~4716 FederalRegister / Vol. 56, No. 239 / Thursday.December12, 1991 / Rules and Regulations

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

5OCFR Part 17RIN 1018-AB56Endangered and Threatened Wildlifeand Plants; Point Arena MountainBeaver (Aplodontia rufa nigra)Determined To Be EndangeredAGENCY: Fish andWildlife Service.Interior.ACTION: Final rule.

SUMMARY: The U.S. FishandWildlifeService(Service)determinesendangeredstatusfor thePointArenamountainbeaver(Aplodontiarufa m~grn)undertheauthorityof theEndangeredSpeciesAct of1973. asamended(Act)Limited in distribution to cool, moistareasalongthePacificcoast.MendocinoCounty,California,the PointArenamountainbeavernow occursinonly 10 knownsites,comprisingatotalof about100 individuals.Within itslocalizedhabitat,threatsto thePointArenamountainbeaverincludelivestockgrazing,highwayconstructionandmaintenance,public accessandrecreationaluse,rodentcontrol, exoticplant expansion,housingdevelopments.streamimpoundmentsandirrigations,predationby feral andpetcatsanddogs,andagriculturaluse.A proposaltoerectamicrowavetowerwithin habitatoccupiedby thelargestknownpopulationis the mostsignificant threatat this time. Theexcavationfor thetower,asoriginally planned,willdestroyhabitatusedby one-halfof theestimated20 Point Arenamountainbeaversat thatsite.Due to the threatposedby this proposal,this listing iseffectiveimmediately.

EFFECTIVE DATE: December12, 1991.

ADDRESSES: Thecompletefile for thisrule is availablefor inspectionbyappointmentduring normalbusinesshoursat U.S. FishandWildlife Service,2800CottageWay, roomE—1803.Sacramento,California95825—1846.FOR FURTHER INFORMATION CONTACT:Mr. MichaelHorton,Wildlife Biologist.at the aboveaddress(phone916/978—4860orFl’S 460—4866).SUPPLEMENTARY INFORMATION:

Background

The PointArenamountainbeaver(Ap/odontiarufa nigra) is amemberofthe family Aplodontidae,whichisrepresentedby amonotypicgenusandspecies.This family is in theorderRodentia,suborderSciuriomorphaandapparentlyrepresentstheoldestknowngroupof living rodents,the Aplodontids,which arethoughtto beancestraltosciuridrodents(Steele1986).

Taylor(1914)describedthe PointArenamountainbeaverasafull species(Aplodontianigra), but laterTaylor(1918)revisedhis treatment,reducingthe taxonto subspecificstatusasAplodontiarufa nigra. Although thetaxonis geographicallyisolated,Taylor(1918)felt the revisionwasjustified.Thepaucityof specimensandtheextensiveoverlapin certaincranialandexternalcharacteristicsledhim to concludethatfull speciesstatuscouldnot be

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supportedin relation to otherCaliforniacoastalmountainbeavers.Severalrevisionsto thespecies(Apiodontiarufa) havebeenmade(DaiquestandScheffer1945, Hall andKelson1959,Hill 1981),with thePoint Arenamountainbeaverbeingmaintainedas asubspecies.

Certaincranial andexternalcharacteristicsseparatethePoint Arenamountainbeaverfrom othersubspeciesof mountainbeavers(Taylor 1918).Forexample,only Ap/odontiarufa nigra hasblack andgray fur on thedorsalsurface.The blackpelagecharacteristicof themaleandfemaleadult Point Arenamountainbeaveris seenasearlyasJulyin youngof theyear.In theothersubspecies,coastalindividuals tendtobe darkerthaninland animals,thoughnoneareasdarkas thePoint Arenamountainbeaver.Osteologically,theoutline andbreadthof thePointArenamountainbeaver’snasalbonesrepresentauniquecranialcharacteristic.ThePoint Arenaform isstockyandcylindrical in body shapewith abroad,massive,laterallycompressedskull. The skull’s flat uppersurfaceandlackof postorbitalprocessesarenoteworthy(Hall 1981).Mountainbeaverspossesssmall eyes,roundedears,andadistinctivecylindrical stumpof a tail. Eachforepawhasanopposablethumbandall digitshavelong, curvedclaws.

Threewell-differentiatedsubspeciesof mountainbeavers,theHumboldtmountainbeaver(Apiodontiarufahumboidtiana),Point Arenamountainbeaver(A. r. nigra), andPoint Reyesmountainbeaver(A.r. phaea)aredistributedalongthenorth coastofCalifornia.Eachof theseisgeographicallyseparatedbyconsiderabledistances(Steele1986).Approximately80 miles separatethePoint Arenamountainbeaverfrom therangeof its northernconspecific.theHumboldt mountainbeaver.To thesouth,the rangeof thePoint Reyesmountainbeaverbeginsabout60 milesfrom thesouthernlimit of thedistributionof the Point Arenataxon.

Of thesevensubspeciesof mountainbeaveroccurringon thecoastor inland,thePoint Arenaform hasthemostlimited distribution andis foundonly incoastalMendocinoCounty.California.Historicalcollectionrecordsnotedpopulationsbetweenthe town ofPointArenaandAlder Creek,adistanceofabout6.8 miles(Camp1918).DatafromtheChristiansenRanchareaincreasedtheknown rangeabout5 milesfurthernorth (Pfeiffer1954). In 1981 Steeleattemptedto relocatethe fourhistoricallyknown populations,but

foundthat only the populationct AlderCreekremained.He did, however,discoverthreepreviouslyunrecordedpopulations(Steele1982). Theseareaswere resurveyedby Steelein 1986,resultingin atotal of eight knownpopulations,four of whichwereobservedduring the1981 field survey(Steele1982.1986). In 1989 and1991, twoadditionalpopulationswerediscoveredatManchesterStateBeach(Dale Steele,ecologist,CaliforniaDepartmentofTransportation,pers.comm.1989;Steele,pers.comm.1991). All 10populationsarelocatedwithin thepreviouslydescribedgeographicalrangeof about12 miles alongthecoastline.Populationsarefoundat Mallo PassCreek,Irish Creek,Alder Creek,ManchesterStateBeach(four sitesincluding the AmericanTelephoneandTelegraphcommunicationfacility),LagoonLake, Minor Hole Road,andPoint Arena,MendocinoCounty.California(Steele1982, 1986;Steele.pers.comm.1989and1991).

Mountain beaversarerestrictedingeographicdistributionto cool,moistareasreceivingheavyrainfall (25—60inchesper year)alongthe PacificCoastandSierraNevada,extendingfromsouthernBritish Columbia to centralCalifornia(Steele1986).ThePoint Arenasubspeciesoccursonly in MendocinoCounty,California,within thecoastal,narrow,andirregularlyshapedvalleys.Thesevalleyshaverelativelywarmtemperaturesbecausetheridgesblockthecool,moist onshoreoceanbreezes.therebylimiting thepotentialmoisthabitatrequiredby thePoint Arenamountainbeaver.

Point Arenamountainbeaverpopulationshavebeenlocatedon steep.northfacingslopesor in protectedgulches.Burrowing activitiesusuallyareconductedunderdensevegetation,wheremoistureconditionsmakethe soilrelatively easyto excavate.Micro-habitatconditionsincludeanabundantsupplyof food plantsandmoderatelydeepandfirm soil with gooddrainage(Steele1986). Thosepopulationsoncoastalstrand/coastalscrubhabitatarelesssheltered;however,strongwindsandapersistentmarineinfluencepreventextremefluctuationsintemperature(Steele1986).

Point Arenamountainbeaversarefoundin habitatswith four basictypesof vegetation:Coastalscrub,coniferousforest, riparian, andstabilizeddunes(coastalstrand).Habitat typesfor the10populationsareasfollows: PointArena—coastalscrub.Minor HoleRoad—coastalscrub/riparian.LagoonLake—coastalscrub,Alder Creek—coastalscrub/riparian,Mallo Pass

Road—coastalscrub/riparian.ManchesterStateBeach(threepopulations)—coastalscrub/coastulstrand,AmericanTelephoneandTelegraphcommunicationfacility atManchesterStateBeach—coastalscrulj/coastalstrand,andIrish Gulch—coastalscrub/riparian/coniferousforest.

Coastalscrubspeciesinclude cow-parsnip(Herocieumlanatum),coyotebrush(Baccharispilularis), wax-myrtle(Myrica ca/il urnica), Californiablackberry(Rubusvitifolius), salal(Gaultheriashe/ion),andpoison-oak(Rhusdivei’siioba). Coastalstrandhabitatconsistsof lupine (Lupinusarborevs), coyotebrush,coastgoldenrod(So/idagaspathu/ate), dunegrasses.andice plant (Mesembryanthemumspp.).Atthe Irish Creekpopulationsite, theconiferousoverstoryis composedprimarily of Douglas-fir(Pseudotsugamenziesii],grandfir (Abiesgrandis).andbishop pine (Pinusinuricata).Riparianandcoastalscrubspeciesareprevalentin theunderstoryof the IrishCreeksiteandincludespeciessuchasthimbleberry(Rubusparvifiorus), nettle(Urtica spp.).swordfern (Polystichummunitum),salmonberi’y(Rubusspectabilis),andelderberry(Sambucusspp.).Riparianvegetationis foundinconjunctionwith otherhabitat typesatMinor Hole Road,AlderCreek,IrishGulch, andMallo PassRoadandincludesskunk-cabbage(Lysichitonamericanum),giant horsetail(Equisetumtelmatela),willows (Salix spp.).redalder(Ainusoregona),woodrose(Rosagymnocarpa),andCaliforniablackberry(HardhamandTrue1972).

At the four siteson ManchesterStateBeach(oneof whichis referredto as theAmericanTelephoneandTelegraphcommunicationfacility), the Point Arenamountainbeaveroccupiesstabilizedsandduneswith coastalscrubcomponents.TheManchesterStateBeachsites, locatedabout0.25milesapart,aresignificantly differentthan theotherknown PointArenamountainbeaverlocationsbecausetheyprovidelesscover, fewerfood plants,andpoorerburrowing substrate.Although mountainbeaversusuallyconstructundergroundburrows,thoseinhabiting thecoastalstrandburrowundershrubbyvegetation.Becausetemperaturesarestill relativelymild with minimumfluctuationsowing to themarineinfluence, thePoint Arenamountainbeaveris ableto toleratethesesurfaceambienttemperaturesin thecoastalstrandenvironment.

No dataareavailableon historicalpopulationdensitiesfor thePoint Arenamountainbeaver.However,estimatesfor othermountainbeaversubspecies

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.rangefrom 1.4 to 2.2 individualsperacre(Neal andBorrecco1981, Lovejoy andBlack1979)up to 9 (or 16 temporarily)animalsper acre(Voth 1968).

Duringa1985—1986statussurvey,Steele(1986)foundatotal of 41 activeburrowsystemsin 8 populations(range2—9 animals/system).He estimatedthatthenumberof individualsper siterangedfrom 3 to 10 or more,for anoverallsubspeciespopulationestimateof approximately41—55 individuals.ThePoint Arenamountainbeaversoccupiedroughly 24 acresof a total ofapproximately83 acresof availablehabitat(Steele1986).Sitesvaryin sizefrom 3.7 to 19.8acresof whichabout1.5to B acreswereoccupiedby themountainbeavers(Steele1986).Byincorporatingdatafrom the 1988and1991 surveys(Steele.pers.comm.),thenumberof siteswasincreasedto 10, thetotal populationestimateto 100, andthetotal availablehabitat to about100acres.

Mountainbeaverslive within anextensivesystemof tunnelsusuallyconstructedaboutafoot from thesurface(Steele1986).Runwaysareenlargedto accommodatenestsandforfood storagefacilities(Steele1986).Theseburrowsarefoundonly inportionsof thehomerange(Martin1971).Limited dataon thePoint Arenamountainbeaverindicatethatanaverageof oneortwo animalsis foundwithin individual burrowsystems(Steele1986).

Radio-telemetrystudiesindicatethatadult mountainbeavershadhomerangesvaryingfrom0.01 to 0.08 acressize(mean0.04 acres),with nosignificantdifferencesbetweenmalesandfemales(Martin1971).Adults do notseemto rangefar fromtheburrowentrancesasevidencedby amaximumrecorded distanceof about 140 feet(Martin1971).During thebreedingseasonindividualsmaytravel outsidethecalculatedhomerange.In thesummermonths,youngmountainbeaversusetheburrowsystemsaswellasgroundsurfaceto dispersefrom thenest(Steele1986).

Mountainbeaversappearto besolitary in their socialstructure,exceptduring thebreedingseason,andintraspecificallydefinedtheir nestsandburrows(Martin1971).Eventhoughhomerangesmay overlap,eachmountainbeaveris solitary whenfeeding(Steele1986).

Aplodontiarufa nigra preferstoforageon succulentherbaceousplantmaterialandthedeciduoustreebarkandleavesforming theunderstory(Steele1982, 1988).Speciesfrequentlyconsumedby the mountainbeaverincludesword fern, cowparsnip, salal,

nettle,salmonberry,andlupine.Itappearsthat thePoint Arenamountainbeaveris primarily a nocturnalforager(Steele1986).

In comparisonto theabilitiesof manyotherrodents,themountainbeaverisphysiologicallysomewhatlimited inmaintainingits waterbalanceandinthermoregulating(Dolphet ci. 1962;GreenbaumandDicker1963; HouseetaL 1963; Druzinsky1983. 1984;Johnson1971;Kinney 1971; andothers).Anatomicalandphysiologicaldataindicatethatmountainbeaversareincapableof producingaconcentratedurineand, therefore,requiresubstantialdaily amountsof water.It is thoughtthatthelimited osmoregulatoryabilitiesofthemountainbeaverareresponsibleforits localizeddistribution,confiningit tocool, moist areas(NungesserandPfeiffer 1965).Work with Apiodontiarufa pacifica in Oregonfoundthat thenestandburrowsystemeffectivelymediatewarmsurfacetemperaturesandseasonalchangesin humidity(Johnson1971, Kinney 1971).Furtherevidencestemsfrom work ondehydrationstudiesof mountainbeaverssuchasthe findingthatA. rufa hasalimited ability toincreasereabsorptionof sodiumin thekidneywhendehydrated(Schmidt-NielsonandPfeiffer1970).To excretethis excesssodiumrequiresthelossofwatervia theurine.Further,therearenoindicationsthatmountainbeaverscanenhanceevaporativewaterlosswhenheat-stressed,amethodusedby somemammalsto maintainhomeothermy(Goslow1964, Johnson1971,Kinney1971).

In mountainbeavers,it appearsthattherelativelyprimitive thermoregulatoryability limits theanimal’ssurfaceactivity to moderatetemperaturedays.Mountain beaverscanthermoregulateadequatelyonly overarelativelynarrowbandof ambienttemperatures(6to 16 degreesC) whichcorrespondstothenormal temperaturerangewithin theburrows(Kinney1971). Animalsexposedto environmentaltemperaturesof around30 degreesC mayexperiencetheupperthermaltolerancelimit(Kinney 1971).When surfacetemperaturesaretoowarm, themountainbeaverwill eitherseekrefugein its burrowor orientits body tomaximizeits ability to losebodyheatpassively.In laboratoryexperiments,mountainbeaversundergoingheatstressrespondedby decreasingmetabolicandrespiratoryratesandbychangingpostureto maintainarelativelyconstantbody temperature(Steele1986).

Mountainbeaversusuallyreachsexualmaturityduringthesecondyear.Becauseit is monestrousandall females

in agivenpopulationovulateat aboutthesametime (duringaperiodof 5—7weeksin mid or latewinter), Thebreedingseasonis quite limited (Pfeiffer1958). It appearsthat thegestationperiodis 28 to 30 days(Pfeiffer 1958).InlateFebruaryandMarch,the litter isborn,containingusually two to three,infrequentlyfour, individuals(Steele1986).Only onelitter perfemaleisproducedper year (Steele1986).

Demographicinformation suchasageclassstrcutureand distribution on thePoint Arenamountainbeaveris sparse.Data from Apiodontiarufa pacificaindicatean adult sexratio of 1.2 to 1.0(maleto female)(Lovejoy andBlack1979).OtherApiodontiasubspeciesareknown to have survived for 6 or moreyears(LovejoyandBlack1979).

Becauseof their burrowinghabitsandforaging in gardens,croplands,andforests,mountain beaverscan causeextensivedamageand areconsideredanuisancein someareas(Steele1986).For example,in certainareasof coastalOregonand Washington, themountainbeaveris numerousand regardedas apest(Scheffer1929,Phillips 1982).Mountain beaverscan be particularlydestructive In Douglas-fir forests byclippingconiferseedlings,basalgirdlingsaplings,andunderminingrootsbyburrowing(Neal and Borrecco1981).However,noneof the subspeciesendemicto California are known tocausesubstantial damageto crops, norare they generally found in intensivelymanagedforesttracts.

Of the10 knownpopulationsof PointArena mountainbeaver, 3occur totallyonprivate land (Minor Road,LagoonLake, and American TelephoneandTelegraph communication facility). Fourothers(Point Arena, Alder Creek, IrishGulch, and Mallo Creek) arepartlyonprivate land. The Stateof California hasjurisdiction over three of four mountainbeaverlocations at ManchesterStateBeach(California Department of Parksand Recreation), and alsoowns portionsof Alder Creek,and highway rights-of-way on the Point Arena, Irish Gulch, andMallo Creek sites.The other mountainbeaversiteat ManchesterStateBeachoccurson thecommunicationfacilityowned by the American TelephoneandTelegraph Company; this private land isencircledby Stateland(ManchesterStateBeach).On Minor Road, theCounty of Mendocinohasahighwayright-of.way.

The Point Arena mountain beaverisincludedasa category1 taxon in theService’smost recentAnimal Notice ofReview,published in the FederalRegisteron January6, 1989 (54 FR 554).For taxain this category,the Servicehas

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substantialinformationon handtosupportthe biological appropriatenessof proposingto list suchtaxaasendangeredor threatenedspecies.Aproposedruleto list this speciesasendangeredwaspublishedin theFederalRegisteron February15, 1991(56FR 6353). Thecommentperiodclosedon April 16, 1991.

ThePointArenamountainbeaver,with alimiteddistribution(i.e., 10sites)andnarrowphysiologicalhabitattolerances,facesthreatsfrom urbandevelopment,predation,humandisturbance,rodentcontrolactivities,anddecreasedgeneticvariability duetothe smallnumberof remainingindividuals.This speciesfacesanimmediatethreatfrom aproposaltoerectamicrowavetowerwithin habitatoccupiedby the largestknownpopulation.The projectasoriginallyplannedwould destroyhabitatusedby10 out of the20 animalsatthis site. Withonly 100 PointArenamountainbeaversremaining,thelossof anyindividualswould besignificantandcouldbepotentiallydevastatingto thesubspecies.Becauseof theimmediatethreatposedby this proposal,theServicefinds thatgoodcauseexistsforthis ruleto takeeffect immediatelyuponpublicationin accordancewith 5U.S.C.553(d)(3).

Summaryof CommentsandRecommendations

In theFebruary15., 1991, proposedrule, all interestedpartieswererequestedto submitcommentsorsuggestionsconcerningtheproposal.AppropriateStateagencies,countygovernments,Federalagencies,scientificorganizations,andotherinterestedpartieswerecontactedandrequestedto comment.Newspapernoticeswerepublishedin theIndependentCoastObserverandthePacificCoastNews inviting thepublic tocommentCommentsparticularlyweresoughtconcerning:

(1) Biological,commercialtrade.,orotherrelevantdataconcerninganythreat(or lackthereof) to thePointArenamountainbeaver;

(2) Thelocationof anyadditionalpopulationsof this speciesandwhy anyhabitatshould or shouldnot bedeterminedto becritical habitatasprovidedby section4 of theAct;

(3) Additional informationconcerningtherangeanddistributionof thisspecies;and

(4) Currentor planned activities in thesubjectareaandtheir possibleimpactson this species.

No publichearingwasrequestedorheld.TheServicereceiveda ttrtal of 10publiccomments.Nine commentswere

receivedin supportof theproposedlisting; onecommentopposedthisaction. Of these,sixwerereceivedfromindividuals in thePoint Arenaarea;onefromthe MendocinoDistrict of theDepartmentof ParksandRecreation;onefrom theDepartmentof Fish andGame,Sacramento,California;andtwoothersfrom individuals outsidethePointArenaarea.Oneletterexpressedconcernaboutthelow populationlevelsof thespecies,andfourexpressedconcernaboutthedecreasinghabitatavailability.

DaleT. Steele,an ecologistfor theCaliforniaDepartmentofTransportation,confirmedtheaccuracyof theinformationin theproposedruleconcerningthegeographicalseparationof thepopulations.However, frompersonalinvestigation,he now hasfound10 knownpopulationsof PointArenamountainbeaverratherthanthe9previouslyreported.Four distinctpopulationsarenow knownto occuratManchesterStateBeachinsteadof thethreereportedin the proposal.Mr.Steelealsoestimatesapopulationof 100individualsratherthanthe51—65individualsstatedin theproposal.Theappropriatechangeshavebeenmadeinthefinal rule. Theserevisedpopulationestimatesdonot affect theneedto listthespecies.In addition,Mr. Steelereportsthefinding of adeadPointArenamountainbeaverthatwaskilledby a domesticdog.This is the firstfinding of this natureknownto theService.Mr. SteelealsonotedthatPointArenamountainbeaverburrowsaretypically closerto onefoot in depthratherthanseveralinches,asstatedintheproposedrule. Again, theappropriatechangehasbeenmadeinthe final rule.

Anothercommenterexpressedconcernabouttheimpactsof severalconstructionprojectson Point Arenamountainbeaverin thearea—thePointArenawharfprojectonthebanknorthof thePointArenacreek,andtheconstructionof atleastthreegravelplantsin thearea.

TheServicereceivedonecommentopposinglisting, whichclaimedthatthepopulationsof this subspecieshaveincreasedconsiderablyduringthelast25 yearsandthat it is not likely todecline.Thecommenteralsostatedthatthespeciesdoesnot inhabit moist lowland areasandthat cattletend to avoidareasusedby themountainbeaver.Nodocumentationwassubmittedtosupportthesestatements.Thebestscientificandcommercialinformationavailableto theServicedoesnotsupportthis position.

Summaryof FactorsAffecting theSpecies

After athoroughreviewandconsiderationof all informationavailable,the Servicehasdeterminedthat thePoint Arenamountainbeaver{Aplodontiarufa thgra) should beclassifiedasanendangeredspecies.Proceduresfoundat section4(a)(1)oftheEndangeredSpeciesAct (16U.S.C.1531etseq.)andregulations(50 CFRpart424)promulgatedto implementthelistingprovisionsof theAct werefollowed, A speciesmaybedeterminedto beanendangeredor threatenedspeciesdueto oneor more of the fivefactorsdescribedin section4[a)(1).Thesefactorsandtheir applicationtothePoint Arenamountainbeaver(Apiodontiarufa nigro) areasfollows:

A. ThePresentor ThreatenedDestruction.Modificution,orCurtaiL’nentofIts Habitator Range

Although thereareno estimatesavailableon theamountof historicalhabitat for thePoint Arenamountainbeaver,given theamountof habitat thatalreadyhasbeendevelopedfor urbanandagriculturalpurposes,it is likelythatsubstantialhabitatlosshasoccurred.Livestockproduction,datingfrom the time of introduction of cattlebythe Spanish,maywell havesubstantiallymodifiedhistoricalAplodontiahabitats(Steele1986).EarlierknownPoint Arenamountainbeaverpopulationsweresituatednearfarmingorranchingactivities.Livestockgrazingandbrushclearinghaveeliminatedmuchcoastalscrubhabitat intheareaISteele1986).Moreover,cattlehavesteppedon Aplodontic burrowsanddestroyedrunways(Steele1986).Ofthe 10presentlyknownpopulations,5arefoundnearagriculturalor ranchlandandaresubjectto continuedimpactsfrom theseactivities(Steele1986).

Constructionof privateandcountyroadshasresultedin the loss of habitat.NewhomeconstructionatIrish Beachandin Irish Creekupslopefrom themountainbeaverpopulationhasaffectedthehabitatquality. Lossofhabitat,dumpingof trash,andanincreasein predationby feral andnon-feral housepetsmayhavereducedthePoint ArenamountainbeaverpopulationatIrish Creek.About 150homeshavebeencompletedasof 1991, aspart of aplanneddevelopmentof 1,091 homes(Steele1986;SharonFraser,Irish BeachRentalAgency, pers.comm.1991).Anadjunctpartof thisproject includedconstructingawaterdiversionsystematMallo Creekto supplythedomesticwaterrequirementsof the deve’opment.

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Recentlythe CoastalCommissionapprovedthewithdrawal of up to 50cubic feetpersecondof waterfromMallo Creekfor residentialuseat theIrish Beachsubdivision(B. NoahTilghman,California CoastalCommission,letterdatedJune22, 1988).Such awaterdiversionhasthepotentialto adverselyaffect themountainbeaverby reducingthe amountandquality ofavailablehabitat.Ancillary facilitiesincludingamarket,motel,andofficesalsowere tentativelyplannedforconstruction(Steele1986).Thelatestrevisionto theMendocinoCountyLandUsePlan showsincreasinghousingdevelopments,creatingapotentialforadditional indirectanddirectdisturbanceto themountainbeaversinthe Irish Creekarea.

A subdivisionalsohasbeenplannedfor LagoonLake.Although theroadsarenow in, only a coupleof homeshavebeenbuilt there.However,ifdevelopmentproceedsasoriginallyenvisioned,homescouldbe built up toseveralhundredfeet awayfrom thePoint Arenamountainbeaversite atLagoonLake. Someof the lots thatarepartof the Hunter’sLagoonprojectatLagoonLakehavebeenpurchasedbytheCaliforniaDepartmentof ParksandRecreationasadditionallandforManchesterStateBeach(DaveBarlett,CaliforniaDepartmentof ParksandRecreation,pers.comm.).With suchcloseurbandevelopment,themountainbeaverswill be subjectto increasedhumandisturbanceandprobablyaugmentedpredationpressureby housepets.Urbandevelopmentin theLagoonLakeareamayadverselymodifyexisting mountainbeaverhabitatandreducethe numberof animals.

The Irish Beach-to-ManchesterAlternativeCoastalTrail hasbeenproposedto providenon-vehicularbeachassessat Irish Beach,Alder CreekBeachRoad,Kinney Road,andStoneboroRoad.This projectincludesconstructionof aparkingarea,constructionof an interpretativecenter,andestablishingaccessto theproposedtrail at both Irish CreekandAlderCreek.This would increasehumandisturbanceto the mountainbeaverpopulationandresultin areductioninhabitatquality. Thereis no informationavailableto indicatethat the PointArenamountainbeavercan toleratethisdegreeof humandisturbance.However,evenalimited effecton themountainbeaver’sreproductivesuccessormortality ratesfrom predationcouldextirpatethis populationofapproximatelyfive animals.

It is likely that therehasbeenprevioushabitat lossat theAmerican

TelephoneandTelegraphcommunicationfacility resultingfromconstructionandsecondaryimpactsfromuseof the facility. It is not knownhow largethis populationwasprior toconstructionof the communicationfacility; however,thepresentpopulationof approximately20 animalsis nowthreatenedby theproposedconstructionof amicrowavetower.The proposedprojectwould involve theexcavationofaportion of this 3.7 acresite (Steele,pers.comm.1991).

B. Overutilizationfor Commercial,Recreational,Scientific,or EducationalPurposes

Overutilizationis not known to be aproblem.However,theverylow numberof individualsat theseisolatedremainingsites makeseachpopulationvulnerableto extirpationfrom collectionfor scientificor otherpurposes.

C. Diseaseor Predation

Predationby domesticandferaldogs,aswell ascats, is amortality factor formountainbeaver,particularly in siteslocatedadjacentto existingurbanandagriculturaldevelopmentssuchasatIrish Gulch, Alder Creek,andPointArena.This conclusionis supportedbythediscoveryof aPoint Arenamountainheaverwhichwaskilled by adomesticdog(Steele,pers.comm.1991).Theimpactof this predationpressureonsuchsmallpopulationshasthe potentialto becomecritical, sinceonedeterminedpredatorcouldseriouslyimpact,andpossiblyevenextirpate,anyof theremainingpopulations.

D. Inadequacyof ExistingRegulatoryMechanisms

The CaliforniaDepartmentof FishandGameconsidersthePoint Arenamountainbeavera“Speciesof SpecialConcern”andis in theprocessofpreparingthe documentationto requestthat theStateFishandGameCommissiondesignatethis taxonasendangered.Although the CaliforniaDepartmentof FishandGamerequiresspecialauthorization(eitheracollectingpermitor memorandumofunderstanding)to collectthis subspeciesfor scientificpurposes,thereis no legalstatusto protectits habitat.Furthermore,becausethePoint Arenamountainbeaveris classifiedby theStateof Californiaasa non-gameanimal,farmersand/orotherlandownersmay legally taketheanimalswithout obtainingapermit if theanimalsaredeemeddestructivetopropertysuchascrops,

All knownPoint Arenamountainheaverpopulationsarewithin theCoastalZone and,therefore,subjectto

the provisionsof theCalifornia CoastalAct (California StatePublicResourcesCode,Division 20; California..CoastalActof 1976).The primarygoalof theCoastalAct is to preserveandprotectnaturalresources,primeagriculturalland,andtimber land.TheCoastalCommissionis authorizedto approveonly thoseactivities thataredependenton theseresources.However,activitiessuchas dredging,channelization,constructionof pipelines,transmissionlines, waterdiversions,andexistingagriculturaloperationsmaybepermitted.Local coastalplansmustbedevelopedby coastalcitiesandcountiesandincludea landuseplan,zoningordinances,andzoningmops.A landuseplanhasbeendevelopedfor theInversonPlanningArea (LandUsePlan:Mallo PassCreekto InversonRoad).This planningareaplus asmall sectionof theNavarroRiverto Mallo PassCreekPlanningArea includestheentireknown distributionof thePointArenamountainbeaver.However,this plandoesnot containanyspecificactionsdesignedto protectthe mountainbeaveror its habitat.

The CoastalAct andMendocinoCountyLandUsePlanprovideindirecthabitatprotectionto the mountainbeaver.However,suchlanduseplansarenot requiredto minimize activitiesadjacentto sensitivehabitatsuchasconstructionof housingtracts,diversionor retentionof drainagewaters,increasedhumanintrusion,oradverseimpactsby livestock.Further,mountainbeaversarenot presentlyprotectedfromdevelopmentactivities orotherpotentiallyadverseimpactsbecausethereareno regulationsorguidelinesthatprotecttheanimalor its habitat.

E. OtherNaturalandManmadeFactorsAffectingIts ContinuedExistence

Constructionof roadsmayreduceorpossibly eliminatethe ability of youngPoint Arenamountainbeaverstosuccessfullydispersefrom natalareas.PointArenamountainbeaversmaybekilled by carsas they attemptto crossroadsalthoughnonehavebeenrecordectto date.Both theMinor Hole RoadandAlderCreekpopulationshaveburrowsnearandunderroadways(Steele1986),thusincreasingthelikelihood thatmountainbeaverswill wanderonto thepavement.Thenocturnalhabitsof theanimalmaketheir attemptsat roadcrossingevenmorehazardous.

Rodentcontrolby trappingandbaiting is still fairly commonalongtheMendocinocoastandoftenis associatedwith residentialandfamily gardenpractices(Steele1986).Baits lacedwithstrychnineor anticoagulantsarethe

FederalRegister 1 Vol. 56, No. 239 1 Thursday, December12, 1991 ,/ Rules and Regulations 64721

mostwidely used(Steele1986).Also,wetspotsandseepssometimesaretreatedwith applicationsof coppersulfateto controlsheepliver fluke(Steele1986),Although thereis noinformationavailableassessingtheimpactsof suchprogramson thePointArenamountainbeaver,theseactivitiesrepresentapotentialthreat.Maintenanceworkersat theKampgroundsof Americafacility nearthemountainbeaversiteatPoint Arenaplacedpoisonbait andtrapsout to killthemountainbeaverstheymistakenlyidentifiedasgophers.It is unknownifanyPoint Arenamountainbeaverssuccumbed:however, this demonstratesthethreatthatrodentcontrol activitiespresentandalsohow anactofvandalismthroughtrappingorapplicationofpoisonedbait couldseverelyimpact thespecies.Althoughno suchvandalismhasbeenreported,thepotentialexiststo extirpatethesesmall, disjunctpopulations.

Severalexotic plantsoccurin PointArenamountainbeaverhabitat,including gorse(Ulexeuropaeus),broom(Cytisusapp.),pampasgrass(Cortaderiaselloana).andothers.In someareasthesespecieshavebecomeestablishedandrelativelywidespread,therebyreducingthequalityandquantityof thenativeecosystemof the PointArenamountainbeaver.

BecausetheremainingPoint Arenamountainbeavershavealocalizeddistribution,they areextremelyvulnerableto catastrophiceventssuchasfire, flooding,disease,drought,orearthquake.Such eventscouldeliminateall individualsor furtherdepressthealreadylow populationnumbersto apoint wherethey couldnot recover.

Additionally, thepopulationnumbersarenow sufficiently low so that theeffectsof inbreedingdepression(wherebycloselyrelatedindividualsbreed)mayresultin theexpressionof adeleteriousgenein the population.Individuals possessingsuchdeleteriousallelesarelesslikely to effectivelycopewith theenvironmentalconditionsor toadaptto environmentalchanges,evenrelativelyminor ones.Moreover,smallpopulations(especiallythosewith lessthan50 individuals), aresubjectto theeffectsof geneticdrift. This meansthatby chanceeventsthegeneticvariabilityeventuallywill declinein smallpopulations,thuslimiting the flexibilityof apopulationto respondtoenvironmentalchanges.Theeffectsofgeneticdrift andinbreedingdepressionaregeneticallysimilar, Individualpopulationsof mountainbeaversnumberfrom about3 to 20 animals,and,therefore,thegeneticeffectsof small

sizearelikely to be a significantfactorin the taxon’s long-termsurvivability.

Small populationsmay alsosufferfrom the effectsof habitatfragmentation.Subdivisionof habitatinto smallerblocksof land oftenis theresultof human-relatedactivitiessuchasfire, waterdiversion,livestockgrazing,roadconstruction,andurbandevelopmentandservesto exacerbatethesegregationof theextantpopulations.Habitat fragmentation,byfurtherreducingpopulationsize,increasestheprobability of geneticdriftandinbreedingdepressionthatmayresultin lessvigorousandadaptablepopulationsof mountainbeavers.

TheServicehascarefullyassessedthebestscientificandcommercialinformationavailableregardingthepast,present,andfuturethreatsfacedby thisspeciesin determiningto makethis rulefinal. Basedon this evaluation,thepreferredactionis to list thePointArenamountainbeaver(Apladontiarufa nigra) asendangered.The limiteddistribution(10sites),narrowphysiologicalhabitattolerances,smalloverallpopulationnumber,andthreatsof habitatloss from urbandevelopment,pesticideapplication,predationby feralanimalsaswell ashousepets,aridhumandisturbancemakeendangeredstatuswarrantedin lieu of threatenedstatus.Giventhesethreatsandwithonly about100 individuals remainingonabout100acresof habitat,the taxonisnow facing~extinction.Critical habitatisnot beingdesignatedfor reasonsenumeratedundertheCritical Habitatsection.

Critical Hab&tat

Section4(a)(3)oftheAct, asamended,requiresthatto themaximumextentprudentanddeterminable,theSecretarydesignatecriticalhabitatconcurrentlywith determiningaspeciesto beendangeredor threatened.BecausethePointArenamountainheavernowoccursin smallpopulations(3 to 20individualspersite) andis limited to 10known siteswith arestricteddistributionof about100acres,anyactsof vandalism,suchastrapping,poisoning,or collection,couldseriouslyreducetheoutstandingnumbersifindividuals andcauseirreparableharm.Further,interestedpartieshavebeennotified ofthe statusof thetaxonincluding landownersaswell asprivate,State,city, county,andFederalagencies.Therefore,becausetheconcernedlandownersalreadyhavebeennotifiedandanyproposalfor criticalhabitatrequirespublicationof preciselocationmapsin theFederalRegisterwhichcouldresult in vandalismor collection,theServicehasdeterminedthat

designationof critical habitatwould not

beprudent.

AvailableConservafionMeasures

ConservationmeasuresprovidedtospecieslistedasendangeredorthreatenedundertheEndangeredSpeciesAct include recognition.recoveryactions,requirementsfürFederalprotection,andprohibitionsagainstcertainactivities.Recognitionthroughlistingencouragesandresultsinconservationactionsby Federal,State,andprivateagencies,groups,andindividuals.TheEndangeredSpeciesAct providesfor possiblelandacquisitionandcooperationwith theStatesandrequiresthatrecoveryactionsbe carriedout for all listedspecies.Potentialrecoveryactionscouldincludeestablishingabufferaroundeachpopulationsiteandexcludingfurtherurbanor otherdevelopmentwithin this zoneof about100acresoftotal habitator within adjacentpotentialhabitat;installingprotectivefencing;implementingcooperativeagreementstomanagethespecies;andrestrictingpesticideapplication.Such actionsmaybe initiated following listing. Theprotectionrequiredof Federalagenciesandthe prohibitionsagainsttakingandharmarediscussed,in part. below.

Section7(a)of theAct, asamended,requiresFederalagenciesto evaluatetheiractions‘with respectto anyspeciesthat is proposedor listedasendangeredorthreatenedandwith respectto itscriticalhabitat,if anyis beingdesignated.Regulationsimplementingthis interagencycooperationprovisionof theAct arecodifiedat 50 CFR part402. Section7(a~(2)of the Act requiresFederalagenciesto ensurethatactivitiestheyaulhorize,fund, or carryout arenot likely to jeopardizethecontinuedexistenceof listed speciesorto~~s~oyoradverselymodify itscritical habitat.if a Federalactionmayaffectalistedspeciesor its criticalhabitat,theresponsibleFederalagencymustenterinto formalconsultationwiththe Service.Federalinvolvementmayoccurif theFederalHighwaysAdministration providesfundingto theCaliforniaDepartmentof Transportation(Caltrans)to constructnewhighwaysorrepairexisting ones.The AmericanTelephoneandTelegraphCompanyproposedto install asubterminalfiberopticscablein a six-footdeeptrenchaspartof its submarinelightguidecableinstallationprojectunderitscommunicationfacility. In considerationof the mountainbeaveron the site,theproposalwasmodified to borethecablethroughthe siteratherthanexcavateasix-footdeeptrench.If hydroelectric

64722 Federal Register / Vol. 56, No. 239 / Thursday, December12, 1991 / Rules and Regulations

facilities areproposedfor thestreamswithin or adjacentto PointArenamountainbeaverhabitat,a FederalEnergyRegulatoryCommissionpermitwill berequiredthat mayincorporatemeasuresto protectthemountainbeaverandits habitat.No suchhydroelectricfacilitiesareknown to beplanned.

The Act andits implementingregulationsfoundat 50 CFR 17.21 setforth a seriesof generalprohibitionsandexceptionsthatapply to all endangeredwildlife. Theseprohibitions.in part,makeit illegal for anypersonsubjecttothejurisdiction of the United Statestotake(includingharass,harm,pursue,hunt, shoot,wound,kill, trap, capture,collect, orattemptanysuchconduct),importor export, transportin interstateor foreigncommercein the courseofcommercialactivity, or sell or offer forsalein interstateor foreign commerceanylistedspecies.It alsois illegal topossess,sell, deliver, carry, transport,orship any suchwildlife that hasbeentakenillegally. Certainexceptionsapplyto agentsof the ServiceandStateconservationagencies.

Permitsmaybeissuedto carryoutotherwiseprohibitedactivities involvingendangeredwildlife speciesundercertaincircumstances.Regulationsgoverningpermitsareat 50 CFR 17.22and17.23.Such permitsareavailableforscientificpurposes,to enhancethepropagationor survival of thespecies,and/orfor incidentaltakein connectionwith otherwiselawful activities.In someinstances,permits maybeissuedduringa specifiedperiodof time to relieveundueeconomichardshipthat wouldbesuffered if suchrelief werenotavailable.

NationalEnvironmentalPolicy Act

TheServicehasdeterminedthat anEnvironmentalAssessment,asdefinedundertheauthority of theNationalEnvironmentalPolicy Actof 1969, neednot bepreparedin connectionwithregulationsadoptedpursuantto section4(a) of the EndangeredSpeciesAct of1973, asamended.A noticeoutlining theService’sreasonsfor this determinationwas published in theFederalRegisteronOctober25, 1983 (48FR 49244).

References

Camp,C.L. 1918. Excavationsof burrowsoftherodentAp/odontiawith observationson thehabitatsof theanimal.Universityof CaliforniaPublicationsin Zoology17:517—535.

Dalguest,W.. andV. Scheffer.1945.Thesystematicstatusof theracesof themountainbeaver(Ap/odontiarufo) inWashington.Murrelet26:34—37.

Doiph.C.. H. Braun,andE. Pfeiffer. 1962.Theeffectof vasopressinupon urineconcentrationin Aplodontiarufa(sewellel)andtherabbit.PhysiologicalZoology35:263—269.

Druzinsky.R. 1983. AnatomyandEMG of themasseterof Aplondontiarufa.FirstInternationalSymposiumof VertebrateMorphologists.Giessen,W. Germany.

Druzinsky,R. 1984. AnatomyandEMG of themasseterof Aplodontiarufa andMarmotamonax.Presentedat the1984Meetingof theUniversityof Illinois,ChicagoChapterof Sigma Xi.

Goslow,G. 1964. Themountainbeaver,Aplodontiarufa. UnpublishedMastersThesis.California StateUniversity.Humboldt,74 pp.

Greenbaum,A.. and S.Dicker. 1963. Swellingofmitochondriafrom theliver andkidneyof a primitive rodent.I3iochimicaetBiophysicaActa. 12:402—404.

Hall, E., andK. Kelson.1959. ThemammalsofNorth America.NewYork, N.Y. 2 vol.

Hall, E. 1981. Themammalsof NorthAmerica.Vol. 1, secondedition.WileyandSons,NewYork, N.Y.

Ffardham,C.. andC.True. 1972.A floristicstudyof PointArena,MendocinoCounty,California.Madrono 21:499—504.

House,E., E. Pfeiffer,and I-I. Braun.1963.Influenceof diet onurineconcentrationin Aplodontiarufa andtherabbit. Nature199:181—182.

Johnson,S. 1971. Thermoregulation,microclimateanddistributionofAplodontiarufa. UnpublishedPh.D.Thesis,OregonStateUniversity.164 pp.

Kinney, J. 1971. Environmentalphysiologyofa primitive rodent(Aplodontiarufa).UnpublishedPh.D.Thesis,UniversityofOregon.181 pp.

Lovejoy, G., andH. Black. 1979.Populationanalysisof themountainbeaver,Aplodontiarufa pacificain westernOregon.NorthwestScience52(2):82—89.

Martin, P. 1971. Movementsandactivitiesofthemountainbeaver(Aplodontiarufa).Journalof Mammalogy52:717—723.

Neal, F., andJ. Borrecco.1981. Distributionandrelationshipof mountainbeavertoopeningsin saplingstands.NorthwestScience55:79—82.

Nungesser,W., andE. Pfeiffer. 1965.Waterbalanceandthemaximumconcentratingcapacityin theprimitive rodent,Aplodontiarufa.ComparativeBiochemicalPhysiology14:289—297.

Pfeiffer, F. 1954.Reproductionin a primitiverodent,Aplodontiarufa. UnpublishedPh.D.Thesis.Universityof California.Berkeley.177 pp.

Pfeiffer, E. 1958. Thereproductivecycleof thefemalemountainbeaver.lourualofMammalogy39:223—235.

Phillips. J. 1982. Natural‘boomer’ control.ForestLog.Jan.1982.

Scheffer,T. 1929.Mountainbeaversin thePacific Northwest:Their habits,economicstatusandcontrol.U.S.D.A.Farmers’Bulletin. Ne. 1958.

Schmidt-Nielson,B., and E.Pfeiffer. 1970.Ureaandurinary concentratingability ofthe mountainbeaver,Ap/odontiarufa.AmericanJournalof Physiology218:1170—1375.

Steele,U. 1982. An ecologicalsurveyofmountainbeaver(Aplodontiarufa) inCalifornia.Non-gameWildlifeInvestigations.Job IV—16.1. CaliforniaDept. ofFishand Game.

Steele.U. 1986. Themountainbeaver[Aplodontia ruful in California.UnpublishedMaster’sThesis,Universityof California,Davis.93 pp.

Taylor, W. 1914. A previouslyundescribedAplodontia from themiddle coastofCalifornia.Universityof CaliforniaPublicationsin Zoology 12:297—300.

Taylor, W. 1918. Revision of therodentgenusAplodontia.Universityof CaliforniaPublicationsin Zoology 17:435—504.

Voth, E. 1968. Foodhabitsof thePacificmountainbeaver,Ap/odontiarufapacifica.UnpublishedPh.D.Thesis,OregonStateUniversity.263 pp.

Authors

Theauthorsof this ruleareMr.MichaelHortonandDr. KathleenE.Franzreb,SacramentoField Office, U.S.FishandWildlife Service,2800CottageWayE—1823, Sacramento,California95825—1846,(916/978—4866or FTS460—4866).

List of Subjectsin 50 CFR Part17

Endangeredandthreatenedspecies,Exports,Imports,Reportingandrecordkeepingrequirements,andTransportation.

Final Regulation Promulgation

Accordingly,part17, subchapterB ofchapterI, title 50 of the Codeof FederalRegulations,is amendedassetforthbelow:

PART 17—EAMENDED]

1. The authoritycitation for part17continuesto readasfollows:

Authority: 16 U.S.C.1361—1470; 16 U.S.C.1531—1544;18 U.S.C.4201—4245;Pub.L. 99~.625, 100 Stat.3500;unlessotherwisenoted,

2. Amend § 17.11(h)by addingthefollowing, in alphabeticalorderunderMammals,to the List of EndangeredandThreatenedWildlife:

§ 17.11 Endangered and threatenedwildlife.

(h) * * *

FederalRegister / Vol. 56, No. 239 / Thursday. December12, 1991 / Rules and Regulations 64723

SpeciesHstorica) ran e

~Vertebrate population where

endangeredor threatenedStat aU

When CriticS?tisted - habitat

SpecialrulesCommon name

—

Scientific name

Mammals:

BeaverPointArena mountam.... Ap/odant/a rufa nigra U.S.A. (CA) Entire E • 454 NA • NA

Dated:December4. 1991.RichardN. Smith.Acting Director, U.S.FishandWildlifeService.FR Doc.91—29733Filed 12—11—91:8:45 am)

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