(Festucaidahoensis),and Indian rice grass Achnatherumhymenoides). Commonforbs were
stemless mockgoldenweed(Stenotis acaulis),Hood’s phlox (Phloxhoodii),aster
(Symphyotrichumspp.), pricklypear (Opuntiaspp.),andbuckwheat (Erigoniumspp.). Sites
typicallyhad anextensivelayerofvagrant lichen (Rhizoplacaspp., Xanthoparmeliaspp.)and
evidenceofmoss/lichenbiological soil crusts. Shrubs, forbs, grasses, and vagrant lichens
exhibitedrobust growthandvigor across thestudyareaduetohigherthan averageprecipitation
duringthe2010 water year(NRCS 2010a).
Soil Associations—Sites occupiedbyIPG were associatedwith8SSURGOsoil types (Table
4). Sharedcharacteristics amongsoil types were geologiclandform (e.g., outwash fan,fan
terrace); gravellytogravellyloam surfaceprofiles; loamy-skeletal1 taxonomicclass; and
formationinalluvium orcolluvium derivedfrom limestoneparent material (i.e.,calcareous
properties).
Identification and Behavior
Weidentifiedandaged IPGs inthefieldfrom Scoggan and Brusven’s (1972)technical
descriptions offirst throughfifthinstars andasinglephotographofan adult specimencollected
in1972byBrusven(Baker2003). Distinguishingcharacteristics wereits conspicuous apple-
greenand whitemottledcolorpattern, acutelyslantedface,filiform (thread-like)antennae,and
long,densepubescenceoverits body(Fig.3). Fieldidentificationwas subsequentlyverifiedon
thebasis ofspecimens (Frank Merickel,W.B.BarrMuseum ofEntomology, Universityof
Idaho). Wefound53of 55 IPGs intheadult stagewithfullydevelopedreproductiveorgans and
wings. Among50individuals inwhichsex was determined,44%weremaleand56%female.
Among40individuals inwhichsex andlength(front ofheadtotipofwings)wererecorded, we
observedconsiderablesexual dimorphisminsizeand coloration. Adult males (n=17)measured
20mm to26mm inlength(x=22mm,SD=1.6) andadult females (n=23)measured27 mm to
37mm inlength(x=31.65mm,SD=2.1). Adult femalelengthaveraged 44%greaterthan
malelength. Sexual dimorphism was also expressedinadult coloration. Whereas females were
predominantlygreen withwhitemottling,males exhibitedsometancolorationtingedwithrufous
ontheantennae,distal edgeofthepronotum,femora,andforewings (Fig.4).
1Skeletalsoilsaresoilshavingnoclearlyexpressedsoilmorphologyandconsistingofafreshlyandimperfectly
weatheredmassofrockfragments.
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Ourabilitytodetect and capture IPGs was aidedbyits uniqueresponsetovisual stimuli
comparedtomost other grasshoppers weencountered. Uponour approach, it remained
quiescent,shiftedslightly, ormadea fewshort hops. Individuals were easilycapturedbyhand,
whereas, most other grasshoppers respondedtoourapproachwithrapidjumpingandflight,
requiringouruseofsweepnets. Wefound IPGs onthegroundin89%(n= 49)ofdetections. In
thefewinstances wedetected IPGonvegetation(n=6),individuals were restingor feedingon
stemless mockgoldenweed. Incontrast tomost herbaceous plants at surveysites, stemless mock
goldenweedhadnot yet transitionedtosenescence. Adult IPGwere remarkablycamouflaged
against thegreenanddriedleaves andpeduncles ofstemless mockgoldenweed,exhibitingan
effectivecombinationof disruptivecolorationand crypsis that madevisual detectionespecially
challenging(Fig.5).
Wedocumentedreproductivebehaviors of IPGunreportedintheliterature. At thePass Creek
surveysiteon28July,weencountereda “lek”of several males producingcallingsongs. Songs
consistedofaseries of2 to9brief“chirps”producedbyrubbingofthe femuragainst the
forewing(stridulation), whichwereaudiblefrom 8m. Wefollowedmalecallingsongs tolocate,
photograph,andfilm stridulatingmales and acopulatingpair (Fig.6). We documenteda
stridulatingfemaleat the EightmileCanyonFlats surveysite,establishingthat bothsexes
communicateinthis manner. Notably,wedocumentedcrepitationbehavior(visual/acoustical
communicationinvolvingrapidflexingorsnappingofthe hindwings inflight)by1male and2
females at leksites. This findingis apparentlyuncommonamongotherspecies ofthe
Gomphocerinaesubfamily, of whichonlyafewareknowntocrepitate(Richmondet al.1993).
Wedidnot document eggdepositionbygravidfemales, but suspect egg-layingoccurredat or
nearsites wheremales wereattendingfemales. Thesesites appearedtohaveloamiersoils than
otherdetectionsites, suggestinganimportant soils characteristicforoviposition.
DISCUSSION
Wedemonstratedthat the IPGis anextant species inClarkandCustercounties,occupying5of7
historical sites ofcollectionand6newlydiscoveredsites. Oursurveys contributed55new
occurrencerecords, increasingthenumberofknownrecords by>3-fold. Oursurveywas
conductedafter2 consecutive years of abovenormal precipitationas recommendedbyBaker
(2003). Hesuggestedthat suchconditions wouldallowpotentiallydrought-stressed IPG
populations torecover,therebyincreasingits detectability. Weattributeour success infinding
IPGinpart tofavorableclimaticandrange conditions, but also tosurveytimingwhichcoincided
withgregarious matingbehaviors,which enabled visual andauditorydetectionofthis species.
Thelackof IPGdetections inthe Little Lost drainagemayhavebeen“false absences”(i.e.,it
was present but undetected)possiblyduetosamplingconditions (e.g.,densegrass growth). As
theinterveningdrainage betweenthe BigLost and BirchCreekdrainages, the Little Lost is
situatedas aprobablelinkagezonebetweenextant populations. Environmental features (e.g.,
vegetation,soils, andlandform)wereconsistent withoccupiedsites intheBig Lost andBirch
Creekdrainages. Given bothphysiographic andhabitat suitability,webelieveextant populations
likelyoccupythe Little Lost drainageand recommendthat futuresurveys forthis species be
attempted.
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