lAWHE-dtyMT Abandoned Assessment of Mines Bat Use on for Bureau Land Management of Lands in Southwestern Montana: 1997-1998 Submitted to the Biological Resources Division, Midcontinent Ecological Science Center and Bureau ofLand Management, Dillon Field Office Paul Hendricks David Kampwerth Michelle Brown November, 1999 / MONTANA firf" [yjk Natural Heritage Program SEjp CAV * • S 599.41518 N11AAMBLM 1999 1 _ §XJMT-fc.iJLj MontanaStateLibrary II II I I II II 3 0864 1004 6948 8 oi aanssi © 1999 MontanaNaturalHeritage Program 1515 East SixthAvenue, Helena, MT 59620-1800 Thisdocument shouldbecitedasfollows: Hendricks, P, D. Kampwerth, andM. Brown. 1999. Assessmentofabandoned minesforbat use onBureauofLandManagement landsin southwesternMontana: 1997-1998. MontanaNatural MT HeritageProgram. Helena, 29pp. ABSTRACT Onehundredandseventy-threeabandonedmineworkings(77adits, 96"shafts"andpits) at 88 minesites in southwestern Montana(Beaverhead, Madison,and SilverBowcounties)were investigated forevidenceofuseby batsduring 1997-1998. Ofthemineworkings,40(23.1%) werepartlyorcompletelycollapsed. Evidenceofbatusewascollected from66workingsat49 minesites. Batactivity wasdetectedwithultrasonicbatdetectorsortrappingat61 workingsof 45 mine sites. Batguano(usuallyonlyoneorafewdroppings) waspresentat 5 additional mine workingsat4 mine siteswheretherewasnootherevidenceofbatuse. No maternity siteswere found(although single lactating femaleswerecapturedtwiceatonemine);the majorityofused workingswereprobably nightroosts. Onlyoneworkingwasconfirmedasahibernaculum, but several othersmay besoused. Sixty-fourindividualsrepresentedby WesternSmall-footedMyotis(Myotisciliolabrum). Western Long-eared Myotis(M. evotis). BigBrownBat(EptesicusJuscus),andTownsend's Big-earedBat(Corynorhinustownsendii), werecapturedorobservedat 17, 5,2,and3 mine workings,respectively. Sexratioofcapturedbatswasextremely malebiased. Mostbatdetector results(at47of50workingswithdetections)were identifiedasunknownbatorunknown Myotis, butspecies identificationsweretentativelyassignedtoM. evotisat 10workings,E. fuscusat 12 workings, C. townsendiiat6workings,andLasionycterisnoctivaganslLasiurus cinereusat4 workings. Monitored minesathigherelevationswereused lessoftenthan minesbelow6000'. Unobstructed mine workingswereused moreoftenthanworkingswithpartial obstructions, and adits in bothcategorieswere used moreoften by batsthanwereshafts. Theelevation distributionsofmonitored aditsand shaftsweresimilar, andthereforenotafactorconfounding thegeneral elevation partemofuse. Dominantvegetationatmost(87%)ofthemonitored workings was sagebrush shrubland. and wasalsonotaconfounding factorinthedetected patternsofmineuse. Neitherportal sizenorthenumberofopen portalsataminesite appeared toaffectuseby bats. Proximity to watercouldnotbe accuratelydetermined, butmostworkings were <2 km from known surfacewater, which isprobably withinthenightly foragingrangeof mostbats. Twelvemine workingswere inspected internally forthepresenceofbats. Mineschosen forentrywereselected basedonrelativehazardandpriorevidenceofbatuse. Bats(fourtotal) were found in three mines. Dataloggerswere installed insix mineworkingstorecordover- wintermineairtemperature andrelative humidityevery six hours. Dataloggerresultsarenot included in thisreport, butwill beprovidedasan addendum. Climatedatatakenatthetimeof entry indicate mostsitesprobably aretoocold formaternitycolonies. Itisrecommended thatall open workingsbeconsideredas potential habitat forbatsin thisarea. Noneofthe workingswherebatactivitywasconfirmed shouldbeclosed, although monetary considerationscould limitthe numberofworkingsmodifiedtoprotectbatswhile restrictingaccesstohumans. Instead, otherprotectiveand bat-friendly measuresshould be considered, suchasthe installationofgates. Highestpriority sitesarethoseconfirmed, orwith the potential, to be maternity and/orhibernationroosts. The current method forclosing shafts and other"vertical" workings (ground-level gratingwith 1x3 inchopenings)effectivelyprohibits accessby bats. Replacementoffine-meshed grateswithanalternative, bat-friendly design might allowbatsto useanumberofthese workings. TABLEOFCONTENTS ABSTRACT ACKNOWLEDGEMENTS INTRODUCTION 1 STUDYAREAANDMETHODS 2 RESULTS 4 General SummaryofExternal Surveys 4 Bat SpeciesCapturedorObserved 4 UltrasonicMonitoring 5 PatternsofMineUse 5 Internal Surveys 6 DISCUSSION 7 General 7 Mine Selection 8 MANAGEMENTCONSIDERATIONS 9 LITERATURECITED 12 TABLE 1. Mine Sites Surveyed forPotential/actualUsebyBats 15 TABLE 2. BatsCapturedorObserved in 1997-1998 20 TABLE 3. BatsDetectedwithANABATUltrasoundMonitors 21 TABLE4. Minessurveyed internally in 1998 23 FIGURE 1. Elevational DistributionofMonitoredMinesWorkings 25 FIGURE 2. RelationshipBetweenElevationandUsedMine Sites 27 FIGURE 3 RelationshipBetween TypeofMineWorkingand Bat 29 ACKNOWLEDGMENTS Thisprojecthad itsoriginsinthefertile mindsofDaveGenter(MTNHP)and Tom O'Shea(BRD/USGS). Withouttheirinitial planningand designeffortsincoordinationwithDK theprojectwouldn't haveseenthelight ofday. Intheearly stages(1997)PeteFeigley MB supervisedand fine-tunedtheproject, both intheofficeandthe field, withthehelpof and SamMartinez. External field surveyswereconductedin 1998 byPH, TomO'Shea, MB, and JanelleCorn;thebulkoftheworkwascarriedoutbythelattertwoindividuals. Internal surveys wereconductedbyPH, DK(whoalso organizedthesafetyprotocols fortheproject), Sam Martinez, MB, andTomO'Shea RobinMcCulloch(MontanaBureauofMinesandGeology) providedanMSHAtrainingsessionforthoseofus scheduledtogounderground. JohnHinshaw (MTNHP)correctedtheGPS datawebroughttohim, Kate Schletz(MTNHP)interpretedbat callsrecordedoncassettetapesat surveyed mines. TomO'Sheaprovidednumeroussuggestions onanearlierdraftofthisreportthat significantly improved itscontent. Theprojectwas funded throughCooperative AgreementNo. 1434-CR-97-AG-00008 betweentheUSGS-Biological ResourcesDivision, MidcontinentEcological ScienceCenterandtheMontanaNaturalHeritage Program, undertheUSGS Species-At-Riskprogram. INTRODUCTION Several speciesofNorth American cave-dwellingbatshave been adversely affected in recent decadesby avarietyofhuman-induced environmental changesto caves, includingcave closures, impoundments, and vandalism orotherdirect human disturbances (see Humphrey 1978, Turtle 1979, LaVal and LaVal 1980, Sheffield et al. 1992 ) These, and landscapechanges suchasdeforestation (including loss oflargetreeswith basal hollows) and agricultural development, have forced many bat speciesto abandontraditional sites in searchofnewroosts and hibernacula. Asaresult ofthesewide-spread disturbances, somecave-dwelling species in theeasternand Midwestern United Stateshavebeen listed asthreatened orendangered underthe U.S. Endangered Species Act Abandoned minesofferavarietyofsubterranean microclimates similartothosein natural caves(Turtleand Stevenson 1978, Turtleand Taylor 1994) and can provide suitablehabitat forroostingand hibernatingbats. Abandoned mines now serveas principleroostsand hibernacula formany cave-dwelling species(Turtleand Taylor 1994), and areimportantforpopulationsoccupying marginal habitats(Gateset al. 1984) in areaswhere there arecontinuedthreatsto primary natural roosts. It iswidelyacknowledgedthat natural cave environmentsarethe most stable and desirable long-term habitatsforbats, but abandoned mines may providea suitablealternative. Mine reclamation(includingclosuretorestrict humanaccess) isofinteresttowildlife managersbecausereclamationactivitiescan havesignificant negative impactson bat populations (see Sheffield et al 1992, Richteretal. 1993). Therefore, it is importantthat closure isdone in such awayasto minimizedisturbanceto bats inthe minesaffected. Because the majorityofbat species in Montanause cavesand mines, it isespecially importanttodeterminethe extent and magnitudeofmineuse by bats inthe state, and identify situationswhereaccessby humansto abandoned minescan be restricted while maintaining mineattractivenesstobats Increased concernoverbat populationsnationally, coupled with increased emphasison theclosureofabandoned mineson public lands, hasprompted Bureau ofLand Management (BLM) biologists in Montanatoassessabandoned minesforbat activity priorto mineclosure (e.g., Hendricks 1997) Anumberofabandoned minesonBLM land in southwestern Montana are scheduled forclosureinthe near future. Someofthese mines may provide habitat critical for hibernation, reproduction, and warm-season roostingby bats, includingTownsend'sBig-eared Bat (Corynorhmustownsendu), adesignated Special Status speciesby the BLM in Montana, identified asa high priority species in 1998 bytheWestern Bat Working Group, and designated asa speciesofconcern(formerC-2 candidate forlisting)by the US Fish and Wildlife Service Primary objectivesofthe 1997-1998 abandoned mine inventoryon BLM lands in southwestern Montanawere to I) identify specific mineworkings used by bats, 2)gather external mine attribute datathat might aid in identifyingthe suitability ofunsurveyed workings and predicting broader patternsofmineuse, 3) gatherinternal mineattribute datathat will providebaselineenvironmental information on abandoned minesused by bats, with the expectation thatthesedata will beuseful in identifying suitable mine workings, even in the absence ofbats, and 4) captureand identify bat speciesusingabandoned mines in the project area STUDYAREAAND METHODS ThestudyareaisintheBeaverhead SectionecologicalunitoftheU.S. Forest Service NorthernRegion(Nesseretal. 1997). Thissectionhasacoldcontinentalclimatecharacterized byawarm, drysummerandacold, drywinter; meanannual precipitationrangesfrom9-20 inches(23-51 cm), withabout 10%fallingassnow. Largegravel filledvalleys, surroundedby steepfaultblockmountainsofavarietyofbedrocktypes, dominatethetopography. Valley elevationrangesfrom4700-7600feet, potential naturalvegetation islargely sagebrush-steppe. Themajorityofminessurveyedwereinthis SouthwestMontanaIntermontaneBasinsand Valleys subsection. Listsand locationofminesitesandworkingstobevisitedwereobtained fromtheDillon andHeadwatersResourceAreas-BLM(=DillonandButteField Offices, respectively), from databasesdeveloped bytheMontanaBureauofMinesandGeology, anddirectlyfrom topographicmaps. AreasoffocustendedtobeatandnearminesontheBLM lists, and particularly in miningdistricts(Ermont, Rochester, TidalWave) scheduled firstformine reclamationactivities. Themajorityofmineworkingssurveyedwerelocated in southwestern Montana, inBeaverheadandMadisoncounties, withahandful ofsitesinextreme southern SilverBowCounty. Preciselocationof52 siteswasrecordedonadifferentially-correctableTrimble GeoexplorerIIGPSunit, but some siteswereneverrecordedand somefileswere inadvertently lost. ThustherecordofGPS locations inTable 1 isincompletebecauseofmissingdata, andthe productionofmapsfromtheavailabledataseemed pointless. Nevertheless, all minessurveyed wererecordedtoquarter-quartersectionprecision(seeTable 1), andphotographs, wheretaken, werefiled forfuturereferencewithoriginal fielddatasheetsattheMontanaNaturalHeritage ProgramHelenaoffice. Mineworkingsrepresent acontinuumoftypes, but wereclassified intothreebasic categories: adits(horizontal slenderworkings), shafts(vertical slenderworkings), andpits (vertical broadworkings). Someworkingsfell somewherebetweenaditsand shafts, and are moreaccuratelytermed "inclines"; inclinesusuallyappearontopographicmaps(ifportrayedat all) asshafts. Mostoften, inclinedworkingswereangled> 30°, and containedremainsof laddersinthemainpassageto aid movement. Inthisreportinclinedworkings steepenoughfor ladderstobehelpfularecategorizedas shaftsandthoseoflesseranglearetermedadits, for reasonsofsimplicityand lack ofclearcriteriafordemarcationbetweenadits, inclines, and shafts. Foreach minesitevisited, thepresenceorabsenceofopenportalswasthefirstvariable noted. Ifamineworking had not collapsed, thenthedimensionsofeachopeningweremeasured orestimated, anyobstructions(grating, cablenetting, fallentimbersorrock, etc.) noted, and if accessibletheentrancewasinspected forbatspoor(primarilydroppings). Temperatureof outwardairflow, ifpresent, wasalso measured. Dominantcover-typeofthe surroundinghabitat at mineswasclassified followingastandardized schemeusedby MontanaPartners-In-Flightfor point-countmonitoringofbirds(HuttoandYoung 1999). Asmall subset ofmineworkingswasexamined internally forbatsandtoinstall electronicdataloggers(HOBO; Onset ComputerCorporation, Bourne, MA) Dataloggerswere settorecord mineairtemperatureandrelativehumidityevery6 h, putinthe selectedminesin September 1998, and left insituduringwinter 1998-1999. Theundergroundclimatedata capturedbythedataloggersarenot availableforthisreport. Undergroundworkingswere crudely mapped as farastheywereexamined, and carefully inspected forbatsand bat guano in sections deemed safeto explore. Twelveworkingswerethusexamined (Table 1), and data loggerswere left in six ofthese Bat detectors(ANABAT II, Titley Electronics, Ballina, Australia), mist nets, and/orharp trapsweredeployed at workingswhere spoorwaspresent orthemineworkingotherwise appeared potentially suitable forbats Detectorunits(consistingofan ultrasound detector, timer/tape-driver, and avoice-activated cassettetaperecorder)were set beforedusk facing portalsoraimed across shafts, and left in placeovernight. Recorded callswereanalyzed on an IBM compatiblePC usingANABAT II zero-crossingsanalysis interface module(ZCAIM) and software. Assignment ofvocalizationstoaparticularspeciesofbat wasachieved by matching time-frequency structureoffield recordingswithareference set ofcallsobtained from captured individualsand published descriptionsofvocalizations(e.g., Fentonet aJ. 1983, O'Farrell 1997) However, bat speciescan show significant variation in call structure(Berts 1998, Barclay 1999), and wedid not activelytrack and record flyingbats(O'Farrell et al. 1999)tomaximizequality and quantityofdiagnostic sequences Furthermore, units recordedbatsexitingroostsorflying nearpotential roosts Roost-exit callsand calls inhigh cluttertendtobe fragmentary, lacking diagnostic featuresnecessary forspecies identification (O'Farrell 1999). Therefore, all species- level identificationsbased on recordedvocalizations, where made inthis study, areconsidered tentative. Myotisdesignations(asagroup)wereassignedto recordingswith vocalizationsofshort duration(< 3 msec)with arelatiMvely linear, perpendicularcall pattern. In somecases,Myotis call sequenceswere assigned to evotisifsweep pattern ranged from a maximum 90 kHzto a minimum 35-40 kHz, otherwiseall wereclassifiedMyotisspecies Calls witha bilinear(extreme curvilinear) pattern weretentativelyassignedtoanon-Myotisspeciesorclassified asunknown bat. Passeswith call fragmentswerealsodesignated unknown bat ifno associated calls allowed finerresolution Most bilinearcall sequenceswereassigned toEptesicusfuscusifacontinuous frequencytail ranged from 33-28 kHz Thiscould result in confusion withLasionyctens noctivagans(Berts 1998), which hasa similarcall structure, but most ofourrecordingswere made atthe mouthsofmineswherethe latterspecies isunlikelytooccur. Numberof "passes" (defined hereasadistinct vocalization with at least a 1 secgap between priorand followingvocalizations) wasrecorded asa measure ofrelativeactivity at each site. Atfive siteswith bat activity, equipment malfunctioned prematurely Therefore, relative activity aspresented here isuseful primarily asan index with variable degreesoferror Batswerecaptured using 50-deniermist netsofvarious lengths(most often6 and 9 meter) and set in avarietyofarraysacross portals, dependingon site morphology Netstypically wereoperated forat least threehours(usuallv until midnightor01 00 MDT) Less frequently a harp trap was set inthe portal ofan adit and left overnight Captured batswereidentified with aid ofkeys in vanZyll deJong(1985)orNagorsen and Brigham (1993) Individualswere sexed, aged, measured (forearm, weight), reproductive status noted, then released. Where dataare analyzed statistically, standard proceduresand testswerefollowed as described by Sokal and Rohlf(1981) G-testswereused toexaminethe null hypothesis ofequal proportions in frequency distributions, the null hypothesisofequal means in normally-distributed data setswasexamined usingt-tests No particularprobability level wasassumed as representing statistical significance, otherthan to considera/-"-value of 05 orlesstofall within thatnebulouscategory. Sometestswererunusing STATISTIXversion2.0(Analytical Software; Tallahassee, Florida). RESULTS GeneralSummaryofExternalSurveys External inspectionsof173 workingsat 88 abandoned minesitesweredocumented in 1997-1998 duringthissurvey(Table 1). Oftheseworkings, 77wereadits, 90were"shafts" (see Methods), and6werepits. Ninety-twoworkingsweremonitoredforbatactivityatleastone night: 78withbat detectorsand 39(14exclusively)withmist netsand/oraharptrap. Some workingsweremonitoredmorethanonceusingmorethanonemethod(Table 1). Elevationof mineworkingsranged from4970'to 8700'. Monitoredadits(46)and shafts/pits(46)were distributedsimilarlybyelevation(Fig. 1;G= 1.780, df=2,P>0.4). Dominantvegetation (covertype)wasrecordedat 87(94.6%)ofthemonitoredmineworkings, ofwhich 76(87.4%) were in sagebrushsteppe. Remainingcovertypesat mineworkingsincludedgrassland (1), Douglas-fir(5), mixedconifer(1), spruce/fir(3), andwhitebark/limberpine(1). Evidenceofbatusewasgatheredat66workingsof49 minesites, ranginginelevation from4970'to 7640', whileelevationrangeofunused mineworkingswas 5150'to 8700'. Of these, in-hand identificationofbatswas madeat20workingsof16mine sites(Table2). Bat activitywasrecordedbybat detectorsat 50workingsof40 mine sites(Table3); ofthese, 41 workingsat 30 minesiteswereat locationswherebatswerenotvisuallyidentified. Batuse basedonlyonthepresenceofguano (usuallyonlyoneorafewpellets)wasrecordedat 5 workingsof4 mine sites. Bat activitywasrecordedat48(63.2%)oftheworkingsinsagebrush habitat, 4(80%) in Douglas-firhabitat, each singleworking inthegrassland, mixed conifer, and whitebark/limberpine habitats, and noneoftheworkingsin spruce/firhabitat. BatSpeciesCapturedorObserved During 1997-1998, 64batsrepresentingfourspecieswerecapturedorobservedat 20 differentworkingsof16 mine sites(Table2). Sixindividualsoftwospecies may havebeen sampledtwice<twoweeksapart attheunnamedadit T4SR8WS18SENW, asthesexesand numbersofeach species ineach samplewereidentical. However, forearm measurementsand scarsdid notclosely match, sohereI assumethat 12 differentindividualswerecaptured. The Western Small-footedMyotis(Myotisciliolabrum)represented 78.1%ofthetotal(n=44m, 5 f, 1 ?), WesternLong-earedMyotis(M evotis) 14.1%(n= 7m, 2 f), Townsend'sBig-earedBat (Corynorhinustownsendii)4.7%(n=2 m, 1 ?), andBigBrownBat(Eptesicusfuscus) 3.1%(n= 1 m, 1 ?). These specieswerecapturedorobservedat 17, 5, 3, and2 workings, respectively. Maximum numberofcapturesduringnightswhenbatswerecaptured (n= 17)was9bats,the meanwas3.12±2.29/night. Successful trappingoccurredbetween 11 Juneand21 August. Sexratioofthe61 batsassignedto sexwasextremely male-biased (7.71 males forevery f«emale). SexratioforthetwoMyotisspeciescombinedwas 7.29 males:1 female(G= 37.683,«P 0.001). SexratioofeachspecieswasM ciliolabrum= 8.8 males:1 female(G= 17.817,P 0.001), andM evotis=3.5 males:1 female. M Evidenceofreproductiveactivitywas scant. Alactatingfemale evotiswasMcaptured on6 August 1998attheunnamedadit T4SR8WS18SENW, asecMond lactatingfemale evotis wascapturedon 17 August 1998 atthesameadit. Threefemale ciliolabrumwithevident teats(non-nursing)werecapturedon 11 June 1998 attheunnamedadit T3SR7WS8SESE. Three