ITIE R0l;g 0F fil,uil,L Li¿ilrl'ilJ"S À5 FiìtrDirTORS Q"ts' [iE LARCH SÀirIFLYe

FBI€íTT1)4oR$L IIFICüSON}I (HTG" ), IN EJ¡S'llEì]d i'dù1iIToBråu

.& Thesis

Subruit,ted. to the Facr:lty

of Grad.uate Studies and Researcb University of lvianitoba

In Partial Fulfitment

the Requirernentg for the Ðegree of fuiaster of Science

iry

Charles Henry Buekner

S,pril 1954

r:i s 'ë ià::f.è. t.di {Ç&-f,, TF;6 ROIE 0F Siri¿i*:. iLailIiULiS åS PRñDii11l?"S 0F Td Lpilitn SAit-¡'¡Y.

?RisTIpHOILi trRIC¡_ISQNII (IITG" ) u lr"t E"âSrARi\r LIAIüTOBA,

Gharles H" Buckner

åtsSTzuC1

T'he probleni preseated. j-n this thesis was approacned from a predaÙor-prey population st'andpointn Population saropling technio.ues v'¡ere d.eveloped. for the host insect in stages relevant to the study and. ''' for the predator species, and. population trend-s v¡ere stud.Íed. using t.lrese teeirniques" Ooactions of the larch savifly and srnal-l mamnrals were investigaied in a restricted. u::iverse and. it was found that small mammals, particularly shrer{s caJr discrlmÍnate ìretv¡een sour.d, parasit- ized., diseased-, and dead. prey insects" Predat,ion in the field was estimated. utilizing a mod.ificatÍon of an earl_ier cocoon planting technique and by this means ti:e relative importance of raice and. shrews as pred.ators of the larch sawfly v¡as clarifíed" The method. also in- d.icated tb.at' the tine of predation on this insect is more lfurited. than rras previously supposed. and. that predation in this case nay not be a siriple d.ensity d.epend.ent one " It was fr-¿rtirer d.emonstrated- that pred.a* ;,/ tion upon larch sat,lfly cocoons by small mami.rals eonstitutes one of the largest natural control faetors operating against populations of tiris insectu Î}àBTE OF ÜOI$IUI.iTS Fage

INTRODUCTION I " o o o o o o ø o e o o ê o 6s o o 6 oo o o o o o ô s oo o o &o o o o o o o o o ø o o øo E I

IT REVIEIII OF ilE LIT|ÐR"STUffiI è o ø ø øo e e e o ô o o o e ð o @ o Þ o ú à @ o ø õ 6 ø ø o o o o @ s 4

Snall I'fammal PopulatiollS . o o o q o ó ð ê o o ø o o o o ø é s. o Þ o o o ø s o o & ïIome ranges and cnlising radii èoøooôoÞo6ooô0,6es 4 Usg of d,ead trapS oooôêeoðô6soeoooosoooooèqoû€o€ usg of live traps eoqooøoo6oúoô€o@oso6ó€ûøos6ëoô o

lii¡rnrnalian Fred.ators of Forest Insects o &,o @ øoâÐÈ€ô€å*.{È

III n'.IiÜ sTtJ-DY Á&il¿! iillD PLOT DöSORæTIOI{S " ó ð o o Þo e ôo ûê oo 6 6,i o6 o E o ø s 1I IV Sivleãà iiiñ+ri¿il* POFU-j"åTIONS "oaçEoèðooosoos6oeøoosoe?oôoosooeqoê 16 I'ield TeeÌ:aiques s a o ooq 6 e eo o o o oo ô oooo o 6o o ö ó ø êo ø ø s o o € oo t6

ROSUItS e o è e o o o s¿o s go è E o 6 o o o9 oo oso 8ø€ o o o e @ o e o ¿ o ó è e oo s a 2Q Bait effect,iveness roûooo o o{ ' ô oo o ooo o e o e ô o ósô o ê û P0 Specíes conpleäient of a ta¡lanack bog .å6ðae*éóoÉ 2L Ilome ranggs o oo o È e s È ûoq ô o ú ôú o o ê o ¿ o è 6 6 ô e o o oo o s ó ðe Az ,ilopulatioll.s o s o D s o a é s o o e o ô o o o e o o o o o e e ô o € o o ê þ o o € a 24 Refining teehniqueB o ø o o o e óoó o o o ô ¿ ô o e s o o o ê o o o o o o 50 Ilatura1 history notes ôo06ooeóøoooosoooooeoo€oó, 32

lAA V POPUiJaTIOIìS 0¡' ïlE i"lìAÇi{. SÀi'd¡'LY ú ó ôo o øe6Õ 6 èss o 6 oøeoeó oè e6o êo s

VT TÍTE EF¡ECT OF S!i]àLL i,fÁJ',Íi,üìJ. ?BMÀTTOT{ ON T.r*RCE SA'IifFT-Y F0PU-UitfOi"iS ô ¿êø o o o o6 o o o é oco o o oo ôo 6 ¿ o oo 6o e o o c oo ôô o oo o o ê o ô o o 4I The Role of the Frgd.ator ôooôôooooôoEoû¿o@ùooêGoeqssaÕ 4l linoriun Pred.ators of ttre 3.arch. Sav¡fl-y e6ôê6eê*,oÉosoöoé&ô +2 reed.ing Expgrimgnts ' no oÉ o o r 6o ðoòøó oo 6 c c o ê s o o ó e e øåo øðó 4'3 Cocoon ?redar;ion 'Irends Using'the trOocoon llantÉ8 Techni que o o o o o ô o o ü ô 6 o o o o o q o o o o a s ù e o o e o 6 o s ç o o o ø o o o e * +? satr:rati-on Trapping o o ô ê o o 6 ô e qe ê ô o o o Ê É ê q o ø e o oo o6 o o o oès 5?

VTT gunn'ßfi.Y DISÛUSSI0I{ "åiÐ 6 6 ø 6 o á ô 6 ô è ô ó o o ó 6 s a a o o s o 6 o ø o ô o o o o s ø o o s ü 60 Fred.ator and. Prey Populations o*òaooôeooeoø@oesooeeo€o 60 coactíons of snart l\{arLqrals and. the barch sawfly èøËoô n 62

;:(jI]ioirflùDGEiiffii{f$ 6 6 6 6 ø øeõ bøo ø ô ô @soø Eóø@ 3 è ô 6e o oe o o s ø o o Õ 6 o o€ø é è e oøE 65

BIEi.rJOGFAPi{Y . t â ê oe o o @ ø o e $ q 6 o 6o o ê ó o s ê o ô Þ o o e ê * ø o o ø o s o E 6 o ø 6 â ô s ô ô ôoe 66 L]ST 0F Dl'q¡.ïiS

Tabl-e Page

I Per Cent Ground. Cover on ËmalI iåa:rrnal Plots ôoosøooÉ@ou".nu. 12

II Trge Cover on Small lr'ianmaf Plots ooôoo6€oøo6oøeoøooeôøoooou" 14

1Iï The llffect of Bait on Trapping Small i'rlarnrnals ooüoôooeoo@êeøs ZL

IV i{ome Range of 9]gtþgipggntJ|g, I;iicro_LUs¡ aLd. Sorexu60çøo,.u*,¿ 25

V !, Íest for SÍgnificant Differences in the Ra¡gss s3 Iäicrotus and ole_tl¡4io:roffi, on Flot 1 a¡d 2" øéeooosooo uo.o 26

TI tincoln Ind.ex for Ç]._etþiSgggyÊ €epjp.eri, 1952 ,eô€eeqáeoôoeo 27 ffiI X,incoln Index for 4icro-bus p_e_nnsyl_vqnígus_, 1952 osoeoooooáôå 28

TIIï tÍncoln Jnd.ex for $o,rex !ig_?{gllÊ, 1955 .ðóaöeâøoooéoeoaeoo&6 2B

i þffective Trapping"¿àrea for Sna1l LiarnaI Species øøçøêqoae6o -z.ì

X Fopulatíons of Smal} L,iarnmals Expressed as .Àniraals pef Jt0fe ooÊooooooooo€ê6 øøø@q s@6o€s€@ôoosgoe @øog oE ooooEðgp 3L

ãI Comparison of Snall Åtammal- Poprúations per åcre Using tlrapping Thrgg Teehniques oøø6ðêoôs ó oôoè€ ooao oooaeoÞËóur"* 52 ruf *.nalysÍs of Variance on Erapping lechn:i-ques oos@oøâs6¿6ü6uo" 32

XI3 l{atural rlistory Ðata on Sma1l iliaænal PopulatioÐs oEeoe€ono"' 55 llJV tarval ürcp Íryressed. as i:he }'verage Nu:uber of Larvae

pef G ô @ o ø FUnnel r r o o o o ó o o e ó o o ¿ 6 6 € o o o s o o o 6 o o o e o a o o o ó o o o u " t n 37 XU Savufly Populations on Srnall tíia¡n¡nal Flots Ðuring 19ã2 Expressed. as fnsects per /¿cre u øøøø@osøooeoøoeooeeooooôq"" 58

Xfr Sawf1y Populations on Srnall líavimal ?lots During 1955 E4rressecl as Insgcts per Àcrg .6ooosoeáøooésè@oooo66¿o6è"n 38

};V-iT Feed.ing Ex¡rerinent,s üond.u.cted on Three Specíes of S¡¡aLl liäaiurtals o ðo øs o6o eeooeee€@eøoo oo ô@go ooe eoooø E€ o o ô."oø 45 XVïffi Test for Ðeter¡rj.ning åccr:.racy of Cl-asses in Differ* eni:iat'Íng iiioused a¡d Shrev¡ed. Cocoons ooaâooaEooðøo oø&øoaøø 49 rTìa lr-ì a Fage i(H Pred.ation, SruaIl }Íanrnal- J?opulaiions and Sav,ifly Fopulations on Plot I oEeoooooôô sooøo øøø ø 4o',ÐÐøêo6øoøoo€ 52 lüt Fredation, Small ìia¡n¡¡ial Fopul-ations and. Sa¡,'vfl-y Populations on Plot ? ooøooôóôðø@ooôôéoqeeoôoèéûôo6é6ô6eo 53

7 i Pretiaticno Sr:ra11 Ïiia¡rr¡ral ã'c.loul-ations anó Sav'rf15r Populations on PIot S oÞ¿oøeoooeo€ú€oê6oooøeooosoooøo"u"o 54 lüüI Correlation Coefficien.ts on ?redaùion, ii,tammal PopulatíoEg, and Sawfly Populatíolrs oooê ooo oÉ ø6ðoEoo ø E6a6 56 jt{3l1 Relationship Between Pred.atíon and Savlfly Eroergence 6óo6e"or 59 LTST OF T'IGIJRES

Figure FaEe

J." fhe fflrerman }oive Trap Ïd-ith Door Opea "€o6soÞooeø6øÞsooooe@oo l? 2u Tbe Sh.ernan Live TrâF lirith Door ülosed. ø@@êéoEoeooéoøo r"uo*ø L?

ßø TrÍp iiieehaaism of the ,She:man Live Trap u8ø@@oeo@eo@o6ee"".ø lB

4ø Mod"ified Ear 01Íp ldumbering $ystem 606øoøe@ooooøøôs66oo""""* 18

5" Ðiagran of Larva1 tr"r:¡net Used. in !952 too6s@sôoøoô6ðo@no"oog 54 -tjsed. 6u ãrarval Tree Fun:oel in 195õ oóosùoqoosøq@€o@ooøoeoooô.ra 59

7. Comparison of Sound Cocooa and Cocoons Opened. by ltouse

and Shrew s ø oøo Õ € oo o 66 oe o o ô e â qé ø o o e þ o o o o ø ø o e ô @ o o o e e ô 6 o en e 43 " I Ð{TRODUCTIOIII The larch sav,fly, Pristiplrora ericìrsonii (iItg.), is probably tne chief suppressive agent in stands of ta¡n¿irack, LaXi!! laricina (lu noi) (K, Koch") (2I, 58)" lbe insect vras probably introduced from Europe, ancl appears to have been present in North iårnerica since about the beginning of the nineteenùh century (tS, Zt, 31) " Ä nrlnber of serious outbreaks of tb'e larch sav'rfly have T.reen recorded on tiris con- tinent since 1882, causJ.ng sucìr severe morta-Lity to the host tree that it has fallen fron h.igh econornic importance to relative insignificance

(SZI, ;¿ recent outbreak began in I'ianitoba about 1958 and the insect

norrT occurs in eirld.eiiric proportions over extensive areas of ;t"¡itoba¡

Saskatcirer,tan, ontario, and the Lake States (5gi" T-ejeune (fg) nas

.oointed. out ùirat soil ¡noisture, parasites, pred.ators, and. the grovrth habits of the tatnarack itself are imporùant ecological factors govern-

ing populations of the larcb sav,if,ly"

iilthough cìre¡tical control b.as achieved. remarkable success in the control of soitre forest insect pes'bs, tb.e larch savrfly has received tittle attention in this respect" There are two Íìai¡1 ss.rons for this

situation; firstly, taruaraek usually grows in isolated pockets on boggv sites, thus affording a poor target for aircraft treatment.

second.ry, tire larval stage of the lnsect is staggered. over sucb. a long period. that a single ap;olicationu even if it destroyed. atr the exposed. insecfs, r,voulcl only partÍalry red.uce the population (r+) " rbus it appears th¿it contro] by use of natural factors offers grezt,et prom'ise than the use of iosecticides. 2

The.effect of soil moist'r-re ap,ûears to be the rnost iur¡lorbant physical factor governing lareir salvfry abr.rndance. rnsects in post diapause and pre-ôiapause stages are rapidry kirred by frood.ing, but this control is limited to two short and. vuel-L defj¡ed period,s in the d.evelopment of tÌre insecb" Furthermore, -rnhere onJ-y partial control

of tbe inseet occurs during flood:ingu ao adverse effect rnay be exerted.

upon t,iie resident parasite and. predator populations (gS)" .Àpparently the principal control agency of the larcb sawfly in

earry outbreaks nas the introd.uceo ichneurnonid. parasite, Mesorglus

teaùirredinis iilorley, wìrich. nas been credited. lvitb. uJ-rÍnraitely decimating outbreak pop-uiations (L5, 5j-¡ " fn the present infesùation, Ìrowever, iríuld.rew ( 52i has shown that the hosi; has oeveloped. a natural immrrnity to the perrasite in central Canad-a, Èhus d.rarnatieatly reducing its con-

tror varue. unpublished resurts of Lejeune and. HÍldahr (40) sugges! that the only other irnporùant parasite of the insect, the tachinid., Bessa barveyi (T.T"), has not been abre to reach population l-evels to an extent where the hosi populatlon is appreciably affeeted. Parasite releases of tliese tr'¡o and other species of parasites have been 1argely unsuccessful 1n the present outbreak"

The grorrtir irabits of the host tree also tend. to discourage tbe maintenance of high insect popr.rlations over a period. of years" Ás cÌefoLiatíon progresses the vigor of the ta¡sarack is red.uced with an acconpanyiag d.rop in fotiage production, This causes severe competi- tion amongst the larvae, but at'r,he sa:ne time it inrperirs the life of the tree. 3

SrnaII na¡runal pred.ation of larch sa-wfly cocoons has been shov¡n

to be a major cc¡ntro1lÍng fac't or in t,he presenù out,break, having

almost exberminated the insect fro;n scile sta:¡d.s ( z,tJ . llarry vsork in- dicates that tirese animals usually account for about b0 per cent of

tr.e toÙa} rnortality, and ocsasionatly 100 per ceat of the cocoons have been destroyed. by srnall namrnalsu Despite their inportance, litt1e re- search has been camied out to d.eter,aine in rrrore than general terins,

the rofe of ma:umalian Ínseet pred.ators" rsolated notes âp.oear to be tlre only references available in tbis field (Zt, ZZr 50).

Tiris project r,Jas initiated. j.n ord-er to d.eterinine rrrore preclsely tbe effect oll ¡-nanunalian pred.ators on üre population of the larch savlfly" lield. research lvas cond.ucted in the ïíhiteshell Forest Reserve

in eastern lüanitoba. The stuoy may be conveniently subclivid.ed. into tirree phases as follows;

(I) studies on s¡rall rna.rn¡nal oopuLations (e) stud.ies on Larch sa-wfly populations

(5) sùudies on the coactions of r¡rarn¡iials and larch savlftr¡ II ÊlìVIlfd _0!. -Tlü LI'ltiE4,|L'UlìE

S¡,{¿rïJ, i#Jrii'lÁL P OP-tIl¿TIú}rS

i¿ fund.a¡oental proble¡r in ecological investigations ís the enu:neration of the organisr¿ in its naturaL habitat. ÄIlee et al (z) have ad.vanced, seven categories by neans of which anirüals may be censuseô, but in dealing v¡ith srnall marunals this can be red.used to four;: ]- Direct cor:nts ?u Line censusine 3. Trapping

4, Ind.irect metlroos

lhe direct count is öhe rnost simple of aLt tecirniques of anÍrna1 census, but si¡rce ¡iiost small ma¡ruäals ¿rre eÍther noctu-rT.a] or secretÍve in their habitso tire rneth.od is of limited. use" similarly üre strip or iine census (ee, 4L) is oaly prercticar in censusing sucb. diurnaL aninrals a.s squirrelsu ci:ipmunks, gophersc and. h.ares"

f,n d.eterlnining sinall maumar populations, the most v¡id.el-y used

¡netbod.s are tnose utilizlng traps, altirough indirect meùirod.s have been used. to a liiiited degree (411. ttome ranges ancl cruisin,q rad.ii

Before the merits of the trappÍng rrethods can be property discussed.e the nethods of measuring horne range shourd. be reviewed." The significance of hone range wilr be apparent luhen trapping for population assessnent is d.iscussed.n 5

althougir inoirect method"s irave also been used. (16, 6f ) , tlle conventional itay of d.etermining the hone range of an anirnal is tÌlrough

recapture data. Live traps are set in a regular patterrn, and. tb.e animals are lnarked. and. released. in an attempt to catch the¡r at various points in their range" ivianville (46) has reviewed the nethod.s used. in rnaricing sraall m.annalso Once tÌre d.ata have been eollected., there remains the problero of treating them. Several techniques have been advanced to measure ranges frorn recapture oata (600 2?, L3), but these rnake no correctj.on for animal-s extend,ing beyood. ùhe uåtrap reveared.* home rarge, or are infruencecì. by nu:aan jud.gnrent" Blaj.rls ¡retiiort (B) apileal:s to be the most discri::iin¿rting technÍque ad.vanced., rargely oveïcon:ing these objections, anil ii; has been shov¡n to glve the nost accura-te resu-Its on ex*ceqiinental po¡lulations ( 61) "

Use ¡¡f_de¿i{ trai¡s_.

In ¡rost eariy population stud.ies conce¡ning snalt mam¡ra1s u the d.ead trap has been used." Ðíce (rz) suggest,ed that snap-back .i;raps eouto be used. to indicate tire re]ative abund.ance of any one species j.u various habii:a-ts and in d.ifferent seasons or yeaïs, r'lirereas Bole (9) set snap-backs in a grid and. conclud.ed. tba'L tbe number of individ- uals d.Ívided by the area gave an absorute population figure" stickle

{60) hor"rever, pointed out that in either rive trapping or grid^ tr'apping the Ìro¡ne range of the aninals bein.g stud-ied would influence tire resul-ts" Jrni¡nal s otber than those living on the plot wou1d" also be trapped and. this v¿ould greatly increase the population estilrnre.

stickl-e furtherrnore silggested that t,i:e horne range of nany ani¡nars

varied. with popul¿rtion d.ensity, season, ¿rnd. habitat. Trdp d.esigir and. arrangensnt arso alrpear to influence trap-revealed. poi:ulations

(te, fO, 46). Saunclerson (DB) gives evidence tjrat small ruamal-s cannot be trapped. out of an area, but rirost otlier authors suggest tbat the sLevelting offø effect after three -i;rapping nigbts 1s due to in- f].ux from other places. Uayne (ZS) iras advanced. a rnetbod of plotting the results in ord-er to deterrrine wnen tiris occurs"

The meti:rod. of d.ead trapping as a neasure of ani¡na1 populations

is crud.e. unly vague relative figures can be d.erived. until the bome range problen nas been settled..

Use of live traps"

Íhe method. of srnal}-narrmral census that has been exploited to consid.erable erbent recently is the use of live trapping experi¡rents" iJanville (+?i has reviewed. the literature and lists the quarities that a good iive trap shou-]d possess; effectiveness, porbability,

durabii-ity and econoÍlyo ¡rni¡lals captured in tive traps for the purpose of population studies are rnarked ano returned. -bo the population. The traps are usually laid. in grid. faehion and the individuals captured are munbered so that tbey can be recognized. when they are reeaptured." Feterseu

(54r 55) working on fish populations, and. l,incoln (4p) studying i,uater fovrl populations independ.ently derived a ¡ûeti:rod for est,i"rnating the popìúatÍon utilizing the raùio of narlced to unnarked ind.ivicluals in tire recaptwe sanple, ?he forrrula is .I * fir4 where T = total population x ilI = nÌ¡nber originally narked. n - nulo.ber in the sarnple x = nuaber mrked. in the sample fi.icker (5?i ad.vanced. the follov¡ing stipulations on the use of the Lincoln or Fetersen Index:

{ð(1) The marked. anima}s must suffer the same natural mortatiÈy as the unmarked.:

{2) The ¡,rarked. aair:rals ¡nust not lose their nrarks; {5} I'iarlced and. unnarlced. anirnals must be eo¡rally subjeet to sarnp}ing;

(4) lhe ¡narked. anirrral-s must becone rand.ornly mixed. with the unnarl

(5) ¿ff ¡iarked. animals rnust be recognized. and. reported. on recoveryo (6) There can be only a negllgibte arnount of recruitment to the population being sampled. ôuring the sauipling period."$ Using th:is metbod., na-bural migratlon can be accounted. for (bi , a¡ð in íusta¡.ces involving large samples correcÈions can be made for birùh and death raies in natural populations (5.5, gqe 55,9,6, 4i,1, .¿ldarns ili has pointed. out that the raethod. is subject to statistical errors of probability a¡rd has published. gra¡rhs from which the confid.ence lirnits aL t'h.e g5 a¡rd 99 por cent levels can be readlly obtained.. An excellenÈ reviev¡ of ti:e techniques involved. in the use of recapture d.ata has been trrublisbed by Bailey ( 6) ,

In work on s¡nall plots, nlany of the anirnals captured in Èhe outsid.e lines of traps are living oniy on a portion of the plot and I tlrese aninals v;ill increase the population estimat,e manifold ( oo) " Blair (B) suggests that t¡cere no natural barrier oceurs arou"nd. the plot, a bound.ary strip be ínclud"ed. equal to the cruising radius of the e4leriurental anir¡1al, Tire @area trappedrt is thus the area. encompassed. by the traps whilst the iteffective trapping area* is the area trapped. plus the bound.ary strip" Stickle (60) r¡.akes a sirnilar corection for circular plots,

Tb-e }ive trapping method. overcorûes many of the difficuJties experienced. Ín d.ead. trapping, since räJlges can be calculated for each species, sex, age, habiiat and season stud.ied. at the tj-lne i,Le popula-

Ùion is being a.ssessed." Ït is, holvevere more expensive and. laboriousu and. is i:*practical- r,.¡here only general treno.s are required "

j!iiú11,44¡Ji!N g¡ijül4IIû8L g¡'. FOBusT INSIçTS

The role of small- llla¡ünâls as predators of forest insects has receÍved. varied. attention in ecorogica] lsyestigations" Hewitt (5r)

¡rentions ma¡uialian pred.ators of the rarch savifly as d.oes c,ra¡ra¡r (a3i and several otner authors" Bess, spurru and Littlefield (?) su.ggest that marn¡Els are important in controlling the gypsy motJr, uar¿y (zo)

¡nenùions taeir inrportance as predators of giIr¿-on simitis in Ëoland., Schuinanov (59i consj.d.ers then effective Ín controtling cicada outbreaks in, Russia, and. I'iomis (48) has sb.ov¡n them to be important pred.ators of the European sprüce sal,,ifly" Tbe List of l\]ortb. .{merican mamnialian species hrown to prey upon forest insects now nw¿bers 20, iucluding two rnolesr seven shrews, one chipmunk, one flying squirrel, two deer nice, flve voLes, and. two jumping rnice. In addition to these t,here aye L4

species tnat are suspected. of preying u*oon insecÌ;s, including tv;o leinmings, one chipäimk, one flying squirrel, t]:.ree ground. squirrels,

three squirrels, one skrlnku and. tnree weasels, as d.eierrtined by l-aboratory änd f ieid observai,ions"

Tìre effect of s¡ra1l ¡ûaÍunal predat'ion on forest j-nseci poirula- tions has recelved attention fron severaf autirors vuith varying con-

clusions. Her,uitt ( 5l) in 191-2 ¡roted. that small na:rnnals feed. upon cocooned. Iarcir sawfly larvae but placed. Iitile value in this predation as a natural control" grah.an (21) usiug cocoon collectrons errid plarLted. cocoons suggested. that sr'nalL rnar-rnials exert considerable con- trol on larch sai';fly populations, often consuruing 5úlo of t,he over- wintering populal,ion and. occasionatly taking 80 - Ieoþ" He consid.ered. inice to be ¡nore inportant than si:.rews by virtue of the hlgher popula- tions exhÍbited. by ni-i.ce" Tiiis view is supported. by Fla-rnilton and Cook

(24) wno suggest thaù s¡ÌaL1 marrnals often hold. in check insects whlch would. otirerwise become an econoÍûic problem" Hard.y (zo) using cocoon col-Iections has sirown l\at 46ji of lliorion similis in ?oland. were opened. by smll rna-mrnals d.uring 19:16" IIe points out that there is ofien consid.erable overla-opÍng of control factors, since srnal} ¡nanurals wiLL pTey upon parasitÍzed and. diseased cocoons" IIe suggesi;s tbat this overlappíng occurs randonly. iIoruÍs ( 5t)i on i:he other hand d.isagrees v¡iüh this asswapùion since he has sj:own that mamrnals can differentiate between sound and. unsound. cocoons to varying degrees cìepend.ing upon their insect,ivorous nature" TO

It is C.ifficult at the present time to d.efine the impor-banee of small namnr¡Is as forest inseci pred.aùors, sin.ce Graha¡r (¿e) r'Ianilton and. Oook 124i, and. i*omis (SO), suggest thaü tnese animals exerù eon- sid.erable control on sawflies, wjrereas Hewitt (51), I{ardy (eS) ,

Balch (4j, and Bess, Spurr and Littlefiefo (?) corisider theilr as a reiatively riÈnor natural control factcr"

The role of srnall marmnal pred.ation on forest lnsects is re- ceived. with nixeô opinions by entomologists. ft seeJns tlat "otd*tr small ¡nannrnals d.o exert sone control on irrsect populations and it appears fron tire literature that at tines tbis may be consio.erabie.

Frevio¿s investigations have no'u exa.-rnined. the problen fro¡n a pred.ator-prey po-oulaiion vievrpoint, and. at present this seeJTrs to þe the most promisiag apÐroach. Once the role of nammalian predation on forest insects iras been estabiisned, a bettæ id-ea of ùhe control thai; rigJrt be eryected. fro¡r this source will be gained, and. in developlng manageinenù plans the utilization of sniall ¡iamrnals as rÂre}} as other natural control factors sirou]-d. be consid.ered.o ïn ad.d.ition to this, srruarl ¡na¡un1s night aid. in spray controls by eorrsurulng in- sects that are knocked. d.or,¡n by tÌre spxay but are not affected strongly enough to be killed." III ni4 SIIùÐY *StE¿i lil\jÐ 9L0T DSS0ËPjIONS* LI

Ðuring tire spring arld early sur¡ner of 1952, four small-maÍunal plots were estab]lshed. in the lïhiteshel-I Forest Reserve in eastern ¡ranitoba" trlJ- plots are so*u,are, enclosing aa. area of 4,9 acres (i.e, ? chai¡rs squarej, Trap positions are at one chain intervals and. are located. by a four-sid.ed. blaze on the nearest treeo This gives eigb,t trap positions per line, or ô4 per plob" The one chain lnterval was arbitrarily chosen by Ðr. R.F. ì,lorris (49) a¡d. it v¡as d.eened appropriate t,o ad.here to this spacing in or.oer to niake data of this

eryeriment comparable, especially since lta¡ne (50) has shov,¡n a varÍ- ation in the apparent hone range (of ì',iíÍcrgtus) in relation to the intervaJ- betv¡een the traps"

Tables I a¡id. IÏ give the d.etailed ecologÍcal description of t}.e pÌoù s. Plo'b I.

l.his plot is situated,2;¿ miLes south of Red Rock lake and. may be d.escribed. as tall trees on a dry site" Tire tamarack in this bog are 50-40 feet in height. Black q)ruce, of ti:Le saÍre general height as tire ta¡raracks occurs tirrougþout the plob and is the pred.ornina¡t s¡recies in tire southwest corner of the plob. The ptot is bounded. on the ea.st sio.e by a road-, on the north by a drai-nage diteh, and on tbe vrest by a rock rid.ge" The und.erstory is chiefly ald.er on th.e east side, clranging to labrador tea tov¿ard.s the v¡est"

3Io! 2"

'Ihis plot is situateô near the Trans-Cariada Highuiay, approxi- lz mately five ¡uiles east of lìen:rie, Ì*ia.nitoba" [he site is ory and. open witli Ín.terrningled ta¡rarack and blaclc spruce about 6-l-2 feet high"

Ground cover is raainly labrad.or tea, aod.-pitcher plants are corülion tirroughout,

B_lot _2å..

DurirLg the spring of 1955 one ¿rcld.itional plot tuas establ-ished" Thls plot is l0 chains west of Plot 2 and. is similar to it,

Àf,vu vo

,Or".*"" is located near the north. end of Red Rocic l,ake in an ex'bensive, pure tarnarack stand" fite trees are tall (about 4û feet in iielght) ema 'i;rre site is i,uet" Uod*"utory is ciiiefly alder.

Irlot Þsr.

Tiris plot is about five chains south of Plot 3 and in tbe same stand.. The general description is the saine as tlr.at of PIot 3 u -with the exception thaù in the easterly tv'¡o chains the ta¡iarack tend to thin oui and beco¡ne sonewhat smaller (approxinntely ?O-50 feet). TjrÊr,E 1

Per Cent Grormd. Cover on Slnal-l jüsJnnal F,lots"

Component ¡rlot l- Plot 2 stot ilr P]'ot 5 Plot 3A

lvioss t 56"0 4"6 zL"$ t 7"2 ].9"4 t 4,A 16"g È 3"5 11.6 t 2"9 I'ern "4 ug- "1 Herbacious plants

Grass 4"0 * 1"2 16"5 å 5.9 r rl-U l8,e 4.1 IO o'¡f " D L6"g t 5.5 a^+ Þeo.ge -Lc-á t ó ¿ -,'+-^ å ¡z a* " 6"9 ¿00 C.b InU Qøó - oY ?.4 ! L.L Smilacina 2.O t 2"8 t 1"3 ! ".L L"Z "5 Viola o4 -¡*-.,O ¿ IoU : -Lo 5"9 "g ta J- l+ragilus sO - oJ- ^! ;. oë 'l- 2"4 t ,1 i\,iianthemun ¡1 erÈ - "V{! Caltira L.2 - "L2 L"2 - ,25 ¡ ¿;1 Sarracènia OoÕ : .I 9,5 t 2,5 Unidentified. a "2 1.9 iüoody plants

Jrlnus 5"2 f t L,2 2"5 1"1 4.1 : 1"6 '1 X Êô+añ "6 L.? Qotr¡ - Lo. lJ u ru!RI']ï' I (Contsd)

ler Cent Ground. Cover on SliaLl Àitanrnal Flots"

Conponenù Fl-ot 1 PIot 2 Plot 2A Plot 3 Flot &l

Ledum 26"0 É 5.5 L',l ,'Ì * ',ó.5 10"5 É 2.9 11.6 t 2.9 10"6 É 3"2

Vaccini¡¡n u4 'l ,2 È 2"3 +,Y r r.ö

È ^^+-^ + ^¡4r- on{-a .frromeda 2.8 1.7 6"2 t 1.9 ö"4È Ioö äø¿*. t Lul- úoV ^ oI -E iJrunus 2.4 "L Saplíngs

ìÊ+ô Betula 2n0 É ¿oLJ oá t "1 - l"g "B È Ficea "4 5"1 1"6 4"E-t L"7

+-. Pì'..+^- Surface v¿ater 7.2 È 3n? 9"6 *' 2"0 JU uI ; b"b 29" 6 É15 ,5 ÓbOU å öôi, titter 6"Q x 2"4 t tz o1't ¡ "4 u4 ,t"z !"¿L .)ø 6¿ - )-6'! Ðecaying È n-l- logs 1"6 2"9 "4 oÕ - oI

H+ ThBl,It II

Tree Cover on Small lilarnmåI Plots,

tonrponent Plot L Plot 2 Flot ?*; Plot 3 Plot 5A

Tar¡rarack

Àverage D"B"lI" 5"9 2"2 5"0 5"f 4"9

Íltems per acre 512,0 187*0 205n0 260 285"0 "O Black ,Spruce

ilverage D.B"H" 5,4 9,6 5,9

Stems per acre 156"0 1e8"0 217"0 Jaek Fine

åverage D"B"H" 5"1

Sbeurs per acre e"0 / É Ë r- Àñ t A þ Qtown cfosuse +8"5 5"+ 1].3 5"5 15"L 5"6 55,9 t 5,6 *l ø9^ ' *oY^

H ïV Sì'JAIÃ iúi'iliivr-¿{L POPUiJiTIONS 16

FIEIÐ TECiiI.rIGJirS

ïn ord.er to study the populations of small ¡nam:aa1s, a supply of ?5 Shernan traps was obtained (see 3-igure 1), as it was found that t-aey neet, tÌre d.esirable characters outll¡red. by Ìlfanville (46). The trap is constructed enti:e ly of rtetal. and is set by press- ing the d.oor, which is hinged at th.e bottom, into a horizontal posÍ- tion wirere it is caught by the treadle ( see Figures 2 and 5) " r'enj.inaLs are attracùed. by tne bait v¡hich is placed. on a platforn at the back of the trap, anð are captured lEhen tire door is released- after the anirnal

ì:as passed. to the treadle, ¿rithougb several baits ¡¡ere testeclu a paste of oatmeal and. peanut butter was found to be tire most effective, and. this ean be placed. in tbe trap before tra:asporting it to the field" The traps were placed. and. set in tbe rnorn:ing of the first t,rapping day of eacir.oeriod,, and. exanlned. in the morning each day" A tally v'ras mad.e of all aniinals ca-otured., u¡rder the follov¡ing categories;- trap mxrrber, species, small nan¡na1 nu¡rber, sex, age, parasites, i'{hether tarked. or un-rnar1ced., and. -vuheùher iiving or dead" Living ani¡irals were handled by siiaking the¡n lnto a i,uide mouthed ga1lon jar" The n-r.uubering systenr used in 1952 v¡as a nodj-ficatlon of that outlined. by

Burt (15), vuhich" utllized. ear c'l ipping. Burt nu¡rbered iils animals by punching a snaIl hole in the edge of the ear, using five positions" Morris (51) found. five positions d.ifficult to recognize on snall-eared. forrns such as slsre!_llås ancl recLuced. tiiis to tirree (see }-igure 4) " irfinety-nine mice san be nunrbered'oy tiris systern, and since no ;olot on }-Ígure lo

Sherman Live Trap with Ðoor Open

Figrrre Z"

Shennaa Live Trap with Door Closed.

Sigure 5o

Tríp iliechanis{r of the Sherrnaa },ive

Figure 4,

Itfodified Ïar tlip Nulrbering System

¡g r,'¿hich Live i;racs are used is close to any otber, tire ani:Lals of each plot are nuiabered. consecutiveJ-y, beginning at nuinber one" Each species was numbered. sei:arately.

In 1955 tìre ear-clipping netliod. of nu:nbering vlas replacecl by the use of metal ear ùags applied. r,uitr a pair of pincers, and. the handling jar replaced with plastíe food. bags"

In ad.dition to live traps, snap-back trErs of the household. variet'y vuere used. on PIot 5å and. in bait effectiveness eçperinents, and. on;llots ll¿i and Ùit ín refining trapoing t,echniques" -å furti-ler problem is keeping anilrials alive in the traps for perioos of Írorrr elgirt to ten Ìrours. shrews, especiarly of the genus

Sorexo are par-f icuiarly d.ifficult to lceep ¿. live, evetr Ín v¡ann rveatb.er,

Pearson, (53) points out that resti^ng sÌrrews.Lrave a higher rneüabolie rate tb.an ¡irice of tire same size, and therefore require a prod.igious a.nount of' food., Llewelþn (44) suggests that an abund.ance of food. in tbe traps i¡¡il] reduce nrortality and. erim-inate the need for cotton bed.d.ing i¡ cold.ln¡eather" /L inouse carcass was used. as food. for shrews in 1,he live traps, but five sbrews captured r¡¡d.er these cond.itions rvere f orurd dead, the carcasses left untoucheo" possibly tj:e sÌ:rews e4rend. their energy f igirting tire traps and, refuse f ood., IIovJever¡ a snrall c¡:antity of oatrnear;olaced..ln the traps in l{ovember seemed. to aid. in prolongine ljf e of trapped ifictqLge and cleLhrionomys" Dr:ring L953, si:rews rì¡ere successfully live trap*ced. lry rrnning tÌie lines hourly during the nightn IIíJSÚLTS 20 Bait effectiveness Dr.uing tile 1952 season the effeetiveness of three tylies of baits vlas stud.ied." Frelim:inarl' experinrents ind-icated. tbat a mixture

of peanut butter and. oatnieal v¡as superior to bacon rind. as a ba1t. A trapline of 50 snap-baek traps baited. with bacon rind. yielded four iviicrotus Ín the first tbree nigbts, but l¡¡Ien the bait v'¡as changed. to the oat¡ieal a¡d. peanut butter rnixùure, the following tirree nights yÍelded. seven ad.diì;iona} I{icqo'Euq and. five 9}etTrrionornys.

¿r.n obvj.ous objection to tne prelimj.nary experiment is tirat the effects of the bait nere not tested. on the saroe nights" liie difference eouJd. írave been caused by some other factoru such as meteorological- changes" In ord.er to overcome this, it was deceid.ed to test the bait t;;pes simuLtaneously'" Ðuring live trapping in early Ju]-y on Plot 2a tvso Lines of träps (16 traps) irere bajted. with oatrri.eal and. peanut buùter and. t'wo }ines witb old cheeseo Tlrree n:Lghts of trapplng captured sÍx if1cgo,Þng and. three Cle.th_rionorn¡¡s using the peaaut butter and oatrneal, wi:ile not a single aniütal was captured in the traps baiteC. i,Jitn o1o. cheese.

lSefore tl:re first trappl¡g period. on FIot 5.1å, the three t¡pes of bai1; v¡ere used. on six lines of snap-back traps, fV¡o lines ln¡ere set usÍng eacb b¿rit type, and eacÌr bait type Tr¡as separated. by an intervenirrg iine" Ti:is arrangenent r,,¡as maint¿iined. for ùirree nighùs, givÍng 48 trap nigbts for each baj.t (i,e" one trap for one nÍgbt is one trap night, hence 16 t,raps for three nigþts is 48 trap nigjrts].

'Iable Ifl sirorvs a d.efinite preference for peanut bu-r,ter and oatmeal . Î*¡RL;E III 2L

The nffect of Bait in Trapping Snall ir/ianunals"

No. of captures in 48 trap nights

Oatmeal and. Bacon Old Species Feanut Butter Rind. Cheese

Sorex einereus l0 4 0

S. arcticug 2 o 0

Ê. {.t¡nnqg

Clethrionornys &app eri 1 I 0 i:iicrotus pennsyivanicus z I 0

ïota1 16

Species complement of a tanaraek bog.

The follor,uing is a tist of rnarnmals wÌricir Ìvere eaptured. or ob- served. on or near penilanenù plots durlng the study" Subspecific id.entification f olloiqs, jrnderson (5) " Sorex eineqeus ci4erqgs r Keæu - cinereous sirrew

g, arctíggg a{elisug, ?ierr. - Sad.d.le-backed. sirrev¡ S" fru¿eus furneus- niiitter - Snoky sitew

l3l-arina bre-vicaud.a nianitobensis - short-taiLed. shrew I;1uste1a, err+iqea rigirardsonii, BonaparÈe - RichariLsones ermine ?erornyqsus rnanicuratus baird.ii (-Hey an¿ Ken¡icot) - Deer nouse ClethrionoraE; Aaoperi ]-oringi (Aa:.feyi - Red.-backed vole Micg:tus psnnsylvanicus d.n¡-nmond.iÍ (¿ud.ubon a na*ärani - Fietd. vole

zapus iruf.sonius hudsonius (åinuuernran) - Mead.our jurnping mouse 22 9ite!-us trid.ece¡lLineatus tridecerlineatus (líit,chel}) - Tiri.rteen- Striped Ground squirrel !" frqnkl.Lnji (SaUine) - Frankl-ines ground squirrel Tamiag striatus_ Arlseus ,iciearns"., - Easiern chipmü¡ric Eglaniå-s- miLjgnus negl-_qc_!Uå (Átlen) - Tfestern chipmunk Ta¡riasciurus hud.soni.cus hud.sogicus (ErxÌeben¡ - Red squirrel

Frobably fev¿ of the above species can be consid.ered. inpori;ant as pred.ators of sai,vfly cocooas if it is assumed that relative abund.ance of t'he various pred.ators d.etenn-Lnes the extent, of pred.ation,

The recl-baciced. vole, (ttethrionou¡r.å åal¿perl) . is universai on l;Ìre plots exa¡nined. tino is possibly the most impor-Lant rnamrnalian insect predaior in this regi-oa" IligÌrest d.ensities of this animal were recorded. ín the ta}l, d.ry sta:ad." The field. vole (iriicrctlrs pen:esy.lgaqicu,q) is prob-

ably of consid.erable importance in dry, open stand.s, wbire the shrews,

(S,orex g!ngå*å, S. arctic"rlg, Ë" f\¡¡!eÈs, and. i3lerrina þrevicaud.a) , are imporbant pred.ators in dense, vuet stand.s. The deer rnouse (Perqmtrscus

manåculatus) an¿ the mead.olt jumping rrtouse (Zapus hudsonius) vsere taken

in sna]l- nurbers on the peripheral regions of tr'¡o bogs and they are

probabl y of minor ilrportance as pred.ators of tbe }arch sauif ly.

Home r?påqs_"

T{}ren trapping on small areas it is d.ifficurt to derive a true po.oulation per acre figure, since rnaay aoiriLaLs vririch reside iminediately

ouùsid.e the trap bo-r¡nd-aries, wand.er onto tl:re plot ana are captured."

Tiris error can be eorrected. by ad.oing a bounoary strip to includ.e 23 aninals living outsirle the trapping area, lies-r, autb.ors agree that this bound.ary strip should. be the v¡idth of tb.e emising rad.ius of each a¡ir¡ial slrecies concerned, and. perhaps of eacb. age class and. sex as v¡ell" In order to calculate ihe bound.ary strip therefore, the home

of the various speci.es must be lcrownn "anges The usual procedure in determining tire horne ranges of snall r¿arnrnaLs consists of trapping, numberíngu and. recapturingn i{ovuever there is consid.erable d.isagreement a:nong the varÍous authors as to how the d.ata should. be treated."

iluci

(b) The boundary is noù subject, to hrunan eruor or jud.gnent" tcj The method. can be used. in a r:niform manner by each person

concerned, with the C.ata,

(a) Lrire rnethod. is botÌr sinple .and. aecurate"

B,egardless of tire meti:od eroployed., a certain amount of judgnent must be exerted., particularly to exclud.e insufficÍent data" l"niroals captured. consistently in outsio.e lines should. be excluo.ed, and each anii::al should. be captured. in at leasi four o.ifferent traps before it is inciud.ed. in tire salcLrlation of home rangese i"íhere an aninal con- stantly returns to ùire sarne trap, tire trap sirould- be kept closed. so t'hat tile aniual wi}l have an opporbuniff of being capi;ured. in other 24 par"ts of Íts ¡nngêo Table IV tists the home ranges of tbree specieso It is of interesi to note that i;he horre range of Ctetþriono-qyq is similar on both d.eterminations on Plot 2o but these do not compare v¡ith the ranges on Plot 1" Since the oopulation on plot Z had approxinately doubled. by the second d.ete¡mina,tion (see Table ]i pagebil 1t suggests that the range of tbis species varies u¡ith habítat, but g! vrith ciensity, for the population leveLs experienced. during the e4periment" Table V shows t'hat no significant differences rryere found. in tire cruising radii of male and fe¡¡ra1e lÍicrotus, nuile anC. fenale clethrionomys, and. in the ranges of Qlg!þr¿enqnf,Ê at two different periods Ín ü¡e year on the sa¡re plot" F'owever, the difference in the extent of the ranges of c1_eler_ienq¡gy€. on closed., clry site (ptot li a¡d on open dry siùe (i'lot 2) r,¡as hiehly significant.

Populationso

There are severaL ;netbod"s for deterroining populations of srnall

¡rai-ornals, nost of which give only relative abundance. It is of ad- vantage in woric of this naturo, hov¡ever, to oerive population per acre figuresu aod for that reason ihe Lincola Inclex ¡netirod. vras eid.opte¿ (+g)"

Tabies Tr, vrr, ard lrfr List the populatíons of cle_tèr:þrqqirs and.

¡,{lgg!g€ and. Sorex as d.etermined. by the llinco}n Ind.ex"

In srualI rna¡amal poptl-tation v¡ork a l,incoln Ind.ex ca¡ be d.erived for each day except the first (no a¡inals aïe rriarked. until after the first day). This raises the question of accuracy of the various d.e- terninations" There are several possibirities to consider when 'üim"d ïv

Home Range of tlethrionomys, I1Ícrotus and. Sore¡c"

Range Cruising Standartt Nr:¡nber of Date Speeies ia radius d.evla- meaSUire-

I 2',1/Trr./52 tletnrionomlg &1" -^ gg "60 90 Ê, r'l ¡-*-* t-. ^- fl !8 t- i¿'r/ u Lrl Ð'¿ ¡'" u52 fÐ

fg ff L6/\IATL/52 MN .@ 64 No range

SP fg | t6/wr/5?, no .4'l ,77 f 'áð^^

- ^ l*+ l-^ ft¡ td Lo/ u LLl Dra luuF .4Q 7I " J,, uì p-2. / ?g/urrT/52 ill" u49 fIU-^ -, zLlvrrr/52 t0 JoTN 'to "43 fL4 }L]vtTT/52 uu TiI"F. "46 tr" L4 A.lI periods ¡g t? ii;i"I. I -^ "43 76 Éru-r.^ 2T Éf rt VA 2't/vrr/5a l\,i u ¡' otÆ eo " f, L¿h 11 r6/vrr/52 ],iicrotus p. M" 68 "46 tL7 r6/vrr/5?, ff 9s F" v8 /o¡ "4Q rav l-*-- l-^ ^La/ ^ uLLl Ði. fd f8 lú,!-'" 1"40 73 i'n L2 r t-a.-- t -- - -- Qnrov a Ìú Lvl r.t;/ Ð,5 vv¿và vc 2 tõ9 (range L3+^L4+I qtl TJrtsLlt V t Test For Significant Differences in the Ranges of iriicrotus

and. Clethrionornys on Plots I and 2,

iuiean dif* "a'l ¡F + Species ^+ Source ferenee S*.I¡ UoJ- 6 l'.05 iriicrotus á females rso males of7 8'2 11 1,06 7,"20L

0lethrionorn[Ê 2 f8 tt fs 'l "44 l-9 1"08 2,095 .f8 2 period. 1 rt period 2 19 l-o23 2.095

1d I and. Ê l'Iabitat If$ habitat B 15.5 L,?4 30 8.8& & 2.Q42

& & Signif icant at }p levelu

t\) 2r7 Tå.BLE VI

Lincofn Index for ülqLhqigu.eliyq gqp_Lqq!, Ig5Z" li"pproximate Pfot Date m x n g 95'lt Dead. Fopulation confidence (D) estinate terval TéD - ^^ /-...- J àial u tL 6-- 251,{ÍÍ 647I1 7-26 11 24/vU 958L4 LO-?7 L+ ^ é /rì-+ i¿Ðl v rL 1r91620 14-53 I ZL ?,6/1frr Ir9112L 19-Ê9 2 z3 2't /urr 19 11 L2 2L 20*?,7 2 23

¿ecu:nulative 27 23-58 ãY

!-iaa1 3 d.ays 29 59 26 22-40 2 28

2 Ig,/T-tIr/---*- 2 '¿;u^- ULLL 221919 TJuu ;; i¿íal u lLL 16?L+52 25-50 t qrz, /-t--* i¿'ôl^- v lLL ¿0 10 19 58 51-56 4T ,!+/ u LLL 28 I? 16 5? 35-+8 + +L

¿ccr¡nulatlve oö 6l- 48-85 65

Final 3 days ,a ?9 49 47 +o-62

9 1/Ð 4 al-LL ? ¿ L2 ã]too L4

Temn/X vsnere T = total population n = number origina_lly marked n s size of sarople x g raarked. aninals in the sa¡nple 'Irim-Ë V-II 28

Lincoln Inùex for i4Lgsqbus pennsyl_gani_cgge L952.

.l'rÞp30x1nate P]-ot Date 95ib Dead Pooulation confi dence (D) estirnate intervaL T / D 2 eivri -; I loiltlr 2832 I8-6? .Ã - ,/.*- IJ-,/- Vr¿ 1e +72L 15-35 F 26 La/\Tr:r. 15 7l,226 19-40 51

Cr.muLative I5 t5 27 sL 22-50 'i! IÐ./ VJr L? =LUQA 58-89 I ort Á/l q LOI^^/ñ- u LL 25 R 1L g4-64 53

Cu:nuLative 25 L2 27 47 46-83

î*rRiR VIï3

Lincoln Index for Sorex cinereus,u 1955. Jrpproxinate PIot Date Time ¡r x n T 93/' Dead PopulatÍon confidence (l) estinate intervaL f I D

2L/-)ü. ¿400 2 'l 100 <) 56 ã-ro o 200 14. 2 69 4-42 '1 I0 500 Ã 7r2 't-ôö 2 L4 400 6 3 5I0 7-2r. ñ 15 22/XJ 23/VJ 2+OO 6 ^ 7tI ?-46 7 ]-8 100 ñ ?IL 9-?,L 19 g r^ 200 ? ö^ -LU Y-L'I I 19 i]UU 10 ô 815 10-25 2L

Cunu].ative l_0 51 5t L? L2*28 26

Fina1 5 hours 10 t-8 2"5 15 LO-22 29

cboosing the final population figure, The final d.eterminatioa might be

used-, an averate of alr the d.eter¡ainations, the plotting method of Hayae (29) (rejected by ùhe autb.or, 1931) or a method invorving the conbining of the d.ata of the final three d.ays, suggested to the author by Ðr" G"B" 0akluJrd"' 'ldhen the tincoln lad.ices have b een ceJ-culated", a cleeision must be rnad.e as to whicÌr value is the most accurateo Upon examination of

Tables \rf e lTI, and. VTII iü appears tirat the accumulation of the finaf tbree determinatÍons gives the least variation in confid-ence íntervals and. ít wi]I, thereforeu be used. in further work on populati.ons*

fa sone cases, the numbers ivere too few to cornpute a Lincoln

Ind,ex, so the number of individuafs captured. v¡as used as the nurnber of

individ.uals living on the Éeffective trapping areat?"

l?hen trapp.ing on s¡ia}l, plots there are often considerable øbord.er effectsrf caused by aninals resid.j-ng rnainly off the plot vran¿er* ing onto tbe plot ano. being captured. in the outside lines (eu oo) o rn ord.er to calcuteite the rseffective tratrlping area", a borrnd.ary strip is ad.d-ed. to tire pIot," This strip is the average cruising rad.ius for the specíes concernedo Table ffi gives the effective trapping area for the species encountered. on the various plots"

1" P ersonal con¡nirnícation. Gn B, Oakland, Ottawa, Llay 7 e ]-,953" IhB[Æ Ði 50

iiffective Trapping Area for S¡r:a}l liia¡r:na} Species. Effective Flot Species Cruisine Radius /*uthority trapping area

- tñ r \ LandS Clethriono¡rys B9 feet uâJculated t.Y f, 9,4 acres Xiíerot,us ?3 s8 39 (pZ) 8"5 Sorex 159 ff ,f (P2) LZ,2 ft Peromyscus r55 1S liorris (fs+e) L2"L e1 Zanus r35 {_1 QuÍ-nby (re¿ri 12.1

Clethrionomyé 76 Calculated. 8ne Iiicrotus 73 8,5 Íî f: Sorex 159 T L2"2 Peromysggls 13õ f$ tuiorris ( fg+a) 12"I . / - \ Zapus L55 fi quxÏioy \IvÐI,^-- L2.T tg

The popuJ-ationsof the various species of snal.l roa¡o¡rals on

FLots 1, 2 and 5 are shoun in Table X"

RefininB techÅ1ques"

In refining small roammal population technio-ues j-t luould. be of ad.vaatage to d.ispense with live traps in favour of the more convenient snap*back traps" Ðurrng the 1955 season a plot símilar to FIot Z was established. (?rot âÀ) and. snap-baclc trairped before one perÍod. of }íve trapping oa Plot 2" In ad.ditÍon a standard t,rap line consisting of õ0 traps placed. in groups of five (one yard. apart) at lo yard inter* vals al-ong a 100 yard. line Ìvas operated. concurrently vrith the snap-baek grid. trapping" The results are shoi¡¡n in Tabies lf and ËI"

The analysis of varÍance ind.icates that the three meihods of t'rapping yield. sirailar results" Ifov¡ever the experiment should be replicated. witir the tbree types of trapplng rui. concurrently before final conciusions are d.rav¡r. TA.B1,T X

Populations of s¡natr r{ammals rl:rpressed as .aninars per "acre,

Total Total Plot Date Cl-et,hriononryg ldicrotus Screx l'erotnyscì.ts zapus iiitlce Shrews

2? /vß/ 52 5"0 o02 oV ,8 4,02 ¡ ' l*- t-- Lt+t u Ð.1 "2 "'l Ll u1O6 r2% ,825 0 ,w2 .825 L6lrw 5-ó ln 710 o 706 L.520 "169 4,916 Iu3Ð Mlurr/52 4n24 Â ta*+ t-^ ^ J-o/ u LLl Ð'¿) l.r0 6059 øQil u01 0 8.70 ,20 2+/Vr:rr/52 6a22 o59 "33 ,oI 7,I5 L/w/52 4* 50 ,15 oJL, rzlvl53 "11 0 4" 96 u15 "481 "L18 r'à48 U 605 ,2+8 ffil\rul55 608 99'i¡ " " ,705 0 1"478 2,23 zlufir/5ú ,82+ 5.06 "165 "?:3L "165 0 L,?eo 5006 zl]Jvæ e r.09 1"17 5" 5l 0 0 2"26 17 r21 æ/TWo."5 ]"09 L,29 1"89 o165 ñ 2u545 l_"89

L2/VAL/52 ie 2,23 0 0 L"24 ^ /-- t-^ | "64 "60 2,29 ólullc,5 & o 5S5 *235 5"22 n 0 768 3,22 " ?,O/wrT./ 53 *745 5" 2g 0 "000 0 "745 5.28

& De'bernlned by snap-baci< traps in close proxiníty to perrnanent sanple plots*

HCrl 32

LABIE ru

Oornparison cf S¡rta}} L,ia¡nmal. PoprrlatÍons per ¿cre Using Three Trapping

'Iechniquesu

Type of trapping Date GlejLþrio_nomye ii,Iicrgtus Sorex Lgrlmuicus

:--* I Live traps on gr1d i.,51L.t/^- Ð,5-- 1n09 Ln?9 n165 t--- t-- Snap*backs on gÏrd al^ LÀ/ c,5 lo 09 ]-*17 o000 Snap-baeks on 2/IW53 Io54 1" 38 2"+2 line "o00

TIqBIE ]ItI

}-nalysis of Varlance on Trapping TecJ:niques"

Source d."f s ns. lf"s. !'6 F"05 " Ir nr

q Species I 5.096 19 97&ç& 4.76 9.78 "295 " Trapping á 165 o UöÐ " "5r5 Error 6 .941 ,L55

Total I} L0"407

Natura] history notes,

lL'bougli the primary interest is populations u certain da.i;a were colfected. on the life historÍes of the species soncerned.n The vital statÍstics are stj.ovùla in Table åTII" Figures are based upon IO or rûore animals"

Recc¡rd.s of fleas were also taken but r.sere not ,jneorporated into the t,able since they are so easlly ¡rÍssed.n

There is evidence tbat the Microtus population experienced, a TABT,E Jf,TT

I\atural liistory Ðata on Snall i.Ia¡unal Fopulations.

ib fô Breed- þ tsxeed- iá üith Plot Date Species !{ales ing liales ing Fe- ,Ear Iiiites ¡nales

2? /\ffT/52 Ctettrriogornys 5|5 ÞU 10 6B Pero¡qyscqg 60 43 66 o OlethJ:ionomys 56 2e 29 88 j'Íicrotus 38 33 40 25 Sorex 6+ ?9 75 0

^ ^ /: t-^ Lo/ u LLl- Ði¿ ClethrionlinJs 25 50 55 ::äicrotus 59 2 60 zLlutrr/52 Clethriononrys 5'1 23 22 32 blicrotus 25 U 53 25 Í-¿.- ,-^ -¿/;tJl^ Dì. 6lethrionomys 4A o 0 alwJ ss Sorex_ 52 Ãn \J lvlicrotus æ o ælwJ53 Sorex j,ficrotus 64 29 U

,a.>6a t-^ Lil/- ^ uJtL! Ðì¿ sorex 45 6rl 27 8/VI/53 Sorex AI 13 0 zo/iÆrr/æ ffi; 59 +t 0

¡åcrashrr during the spring or early sutrmer of 1955, Table h,, ind.ieates a reLatively Ìrigb. population of this speeies in early Jr-rJ-y on Plot zg but by.ai:gust very few I'iíerotuÊ were captured" -þ-ive dead. animals were fou¡d d.uring late July and. early .august on Flot z and. two on plot l-ø

Tìre d.ead. a¡ri¡¡als lvere sub*ad.ults and adultsn Tirere is a possibility that this sharp population decl-ine nTas caused. by an epizootieu

Clethrlonomys shov;ed. no sucb d.eclines

Tire follor,uing pred.ators r¡ere observed. or captured. on the per- manent plotsa-

{a) i'larsh havrk * observed l:untine on Plot B Figure 5"

Ðiagra.rrr of Larval" Íum.el Useû rn 1952 I

I I

\ t (

I 7

I t_

( l- f ì I 17" t2" -l f-- -.1*I I { I { I I I I COTTON -Z I

I QIL GAN

/I ,\l 4

^,)x^r..^ /,@ 55 (b) Red-tailed hawk - observed. trunting on plot

ic) Broad--winged. hawk * observed. hunting on Plot 2

(A) ¡,ong-eared. owl - five specirens were recorded roosting on

Plot 2 d.uring the weelc July 5-lZ, 1952ù tu¡o of t,hese

v¡ere siiill roostíng on the lrlot on Áug;st 51, 1952u

(e) l¡ïeasel - one ad,ult and. two juveniles vrere captured on

Plot 2 on Àugust 19" Cne ad.ult ehanging pelage vras

observed. on Plot ] on ûctober ]-I Six additional v¡easels

vøere captured. on Pfot 2 in I9i5, ano one oIr Plot fa

One fe¡aale i,,iic*lqLgq gave birtir to tirree young in a trap on

Plot 2u lne young rúce perish.ed before the trap had. been opened.. upoa two subsecluent captures the aniinal- was not lactatÍng, suggesting ti:at suckling is necessary to produce lactatlone

yu¿r¿ËÎ'b'-i-- +1-,^,,,¡e 1953lC)ÃU trapping+-^^-;*^ sessions^^^J ^*^ on^- PlotDl ^¿ IoI 2Õ specimens--^^-i--^-- of

Peromyesgs (male and fe¡nale) and one of Zapus (femate) were taken wlrich had been ¡erked. in tlie l_9bp seasono Àt the tirne of original narkingu all speeinens lsere adults and. iñere assuned to be a ¡¡:inimr:rn of 10 nonths of age" This places a ruininrr.i-m. of 23 ¡aonths of age on these in- d.ivid.uals. *'r1 tbree animals vJere â.pparently in good, condition and the Zapgg specirrren was lactaiingo Thus the longevity of these species rinder aatural conditÍons flay be consid.erably ovet 2 ]rearso V ?OPÏIJ.JITIONS OF NÌN LAJICH S/ii.¡FLY

The larch savrfJy, Bristipþra eri_chsoniå (Htg"i (Order Í-I¡rrnenoptera, Farnily Tenthrid.inidae) is a serious pest of tamaract (¿g)"

'rd.u1ts of this insect eru.erge from fate in Jlriay to abqrt rald.-Ju]y, a¡d. deposit eggs on the new shoots of the host tree" åfter haichine from tbe eggs, the young gregarious larvae feed. voracíously upon the ta.tnarack foliageu :¿fter passing through five instars, the mature larvae drop fron tbe trees and. spin cocoons in th.e lnossø It is while ia tÌris stadíu,n that the insect is vulnerable to malønalian pred.atioaø

Th.e ad.ults etnerge from the cocoon in tire f oIÌowing springu or, in a low percentage of cases, renain in d.iapause untir tire second. springo

sirtce s¡:ialI ma¡umal preciators are primariry concerned. v¡ith cocooned sawflies, no at,ternpt was ¡nad.e to sample populations of eggs or rarvaeu Holvever, in lgbze a:r effort was re.de to esti.im.te cocoon population on the ground by ineans of funnels to co]Iect d.ropping mature larvae" These eonsisted. of wire hoops l7 inches in d.iameter suspended. one foot from the trunk" À cotton fun:rel lvas attached to the hoop and. at the lrottom of the funnef was suspended. an oi} can with the top rerooved. anÖ the bottom perforated.e Danrp rnoss was placed in the can. The funner ís shov,¡n Ín Figwe 5" Ten of these fu¡uiels lrere placed. on representative tarnarack trees on each of Ptots Lu zu

5, and. 5;r. Tirese f-r¡¡nels r{ere eranined. weekly and, the cocoons or larvae rernov ed and. tallied-" The result,s are shown in Table XIV*

Fron t,hese d.ata the cocoon population per acre ïüas estinated. in the following fl.ar"ner, assum:ing that aIL ¡nature larvae spun cocoonsa QN

'Il{Bl,E :CV

Larva} Ðrop trxf:ressed as the "{verage Nurrber of Larvae per Funnel"

Jr¡fy JuIy Ml$ u 6Uës -É,ugn Seasonal Stand.ard. Plot 23 50 6 13 e0 "LveraEe Deviati on

1 4ac 'l .2 !3,3 L "o- I L,2 4,8 5*7 U LZoS t r^t'

q, lc"0 1102 IO9 "f zBUI {to"o rArt Å^^ 5n0 7"0 10n 6 rl å9,0 '- ösö

Using Turnock?s d.ata (64) frorn experínents conduct,ed at Prince

Albert, Saskatchewang ;-Lib of the total larvae on a tree fall lr¡itai-n

18 i:rcires of the trunlc a¡;d F¡9/; betl'ueen tB aad. 55 inches from the trunk,

Àccording] y, tho funnel used in this experiment should- capt',-rre Ir541; of the larvae falling from the treen Thus having an estirnaie of th.e larrrae per tree and. the trees per acre the cocoon populations per acre were calculated. on tire various plots" ll'he results of thÍs c¿ilcu1a* tion are sirowa Ín fable XV"

Ðuring 1955 all the larvae r/üere colLected from tiiro trees on eacb plot in connection v¡ith a¡other experi-nent,, by rreans of funnels which complei;eiy encircied the tree (see Figure 6)" laking the aver* age of these anci icnoio¡ing the m¡.nber of trees per acre, the sar,rfly coeoon population sras calcufated, The results are shorryn in Table XVI, Ebese two methods of esÈimating cocoon popuJ-atíori.s are rather crud.e, but show reasonably good. agreenent on per acre estimates, Therefore, it ís feit thaù they are jusiified. rai;irer than attemptlng relative loopulations, since any co::rparison betv¡een predation and sallrfly populatioTLs becorúe so vaÃue ti:ai conclusions are Ii¡rited* i'igure 6ø i.arual Tree Funnel Used in 1956

40

TJ,]]TJ lV

Sal',ifly ?opulations on S¡nall Ïiair¡i;ral PIo1,s During 1952 Expressed.

as Insecùs Per "iåcreo

Ðate Plot L PIot 2 PIot 3 ¡-t. tÆ

23/Vrr/52 26,3OO 14r600 90 ,000 9 2,000

'30/UE/52 97 ,500 ?2 r800 25?,00ü z15,000

^ t--æ-.+ t-^ 6/ V ILLl c¡. 245r000 14er0oo 445r000 431 3000

ß/varl52 ?69,000 150 ,5oo 475,QQO 551 , ooo zolvrrr/52 269 r000 15C,500 475r000 555e000

TABIÀ X\ru

Sal'ufly Populations on S¡ral1 ivianunal Plots During 1953 Ëxpressed.

as fnseCts Fer .1åCre.

Date Plot I Plob 2 4É Plot 5

- t*- !-_ LDI- ULLI C,5 4,100 322e^OA z+iwrl53 26,2OO 56 r900 657,400

2e/\nr/53 79,100 128r 300 899,500

, I-*++ --, +/ UJLL/ ' Ð,5 81rã00 170, 700 963 r 500

Lel\ftrr/58 92 r800 180,100 9?2r4QO

þ Only one t,ree was used since the second was obviously larger tb.an the general st¿¡¡d" typeo VI jEIE ËFFË9T oF qiú!!¡. iúi\xSAJ, piTEDåffioN qI

01ù_¡4kRCt'I SAI¡FLY poglLÀTIONÉ

TË1ü RoJ,E CIF ffilI PRI'DåTOR The role of the pred.ator has received. considerable attention

in tne literature, a}lee et ar (a) d.efine ti,vo rnajor types of preda*

tion -: caruribarism and interspecies pred.ation" Both types have been

silourn to be import'ant in red.ucing populations ia certain instancege ]"eopoLd. (41) in a treatise on gane management has outlined the follovr- ing variables tirat infl-uense the nortatity of a pïey speeÍes frorr pred.ati on eff ects; 1o Ðeasit,y of î5gameffi populatÍons

2o Density of pred.ator popr:_lation

5* Food preferences of the ored.ator 4ø 'Fbysieal cond.ition of e?ganre{8

5u ¿lbunda¡rce of buffer speeius ( ine, alternative prey)

Tbe author consid.ers the interpred.ation betrr¡een predator species as an

ad.d.itíonal factor virbich is iraportant in assessing predatÍon ]osses from a prey specieso

fbe first two factors influencing predation intfurate that the

effects of rred.ation are d.ensity d.ependent" Har-bley (eo) uas f ound. that sparrow hawks preying upon song bird.s fo]Iov¡ this ru].e within

certaln linits, These li¡Éts are defined by Àrrington (19) v¡iro states that' any habitat can support only a given nurber of indivíd.uals. iThen the populatÍon of prey specÍes ie lor.rer than this liloit, little preda* tion is exlerieneed., but oace the popr:lation rises above_i,ås.¡th*,,ggþ.",g¿d \'-rr'.i'"i :'* ,:1q,. i: ñvt-¿'! :ì!, " I { ,il*¿,, $ t'- ! lît' ¡'-; 1 '9' r:::: \'/ í 'af',''-- .r,,---_;t, t',_.J' 1 +2 of securlty this biological surplus is heavily preyecl uþorls

From the eoncepts advanced. in tìre literature it, seerns evÍd.enÈ tbat tbe f ollowing rnajor lines of investigation shou-]d be ini-tiated.;* (a) a d.etaiLed list of all the knorvn pred_ators of the prey species involved

(b) the food. preferences and. capacities of the pred.atoro (c) population stud.ies of both predator and prey

(¿) effect of pred.at,ors upon ühe prey species population (e) d.efenses of prey ryecies against the predator (f) lnterpred.ator effects

lq{Os.Ji{ PRUDATOIìÊ OF Í}ü IÆÌCIî SriIúFl,Y

The nrammalian species oceuy'ing in ta¡¡Erack bogs of Eastern &lanitoba bave been lÍsted. earlier in this papero In all, 14 speeies t¡¡ere noted. but it was suggested that fev¡ of these could. be considered important as predators of the Larch sawflyu By virtue of their low occurbnee it is possibre to elíminate the chipmunks, so,uirrelsn and weasels as significant cocoon predators" Sj-ruLlarlyn Feromyscus and. zapus were taken only in tbe peripheral regions of the bogs and. migþ.t also be o¡n:itted, 0f tire shreî¡s, sor€ë, e¿Egrerls was tire only one that maintained. reasonably bigh popuiation levels, and so from the stand* poínt of lareh sai,lfly cocoon pred.ation, onfy Sorex cinereus, Gletè* rionornys -gem.Êr!¡ and ¡4¿_grgtgq. pennsylvanícus appear to be important' Qbservations on caged. Perorayscus Índi cate that Íf these aninals in- vad.ed t.l:e bogs srore extensively, they too would ruerit attentiono 45

FII|DI IrtG Iü'?EFJ. l¡El'B S

In order to ascertain the food. capacities and. preferences of

s¡nal} ¡nar¡urals, feedíng experirnents 1r¡ere eondueted on caged. animals*

Frelininary experi:¡rents ín 1952 using 18 inch cube cages lvith sphagnum

covered. floor sirowed" that the cage was too sura]I to assess adequately

the norrø1 feeding habits of C1eùÌ:riogol4yÊ" Cocoons and nor¡-oa} vegetation were supplied,

A ¡elee sub-aduft, 0l_eüeipgg!!Ë- nas caged for 24 hor:rs !{ith 60

cocoons as foLlov¡s;

Jlpparently sound. 50 opened 50

¡earl 2A opened. tB

B" harveJi enrerged 10 opened. 5

The ex¡lerinient was repeated., using 150 cocoons and a fe¡rale

sub-ad.ult Clethrionomys .

Sound. '75 opened 75

Ðead. 60 opened 11

Þ" þarvetrL ernerged 15 opened 6 !'ollowing thisu 500 apparently sound. co@ons lvere placed. in the cage vrith a¡r adult rnale ClethrìLsIrcE)¡s, Of these , 4gg v'rere recovered and. found to be opened. The experiment was d.lscoptinued- beeause of

cocoon shortages,

The erperiment nas repeated during 19511 using a cage ïrith about

156 square feet of floor space covered to a d.eptir of about four inclies v;!th spba.gnurrr lnosso il-aùuraL foocl r,¡as al-so inserted so that the anir¿als isould. not feeê upon t.lre cocoons througb starvaÈion" Tire following +4 cocoon types r,'¡ere then scatl,ered under the rnoss;

(a) sound. cocoons of g. er:þþsoÄii" (¡) cocoons con'taÍning livi-ng !" har.r'e$L parasite la-rvaen (c) cocoons attacked. by a fungal grol.ith"

(d') cocoons fronr wirich B" þg-rveyi had. emerged.. (e) sorxrcl cocoons *i=uJorrto ûree tagse The cocoon; categories, r{ere obtaíned by rearing fielô co}}ee- tions of fÍftb instar larvae" Thus tbe sound. coeoons were produced by apparently nornal ]arvae¡ and sÍm'ilarly, those containing living lai:r¡ae of the d:ipterous parasite å" barvey:L i{ere ,ororluced by }arvae harbouring the parasi'i;e eggs" fa ad-clition to tb.e previously roentioned sawfly cocoons, five

B" h-e,rgeyi pupariau five emerged g" harveul puparia, and two Large ua* d.etermined. d.ipterous puparía r/Iere placed in the f eeding cageo These re¡aained. untouched. througbout the erperinæ nt" The follol'ring animals v{ere admitted. to the cage inclividual.ly for 12 boins"

(a) ad.uLt male Clethri.onomys"

( b) sub-adult f ernale -ü_þ!Eåggeqyg. (c) ad.ul,t fenale irlicrotus,

( d) tv¿o ad.u]-t sorexs

Table IIVII shoi¡',¡s the results of ùhe ex.perirent, testecl by roeans of ind.ivíd"ua} 2 x 2 Ciri-square testsu IUBI"E ,-nm

treed.ing Elperírnents Concluctecl on Three Species of Small L[anulal-s"

ohi*

tLethrionornys Sound }}4 42 156 73 -]uo* Sound on t,ags 54 26 80 68 ;- "ao *piioo" Living Bessa 11 27 29 26.09 T Iess tha¡. q "01 Bqg"gg energed i53 42 ?9 o422 I u50 approx" erirerged. aa Sawfly '+â ZL 65"15 I Iess than ,01 1'ungus 0 58 38 0 6?"96 1 less than ,01

,12 lvllgggtuq Sorinô 56 7B dd q Sor¡rd- on tags 51 UJ 78 ' "4++ I oÐU appTOXo Living Bessa I i.0 19 47 4"L24 I approxo ,l '05 Bossa enrerged. L4 2L 67 1 approx" S¿wufLy "?10 "70 energed + L'7 2L 19 20.62 I less than o01 tr'ungus 0 I9 tq 0 50"90 I less than uOl

Ë9198 Ëound L42 14 156 91 Sound arì RA1 on tags t5 5 94 6 u.)L L ø DU Ð.ppTOXo tiving Bessa 11 2? 58 9A ?1"15 1 less than "01 Bessa- enrerged. ? 55 42 20 gg,12 I less than ,01 Sawfly emerged 0 42 42 U L33^ZB t less tha¡ Fungus aa "01 0 f51,95 l Iess tha.¡r "0]

rÞ 46

From the preced.ing table it is postulal;ed. tit¿3c (a) tbe tags do noi; attract or repel the aninrals. This conclu- sion is sienificant since predation is assessed. in the field.

by means of coeoons attacired. to tags and later exarúnecl for predation*

(U) alt species can distinguish to some d.egree betv¡een sound

e:rd. parasitized. cocoonsu Ïn the case of 1{lcrotUs the

difference obtained. is signifíeant at the 67å level' Since none of the d.ipterou.s puparía were toucnecl, it is postulated

tirat these are uni:alatable to small rnaruilalso

(ej Sotex rs able to d.etect to so¡ne degree if a parasite iras energecl, tl:e otirers caffioto This nini¡uizes the overlap of

natural controls deteriu:Lned- by cocoon colleetionsu and.

suggests that the selec-bion fou¡d in (b) is dependant upon olfaction" (a) atl species can d.eùect to a great extent whetber or not the sairufly i:as energed.o Sogg4_is unerring in this respecto (e) aII species uneruíngly reject fungused. cocoons' The prelim'inary experiment also ind.icates that ÇIessflenqryå candist1nguisirtoa}ir¿ited"extentsorrnd.anddead"o"ffi*,ou field th:is -l{oufd el-imina.te sorne of the over}ap in controlsø

Th.e ability of d.eterar.ining noused. and. sl:rewed. coeoons is im* portant if any degree of accuracy is to be obtained- in assessing pre* dation by tneans of cocoon plants" 0oeoons opened by sjrrews have serrai;ed. ed.ges and often have a cap or rdfiåee over tlre opened endø 4rl

Cocoons opened by mice b.ave seallo-ired. ed.ges. Shrews usually r¡ake esly

one openíng in the cocoon, but sometines a second. opening is made, liice however nay open a cocoon in as rírany as three oT more places*

Figure ? shows a moused, sbrewedn and. sound cocoono

Graham (22) has suggested. that it is possible to d.etermine whether a cocoon has been opened by a mouse or by a sirrew by examining the opening nade by each, I{orris (50) however, has clairned that this is not possible vüith coeoollÉ of tbe European spruce sawflyu Ïn order to t,est tirls possibilityu 20 cocoons known to be ¡roused. and 10 cocoons known to be snrewed. fron the preceding experj-ti:ent were ex¿¡.iined by 25 ind.epeud.ant observers ineluding oae housewife, one statistician, tiruo teacirers, tbree clerl

84"5+ * 85.+6%. Similarly shrer,'¡ed cocoons could. be determined. with t,3"6'þ accuïacy with a confid.ence intervaL of the nrean at the 957a level- of 82.8L - 84,39i0o

ffg I' COCOOI{ PElDrimQN_'IB{iriÐS USI t\lG TUE !C Q 0U EI4IüI TECjI'II eIE Tbe pred.ationa] elfect of smafl narninals on larch sawfly cocoons Fipgure 7o

Co:i4larÍson of Sound. 0ocoon and tocoons

Opened. by itlorrse a.ncl Shrelu"

From left to right;*

( a) soirnd. cocooa

(¡) cocooa opened. by mouse shoirriag scalloped. edge

(c) cocoon opened by shrew shouing serrated. ed.ge

(d) cocoon opened by shrelv shorving rsliðÊe or flcapB W WW ffi 49

T-,IBÏ-E E\]TÏT Test for Determiníng *iccuracy of tlasses in

lliff erent iating lious ed. and, Shrewed. C ocoons .

Source Uo I 6 H" S. Fnn

irfoused

(À Between ü]asses I 139.12 Lo572 v67zAA

tr{íthin 0}asses 22 89,5l

Total 2¿L

Sbrev¡ed

Betl"{oen üi.asses .? 467,9+ 3"O72, 3"44

l'dithín Classes 22 I52.32

Total 24 was estirnated. in the field using the î?cocoon plarrtrt method, as previously employed. by Graham (Zai una iuorris (SO). fn""u authors en- elosed fíve cocoons in small cotton bags and buried. the bags on varíous plots" The present author consid.ered this r¡nnaturalu and. in ord.er to simulate natura.l cond.itions roore closely, cocoons v¡ere wj,red. onto silrall tree tagsu Twc eocoons about tlr¡o inches apart, v;ere v'¡ired on each tag and these were buriecl to a depth of about two inches fn sueh a Íianner that the top inch projeeted. fron the soil in ord.er to }ocate the tags d.uring subsequent examinations" One hu¡dred sets vrere planted. on each plot" These rùere exa::tined- at ini:ervals and tbe indÍvid.ual cocoons recoråed as being untoucbed., attaeked liy fungus, parasiüe emerged, 50

opened. by a r-aouseu openeo by a shrew, oT removed. (presumabfy by a s¡:al}

mar¡ma} )¿ Cocoons that vuere missing or opened- uiere renewed after each examination,

Using this technique it uas found. that srnall mamr¿als prey upon

farch sawfly coeoons onl.y d.uring a definite and firn-1ted. seasolts It was formerly supposed. that this insecù r¡las particularly vulnerable to ma:ryralial predation because it renaiaed. in tTre ground within the

cocoon for some I0 nonths of the year, thus affording an extended. period. in which slrall rnar¡¡u.als cou-ld. prey upon it u llovuever it is ap* parent that light pred.ation begins in late aruguste reacires rLs greatest intensí'cy duríng Septetnber, and. then slor,¡ly aeclines untit N'overnber.

Jlfter tjr-lsu }íttle or no pred.ation occtlTs on this population, Thus it is postulated ii:at, snall marcmals prey upon the lareh sar,vfly to a

Iinited extent' !n Late August, reach a clinax 1n Ssp¿sn¡er, and tb.en slovlly relax ti:.eir pressure u¡tiI tlie ground. is frozen" Thís con* stiitutes tbe entire predation until the follcn¡ing August whea memnalÍan pred.ators agaia begin to d.estroy cocoons. From observ'ations it was found. thai; sma}l ma¡rnial.s prey upon cached. cocoons d.uring the winter months" Iiowever these have alread.y been reiûoved. from t,h.e field popu* lation, End. once cached. are potentially d.estroyed..

The results of the erperinent are record.ed in Tables ]ü,1i, lilCe anô l{3ïu ?opulations of predators and. prey are included. ín the tables since Craha:n (22) suggested that variatisns in mou-se populations are reftected in tire pred.ation of the larcb savrfly, and nrrinelon (fg) suggests that pred.ationu witbin certain li¡rrlts, Ís d.epend.ent upon the 51

popul-ation density of predator and. preyo In rrrany cases, the entire

cocoon was reilloved. fro¡r the tag leaving no evidence of i;he pred.atorø

It r,,Jas assuned. tirat thls cbaracteristic was random for both mice and.

shrewsu SnaII ¡ra¡runal populations lqJere taken from the seasonal popu*

lation curves for the various plots, Larch sawfly populations r,üere estimated. as outlinecl in Section V, and. coruected. for loss through

a* --^å^+ifJJ-'çgcUÄ vti The foregoing tables ino.icate a substa¡tial- reduction in ti:e

larch sar,,lfly cocoon population through tire activities of rna-miialian

pred.at,ors" Si:reln¡se especially d.uring 1955, were particularly active

aÊ ooeoon pred.ators and their value as a natura] control- factor has

apparently been underestirnated. by Graham. (21) . I'Iorris (50) however, has recognized Èhe inrportance of inseetivore preoators of the European

spruce sanfly, During 1955, the cumulative pred.ation v¡as g4"1þ oa- PLot,2, and.9?"61b on,Plot gô Sl:rews accounted. for 88"1 and 88"6 per cent of this respeci;iveIy" Since cther rrrortality factors, such as parasitisrn, operate against the population, it would- appeer that in tirese and. sirnilar areas, inseetivoroirs pred.ators might either ternin: ate a larcir sawfly infestatlon or Cecrease i-bs intensity" Since smal} mairuials appear to reject parasitizecl. cocoons to some extent, the greatest effect of ,ored.ation would oceìrr, tireoretically, as the in* festation approacTred its peak in tbat period just prior to the para* site peaica

üþon exaririnai;ion of tbe coluruns ercocoons o'oened pe:" rodent per d,ayffi and. øúocoons openeô oer. insectlvore per d.ayçe in the foregoíng TA3I,E XI-T

Fredationu Srilall l'{anrnia-l Populations and Sav,¡f}y lopulations on plot l" "i, Cocoons Cocoons open* "lt ?ò TotaL iiiiiee Shrevss Sawflies opened. ed. per Date lvioused shrev¿ed shrew pred.ation per acre per acre per acre per mouse per day

+/rx/52 ZI 52 3"85 o VO 186,000 3?T F,rl,

+L T2 Uxlsz 'r5.+6 u65 130r000 :588

- ..- l---.- I --^. Àrt tÐl Lv/ có Ð L4 57 ,xF, "08 117 r ooo 1Ã pi 24/\¡nr/õ3 Lu62 ooo "86 9l r 208 I51

êi /*-,* /-,- ;rJ"/ vLlJ¿i Ðó 5 f"85 r99 86,400 284 1õ5 vlNss 1q t6 2.O? l.oõ 75,000 685 208 t^.,-- f.,-- L+/^ " Lìt/ Có b9 2"27 T" 28 5Ir0O0 1 r

LIt 14 Cö 60 T7 7rl ]-"f5 1"15 21 e 500 118 lL2

UI to T/IBLE ]A(

Freclation, Sniall lviarmml Populations and. Sav¡fty Fopulations on Plot 2*

Coæong Cocoons open- '1, /o '¡ fotal. h[ice Shrews Savsflies opened. ed. per Shrelr Ðate ùioused. Shrewed Fred.ation per acre per acre per acre per mol.rse per d-ay þer d.ay

- ,--- t-^ Ll Ij/"I Þ'/) L2 2A 6"41 t6 "41 l0Br400 208 405B t50/Ti/52 I6 25 u50 88e 700 ?2 1966

25 63 4"82 55,700 Uw./5?, "24 141 L+'IB 1.- t-Ç t-- LÐ/ u c.) 4L 46 700 t "82 "5I e

44/VIJ.ï"/53 2"29 5"?,9 l75r00o 540

*- /--- / -- ,- t- r?a ,5Lt U LLLl--' Ðó 2,25 140,000 1586

a t+-,. t-- 'tI Lt l c,t 36 2,27 5"05 l15 ro00 1180

l+-- l-- J-+l^ " ü4 Ðó 2"55 2ê.52 92,90C 12?A

t-.-- | iaLl^- Ja\y' o.5-.-, nÊ. 7B 2"9'l 59 s 600 19B 5014

/+-.. | '¿ó/^^ L.t;/ Ð,2-- 81. B6 2.27 L"74 25e5QO 82 r067

AR 4/fJ5ö 9I 2"19 1,58 16 r 500 46 746

LLlil5t5 a'l 9:5 2,O4 1"41 12,600 595

rg/rJ5-ó 87"5 9505 L" 92 r,23 ilrToo 106 scJr ^ê /-- ! -.- i!Ðl À,1 c,t B'l '7 95,7 1"?B I"04 ltr4O0 +L

;---, J -- ^ - Bg" tlil/Ð,5 1 940I lo49 1O e 600 }?B TAruM ]ffT

Pred.ation, Snierll jVlariunat Fopulations and. Sav,if1¡, Populations on plot 3"

tocoons Cocoons open* '/o 1b lb Tot,aL iúice Shrews Sawflies ed. per shrew Date l,ioused Shrewecl predatÍon per acre per acre peï acre per rnouse per day

l---,- I - -. ^ ô/ Ð4"1Ði. 28 I*08 I"19 g42\OOO HH ?185 ',Nl-,.., 1--,- t-^ JL-i{ Ð'/J l5 5l 46 "95 L,06 256 r000 LMz L'IT2 L'/v/53 T7 17.Ð n6L r"g2 P47,000 z+/v]J'r/5'ó "'/b 5"+2 677,000 2'35ã

-.- /-._--- t-- óLl u LtL/ Ð,5 29 u?4 5" 56 5r7 r000 4i-11

't/ñ,t*,- L-.^ LÅ./ Ð,5 56 4L u'13 V aã't 429 r000 ILI4 aL53

- " l^--- 1-- L+l J-Á./ Dô 56 ,7L 5,32 521 ro0o 2900

/-F-*, /¿- illt^- L¿!/ c,t 75 84 5.21 "'lO 116,500 l'P,45 54+Q t--- t-- i!ö/^^ LÀ,/ cô 84 oe "69 5" 0g 50,900 1841 +lxlss 87"5 96" 5 o65 4" 98 25,500 744

- l-.- t-- ILlLl^ cô 88ô 2 97 *2 6lå +uBe 20,400 " 15I

¡-.l-- -Lé/ ^ iLl c,5 gB" 6 9? o6 "60 4"73 17 ,500 88

'Þ tables, it iri}l be noted. that in one case it was cal-cula-r,ed that over

?000 cocoons were -r,aken by the pred.aiors per day, and in ̀Jry ca.ses

about 2000 were takenu Data on caged. aniraals d.o not lend. support to tþese figures" Tbere are three prausible expranations for this d.iscrepancy: -

(l) li[ar¡unat populations were inaccurately rneasuredu

12) Sar,ufly populations $iere inaccurately neasured"

( 5J Sai,fly lar.vae experienced. considerabl-e mortality after falling from the trees lrut before spianing

eocoons, since th.e cocoon populatÍon tias d.eriveô

indirectly from mature farvae ::atirer than cocoon

colfllts o

The author eonsiders that the sma1l manmral. population estimates are reasonabl-y accurate. Furthe::nore, the sarlrfly population would. have to be overestinated frorn four to nine times in ord.er to bríng t,he nunber d.estroyed. per marnrnal ¡rer day within reasonable bound.s" Therefore, tbe tÌrírd. ex¡lranation lvizz that the salufly larvae experience heavy mor- tality afi:er falling from tl:e trees but before spinning cocoons) see¡rs the ¡nost plausíbleu such mortality riay be caused by such factors as nâmríìalian pred.ation of transient larvaeu frog predation, i:redatioa by gror:nd feeding bird.s, diseaseu or u:davourable i¡¡ate:l rel-ationshiþsu

The predator aad. prey poprllations lnere exarûined., to d,eterrruine wirether or not predation is density d.ependent" TIie resuJ-ts of the anarysis siror';n !n Tab1e JQGr, ind.icate that tb.ere is no correlation between pred.ation ano- tire populations of pred.ator ancl prey, although 56 the correlation was caiculated. fron estimates and is therefore statis*

ticatly lleako Grahara (22) has suggested that sitaJ-l ma¡n¡nal populations nay be estirnated. fron th.e resufts of cocoon ernalysis, but tbis pori;ion of the'stud.y indicates that there is probably no sinrple retationship betlveen the predator-prey populations and. the extent cf pred.ation*

[åffi,E ]{XTI

correiation coefficients on Pred.ation, Iiammal poprelations a¡rd

Sa-wf1y Popul ations*

Source d 'f o 3"()E

¡:Iouse population ;/oùioused. vs" ffi ,632 Shrerv Popi¡latíon /o Shreued vs" Saluf1y Population "?'29 "632

iåFreyed.uponvs6 ffi . u'lo .69.2

Þiouse Population '7a i',toused. vs" Salrlfly Population o 602 Shrev¡ Fopulation ;o Shrewed.-- vs" Sav¡fJy Population A^q "1?1

|åPreyed Dþonvs¿ ffi ,226 o602

trrioused. 3opr.ùation - % /o .i,{oused vs. Sald1y Ponulation 165 " ^î1D Shrew ?onulation 7¿' Iinrewed vso Sawfly Fopulation .z2g T2 ,592 _ Sr¡1411 ldanrnal popuLation i0 "Hreyed uoon vsø Salvfly populatíon ,499 LA *552 57

The locat,ion Ín vuhiclr the inseci spins its cocoon rnay be in

part a d.efense against srna1l marrui:al predeition" T'lorkers in tl:e field h.ave noticed that there are several ]ocations in which cocoons are

airuost invariably missed by sinall mam¿al pred.ators. Using the cocoon planting tech:rique it, was found. that cocoons planted besid.e the roots

of trees a¡d in hu¡anocks in the bogs vaere heavÍIy preyed. upon by snal.J. rßani'ilalsn on the other hand., cocoonË in the loiot lying places betl.¡een the hurnmocks were usually missed by raa-n:-malian predators especially wben these l-ocations rïere at or near the water tableo

sÂTuzu{rï_0_NlnìAPP;1{G_

FredatÍon by sriall ma:-nmal_s v¡as also t ested. by means of a saturation trapping tecjrnio;ue" This consisted of snap-back trapping to renove the entire snall ma¡n'r.al popuration fron a ploùu Einerging larcb salvfry ad.uùts viere captüreci by rßeans of emergence cages, and these ntunbers riere corrtpared with erûergence from a simil-ar Þ}ot eon- taining a fu1l coroplement of smal-I mamnals. The experlment nas con- d.ucted on Ploü ãÀ, and FIot 5 ï¡as used as the check plot, The plots i,uere al'*ost id.entícal (see Section III' Tables I and II) and the 1arch sarrifly cocoon populatioÌts'r/'{ere very simllar (see Section V, lable iV}o

The population of manssals ruas assruned. to be tlte sanre on both plots, although no d.eterninatíons could be mad.e on Plot 5 v¡ithout d.isùurbine the small nanna]. population"

JF it is not kaoun conclusively ¿I it is possÍble to re¡rove tire entire snalL iaa.¡nmal comple¡rent fro¡n an âTeâø Saunoerson ( 5S) f oi:nA 58 that d.uring an extend.ed trapping period. of over 40 consecutive days, consid.erable nu¡rrbers of sroalL nari:mals were still being trapped.. Hov,l- ever in the authores experiraent beginning 1-:r July !952.- enimals were captured. up to the sixth d.ay, after v'¡liich no f'urther anímals were captured., .tlfter a:i interval of two weeks, no enimals lvere captured on the bod.y of t,b.e plot, but a fev¡ were taken in the two outsid.e fineso ;as an ad.d.itional check, cocoons were plaoted at each trap position" By the end. of lulay 1955, only 11 cocoons had been talcen, and of these only one ïùas on the body of 'r,he plot " In ad.dition to these e a row of cocoons was planted. around- the Ín:ier square chain on the ploi:, and no raarnmalÍ¿¡¿ pred.at,ion h¿.d. occurred. on these at tirat tine. The results of tÌ:.e test sirongly suggest th.at saturation trapping is pos'sibleø

Trapping vùas resumed. on Plot 5À in early l,{ay of the }955 season in order to keep the narrunal-s fro¡u tne plot, The results of the experl- rnenù are surnmarized in Tablq lo{TIIu 'Ihe ínitial larval ind.ex is the rnea¡l nurcber of larvae captured. per fumeJ. , and. the pred.ation larval

índ.ex is tbls figure corrected. for smali ma¡nma} pred.ation using gocoon plants" The energence lnoex is the ¡æa¡ n'¡nber of aôults cap* tured. in tì¡.e energence cages t¡hicir were set out in three series as folloviss (fi Series å. - Ten cages diarnetrically opposite larval fu¡neIs, (e) Serj-es lln - Ten cages rand.omly placecÌ throughout the plot, (5) Series C. * Ten cages rand,ornly pla.ced in the centre.square chain of tb.e ploto

Table ïilllï ind,icates a close reLationship betv.reen tire per cent pre* 59

dation based. u;oon cocoon plani;s a¡d. tÌre surviving ad.ult population,

TiåR*il lgïïI

Relationship Between Predation and. Sav,ifly Eraergence.

Enereence ïnd.ex Initia]- rledaEl_on Treat¡uent åarval î,arval Series Series Series Ind.ex Ind.ex 4.. B. C-

5 Lianunals present 29"1 L4,6 2,2 3n7

W ilamnials removed 29,A 26"4 Bn0

Ratio of PIot 5 ancl Ptot 5Á "+7 "4õ .46

Álthough. the relationship is close, ilre resurts of this e4peri- raent should. be consid.ered ind.icative ratÌrer tlian conclusive, since it v¿as found that the ad.ult sawfly were able to readily escape from the

base and. edges of the cagesø ¿å.nt,s v¡ere al-so observed. rernoving insects

from the cageo ¿¡, series of six cages vü,as set r-rp in a bog irui:icÌ: pre* srxrabiy contained. no larch sai'ofly, and. ten freshly ernerged. savufly vuere introduced into each cagen These v¿ere exarnined p4 h.ours later and it was found- tirat less t'han hatf the sav¡-fly ad.ults were 1,ecover€do The experiirrent slrould be repeated. after an irnprovecl energence cage has been constructed." Regardless of tÌre inad.eguacies of the experíment n there d-oes appear to be a goocl relationship betr,veen the loss due to predation assessed. by neans of cocoon ptanting and the energence of ad.rrtt sal.,ifly the following yeara

By virtue of the results of this experiment cocoon planting will ire used. in the future in order t,o esti¡ete pred.ation by small rnarunalso Wf DISüUSSION r:'ïfD SUi'tliTiRI 60

pIrÐf"TOtL pmy ér'üD -pgp-rl1ÁTl0i\ s

Previous stud.ies relatÍng to the role of s¡nall mam¡nalÍa¡. Þred.a- tors of tbe lareh savdry b.ave not ap;oroached. the probrem fro¡n a popu*

Iation d.ynaruÍ.c aspectu although a density depend.ent relationshiB vras suggested. by Gra-h.am (ZZ) " Since thÍs seemed to aff ord a promising line of ínvestigation, eonsiderable tine was spent ùrring the presest stud.y in refining popü-laùion assessinent tecÌrniqires for boÈh prey and preda- tor specieso

Because sl'ûal] mammaf predation on the larch savufly concerrrs chiefry cosooned. Ínsects in tire soil, stud.ies on sawfry populations were d.irected. largeJ-y towards that portion of the popuJ-ationo It bas been found. by a nuraber of workers (L4, 23i that sampling cocoons d.irect3-y is not only laborious to the extent of being impractical for a single operator, but also that the stanclard. deviation of the sarnple is so wid.e tha-r, tire value of the inforrnatÍon is seriously lim'ited..

Therefore a metbod. lvas ad.opted whÍch attempted to estimate larval populations d.ropping to soin cocoonsn Funnels were placed und.er representative trees to trap falling larvae and the number cauglrt were related. t,o cocoon populations on the assumption that eacb larva re* presents iì cocoorle The seasonal means and. standard d.eviations for 10 fu¡nels on each of Plots Lu ?u 5, arrd 5À d.uring 1952 v;ere L3,3 É 6,5u t,/i- L2""5 E 12,1, 28,L',- 10,0, and. 29" 0 t 8"8, which indieates tbat the estimate v'¡as reasonably accurate for the stage sanpled wltb the not,able exeeption of those determinations from the very snall trees on Flot 2a 61 iiowever there is some incÌirect evid^ence to support the theorem that there is consid.erable mortality after tìre }arvae have dropped to the ground but before cocoons b.ave been spuné If this is trueo there re* :r¡ains the problem of assessing tbis mortalit¡. before a fu1ly accurate

cocoon population estinate ca.n be rnad.en preliruinary studies on

eruerging ad.u1t populatioas were also cond.ucted using ground. emergense

cagesô Àlt'b.ough the ¡nethod. is theoretically sound.u there are several

technical- d.ifficulties which ¡aust be correeted to achieve reasonable precision' The nain reo-uÍre¡nent is a ¡rodj-fication in basic design of

the trap to prevent tire escape of emerged insects" Howeve¡ usef,¿l

cornparisoÐs tray be derived from data coltected. using the u¡:nod.ified.

efr.ergence cageô

Srnall marrnal popuJ.ations ',,uere measured chiefly by ineans of 1ive tta-os utilizing the inark-release*recapture popula_ teeirnique (b) " tions on ti¿e effective trapping area ïrere d.etermined. by meaas of the l,incoln rnaex (45) aud. it was eonerud.ed. that a pooling of data for the final three determinations for any given trapping period gave the nost aecurate population valueo Home ranges were calculated. for Clqthr_ioqqnys gapll,gli¡ lúicroLus @g, and sorçx cj.nereus; and for these, cruising rad.1i were calculated as fcl]oi,{s:-

Ç-te!4qfq4gmyp 89 feer (pfot L) u ?6 reet (Itot Z) Llicrotus 73 îeef. Sorex 139 feet

The cruising radÍus for eacj: species was then used. as a bound.ary stripu wirieh when ad.ded. to the area enconÐâssed. by the traps, 62

gave the effective traplÍne area for each speeies" sufficient data

r,vere co]lec*,ed. on Clq!_qllongrryq to compare the ¡oo1s sangesø It appears

from the resuLts of this analysis that horoe ranges did. not differ

significantly betweea sexes or betv¿een population densj.ties but a

significant difference t¡ras obtained. betr,¡een home ranges of this species

on two of the habitats st,ud,iedu

In ad.dition, experiment,s l'sere cond.ucted- to assess smll ¡naäma1 populations using snap-baek trapso Àlthough the d.ata are meagre tirere

is some evÍd.ence to suppori; the view that both l-ine and. grid, snap- baek trapfine can be used. to determine absolute populaiions with reasonablê accuracyo Shoul-d furùher studies substantlate this conclu* sion, i'b ruill enable a greater collection of ínformation in terms of energy e4pend.ed."

coi{cTrOI\TS oF sûr¡ii]-l idir}&lü.s Jil'Ð_ ialE LLqcH sa"iir.L-y

*lthough 14 species of sraall ¡¿annafs viere record.ed. as inhabit- ing tamarack bogs of eastern lia¡itoba, fer,v of these can be considered irnportant pred.ators of the larch salvfly, By virtue of their lov¡ populations, all but five of these rníght be excluded. as coeooa pred.a- torso The species wirÍcir maíntain pc;ou1atíons in sufficient numbers to reduce sawfly populations appreciably are CletileionsrûÐe €gÊ!_er!p ivlicrotus pe4gsy_lvanÍcusu 4qpug- hudscnius_, Eero¡rf,gçgg rnanícuI{busu and

Êgqqx SfseregË_u HovEever ã" hu4g-gEigg. and. E'o nrglilgülatUq. occur only on the peripheral regions of the bogs and. for this reason, might also be exclud.ed. as im,oortant pred.ators, since pred.ation ín these fri-nge regions 65 is probabty negligible" Ãltirough all tbvee species of important sinall mamrnal-s occur on all the irabítats investigated., variations ín the populations of these species in each irabitat are evid.ent" g" eepler! cccuffed in highest nunbers in d.ense, reasonably d.ry sites; $" penns_trL- v?nieus in open, raoist si-r,es; and S" c*ineËegg in d.ense, wet sitesu

Habitat variations are Ímportant since the value of these species as coeoon predators dÍffers" Feed.ing er¡leríments rvere conducted on the three iiqrortant

rnaim¡ralian species" Jtlthough the food ca-pacity of eacb. appears roughly eoual, Ê" c-LleÍeuÉ has pov,rers of discrimination not possessed. by the

other species" Ë" glgglgug. habituarly rejects cocoons that have been

attacked. by funguse coeoons from which sawflies or parasites have

emerged, and cocoons parasitized. by B" harveyl; whereas the remaining species rejec-r, tirese cocoons to a lesser extent, å" cinereus therefore appears to be the rnost useful pred.ator from a larch. sawfry control standpoínt since overlapping of controL factors is mini¡úzed.o fuiorris

i50) recognizes the irûportance of shrews as pred.ators of the European spruce savl-fly, r'uhereas tb.e earlier r,vork of Graham t21) exelud.es then as i-:nportant ;ored.ai,ors of th.e tarch sawfly,

Ec modification of the earlier €scoeoon plantingtr technique (22) v;as used. to ascertain the extent of srnalt ma¡snal preAåtion of sawfly cocoons in the field." Preliminary experimeats ind.icated tirat it is possible to d-istinguish r¡¡ith reasonable accuraey between cocoons opened. by m-ice a¡d. those opened by shrews" The technique is probably quite accurate, since it r¡las found thai; d.ecrease in spring ad-urt 64 energence vúas proportionai to pred.atj-onal loss as assessed. by this inethod" The relationship between amou.:rt of predation a¡d abundance of t)re pred.ator andr prey anirnals does not appear to be a simple densíty- d.epend.ent one, although this sannot, be argued. conclusively, as it was pointed. out earlíer that tbere may be a large disere"oancy in estimates of the larch sawfly cocoon populations as determined by fallíng larvae* Th.e ímportance of sb.¡ev¡s is exenrplified. by these results, for the proportion of cocoons opened by shrev¡s to sj:rew populations is con- sid.erably greater t.ban the proportion of cocoons opened by rnice to lrouse populationsø

The cocoon plant,ing technique suggests that 57þ,69uþ, and 4€íib of the eocoon populations on Slots L, 2u and. 5 respectively were d.estroyed by srnall nramrnals cluring the fall of 1952, and. 1?ioo g4,Liø, and. g7"6fo respectively were dest,royed d.uring tb.e fall" of 1955. ït was further fou¡d. i;hat the period of pred.ation is relatively short, lasting f rom the begiruring of Septe;uber to the tirae the grorr.nd. freezesu lhis is contrary to the opinion held by rnany r,vorkers, that predation is ear- ried on throu$rout the spring period untll the coinpletion of sawfly ad.ult e¡nergence (22, 2+, 25) " This lnvestisation ind.icates that sinall man¿nals are one of tbe ,tost írnportant natural control fact,ors operatÍng against the larch sai'rfly in the stud.y areaø 65

r!ü Iú{O}'JI,E D cIiJüj iff s

The data presented. ia this ihesis u'rere cou-ecteù v¿hire ùhe

author r"ras ernployed. by The Division of Forest Biol-ogy, Science Service,

tanad,a Departrnent of ÁgrÍculture" Dr. ii" T,, Prebble, üìrief of the

Division, kind.Iy granted- ;oerrcission to use the data¿ The pr"oblem ïüas suggested. by irfr" RoR. Lejerure, Officer-in-Cbargee

Forest, Biology Laboratory, ifinnipeg, !Íanitoba, and. Dru R. F" i{orrisu

Forest Blology Laboratoryu Fredericton, iùer¡ Brunswick, aad. progress v¡as materially aided by their valuabre suggestions and. by their per- rrission to peruse unpublished technical reports,

l'hanks are also due to Frofessor Ro Jr, idardie and. Ðr. J, Ä. fuicï,eod., l4oology Departrrlent, university of rianitobau for theír irelpful suggestions and. inùerest ín the progress of the project, Tire con- structive suggestions and. eriticisrns of rny colleagues at the Forest tsiolcgy äal:oratory, l'Jirurlpeg, i,rianitoba, aJre gratefulry acknowledgedu BIBLIOG}-ùÏPHY

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55, l-894" 0n the bÍologr of our flat-fishes and on the d.ecrease of our flat,:fish ind.ustríes" Rep" Da:rish Biolo Sta" #4, 146 ppo

56" Quimt'y, Don C", 1951" The Life history ancL ecology of ùhe jurnping mouse, 4gpgg hud.s_oni_us_o Xcol" iiionagr, Zl-t 6l-gb, 57" RÍckeru l.{íl}Íarn E" 1945" Some app}ications of statisticat methods to t,he fisheries problerræ" Biona" BuLl" Lz?T-g"

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