Useof the ForestCanopyby Bats

Laurie Wunder and Andrew B. Carey, USDA Forest Serv ce Pac f c Northwest Research Stat on. 3625 93rd AvenLre SW. Olyr.p a Washington 98512 Use of the Forest Canopy by Bats Abstract Ofihe l5 species of bars in rhc Paciljc N*ofih$est. I I rre known ro nxkc rcglrlar use of the fofest canop] fbr roosling. lor,lging. and feproduction. This papcr rc\ ic$s roosting fequifements, lbraging. and the importance of landscape scale luc(ors 1() canopy using species in thc Noih$est. N4ani nofihr\est bats use sclclal difierent ttpes of tree roosts. Comm|)lr rc'osting silcs are in c.r\ ities. cre!ices. and foliage. Factor\ that mrl be importanl in roost site selection include nicroclinatc. roo\t slructu.c. crown rrchitecture. c anop) |rcc agc and sl)ec ie \. bafk c hrr cteris tic s. ibliagc den sit,v, and srand rnd laDdscape conposilion. Some repre sentatire Prcific \othwest c,r!it) and crevice/hafk-roosting species includc lhe lltlle brown brt {Mrol/r fu.ilr,qrrl. sil\cr haircd bar il.a'idt\..ie s octingans). xndlong lcgged h^r li\,1. rol(ol). Only l$o Pacific North$e\i species afe known torooslin lbliagc. Several \pecies fi)mge in lbrcst gaps. along forest edges. or in iparian arcas. I-ong eared (M. .rrrlrl .rnd Keen's fM l..,riil bats nray forxge $ ithin the lbresr canopy. although forrging behaviof ()1 fiesc spccics in lhe Pacific Nofth$est is not $ell documented. Standrnd landscrpc scrlc complexit! mry he nnpofianl in pro!iding bats \\ith the abundance and di\ersily oi' r..,J r^r,rLr p. -rJ ibern:,rrn .ir(. lhL] -r, L re lntroduction LitLle work has been done on forcst canopy use by bats in the temperate region. particularly in the Pacitic Nonhwest. Moreover, the understanding ofthe significance ofthe forest canopy to bats is complicated by the fact that 1ew temperate spccies are restricted to any one habitat type fbr foraging and roosting. Most species neet only some oftheir requirements within the forest canopy and musi go outside the canopy to satisfy the remain der of their needs. The term canopy is uscd here in the broadcst sense to encompass all components (trunks, as well as branches and firliage) of the upper parts or cro\\,l]s of trees that makc up lbrest stands. A detalled list of canopy attributcs of potential significancc 1o bats and other canopy spccies may be fbund in Carey (this issue). About I I spccies of Pacilic Northwest bats appear to regularly use the tbrest canopy. An ad ditional two species are occasional canopy users (the fringed bat, M. thtsanodes and the vestern small-fboted bat, M. t lliofurDnlr) (Table l ). Forest bat communitics in the Pacific Northwest arc made up of somc six to eight M\dis species and fburnon-M}oti.r species. The most frequently encountcrcd species include the little brown bat (M. ltrtifugtrs). the Yunra bat (M. lwnunentis). the Calitbrniabrt (M. rzldbrirlorr). the longJegged bat (M rolar.r). the long earcd bat (M\?l/.t er,.tl.tJ. the big brown b (Eptesitus f scusl, the silverhaired bat (.Ld.\iot1)-cteris oLti|ugont) a]nd the hoaly bat (Lasfuras cll?"rcrlrJ (Chdsty and West 1993). Torvnsend's big-eared bat (Plecotus l,,rr n't rrilii r also lbraFe. in L'relred cn\ ironrncnl\. Bats use the canopy tbr a variety of purposes, including roosting. foraging, and reproduction. ln this paper. we will examine the usc of the for est canopy by Northwest bats for roosting and foraging. The inpurtanL e,'f lrnrlscirpe (onrpo:i tion to bats, will trlso be discussed. Roosting The roosting ecology of bats has bccn reviewed by Kunz (1982a). Species diversity and population size of colonial bats appear to increase with increased roost availability and diversity (Humphrey 1975. Findley 1993). Areas that offer a variety of tlee, cliff. and cavc roosls. often support the largest number of bat species and individuals (Humphrey l975, Findley 1993). The specilic roost sites selectcd by vaious bat specics may be determined il parl by such factors as morphology, tlight and ccholocation ca pabilities, pro x i m ity to other resources (food, water. hibemation sites). climatic tactofs. and roost availabilitl'. among others. Vaughan ( I 970) has rcv iewed the relation betwccn norphology (skull shape, pelvic girdle, and lirnb proportions) and roost selection in bats. Shunp and Shump ( 1980) found that hoary and red bats. which roost in exposed locatiors, have greatcr pelage insulation than Iittle hr,'u n and big brou n bats. u hich roo.l in m,,re Nofthwest Science, Vrl.70, Special lssue, 1996 19 TABLti L Forcsr cunopv u\e b) Pacitlc Noflh\lest brt specics. Species mafked $ilh rr !\terisk {") are rnlrequent c.rnopl u\cr\: all othefs li\ted are rcgular fanopr usen. the significance of proximit)' of malcrnity roosts to Ii)raging areas and hibernation sites in gray bats (Mtotis grisescensl. Thomas (1988) and Barclay ( 1991 ) have suggested that climate and elcvation may play a rolc in the choice oI roost location and distribution of the sexes in some bat specics. Choice ofroost site mav differ with sex, age. reploductivc condition. and migratory status of an individual. Constantine (1966) observed that young red brts roost higher in trees than do adults. Fentor (1970) found thrt reproductive fcmale little brown bats select dillereDt roost sites than domales, based upon their thermal requiremenls. Most Pacific Northwest species roost in a va del) of situations. rather than in only onc partlcular roost tvpe (van Zyll dc Jong 1985). Thc roosting ecology of Paciflc Nofihwcst bats has been re\icwed bv Christv and West ( 1993). The major typcs of tree roosts uscd by tem peralc bats include cavitics, crevices behind extbliating bark. crevices folmed in rugose bark, cracks in wood. and in lbliage. Rarely. bats have been repofied roosting in nests ofother mantmals (squinels) and in epiphytes (Spanish moss) on trcu. l\eill 1q52. Con.rrnrine lq58). Tree Cav t es Tree cavitics used by bats may be in hollows fbrmed in the trunks or branches ofsnags or damagcd live trees. They generally providc a relati\ely stablc microclimate and offer protection fion prcdators (Kunz 1982a. Tidemann and Flavel 1987). Factors in selecting tree cavities include ni croclimate, structure. tree age. size. and height. Mictoclindt(. Microclimate of a cavity can be affected by llspect. entrance height, canopy cover, density ofsunounding vegetation. fce status (alive o[ dead). thickness and insulating properlics of the cavity walls, trcc diameter, cavity size. and number ofbrts occupving the cavity. Maeda ( 1974) tbtud that largc noctule bats (N_rctala.i /asioplenrs) in Japan pr.efelentially roost in cavities in live trees. which provides nore constant tenpemturcs than cavities in snags. Tideman and Flavel ( 1987) suggestcd that the higher water content of livc trees increases their insulative value and cavity hurnidity. Femalc brts in reproductive condition gencrally hur e dil[<rent hr. c,]in!-.er.on roosrrng requirements than nales and may roost separately fiom CJrot)] t .! Roosring l_o.aging M|oti\ \uDtuk\\i\: V\otis ctllilbnins: Lul,on\ L1erk no.th u!un\t' Pl?tI)tt\ ttrt't\c dii .Vlrrir ,,r'rdro/.r* l M\otisIilijlahtu,i:' X X X X X X X X X X X X X X X X X X Barbour rnd D !i\ 1969. l-aval ct rl. 1977. Fenton ct a]. 1980. fen()n ard Bafcla) 1980. Blllch] and Cash 1985. Fenlon er al. 1980 \ltllZ)lldeJong 1985. 'Krutrsch 195,1 Fenton and Bcll 197q. Fenton et al. 1980. 'Brker rLnd Philljps 1965. \Vhxaker et al. 1977. Fcnton and Bcll 1979 'N,l.rnning rnd.lolrcs 1989. Bafcl.r) 1991. "Co$an and Cuiguet 1965. lenton et.r1. 1980. Brlghrn 1991. 'Con\tinlinc 1966. Shump.rnd Shunrp 19E2. Bluclrr 198.1. Barclay l9E5. 'Constantire 1966. Furlongcr cl aL. 1987. Kunz l98lb, Barcli,,- 1985. Kunz and \,laiin 1981. ' Barborr rnd Dltlis 1969.\\hiFkcrct al. 1q77. 'Fen()n eI al. 1980. !l1n Z)ll de JonS 1985. protected sites. Thesc authors related pelagc difterences to ditlerences in roost condition and gre gariousness in these specics. Hoary bats have a relati\,el)' high aspect ratio and wing-loading and are not well adaptcd tirrhighly maneuverablc flight, uhich mry intluence thcir choice of roost sitcs (Constantine 1966. Barclay 1985). Constantine ( 1966) tbund that hoaD' and rcd bats gcncrally roosl whcrc they could drop down thr-ough an unobstructed distance to attain flight speed. Norberg and Rayner ( 1987.) discuss the relatlon betwccn morphology. flight. and echoloca tion capabilities in bats. Tuttle (1976J cxamrneq lJO Wundcr ancl Carev thcm. Pregnant or lactating lcmales oftel roost colonially at more prolected roost sites that provide thc high temperatures necessary for maximizing growth and development of the young (Barclay l99l). Males and nonreproductive temales commonly roost solitadly or-in small -qroups. in less protected and thermatly stable environments (Barclay 1991 ). StrLlLluret Maeda (197,1) rcported that large noctule bats selcct roosts based on the tbllowing strucluml characteristics of thc roost cavit)': shape, position. cntrance height, size, and clegrcc of eD trance protection. The position ofthe entrance has to permit easy flight from the cavjty. Tidenran and Flavcl ( 1987) studied cavit)-rq)sting bats in Australia and lbund that bats sclect cavities u,ith enffarce holes that arc just larger than the size of the bal hesumably, smallentranccs provide ![eater protection trom prcdators and may reduce conlpctition from birds and otherb:rts. Roost entlances are also oriented to prevent the entry of rrin into the clvlty. Tn, ' ltara, ttri.'ti, ': The JFi,rl .'ir\il) lrcc' is impo ant to bats to the extcnt that it is a lactor in fiequency ofcavity formation, cavity sizc. and cavity characteristics (Tideman and Flavel 1987). Tidernan and Flavel (1987) tailed to tlnd any re lation betweer roost site selection and trce height, for the Australian bats they studied. Lunney et al. ( 1988). found that theAustralian big-earcd bat (Ntr:tophiltrs gotfuli ) rr cavityand crevice roosting species. select large diameter trees, of more than 1J0 cm d.b.h. for roosting. Some examples of Pacific Nofihwest bats krown to usc tree cavities are the little brown bat (Fenton and Barclay l9E0), thc big bro\\"n bat (Bigham 1991), the Ctrlifornia bat (Krutzsch 195'1). and the silverhaired bat (Kunz 1982b). Somc ofthese species (particularly the little brown bat. the big brown bat. and the Calitinnia bal) commonly use buildings as roost sites as well. Barbour and Davis (1969) list buildings as the prelerreLl roi'.1 site. lbr the.e three.pccie.. Tree Crevlces Many trec-roosting bats roost behind cxfoliating bark on trnks or branches of dead or live trees. Bark roosts provide a much less pcnnanent, less secure and less thcrmally stable rcosting environment than cavitics. Bats that roost underbark must ihrngc roosl. more lrequentll thrtt tho.e roo.tinp in cavities because of the nrore ffansient nature of their roost sites (Kunz 1982a). They are probably also mole vulnerable to prcdation and weather. Other types of crevice roosts include cracks in tree trunks and in lugcr branches, and crevices cleated by bark rugosity. Perkins and Cross ( 1988) repofied that silver-haircd bats prefer roost ing in old (> 150 yeu-s) Dixrglas-fit (PseLldotsugu nenz.iesii) forests in Oregon. probably bccause of the bark characteristics of dd trees. Thc bark ol old Douglas fir tend to provide morc cre! rces by sepiuating nore widely tiom thc trunk. Old trees also develop more pronounced ridges and crevices in the bark itself. Bats wcre lound to prefer Douglas-nr to ponderosa pine (Plrris 2o,,rderosri) and true fir (ADies spp.). probably because ofdiflerences in bark charactedstics. The bark ofthese latter species tcnded to be less rugose and generally did not form as deeply creviced furrows. Barclay et al. 1988 observed silver-haired bats rixrsting in spaces behind fitds of bark. in split treetrunks. andin depressions on tree trunks. Other Northwest bats that roost undel bark or in other tree crevices include Lhe long legged bat and the long-eared bat (van Zyll de Jong 1985). Foliage Roosts Foliage roosts providc the most exposed type discussed thus tar. They arc used most frequeotly in lropical regions. Potential foliage roost sites are mr\te JbUndtnt thun crril]- rnJ c|crice-roosl.. but their gfeater exposure makes thcm more haz ardous. Their abundance. howcvcr, makes them easy to find near lirraging arcas, and might help to reduce commuting distance. The abundance of foliage roosts also facilitales the wide distli bution of some tbliage roosting spccies. Preda tion risks are probably higher tirr foliagc roosting bats, and many temperate and tropical ti)liagc roostcrs are cryptically colored and roost solitarily or in small family groups (Kunz 1982a). One Northwest foliage roosting specics, lhe hoary bat. has a chafactedstic grizzled appearance that may contributc to its concealment. Tenrperate firliagc rcosting specics are geDerally wellinsulated against cold temperatur(]s (Shump and Shump 1980) and rrirl mule l,'n3 Ji.t.rnce latitudinal nrilrlrti,,n\ in response to dininished wilter food supplies (Shump and Shump 19821. Foliage roosting bats tend to change roosts nrore fuequently than other species in response to the transicnl nature of their roost sites. Within the Bat Canopy Use 8l same season! thcy may show some fidelity to a general area, howevcr (Kunz 1982a, Lunney et al. 1988.1. Bats that roost in tbliage may roost high in the canopy. in subcanopy trees. or in understory lb1iage. Roost sites may be in densc tbtiage. in relatively exposed locations. among leavcs, or on branches. Sites may be concealed fiom above, but conspicuous t'rom below (Constantine l966, Kunz 1982a). Hoary bats and red bats (Za.rl(/-rs Dorealis) for cxample, have been fbund to select roost sitcs covered by dcnse tbliage abovc and around the sides. but open below. This arange ment presumably reduces their visibility and accessibility k) predators. but permits them to take tlight leadily (Constantine I 966). Location ofthe roost ftee reladvc to sunounding vegetation may also be of impofiance to Sonre species. Certain species may preltr trees within the forest interior. and olhcr species prefer to roost along a forest cdge. Constantine ( 1966) reported thrt hoary and red bat roost sites were usually locateci along a lbrest edge. Perkins and Cross (1988) ti)und that hoary bats rvere primarily associated with old Douglas-fir tbrests in Oregon and hypothesized that this is duc to bats'roosting rcquirements. The large trees al]d largc rnd heterogeneous canopies found in such lbrests may furnish morc roost sites available tbr lbliage roosting bats than young forests. Old conit'erous lbrests arc nore ljkely to provide the canopy structure, including dense tbliage ad iacent to uncluttered flight space. required firr' roosting by these bats. In contrast to youngertrees. older lrccs tend to have crowns that begin ltigher ofT the ground and have the necdles more concentrated toward the edge ofthe canopv (Perkins and Cross 1988). Foraging Foraging tends to bc oppertunistic rather than restlcted to a particular foraging strategy orhabitat lbr trrost North American bat spccies (Vaughan 1980. Barclay l99l.butseeFenton 1982. Furlonger et al. 1987). Furlonger et al. (1987) found rhat bats in eastem Canada exploit concentrated patches ofprey. Thcy suggested that this type offoraging slratcgy may supersedc preferelce for a particuliu type of foraging habitat. Some authors (Black 197,1. Crome and Richards 1988. Findley 1993) maintain that species ofbats mav parlition foraging habitat by vcgetittion stuucture, reflecting differcnces in their morphology. echolocation call structure. and flight capabilitics. Findley (1993) revicws the relation betu'een norphology and c()mmunity structure in bats. Forag ng Hab tat Aldridgc and Rautenbach (1987) divided Alri crn ilt\ccti\.'rtru\ hlt. into i,'ur ntajor er,'up. according to foraging-habitat prel'erence: ( J ) clutter fbragers, maneuverable specics with echolocation calls suited to a cluttered gnvironment and ca pable of foraging within the tirrest canopy; (2) inlcrmediate clutter foragers. moderately naneuverable bats capable of foraging in open areas and open woodland. but not within dense vegctation: (3) woodland-edge foragers; and (4) openair lbragers that lack naneuverability. Oficr authors hrve used sinilar classification schemes to describe North American bat species. Laval et al.( 1977) studied bat populations in Missouri and lbund that hoiuy and red bats tended to tbrage in open areas away trom forest clutter, including high over the lbrest canopy and over opcn fields. Gray bats foraged in riparian areas and overwater Little brown bats fofaged along tbrest edgcs and within the fbrest. The nonhen my otrs (.M. septe tridnlis) a close relative of $e Keen's myotis. a Pacific Northwest species, was a clutter lbrager and tbr aged in forested areas. The Indiana myotis (M sodcll.r), another clutter tbrager, foraged primarily in Lhc canopy, but the northem myotis tbr aged below the cant)py but above the understory shrub laycr. which suggests that sone vertical strlltification nav occur u'ithin bat cornmunities. Crome and Richards (1988) investigated thc differcntial use by bats ofgaps (created by logging) iurd closed canopy areas in an Australian rain fbrest. They divided bat species into canopy specialists (clutler foragers). gap incorporators (intermediate clutter folagers.). and gap specialists (open-air fbragers). Habitat preferencc ofthe bats was found to be related to wing morphology and tlight maneuverabiliry Canopy-specialists wcre highly maneuvemble, and gap specialists werc capable offaster but less maneuverable flight. Gap incorporators. which foraged in both types of habitars. had wing characteristics and flight capabilities internediate between the other two typcs. Crome and Richards (1988) concluded that vegetation structure aitd wing morphology determine allocation of different habitat types among species. 82 Wundcr and Carey Many Pacitic Northwest spccies lorage rn nparian areas (little bn)wn bats and Yuma bats (Kufta 1982. Hcrd and Fentor 1983, Lundc and Harcstad l986, Brigham et al. 1992), in clearings and roads within lbrests (Califbrnia bat. Yuma bat. and longIegged bat (Barbour and Davis 1969. Fenton and Bell 1979. Bdgham et al. 1992) or in open areas or along forest edges (hoary bat, red bat) rConstrntine 195i. Brrrelrr lqR5'. Clelnint.lccies, such as the long eared bat and possibly the Keen's bat. may tbrage within the canopy (Cou'an and Guiguet 1965, Manning and Jones 1989. Barclay l99l ). Nonc of these species are kno$'n to restrict its foraging to iust one habitat type, however. Ripadan areas and forest edges are exploited by many bat spccies to some extent, perhaps because these areas support higher densities of flying insects (Furlonger et al. 1987. Cross 1988, Thomas 1988. Barcla-v 1991). Landscape Context AlLhough several canopy altributes rnay be of consequence to bats (Carey, this issue). the composition of the sunounding landscape may also plaS a role in tleterminrng the relrtire imp,'nancc of spccilic attributes, and nray inlluence bat distribution. Somc landscape scale considerations ue discussed belorv. Distribution of Bats Scveral authon have lookcd at the diYersity of bat communitics iD different broad habitat types. ln general, topographically complex regions tend to suppoft the most bat species. Jones (1965) stud icdbats in the Mogollon MounLrins of NewMexico and Arizona. He rccorded the greatest percentage of capturcs in higher elevation, mixed-conifer. forest: an intemediate perccntage in mid-elevation. pine-oak woodlandi and the Iowest numb,cr of captures in lowland, xeric-shrub. grassland. These dift'erences were presumably related to differences in availability of rq)st sites. food resources. and water. Jones (1965) found that diffelent species donrinate the bat conxnunity in each of thesc habitats. Big brown bats prcdoninate in higher elevation coniferous forest, and hoary bats are most common in tbe pine-oak $'oodland. Tholna. r lvbb' l,'un.l .L Jrrlroportionrte u.e of old-growth Douglas lir stands by bats in the Cascacle Range of \\hshington and Orcgon and Coast Ranges ofOregon. compared to.voung and mature stands. Increased roost availability in old gro\\,th stands probably accounted for this difference because bats did not appear to be concentrating lbraging activity within the forest stands. Besource Proximity Although forest bats may have roosts that neet their primary requirements within a pafiiculal fbrest stand, the composition of the sulTounding landscape is impofiant in determining whether roost sites can be used successfully. Proxinity ofgood qualit.v roost sites to ti)raging and drinking areas. as weli as to hibernation sites, can rgduce thc energctic costs of cornmutirg (Tuttlc 1976). Be (cusc mrn) blt. cunLenlrrtc Iheir loragittg in riparian areas, proximity of roost sites to riparian areas assumes pafiicular importance. whcre roost sites are far t'rorn tbraging areas, iuvenile mortality may be higher Tuttle (1976) lbund that growth and survival ofjuvenile gray bats in the southeastem United States is impaired when the distance from the maternity roost site to foraging areas is too great. Optimal natemity roost conditions, highly productive lbraging sites, and ncarby hibemation sites can compensate fof greaterroostto-fi)raging site distarces, however (Tuttlc 1976). Bill\ 50rnetime. ma) requrrc connecling corridors ofsuitable habitatbetween critical re sources. Tuttle (1976) observed that gmy bats. which roost in caves and forage over water. gencrally fly be tween these sites within the forest canopy. The abun,lunec. Jirer\rl). and relali\e pr.,portion of criticll re\ource\ mJy rl.o bc itnport:lnt to bats. Many bats change roosts liequently and require several difterent roosts of diverse char riler lo cornpen\Jle lor change. in lir temperatwe, weather, predators, prey patches, and other factors. Humphrey et al. (1977) observed a matemity colony of Indiana bats that used two roost sites about 30 m apart. Each roost site had different thermal prepertics. and the colony shilied bet$,ecn them depending on temperaturc and weather conditions. Bats may thcrcfore need a selection ofdifterent roost sites (and perhaps different tree species), with a variety ofthermal and other properties. distributed across the landscape and located within a fairly constrained area. R parian Zones As is true lbr many other vertebrates. riparian zones assume disproponionate impoftance for many bats. Bat Canopy Use 83 \\'hich mrv do most of their forrging in these insecl-rich areas (Brigham et al. 1992). Bats frequently use riparian zones as travcl corridors as uLll. Th,,nrr. alql)tr l,'unLl thirt lbrrging rrtc. tor se\cral Prcific Northwest M-\'otl.i species ale si-unificantly highcr over water than in the ti)rest whcre they roost. Roost sites mav be nore abundant in riparian areas bccause of an increascd numbcr of snags and older trces, as u'ell as rock creYices in eroded strean banks (Cross 1988). For species such as the hoatJ bat, known to roost in dcciduous trees. ripariln areas ntay be preferrcd because of a preponderance of such trees in the riparian zone (Cross 19118). Riparian arcas also ptovide the open flight space and lbrest edgc conditions lequired by sontc species. Role in Forest Ecosystems Tree roosting bats. which deposit large amounts ol nitrocen dch guano at the loost site, may help 10 provide nutdents in tirrest ecosystems with nulricnt-poolsoils. Given thcir great nobilit)'. ba|s niry bc important in traDsporting nutrielts from riparian arcas or locations outsidc the tbrest eco systen into forcst communities (Cross 19E8, Raincv et al. 1992). Continuous occupation ofcavity roosts by bats rttrl tnodiil Ihf tr'\l \uh5lrcle rnLl cn\ irrrnlnenl in ways tl'rat aflcct othel cavity dwellcrs. These effects may inciude erosion of cavity sides. increased hunidity. incrcased antmonia. incrcasecl [en]pcrrture. and an enhuced rate of deterioration of thc roost tree by the accumulation of 1e ces and urine (Kunz 19li2a). Bats corsune lnany insects. such as termitcs. that are considered to bc forest pests (Whitakcr et a]. 1977). Their role in controlling torest pests remrins to be detcrnrinecl. horver,er. Literature Cited Aldfldge. H. D. J N.. and L L. ltaurenbach. 1987. \Iorphol- ^e]. ..'h ".:'r..' :rirJ re. r r. ( -.,rr I,,r' i ir' r' .(. li\orous b.rts. J. Anim. F-col.56:761 778. U.ilcr. R. H.. lnld C. J. Phillip\. 1965. Nlu nrls lioln El Ne\a.lo dc Colim . Me\ico. J. Nlrnnn.rl..16('1):691 693. Brrbour. R W. rnd \\. II. D,r\is 1969. Brrs oi Anrc ca. Unilefsitt Press d KcrtUckr-. Le\ington. Barcllr). R. \I. R. 198.1. Oh\!'r!ations on the migrarion. ccol og) .rnd behr!ioul olbati .rl Dclta N1af\h. Nlanirohi. C.Ln. I-ield Nrt 98(l):lll 316. tsrfcla). R. NL R. lqlts. LonS \crsu\ lho r.rnge for.rgjng \lrlLcgres ol horft (1-(\l|rrrrrk,"lJ] nd,iil\ef haircd (L1sio,rt ttt i\ nodi\It!( .r )b.rts rnd the conscqucnccs lbrpre) \election. Clrn. J. Zoo1.63:1501 2515. Conclusion Bats are a highly diversified taxonomic group whosc small size. low rcproductive rate. high cnergv demand. and conrplex needs have made them, perhaps, more vulnerable thitn many other veftebrate groups. These complex nccds require a complex environnent. Tall canopies and diverse lorest slructure, such as thosc tbund in late scral stages ofconifcrous fbrests may provide some of the complexity needed by bats (Perkins and Cross 1988). For many bat species. a mosaic of habitat types in close proximity to one another, including u ntir ol i,,r.\t:. r,nenil)g:. un.l rip:rrirn rl eas. mry provide optinral habitat. A trernendou: ctn,\unl ,'l re\carch rcrnrins lo be donc to assess the rolc of fbrest canopics in Pacific Northwcst bat communitics. The relative importance of the canopy attributes descdbcd in Carey (this issue), including such lactors as lay ering, dcgree ofcanopy closure, gaps, canopy volume, ittrd ffee species characteristics. need to be investigated. Much of the inlbflnation currently available is anecdotal. often based on unproven assumptions. or represents genemlizations derived from knowledge of bat communities elsewhere. Additional data are needed on roost availability vs. use. insect densities. and prey selection by bats iD the canopy and il lbrest gaps, and elfects oflandscape compositi{)n on bat behavior Effective nanagcment fbr bats in thc Pacilic Northwest will require basic rcsearch ol forest canopy and landscapc use. This type of infirrmation should prove valuable for making management decrslons on car,ity trce retention. cretrtion of multilaycred crnopies. and riparian zone prolcction. Bxrcl.r,,-. R. lU. R. l99l. Popul.rtxm structure ot lcnpemte zone j$ecti\Iyous bats in relrtion toforaging b.hu!iour al1d energ! demand. J. Anin. Ecol. 60:165 178. Barclay. R. I{. R...rnd K. J. C.rsh. 1985. A non cornnensal maternit) roost of tlrc liule bro!\'n bar (Mlrrir /ll.i|, q,r ). J. \IamJnal. 66(1):782,7i11. Barcl l. R. \4. R.. Frure. PA. .rnd I). R. Frrr l9lt8. Roosr inq beha\,ior and roost \electio by nigfating sil\'er haifed bats (L./rirn./. riuor rir..l8.r,rr). J. Nl.tnmal. 69(.1):821 815. B r.l' H. T. n 1. \ rr{ - r( npif., e h]| . ture dpfe,vpoplrlations J.\,l.rm'nal.55(I ):138-157. Brigham. R. trf. 199i. Flcibilit)- in f aging and roosring beh.r\iour b] thc big bro$,n hat (tp.rri.llJ lrlj.!J). Can. .1. Zool. 69:117l2l. lJ,l Wundcr and Carcy Brighan. R. M.. Aldridgc. H. D. J. N. .rnd R. L. Niackc,"-. 1992. Vrriation in habitat usc and pre] seleclion bt Yuina hat\. ,lh orir r r/rrdr{,rr i !. J. N4amnr.1l. 73(l):6.10 6'15. Christ] lt. 8., and S. D. \\tsr l993.Biolo!,vofbatsinDou glr\ llr lbrests. USDA For Sen'. Ccn. Tcch Rep P\1\'- GTR-108 Piciiic Norlh$. Res. Stn.. Podland. Orcgoi. 28 P. Con(!anrinc. D. G. 195iJ. Ecological obscr! alions on lasiufine bats in Ccorgia. J. Nlalnnlal. 39(l):6.1 70. Const.rntire. D. G. 1966. F-cologicll obser!rrions on lasiurinc hal\ i. Io$.r. J. Nlrlmmrl. .11( | ):-11 ,l l Cow.rD. L \1 . and C..1. Cuigucr. I 965. The lnrLnlmals of Brit lsh Colu rbia H.rDdb. I L Briiish ColrnnbiaPro!. NIus. Viclori . British Columbia. Cmme, F. H. J.. rid c. C. Rich.rfds. 19E8. Bats and g.rps: nlicrochlfopteran cLrn)r11uDitr st[lctuf e in .l Queen\land | | n r..i,. fc, l.,p] 6a'ri lu(ru 1 ,0". Cross. S. P 1988. RipariLrn \vstems and small rnanmals and bars r? K. J. Racdckc (ed.) Stfeamside managcmcnl: riplri.rn \iildlile rnd forc\try rnteractions. Uni!efsity of\r.rshington. Insl. For. Resour. Conrib.59. Scarrlc. \U!hington. lentm. \l B. ]970. Population nudies of M\oti\ lrciJitgus (Cliroptera: \t\pertilionidac) in Onturio. Lile Sci. Conrr. R. Ol1t. tr{us.7l:1-3,1. lenton. \,1. B. 1981. Iicholoca{ion. insect hearing. and lied ing ecolog)- of insecti\orou! bats 1, T. il. Kunz (ed.) ticolog) ol bals. Plenuln Pres\ NervYork. Fcnton. NI. B. nd R.lU. R. Barcla) 1980. Mrrri.r /l.l/4/gri. Nlam al. Spccics. l,l2: I -8. Fcrton. M. B.. and G. P Bell. lc)79. Echdoc,rtion and feeding beha\jour jn lbur species of,l/_\yrir (Chiropcra). Can. J. Zool.57rll71 1177. I-enion. Nl.8.. Cl. C. !rlnZ)ll deJone. G. P Ucll. D. B. C.nnpbell. .rnd V. l-apltnlc. 1980. Di\tfibution. partuntion dalcs. aDd fteding of bats i. south ccntrll Bfrlish Colum hia. Clrnad. field-Nrr. 9.1('1):,116 ,120. firdle)-. J. S. 1991. Bats: a comnunit,,- perspecti\,e. Cam bridgc Univorsit)- Pre\s. C.rmbridge. Fuflonger. C. L.. H. J. Derar. and M. B. fenton. I987. Habi trt u\e b\ tirraging insccti!orou\ bats. C.Ln. J. Zool. 65:2E,1 l8E. Herd. R. IL. rnd lvI. B. l-enion. 1981. An elecoophoretic. morphological. .rnd ecological investigation of a pu hlive hlbrid zone bet$een M\?ti\ lucifui s,iJ1(lM\o* \ r/rrz,r.r\6 (Chrroplcr ri \tspenilioridae ). Can..l. Zool. 61:2019 2050. Humphre). S. R. 1975. Nurseri roosts and corrlnunir\' di!.r sil) ol nearctic brl\. J. N{a'nJnal. 56(l)r 321 3'16. Hulnphre!, S. R.. A. R. Richter, and J. B. Cope. 1977. Sum mer habilal rnd ecolog) of the endangered lndirnr bat..t4d,r \rdzrli!. J. lllamnral. 58(31:3-l.l-3'16. Jones. C. 1965. hcologicrl distribution rird rctivity periods 01bal!oi rhe N{ogollon N{ount nsarcaofNc\ }{exico and rdircent Arizona. Iulanc Stud. Zool. l2(.11:91100. Kfutz\ch. P H. 195:1. Notc! on thc habits ofthe brt. Mryri' .a1il1,,n &!. J. Nl.rmntrl. -15(,1):539-515. Kun7. L ll. 1982a. Roosting ecolog\ of bar! 1r T H. Kunz (ed.) Lcolog) ol bats. Plenum Press. Ne$ York. Kunz. T. H. 1982b. tainrr,irr? r ro./ir..rgd,rr. Malnmal. Species. 172:l 5. Kunz. T. H.. and R. A. \{aiin. 1982. Plt.otu\ tott,t\(ndii. Nlalnnlrl. Species. l75rl 6. Knrta. A. l9 8:. Flight prttern s of tpl.rri.rs l,lrcrr and Mf,rir lk rfuSrlr over .r stream. J. N4ammal. 63(2):335-311. Lrval. R. K.. R. L. Clawson. N{. I-. LaVi. and $l Caire. 1971. forrsing beha|ior and noclurnrl rctivit,v pat lcms of NIi\soufi bat!. \|ilh emphasis on the endan gered species M,r.)rir trir-cr.drtj and Mf,/i.l .1o./.rlir. J. N{rm'nal.58(,+lr 591 599. Lurde. R. E. xndA. S. Harlslad.1986.Activit! oflilllcbro\rn bats in coasraltorcs(s. Norrhw Sci.60(.1):206 209. I-unncv. D.. J. Barkef, D. Priddcl. ard NL O Connell. 1988. Roosl selection bvGould slong edred brt, ,\Jr-/,/'/1//irr gorlldiT(nnes ( C h iroptera: Vcspeiiliuridae). in loggcd lbrcst on the south coasr oINew South \\hles. Aust. wildl. Res. 15i375 38,f. Maeda K. I 9 7.1. Eco clhologie de la gr.rnde nociule. Nl./l1/lls ldrn4t(/&r. a S:rpporo JrLpon. Nlammalia. 38(3):,161 - .18t. Nlanning. R. W.. a.d J. K. Jones. 1989. M_\,ri\ (l,dir. Mammal. Sfecies. 329r1 5. Ncill. $'. T. I951. Hoary bat in a squirel s nest. .1. Nlamnal. 33(1):lll. Norberg. U. NI., and J. M. V Rayner. 1987. Ecological mor phology and ilighl in bat\ (N,lammaliar Chiropteftr): wing adaputids. llight performancc. lbnging srrategy and ccholocation. Phil. Trans. R. Soc. Lond. B. 316r335 427. Perkins. J. N{.. and S. P Cross. 1988. Differential use ofsome coniferous Iorcst habit.rts bl hoary and silver h.rired bats in Oregon. Munelet 69:21-2.1. Rainey. W 8., E. I). Picrson. NL Colberg. and J. H. Barcl.rr'. loo2. Bar. n 1oll, $ rcJu.',J.:.er.onr u:e,rrJruie in nutrient ransler into old growth communities. Bar Re!. Ncws 33(,1):71. Shump. K. A. andA. U. Shurnp. 1980. Comparative insula !ion in Vespertilidrid bais. Conp. Biochen. Ph!siol. 66Ar35l 35.1. Shumt. K. A.. and A. U. Shump. 1982. La\tltnll cu.re1!. N{ammi1]. Spccics. 185: 1-5. ThoDras. D. W I 9E 8. Thc distribution of bat! in diilcrent ages of Douglas [r lbrests. J. Wildl. Managc 52(,1):619626. 'Ildenrann. C. R.. rnd S. C. Flavcl. 1987. Factofs affecting choice oi diurnal roon sil. by tfee-hole bals (Micruchircplera)insouth canemAustr. ia.Aus.Wildl. Rcs. 1.1:.159-173. Tuttle. N{. D. 1976. Population ecology officsra} bat (,t _i ori.l g/ird!r.rrr): itrctofs influencing gro\!th and suni\al ofncwh lolent \'oung. Ecolog]'. 57:587,595. Ia. lyll d. Jong C. G. 1985. Handbook ofCanrdilln marn nals. \'(rl. 2: Bals. Naliontl I{useun\ of Canada. Ol Vrughan, T. A. 1910. Thc skcleltrl sr-sten. 1, WA. Wimsatt (ed.l Biolog) of Ba|s. \bl. 1. Acrdemic Prcss. New York. \-JchJn. T A Ln8n. Off.flu r\ . t(<J nr b\ t$..0c( (. ur 16,', J \1.,r n Jl. o rl. llb lt '. Whitakcr. J. O.. N{r\er C., and t-. B. Kcller. 1977. Food hab its ofb ts ofwe\tern Orcgon. Nofth\\,. Sci.5l:,16 55. BaL Canopy Use 85