v70 p10 thompson

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Michael .Thompson,Nlonlana epaftment f F sh ,W d fe and Parks3201SpLrrg Boad[4 ssoua N4ontana980]

WinterForagingResponse f Elk o SpottedKnapweedRemoval

AbstractPiclofain $as u\cd lo con\elt I 10 ha of.Ln hj\toricnlly culti!ated gftrs\land hereaiicrold field) fionl spofiedknrr]$eed (airrrrtrr

/ " , , L k 1 i 1 l , J , ) I o g r . 1 s i 0 n u e ] k ( C . ] - | l l l . / z ? , i l l ! ) q ' i ! c r r 3 n g e i D w e \ t e | n N l o n t a n n ' A b 0 u l 3 0 h a \ \ '

eslzed hat knapxccd rcno\.rl roukl nol: (H,I) xfect inlcr laraging rcrivity of elki (H,r1l) rlect q'interdierst H.,lll) \ rr! in 1tseffects on iirraging aclilil) and diets rc0is the firn lour $irrers ftef knapweed cno\.rll and (H,,lV) aiicc( clk populariondistr jhut io lr . LkNulked n.rd jacentnapreed nd g ssslaDd\ndiscf iJninatc l! .Lr toftged r lm, r c\! tu,r \ t\ rn rh e! r r \ \ \ r . r r l(H,1).Dic lssrmpledbeli teandafterknap$ccdrcmo!alwefenotrankcorrchlcd.andtbmge\characlc ist icoftheoldt le ld( i .c ..

Pod.Dtonlt6. Phl nt) "J.nkedhighcr n dicls .rlier knrpreed remo|al (H,ll). Elk tin.rging aclivir) $as significantl! highcr n thelirsl $i er than n subsequent\rntcA (H,lll). A highef proporljor ol |he estinrted elk popularionused he old-field alicr knap-$,ied relno\'al (H IV). I concludcd hrl rbundant gfeen grassa(raclcd elk to dre old-field in $c lirst uinrer after knap$eedrcmo!al. Cured 8r.r\saffarentlv allraclcd elk ibr ging acti!it) and allccr.d $intef diets ro a lcsscrcrlent in subsequenlwin(ers.wlcn pllnning knrp\reed remo\'al.clk rn.rnrgcfsshouldconsiderpreexisling .rnge ondition and knap!vceddensity.occurrcnccof prclcircd loralre species.currenta d dcsmd elk distribution. and thc probtrbilit!'of rdequatc ranliall fif sub\ianljil g SSgro$th n the i f s t gro$ing eason ilcr hcrbic e applicat ion.

Introduction

Knapweeds C(ntoLtreospp.) are Eurasianspecies occulringon over t lve mill ion hectaresnthc nofthu'estUnitedStates ndsouthwest anada(Lacey1989). nnualproductionfspottcd nap-weed(C rrrrcrlosri) may exceed1,000kg/ha ondisturbedangelandsear oadside eed ources(Carycntcr 986). yseran dKe y (1988)also e-pofied tl're nvasion of spottedknapweed hcrc-aftcr knapweed)llto relativelypristine escue

Easslandsvith a coincident ecline n nativeplantdivcrsity.

Winterrunges f Rocky Mountainelk (Ccnuse aphus esou ) typically nclude angcltrndsLyonan dWard 19821 ulnerableo kna pweed nva-sion Mooers1986). lk arcno tobligate razers.asevidenccd y the 5l winter oragesisredbyNelsonan dLeege 1982). ut nray ose bragingelf iciency Wickstrcmet al. l98.1)whcrcknap-weeddominatesroductire rasslands.lthou-qhspeculative. n Lrnpublishcd orestService eport(Spoon t rl . l9E3)ha softenbccn ef'erencedo

iustify wamings of f'utureelk declines as knap-wced spreads Lo lo NaL iona l o res t 99 l ) .Bedunahand Clrpcnter ( 1989)ertrapolatcd heresults fherbiciderials o mply apotential2..+

lbld increase n rangecanving capacity br elklirllorving

knapweed ontrolandconcunentgrassprocluctiongains.However. resultsreported by

Lavelle 1986) uggest lk can nco rporrte nap

wccd into their winter diets. Participantsat the1989KnapwccdSymposiumdentifiedknap*eedimpactson elk winter ran-eess a researchneed(Fayan dLaccy 9E9).

In May 1989. nrpweedwas removedio mmostof ar historically ult ivated rasslandhere-aftcrold-field) on an elk winterrange n rvcsternMontana.This vegetation onversion rovidedanunusual ppofiunity o studyelkdietary respensesbecausehe vegetation omposition f the old-field wasunique n conrparison ith surround-ing habitats;hus,dietarychanges aused y old-lleld treatments resumablywould be indicatedby coresponding changesn proportionsof oldficlclgrassesn elk feces. hypothesizedhatknap-weed emoval would not: (H1)l) f]'ectu,inter br-agingactivityof elk; (H0lI)aflectwintcr diets:(HnIIl) vary in itseffectson foragingactivity anddietsrcross he first tirur wintersafter knapweedremoval;nd (HoIV)affect 1k opulation istri-buhon.

StudyArea

The study focused on a l:10-haold-licld in thenorthwest ortionof the Threenile Wildlife Man-agementAreaTWMA), Jocatedn RavalliCounty.Montana Figure ). Theold-field s 1.3.10-1.,160

m abovcsea evelon the wcst slopeof the Sap-phireMountains nd normally eccives 2 cm of

NorlhwestScience. ol. 70 ,No. 1, 1996r.!) lrlr6 L.] lr.\o,rlN.{ S!LUr,rir A\oc rrr All ri-.hrr.$r.d

1{ )

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westemwhcatgras! A. stnithii\, i:meth\ .PltleLtnlpraten\e). daho cscue, ulbous lucgrrss Prrrrbu|bostt),,ntd iurada luegrassP. o1tlpressa).

Forbs ndu'oody pccics ereuncommonn theold f ield.

On 5 Ma-v1989. iclorarn asaerirl l l broad-calt (200 cc/ha)over about l0 ha of the oldficld.About30 ha werc efi untreatedFigure1 .D. J. Beclunahpers. omm.)agreedhe vegeta-rion esponseopicloram isually esemblcdha tmeaswed uring heearlierherbiciderialsbv Car-pentcr 1986) ndBedunah ndCarpenter19Ii9).An abrupldcmarc tion between hegrass piclo-ram-treated)ndknapweedLuttrealccl)tands 'asconspicuousrom Septcmber 989hrough 993.Grassgrowth in the old field afierknaptveed c-nr r , \ ! l l eg i l r )r t c in rhe 08o rou in ! . c l r .on .an dwas ikelystinulated y above-normaluly-August ainfall.Grasscsenrainedreen hroughthe ils l winter.bu tgrass hcnologv etumed1()normal n subsequentrowirg seasons. emperaluresandprecipitalionwerebroadlysimilaracross

the our winters f study. heold-field enerally\ !as snow covcred n December-Fcbruarvndsnow-treen March.

Methods

Unlessotherwise tated.1990denolcsDecember 1989-February990 the 'irst vintelof srudy);l ikewise.1993denotesDecembcr1992Febru-ary 1993 the ounh and lnalwinterof studv).

H..l:Foraging Act vlty

I countedrack-trailsno t ndividual racks) ndt'eedilgcraters n the sno$'as evidence f elk

foraging ctivity n the old-fleldknapweed ndgrass tands uring1990 1993. ourparallel clttransects2 x 80 m) u'ereestablishcd irr counting tracksand craten on eachsideof the demar-cationbetween hc knapweed nd grassstaods(Figure ). Transects ereeither50 or,100m (ap-

proxinately)tiom the demarcation. anpling re-quency epended ponenough now o covergrassfoliage ndpreviously ountedrack rails here-alter tracks).Mean mck and cratercounts n thcknapweed nd grass tandswere esled i)r dif-tercnces singa paired test.

H - : D i e t s

Conpositewinterdietsofelk wcrcestimated vfec , r lrn rhs i : t s t c r r rn 96- .T : lb lcr . . r . r lpe l l cs

Figure L. lu\tapo\i t ionof stud! s ires nd cgct. rr ion one\x ith i. thc ainter ome ange adaprcdiom Beall

L c]7.1:701.hcr!) outline n fi gure)of lhcTtueenileel k populNti |)n.99(l l99l.

annualprecipitationCar?enter 986). t is partol an ecotonebetwecnponderosa ine (Pi?r.tponulerosrr)irrestandnative angcland ominatedby bluebunch vheatgt.\ssAg op| ron spi atunt).Idaho fescuc(.Fe.stu(atlahoensis),neeclJegrass(.l l l7ra spp.) and arrowlerf balsamroot

lBaIsantorlt i;u . tgi t t I tut). ivcstockhad beenexcluded incc1967.when heMorllanaDepartnrentof Fish.Wildli lt andParks MDFWP)pur-chased heTWMA to naintain andenhance lk$ inter ange.

Knapu'eed orninatedhe oldJield b1' 1973(HalJm 1975).Carpenter l986.) nd Bcdunah ndCarperter 1989)cimductederbicideritrls n 2ha of theold-fleld n 1985-1988Figure ). Ontheir control plots, annualproduction averaged1.23,1.6g/ha napwcednd 7l1.7 kg.4raurasses.comparcdwith 8.0 kg/ha napwced nd 1.582.9kg/hagrassesnpicloram-treatedlots Carpcn-

ter 1986).PrairiejunegrassKoelerianecruntlto)and Kentuckl'bluegrassPonprrlcrrsis) ncrcased

si-snif icantlvlier realnrcnt. therglassesn theold-fi eld includedclreatgrtssB cnLt.t ec o rLt1 .

E lk Rc . p , ' r r r e , ,K l l p \ \ ced Rcnr , r \ i l l | |

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TABLI L Fcc,rl \amp]ing dcsign br e\rjrnxting i\e $inter diets ofelk on the Threenile \Vildlile \{artrgcncnl Arca. Erch dict

rcprcscnlcd col.rc\pondingo posited,trmpleofl- lpel ler\ l io lnerchofNindi! idudpelletsroups.

llk Pcllcl Croup!

Rcpr( \ . n lJ l , ,n

a;lt , \S90

C] A59I

GRAS93

KNAP9I)

KNAP86

E2

Okl field

Old - f ie ld

Old lield

I I knl south

of o ld f ie ld

Old f ie ld and

immediale ic in it)

Firsr $ ir tcr alicr knaps eeed emo\'al (pelletscollectedon 25 Febmafr- 1990);

dier porcrtirlly rflccrcd by knip$ccd rerrolal

Second inrcra j ic r napnccd rcnrovxl pel le ls ol lected n I I ebruxrf 99l) :

d ic l polc l l l ia l l)at iccrcd ! knapxeed emoval

Fou.th \ in terai ier knap\ieed emolal fe l le ts ol lected n : : N{rfch 199-l) :

dicr porenrialll affectedb) knap$eed e|ln)\'.Ll

First \ i r rer r l ier knrp$ccd cnro!t l (pcl lcrs ol lectcd . l5 Fehruar l 990Jl

dier poteDti|ll) unLrllected ] knlp!\ccd rcno!al

Fouf $ mten belbre nr p$eed eno!.r1 dala iom 1-a!c l lc l91i6 l.pc l lc l \

collecled December 1985 Nlarch 1986)

deposited uring he currentwintcrperiodwereidentif iecly coloran dshapeEbefhardt ndVan

Etten1956). u,as rlikely to mistakenly ollectsummer-rnd all deposit ions ccause ost elkmigrated o the studyarean li,rte ovenrber. arly-

springbiaseswcrc avoided ) selecting gainstfreshlydeposited ellets urjng ate-winter ol-

lectiols.Composite tmplcs ncluded 2 pellets

liom nranl pcllct-groups1(] ncorporatea repre-scnlalive aDge f anilnal and empori,rlariation(Table ). Microhis tological nalyses erepe r

tirrmcd by the Wildlife Habitat I-aboratoryatWhshington trteUniversit)', ullmrn.

Diets ol clk in the old tleld were comparcdam(nr-sbur winte$ (Table ): i.e..one GRAS90.),

two (GRA59l) and bur(GRAS93)wintcrs f tcr

piclorirm leatment,and our winte$ before featmcnt KNAPS6). sanpled il ih diet KNAP90)

to test br temporal-enhancedariationbelweenthc KNAP86 and GRAS9O iets.My sampling

obiecti le br the KNAPgOdict wils o represent

the same ombinalionof foraginghabitatswhichyiclded heKNAPS6 iet.Accordingly.sampledtheKNAP9Oandall otherdietswithin hc winterhome rlnge of thc Threemile elk population(as

dr l ineatcJ1Bca l l ( ) -J l .Ry uh je , i re rs . . . -

mentoltrack patlerns.l oncludedhat he nflu-enceof thepiclor-am-treatedld-ficid could be

excluded rom lhe KNAP9o sample ,vcollect-ing pcllcts 3 km south fthe old-tield Table1.

Figure ). If elk braging istributionseprcscntcd

by the KNAP9OandCRAS90 samples verlappedin the old-field, he probability f clct ccting c-

tual clk dietary responseso knapweed emovalwas reduced.

Diets were comparcd y l irst calculaLingrrreanwinter diet composition ion the lve indi-

vidualdiets.The t 'ewestoragc axa with mcanpcrcent ompositionsotall ing> 75% wer e selected or'lurther analysis.Theseprincipal tbr-ageswere rlnked by their percentagesn eachindividual diet, and he ive dietswere comparedusing Spearman'san kcorrelation. pearmrn'scoellicientsweresegregatedDto hrcedietgroups(i.e.,KNAP versus NAP.GRASvcrsusGRAS.KNAP vcrsusGRAS;Table ) an dgrouped o'efficientswere averaged s an ndex ofdiet sini

ladty fbr comparison nronggroups.Principaltirrageswere softcd by thcir occurrence n threchabitat ategoriesi.e..old-1ield. unounding ativehabitats,nixed) and rankingswere compared.

H"l :Temporarends

Snowdepthwa snrcasurcdo thenearest cm intheold-fieldwheneverfackswerecounted. ountsoftracksan d eeding raters ere ested i)rdif-t'crcnccs elweenyearsusing a I way alalysisof variance. i l lerences etweencarswcre n-

teryreted.n pafi.by testing rackandcratercouDts(dependentariables) orcorrelation it h snow

depth ndjulian ay indcpcndcntariablcs).nclmultiplc near egressionnalyses erepefomed.

12 Thompson

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Juiirnda y beginninglom I December) aspre-sumed1r) eflecta gradual eduction n the ecological netabolisnMocn 1978) f elk benvecnlate fall and nricl-rvinter. umulalivc ti)ra-qe e-moval"and deteioralingsnowconditions i.e.,settlingandcrusting).Dietarl differenccs etween

),eaIS er eexamincd y c onpadng Spearntan'srankcorrelation oeffi icnts.

H.. :E k Dst rbutonI estimatedevelsof winter clk useon the oldlield lbr conparison with previousestinalcs byBeall 197.1), akim (1975)an dLavelle 1986).I r ecordecl l l incidental bsen,ationsf elk inthe old l ield l icinit l. Croup size vasestimatedwhenevera groupof elk lcft tiesh and ndividu-ally distinguishabler. l tck-setseadedn hesamedirection.Pellet groups were countedon thetransectsn Februarl ' 990. nd he otal vas x-

1 '1 . . seJn pc l le ti roup. / l t r r .ub jecr i re. .e . : .meul of 1o\\'. rodelateor high elk usewas madelbllowing thedcscriptions f Beall ( 197.1).on -

sideringall i ldicationsof e1kpresence. nnualaerialsurveys f the Threemilccl k population(single ounts uringMarch or April) continuedthrough hisstudy J.E. Firebaugh crs. omm.).Dit l 'erencesl meanpopulrt ionsizeu ere ested$'ith a t-tcst .The J99211ight roduced n outlying low count 3) thlt wasomitted.

Results

Eightccn urveys f elk tracksand eeding raterswereacconplishcd luringhe irst bur win-ters al'tcr nap*eed emoval Figurc2) . A lacko l l re .h nor , . r , ' ren ledro le h tnonr : : l r r \e )n1992.Coresponding ccalsarnplesbr dietest i-

nlationwele notcollectedhirlwinter.

H!l Forag ng Activity

I counted1.1103racksand l90 lteding craters.Elk walked hroughadjacent napweed ndgrassslandsndiscriminatelr,'.utpawcdonly irur(2.17c)of the cralers n the knapu,eedtand Figure3) .Theretbre. rejectedH,,l andconcluded hat lhc-tols ilssociatedwith ktapweed rcmovalattt-actedeJ k braging ctivity H, l).

Hr l l D e ts

Forty-eight brage axa wcrc identit ied ioln a

combincd700elkpelletgroups trmplcd 1 -avelle

I

1 9 9 0 1 9 9 1 1 9 9 21 9 9 3

Y e a f

Figure . N{can ounl\ r l l t r .rn\ectsonrbricd)ofe lknrcksand ccding ratersn.rnold i le ldon heThreenileWi ld l i i i M.rraSenent fea. ANO\A (1 \ia)) ontrack\ b] yellr: F = 0.809. P = 0..+7:ANO\A (l

$a,""on craters v err: F=;+ 725.P= 0 01. Djflcrent lettefs vithin group\ (i.e.. ruck\ or crao-s)

derore ignif icani i i i i rcnccs P < 0.10) ndicarcd

b] Bonferoni test. N = number of surve]!.

( 1986)and heprescnt tudv.Thirteen 27. %)genera ornprised 7570 fthe averagewinterdiet(Table ). KNAP andGRAS diets Table I ge rerallydisplayed orc sinrilaritywithin groupshanbetwccngroups Table3.).Spcannan'soetlcientsiodicated er ocorrelatioDetween itherKNAPdicr andrhe GRAS93 dicr. rvhile he GRAS93an dGRAS9I dictsdisplayedhehighcst on-elation (Table3). Genera haract eristicf the old-tield (i.e..Poo, Brornus,Pftlearr) rankedhigherin GRASdiets hanKNAPdiets,while he ankingsol widely distributedgcnerrwerevariable nrble2). Therefore, rejectedHnlI and concluded hatfirctorsassociated ith knapweedremovalausedneasulable hif is n elk rinter dicts H"I]).

H,l l Temporalrends

Elk prescncen the old f ield (i .c. . racks)wasconsistent through four witters followinc

S sE (Tracks)

I sE {craiers)j nacks: 1 Observation

: Cralers1 ObsetuationJ

E

F

:Lrl

z

N = 8

l ] '

Elk Responseo Knapweed emoval l3

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70

9 6 0

^ t

L!

E= , ^

egF

: 3 0LIJ* l

b2 c oJ.

= 1 0

Ss e o,""r"rlse (c,er"o)

N = 1 8( 1 9 9 0 - 1 9 9 3 o m b i n e d )

K n a p w e e d l n f e s t e d K n a p w e e d B e m o v e d

Figure -1.Nlean counts of elk rfack\ .Lnd eeding crrters b)sanpling s itc in an old l jc ld on lhe Threein i leWild l i fe ManagementArer. Dif fefent letters

! \ th in gfoup\ ( i .e . . rack\ or c l. t te ls) enorc i g

nit icanl d i l lerenccs P < 0.05). Paircd = 0.5,1(tracks) nd 1.65 craler() .

knapweedemoval Figurc2.1. oragin-qctivityindicated y craters rs highestn 1990. ndwa ssignil icantlyower n subsequent inters.Dur-ing 1990. racksan dcratcrswcrc not corrclatcdwith sno*,dcpth, ut racks cndcd o ncrcasc swinterprogrcsscdTable ). During subsequcnlyears. rackcountsdeclined s snow depths n-clelr.ed nJ u in1qt. rugres.eJ. he nlerr,.ir.rrrof snou,depth and ulian day explained417c of

the vadation n trackcountsduring l99l-1993.The addit ion f data rorn 1990 educedhi sex -plained ariationo 8'lr (Table ). TheCRAS9landGRAS93 iets isplayed ore imilarit),han

any otherdiet comparison, ndboth diets$ererelativel.v issimilar o GRAS90(Table3). Thercfore. I rejectedH,,III and concluded hat elk responses 0 actorsassociated ith knapweed e-movalpersistedhrough he ilst four rvinters fterknapweed emoval, but were more pronouncedin the first \\"inter H,III).

H.lVElkDistr ibut ion

On 3l December 989, counted 5 1i'eshrack

sets eadingwestandverified hatexactly95 freshtrack sets etumed across he old field. This indicatednearly four times the number of elk encoultered duringprevjousstudiesn the old-tleld(Table5). Other measures f elk-use ndicateda170 1.200clrncreasen this studycomparcdwithprevious eports Table5).

lAUl-E 2. Principalplanr genefa n file estim.rted \'irter dier\ of elk on thc Thrccnilc Wildlili Nllanagcmcnl rca (c.g.. rh .

KNAP86diel l -a le l le19861 efr ins o the 1986 Lir ter:Tlb l c 1).

Dicr Compo\ition

RankB\ Winte l

Habltr t

Cenus KN,A.P90 CR,A.S93N,A.PE6 GR,A.S90 CRAS9IO1d'lield gfrssllllld prin.ril)

Po( 11.20

B r o u \ 5 . 7 l

PhltLt 1.58

Sunoundi. g ra. gela.d/lbrest primxf l,v

7 . 1 36.55.1. l.1.1

3 1 01.362 . 89

6.191 . 811 . 99

. 1 . l 0

1.533 . 29-1.51 . 59-1.911 . 95

25

l l

1, 1.1

23

21 l

5I

l l.1

1

22

3

E

I

' l9

16l

1 l

1 iIJ

)

l

I)

l l J

8l 5

.l

6l 2t l

53

1

I

63

tL)l 7l l22

15

1t3l l

I

12

E

B . . r l ' . J ' L . l I d . r r r ^ | | n J r - J, r p e l , rd , r i .

FesI d 12.15

Attr)11\'tott 7.15

(:entuut.u 3.91lbral 16.07

9 . 71

l . 2 l

1.+ Thompson

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TABLE 3. Spcannans correlationcoefficients " denotesP < 0.05, bdenotesP < {) 10) comp.ring live eslimated virter diets ol

c l k o n t h c T h r c c r n i l c w i l d l i f e M a n a g e m e n r A f e r ( e . g . , r h e K N A P s 6 d i e t f l a v e l l e l 9 S f l p e f i a i n s t o t h e l 9 3 6 w i n t e l

Trblc I ).

Diet

1 ) ie t KNAP86 KNAP9O GRAS9I CRAS9]

Poteniirll! .riltcted x potentiall] ttfiectedby knap\-ccd rcmo!al

GRASq0 0.335

CJ R S9

Unailiclcd (KNr\P86) x poientirll,vunrffected b] kn.rp\ieed emolrl

KNAP9o 0.511'

Pote.Iiall! affected un.r*ected or potenti.rlli unaiiecledby knapNccd cmolal

0.'121

0 . 610

0.51

GRAS9O

CRAS9I

GRAS93

0.225 0.526F

0. r0 0 .108-0.005 0.005

0 . l 9

T,A.BLI .1 .Thc nl lucncc l sno$dcprh(c in)andJulirndx)(beginninglDecember)onrviDtefcountsofelktfacksrndfeeding

crrrers, as ndicatcd bt Pcrrson conclalion coeificientsand multiple linear regfes\ion.Threemile Wildlife N{.rnrge-

mentAfer ( ' denoles < 0.05. dcnolcs = 0.01).

Correhtion

N

Dependent

Vttlirblc I)ay

1990

l99t l99l

r990 99-l

Track\

Cmte|s

Tracli\

Cmters'lrrck\

0.26

0.0,1

0 . 17

-0.26

0 . l l

0.5.1

0 . 33

,0.59.

0.06

-0 . 18

0 . 1 9

l l

r8

1.5.lb

0.1.1

0.6.1

2.08

0.,11

0.0-l

0.011

0.12

TABLE 5. Comp.u.rtrle irdic.rtions of $intcr clk prcscnccal1dabundanccon thc old iield grasslandof lhreemile Wildlife

Ntanagement fea.

Vethod PreviousStrrdies This Studv

Subjective

Pc l lc lgroup PC)

Lrrgest elk !ruup

Lruge\t elk group.

judgingn.om0rck\

Nlodcratc ca!] usc. aladonlh ccritcria i Bcall 197,+).

18,1 c,fta

68 8 Jan1993I I '. of N'

95 (-l l)ec lgEq):l3tf oi N'

Lighl elk use,occasion.rLly oderateor no use Beull 191,1).

Fe\ e lk minnnalus e La!el le 1986).

l , l PG/ha Hak im 1975)

ll (La\c l lc 1986)

I 1 9 , l N "

15 .approx. Beall 197.1)

l7 % (l t N"

N'= 1,19 lkcnimlcd in hc Thrccni lcpopulat ion.986 l989rNb= 1. lE lk er l imated.97l- 1973. } Beall1 l97,1)r '= l20 e lk

est inated. 990 19q.1

Elk RespoDseo KnapweedRemoval 15

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Annual trendcountsof the Threerri lc clkpopulation yeraged,lT% igher t = -2.10.P=

0.07.11uringMarch-April 990. 1991. 993 nd199:1 = 165.SD = 38) than ur ing 986-1989(- = 112,SD = 26).Sirnilarmethodsn conrpa-rablecover ard terrain n thc ElkhornMountainsdetected :1.77of87 marked lk(R. M. DeSirnonepers.comm..). rovidinga co[ection factor osuggest he Thrccnile populationaveraged bout

220e lk n 1990-199.1and: l9c lk n l9 l i6 -1989.Beall (197.1) scdnrarked nimals nd multipleccnsus ounts o obtainannual stimalcs f 127-16 8elk n heThrccrnile opulationn l97l 1973.

Elk numbcrs nd indicators fuse n theold-tield lcleasedbeyomd roportionsxplained olelvby thepopulationncrease ocunrcnted uring hisstud]'. I obscrved3l-43% of the estimatcdThreemile opulationn theold-ficld. omparcdwlth fepofisequivalcnt ) | l- l7% of thepopula-tion betor-e napweed emoval(Table5). Therefore. I rcjccted H,,lV and concluded hat factorsassociatedwith knapu,eed emovalattlactedelk

to theold-field.presunably ronrelsewherevithinthe wintcrh()me ange f theThreenilepopula-tion (H"IV).

Discussion

Factors ssociated'ithknapweedemoval n thcold lield apparenLlyttractecllk nunbersequivalcnt k) 1;+-327 f the Threemilcpopulation.naddition o thc cstimrted1J-17%of thepopula-tion that used heold f ield bcforcknapweede-noval (Table ). By definit ion.hisdistf ibutionalshif i o$ard the old f ield (H,tV) alsodecreasedelk-claysfuseelsewherecrosshewintcrhonrerange.Although other$ se unaftectedby knap-weed enoval.elk enain ing n rr dit ionally se dhabitats away from the old f ield nt ay havebenetltted rom reduccdcornpetition br limitedresourccse.9.,Bartmanlet al. 1992). hus ,e1 kredisbibutionn responsco knapweedemovalmay havebeenanalogouso a winterpopulation

reduclion pproaching.l 32./r.. rerious tudieshaveassociatedhangesn population ensitywiLhchanges n th e population dynarnicsof elk(Buechner nd Svanson1955)ard r ed deer Ce. scoti(us.CluttonBrock eLal. 19132:259-285).

Morcover. knapweed emoval expandcd or-agirg options or thc estimated l ,137c f the

el k populationTable ) whichused heold l ield(H.l). A correspondingietary esponseo tac-

tors inked with knapweed emovalwas dctectedin all three vinters H,ll). This dietar1 esponsc\\"asndicated y t 'ecaJnalysis espitc ighen -vironmentll variabil itywhich may haveoverwhelmedhi sstudl'spower o detect ore subtlediclarychanges f potential iologicalsignificance(White1983). nvironmertalariabil ity ashighbecause:l) knapweed emovalmodificdonlyabout5% (i.e..old field) ol the wi nrerhone rangcofliee-roanring elk, (2) lew forage Laxa ccurredin theold-tield comparcd o t he rernailderof Lhcu in terhornc r rnpe.r rJ l ) p l ln t l - r ' l gnr t .n tsntecescollectedn the old-field mayhavebecningcstcd t distant eeding ites cveral ay sbelbredefecationNelson ndLeege1982). interhigh biological significance iom the facl thatadietary esponsettributableo knapveed emovalcouldbedistinguishcdiom the nfluences ftheseuncontrolled afiables. ikewise.Wickstrometd. (198,1:1299)oncludedha tmanagementrac-liccsaft'ectingegetation n winter angesre ikehto havcprofbund npact on ungulate irragingef'liciency during the seasonwhen energybalanceis especiaJlyrit ical.

The KNAP9Oand GRAS9Odiets wererankco[elated (Tablc3). This u,asan expecled csultof samplingboth diets ron the sanrepopulatiot]dudng he samcwinter Table ), anddid notdi -rninish he mportancc fobserveddiflerenccs e-twcen thesediets which werc rtrributed to factofs associalsd ith knapweedemoval(?rble 2).Further, he significant ank correlationbetweenthe KNAPgo and KNAP86 diets. and a lack ofcorrelation etweenhe GRAS90and KNAP86diets (Table 3) , promotedconfidcnce n th eKNAP86d ie t : r r . r l i Jha .e l ineor rs . c . : i n !

dietary hangesinkedwith knapweedemoval.Therctbrc,hepurposeorestimating he KNAP90diet was served.

Only one reatment itc andone controlsilcwerecompared. heretbre.his study acked ep-lication.which precludedhe useof inferentialstatistic! to test for treatmenteffects(Hurlbert198,1).he -test n Figure3 indicatedhatcratercountsdiffered bctweensites \"lile track countsdid no t. Fron this, concludedha telk lbragedmore on the rcated sitethan on the control site.though hey $'alked hroughboth sites ndiscrilrinately. his,considered ith the other esults fthis study. ed me to subjectivelyconclude hat

tactors ssociated ith knapwccd emoval 1.e. ,the featnlent tself)causedhe observcd oraging

16 Thompson

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response. eplication assacril iccd o e!l luate

r t re r lmen lr l ' \ u l ' l i c i cn li te I r r t . -e -s inc t t rn -agcment pplicationsvhi esimultaneouslyon-tlning environmcntal afiation o that ourd withinthe angeof a singleel k populatit)n. cplicated

experiments, swcll asobsen'ational tudies uch

as hi sonc,ar eneededo advance cological n-

dcrstandingEberhrirdt ndThomas1991).

Factors ssociatedith knapweeclemoval

$,eremostattractivc o foragingelk u 1990 H,III,

Figure ).This nit ialattractionppearcdo over-ide the efltcts of snow depth and$'lnter dura-tion rvhich nfluencedbragingactivit l in 1991-

1993 Table;l). Knaprveed cmovrl may have

attracted lkbecau c: I ) knap$,eed\,as emoved.(2) gr:rss tanding lop ncreased,nd/or 3) i) F

agequalitycharacteristicsf thr:grassesmproved.Knaprvccd and grassstalding crops \r'ere con-

sistent cross ll wintcrs l lcrknapweedemo\.alan dcouldno texplain higherattractionn 1990.

Horvever lbrage quality nray havc been higher

in 1990due o: (1 ) a shon{erm erti l izereflect

causedat thc lime of treatnent by a releaseofnutdentspreviouslyoccupiecl y living knapweedplants Harvcyan dNorvierski 989). nd/or 2)

a one time occufienceof abunclant rccn grass

on thc winter ange.

Morc grass itter waspresent ll the old-field

in 1991-1993, ut probablydi d no t explain hc

abrupt rop n firrrging ctivity bservedn 1991.

Jourdonnais nd Bedunah 1990)observedes s

elkfeedinguse frough escueE scabrrllri)plants

with dcnscstanding itter.While rough escueproducesdense ulis of pcrsistcntstanding itter.

the nontut'tedgrasses revalent n the oldjield(c.-r. . luegrassesndbromes) id not.By ocular

estimate. lk consumed bout 35%ol'the grassstanding ropon thc transects efole25 Febm-ary 1990.and he remainingunconsumcdbli-

age ended o tlatten,presentingDo apparent b-structiono elk eeding n current car'sgrowth

in thev in tero f 1991.

The eflects ol knapwccd rcnloval appeared

to continucatlracting lk foragingact ir, i tyan d

influencingwinterdietsn l99l-1993 (Figure :

Tables , 3.and5) .Prior1() napweedemoval.

high densityofcoarse.per-sistent,napwccd tcmsnrry havc dctcrredelk from grazing he scatteredgrassplants n the old-field.compilrablco the

ellectof standing enseiner on clk useof oughfescue Jourdonnaisnd Bedurah 1990).Addi-

t ionally. rass roductiolr ains oncurrcnl vilhknapweed emovalmay have Dcreased lnter

foraging efficiercy. Wickstrom et al. ( 9ll4) rc-pofted hat dry malter ntake atedecleased 'hen

el k grazed rass tands ith t irage biomasscr'-

els below a thresholdof about 1,500kg/ha. andlhcy concludedt wasulplofitable 1breJk o graze

grassswardsof low productivitl,. regardlcssof

digestibil ity. pplying hcir csulls o thepresent

sludy, he ncrease rom about700 kg/hagrass )1.600 g/hr (Carpentcr 986) aused y piclo

ranl treatmentmay have exceeded production

threshold mpoftant n thc foragingenergetics fwintcringelk.

The oraging esponse felk might havebeelstrongern l99l 1993 fnative bunchgra!sesere

more abundantn the old-ficld.Althoughblue-grassesomprised8% of thewinterelk diet n

theElkhornMountains. ordoD1968) eportedthatelk did not usecuredbluegrassoliage. he

cured bliage of Idaho fescLr,cnd bluebunchwheatgrass ere hcprimarywipterfoods eponed

by Gordon(1968.). ikewise. Threemileelk

werc

aftractedo thebluegrass onrinated ld-ficldwhcn

-qrasscs ere predominatelygleen in 1990, but

foraged essn theold-fieldwhenbluegrasscscrcprcdominatelyured n l99l 1993.

Conclusions ndRecommendations

Elk populationsn Montanaareat twentiethcen-

tury highs Firebaugh 993). oincident ith heincrease nd spreadof knapweed Lacey 1989).Although xistin g abitat ould uppotmoreelk,lower populationobiectives re necessaryir r

compatibil ity it h competing unrtrn scs f thcland (Wildl. Div.. Elk Manage.Plan.MDFWP.

Hclcna.1992). hus, hequestior fwhetherex-i . l i ng nap\ \ ed n e \ t r l i ,n \ ne l l r t n le r rngc:limit ccological carrying capacity s somewhatacademic he nel knumbers re imitcd o a owcr

cconomic carrying capacity, as detined byCaughley 1979).

Neve{heless. he esultsofthis study areper-

tinent o elk managementn two respects . irsl.continucd spreadof knapweed beyond current

distdbutions, nd ncreasednap*eeddensit ieswithin cxisting stands, l'rould oncernmalagelsof grassland inter rangeswho strivc o main-tain hccurrenlproductivity fassociated lk herds.

Second.emovalor thinningofexisting krapweedstands n tavorable braging habitatsmay attract

Elk Responseo Knapweed emoval l1

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elk.potcntially ieldingsimilarhabitat ndherdenhancencnt esults s -erti l izing.urning.an dprcscribed att legrazing Ro\\ ' land t al. 191i3.Skor'l in tal .1983. ourdonnaisndBcclunah990.Frisina1992).

I t ' u r rk r r , ' r rr l t j t ce lk ' r r ! i n t re \pon\cr lthe old f ield wa s representati\ef the responsemanagershould xpect r-om napwecdemovalon tr-pical unchgrassvinter t l lces.Recovcryratesof nalivc angeludsnal bc depressedvhistorical se Willns ct a1.191i5), 'hichwouldrenrain factor c-eardlessfknapwccd emoval.Exlrapolrt ing he resultsof the present tudy.knaprl,ecdemoval vouldelicit the atcest or -aging esponse herepreexisting ensities fbothknapweed ld preferrcdirnigegrassesverchigh.Further at leasta pofiioD ol thc elk rcsponse ()knapueed ernovaln theold-field l,asikcly rt -tdbutable 0a short-terlrlbrage uality ncreasein the irst winter blJ owing icloran trcatment.Th ecoinciclencef massir knaprveedortali lyu i th r r leqr ru tc. r in lu l l r ' p rohrh l l rn rupor

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l -101.

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ol !tockirg rate on a rough icscuc gr.rssl|ndvegetr

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