Bat Use of Remnant Old-Growth Redwood Stands WLLLARi1 j. ZIELINSa* AND STIE\;EN T. GELL U.S. Forest Service, Pacific Southwest Research Station, Redwood science;, hrcata, CA 95521, U.S.A. Abstract: ~Ziostof the old-growth redzuood (Sequoia sempen~irens)in Cal@t*tzia has been cut; reg-enerati~zg forests willpt-obably never resemble those that were haniested, and what old growth remains on priuate land occurs in small, isolated remnant patches. The landscapes in which these stands occur dzyfer so markedly from their original condition that their value as habitat to mauy species of wildlzye, iincluding bats, is un- knoufn.Previozks research in zmnfragmented redwoodforests demonstrated that bats use basal hollows itz old- growth redufoodsas roosts. We sought to determine whether bats use similar old-growth trees as roosts when they occur in small, remnant patches of isolated old growth on commercial forest land. We compared bat oc- currence in remnant and contiguoz~sstands by collecting guano in traps suspended in hollows and by moni- toring flight activity with ultrasonic bat detectors. Hollouls in trees zuithin the remnant stands had signzyi- cantly more guano deposited per tree than the trees within the contiguous forest. me mean rzumbers of bat passesper night were statistically indisti~zguishablebetween the two treatments, aldhozk@ mean Fight uctivity in the remnant stands was greater than in the contiguous forest. Bats frequently used basal hollou~sin small ((5 ha) stands of remnant old growth, u~hichmay be due to the closer proximity of remnants to stream courses, to their greater interface with edge where foraging success may be greater, or to the fact that the lower density of hollow-bearirzg trees in remnants than in contiguous forest favored greater use per tree. Sig- nzyicant use of small, residual old-growth redwood provides reason to maintain these remnants in managed landscapes as potentially important habitat for forest bats. Uso de Reinanentes de Bosques Maduros de Secoyas por Murcielagos Resurnen: La mayorfa de 10s bosques maduros de secoyas (Sequoia sempervirens) de Calzyornia ban sido tal- ados, 10s bosques en regeneration quiza rzunca sean lo gue alguna vez fueron 10s bosques talados y lo gue gueda de bosgue maduro en propiedudes privadas ocurre en parches renzanentes pequefios y aislados. Los paisajes en los cuales estos remanentes ocurren difieren tan marcadamente de las cotzdiciorzes originales que su valor como hdbitat para muchas especies de uida siluestre, incluyendo a los nzurci6lagos es desconocido. Inuestigaciones preuias en bosques no fragmentados de secoyns demostrnron que 10s murcie'lagos utilizan huecos en 10s &boles como perchas. Intentamos determinar si 10s murci6lagos usan drboles similat-es a 10s utilizados en bosques maduros cuando estos ocurren en parches de bosque maduro pequeGos y aislados etz tiemsforestales comerciales. Comparatmos la presencia de mut-cie'lagos en sitios renzanentes y etz sitios con- tiguos mediante la coleccion de guano en tmtnpas suspendidas en agujeros y por motzitoreo de la nctividad de vuelo ~nediantedetectores ultmscjnicos de mu~"ci6lagos.Los agujeros en 10s urboles dentro 6le 10s sitios re- tnanetztes tuuieron significatiuamerzte mas guano depositado por arb01 yue los drboles dentro de bosgues contiguos. El nzimero promedio de murci6lngos que pasaron por rzoche fzce estadisticamente irzdistizzguible entre los dos tratamientos, aungue la actiuidadpromedib de vuelo en 10s bosgues remanentesfae nzayor yue en 10s bosques copztigzcos. Los murcie'lagosfrecue~ztefnenteutilizan agujeros busales epz porciofzes remanentes peqzceAas de bosque madzaro (<5 ha), lo czcalpuede deherse a fa cerctzna proximidad de los I-emanentesn los cauces de an-oyos, su gt-an interface con el borde donde el e'xito deforrajeo &he ser mayor, o a1 hecho de yzme la densidad baja de drboles con agzajeros en las bosques remanetztesfacorece un mqyor uso por drbol. El uso signzyicatiuo de pequeAos bosques residuales maduros de secoyas provee una razon para manterzer estos re- matzentes en paisajes manejados como un hdbitat potencia1 para murcielagos de bosque. * email u?zieZinski/[email protected]. us. Paper submitted October 17, 1997; revised manz~scriptaccepted Ma!y 20, 1998. Conservation Biology, Pages 160- 167 Volume 13, No. 1. February 1999 Corsi et nl editors. Large-scale ecology and conservation biology. Blackwell 210 in D. R. McCullough, editor. Metapopulations and wildlife con- Scientific Prtblications, Oxford, Iinited Kingdom. sesvation. 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Der Wolf, Mythos und Verhalten. Meyster Verlag, Wien, tion 6:959-978. Austria. Price, M. V , and M. Gilpin. 1996. Modelers, mammologists. and meta- Zimen, E.. and L. Boitani. 1975. Number and distribution of wolves in populations: designing Stephens' kangaroo rat reserves. Pages 217- Italy. Zeitschsift fiir Saugetierkunde 40:102- 112. Conservation Biology Volume 13, No. 1, Febn~ary1999 Introduction and exists as young, second- or tbird-growth forest. Old- growth forest that occurs outside the bomdaries of fed- With the exception of extensive stands that may occur in eral and state parks does so in the form of small, remnant reserves such as national parks, remnant patches are stands that punctuate the landscape of young forest. about aU that remain of the original forest cover that pre- These small stands are increasingy valued by ddlife ceded European settlement in the United States. Approxi- managers for the unique and rare elements they pro- mately 85%of the primary forests in the United States and vide-large and sometwes hollow live trees, large snags, 95-9896 of those in the conteminous 48 states have been large logs-and by environmentalists who wish to protect harvested (Postel & Ryan 199I). The result has been an in- original forests that are not cunently in reserves. crease in the number of forest fragments, amount of edge, With the knowledge that bats use hollows in old- and isolation of remnant forest patches (Groom Sr Schu- growth redwood forests, we became interested in deter- nlaker 1993). In many cases, small patches of original for- mining whether this use was iduenced by the type of est are all that remain as examples of particular vegetation stand in which the hollow-bearing tree occurred.