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Moths consumed by Corynorhinus townsendii virginianus in eastern Kentucky.

INTRODUCTION

The Virginia big-eared bat (Corynorhinus townsendii virginianus), reclassified from the genus Plecotus (Tumlison and Douglas, 1992), is the most eastern subspecies of Townsend's big-eared bat (C. townsendii; Handley, 1959). Due to a scattered distribution, small population size and an extreme sensitivity to human disturbance, C. t. virginianus was listed as endangered by the U.S. Fish and Wildlife Service in 1979 (Bagley, 1984). The majority of C. t. virginianus in Kentucky hibernates in a single limestone cave and forms maternity colonies in rock shelters in sandstone cliffs (Lacki et al., 1994). Sandstone cliffs and adjacent timber are primary foraging areas (Adam et al., 1994; Burford and Lacki, 1995) for C. t. virginianus in Kentucky, with rock shelters in cliffs used as feeding roosts (Lacki et al., 1993).

Dietary studies reveal that all subspecies of Corynorhinus townsendii are moth specialists (Ross, 1967; Whitaker et al., 1977, 1981; Dalton et al., 1986, 1989; Clark, 1991; Sample and Whitmore, 1993), with both macrolepidopterans (Dalton et al., 1989; Sample and Whitmore, 1993) and microlepidopterans (Ross, 1967; Whitaker et al., 1977) consumed. However, only limited information is available on the species of moths eaten by C. t. virginianus (Sample and Whitmore, 1993).

The majority of the known roosts and foraging areas of Corynorhinus townsendii virginianus in Kentucky are located on public lands managed by the U.S. Forest Service (Adam et al., 1994; Lacki et al., 1994). Timber harvesting is an ongoing management practice on the Daniel Boone National Forest, Kentucky; however, no information exists on whether such activities could impact the species of moths on which C. t. virginianus feeds. We present data on the species of moths eaten by C. t. virginianus in eastern Kentucky and distinguish, from among the species of moths that are eaten, those that are dependent on woody plants for larval development.

STUDY AREA AND METHODS

The study was located in Lee County, Kentucky (37 [degrees] 39[minutes] N, 83 [degrees] 46[minutes] W), on land predominantly managed by the U.S. Forest Service. The terrain is characterized by sandstone cliffs dispersed among hills. Elevations range from 182 m along floodplains to 424 m on ridgetops (Campbell et al., 1989). Limestone deposits below the sandstone contain extensive cave formations.

Eighty percent of Lee County is covered by mixed mesophytic forest (Newton et al., 1974). Forests in our study area were of second growth yellow-poplar (Liriodendron tulipifera - 20-50 yr of age), with sugar maple (Acer saccharum), chestnut oak (Quercus prinus), white oak (Q. alba), scarlet oak (Q. coccinea), black walnut (Juglans nigra), American basswood (Tilia americana), white ash (Fraxinus americana) and eastern hemlock (Tsuga canadensis) (Campbell et al., 1989). The base of cliffs support dense thickets of mountain laurel (Kalmia latifolia) and rhododendron (Rhododendron spp.), with chestnut oak the dominant overstory species. Vegetation on the top of cliffs varied with the breadth of the ridgetop; narrow ridges supported pitch pine (Pinus rigida) and broader ridges were dominated by Virginia pine (P. virginiana) and shortleaf pine (P. echinata).

We located 26 rock shelters within or adjacent to two hollows used as foraging areas by Corynorhinus townsendii virginianus (Adam et al., 1994; Burford and Lacki, 1995). One hollow contained both a limestone cave that served as the hibernaculum and summer bachelor roost of C. t. virginianus and a sandstone cave that served as a summer maternity roost of this species, and the adjacent hollow contained a sandstone rock shelter that also served as a maternity roost (Lacki et al., 1994).

Rock shelters were identified as potential feeding roosts based on our finding culled moth wings or guano of Corynorhinus townsendii virginianus on the shelter floor, or the presence of a roosting C. t. virginianus (Lacki et al., 1993). The floor of each feeding roost was cleared of moth wings before starting sampling. Culled forewings were collected on 26-28 June, 13-15 July and 17-19 August 1992, and placed into plastic bags for later identification. Forewings were identified to the lowest discernible taxon using guides in Holland (1903), Hodges et al. (1983), Covell (1984) and Borror et al. (1989). Each wing was treated as a separate observation, with no attempt to pair right and left forewings. We assumed that all of the moth wings recovered were discarded by C. T. virginianus (Lacki et al., 1993).

Intuitively, wingspan is more likely to be an important feature of moths detected by bats than dimensions of a single wing; thus, we tabulated the average wingspan for each of the species consumed and produced a mean, standard deviation and range of wingspan by family. We used literature values (Covell, 1984) rather than measuring actual wings, because culled wings were seldom fully intact, and estimating the body width would introduce error. Where information was available (Covell, 1984), we distinguished the species of moths eaten by C. t. virginianus that are dependent on woody plants in the larval stage.

RESULTS AND DISCUSSION

We collected 222 identifiable, culled forewings of moths in feeding roosts of Corynorhinus townsendii virginianus, from which we identified 45 species and six families of moths (Table 1), including Noctuidae (n = 139), Sphingidae (n = 41), Geometridae (n = 24), Notodontidae (n = 13), Thyatiridae (n = 3) and Lymantriidae (n = 2). Wings of Noctuid moths were recovered most often in feeding roosts of C. t. virginianus in West Virginia (Sample and Whitmore, 1993), followed by wings of the Notodontidae, Geometridae, Sphingidae and Arctiidae in descending frequency. We recorded no Arctiid wing in any feeding roost of C. t. virginianus in eastern Kentucky.

Forewings of 10 species of moths occurred [greater than or equal to] five times in feeding roosts, including the greater red dart (Abagrotis alternata), the ipsilon dart (Agrotis ipsilon), the azalea sphinx (Darapsa pholus), the lettered sphinx (Deidamia inscripta), the curve-toothed geometer (Eutrapela clemataria), the white-dotted prominent (Nadata gibbosa), the gray quaker (Orthosia alurina), [TABULAR DATA FOR TABLE 1 OMITTED] [TABULAR DATA FOR TABLE 2 OMITTED] the red-lined panopoda (Panopoda rufimargo), the variegated cutworm moth (Peridroma saucia) and the armyworm moth (Pseudaletia unipuncta). Seven species of moths for which wing remains were recovered in feeding roosts of Corynorhinus townsendii virginianus in West Virginia (Sample and Whitmore, 1993) were present in forewings recovered in feeding roosts in eastern Kentucky, including the confused eusarca (Eusarca confusaria), the Canadian melanolophia (Melanolophia canadaria), the red-lined panopoda, the armyworm moth, the white-blotched heterocampa (Heterocampa umbrata), the white-dotted prominent and the walnut sphinx (Laothoe juglandis).

Length of forewings recovered in feeding roosts ranged from 1.3 cm for the lesser maple spanworm moth (Itame pustularia) to 4.1 cm in the bride (Catocala neogama). The average wingspan for the species of moths recovered in feeding roosts was 4.7 cm. The diet of Corynorhinus townsendii virginianus included species of moths at the smaller end of the size range for the Noctuidae and Sphingidae in eastern North America (Table 2).

Our sampling approach was limited to the culled wings of moths deposited in the feeding shelters, and is unlikely to represent the entire species assemblage of moths consumed by Corynorhinus townsendii virginianus in eastern Kentucky. Sample and Whitmore (1993) noted that some moths may be consumed on the wing because of small dimensions and, thus, body parts that do not need to be removed before consumption. They inferred that such prey would not be represented in feeding roosts. We found no moth with a forewing length [less than] 1.3 cm in feeding roosts of C. t. virginianus and suggest that 1.3 cm likely is an upper limit of the size range of prey that C. t. virginianus consumes while in flight.

Families of moths known to be eaten by Corynorhinus townsendii virginianus before this study include Arctiidae, Geometridae, Noctuidae, Notodontidae and Sphingidae (Dalton et al., 1989; Sample and Whitmore, 1993). With the exception of Arctiidae, we recovered forewings of moths from all these families in feeding roosts of C. t. virginianus, along with two forewings of Lymantriidae and three forewings of Thyatiridae.

Based on information in Covell (1984), the majority (77.8%) of, at least, the larger species of moths identified as prey of Corynorhinus townsendii virginianus develop from larvae dependent on forest plant species, with the larval food requirements of three prey species still unknown (Table 1). Ten of the 45 species recorded as prey are pests in the larval stage to their respective host plants (Covell, 1984). The lesser maple spanworm moth, the greater red dart, the ashen pinion (Lithophane antennata), the speckled green fruitworm moth (Orthosia hibisci), the maple looper moth (Parallelia bistriaris) and the variable oakleaf caterpillar moth (Lochmaeus manteo) affect forest hardwoods and orchard trees, whereas the ipsilon dart, the Boston dart (Euxoa bostoniensis), the variegated cutworm moth and the armyworm moth impact cultivated plant species.

These data indicate that Corynorhinus townsendii virginianus feeds on a wide variety of species of moths in Kentucky, and that most of the prey species depend on woody plants for larval development. To adequately manage and protect C. t. virginianus in Kentucky, we recommend that public land agencies evaluate the impact that land use practices, such as timber harvesting, might have on the populations of moth prey species that these bats depend on for their survival.

Acknowledgments. - Funding and support for this project was provided by the U.S. Forest Service and the University of Kentucky College of Agriculture. We are indebted to M. Adam, B. Deetsch and M. Polhill for field assistance, and to C. Covell Jr. for help in identifying forewings. J. MacGregor provided references and constructive comments. This investigation (no. 94-8-238) is connected with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.

LITERATURE CITED

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HODGES, R. W., T. DOMINICK, D. R. DAVIS, D.C. FERGUSON, J. G. FRANCLEMONT, E. G. MUNROE AND J. A. POWELL. 1983. Checklist of the Lepidoptera of America north of Mexico. E. W. Classey Ltd. and the Wedge Entomol. Res. Found. 284 p.

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-----, ----- AND -----. 1993. Characteristics of feeding roosts of Virginia big-cared bats in Daniel Boone National Forest. J. Wildl. Manage., 57:539-543.

NEWTON, J. H., C. W. HAIL, T. P. LEATHERS, P. M. LOVE, J. G. STAPP, V. VAUGHT AND P. E. AVERS. 1974. Soil survey of Lee and Estill counties, Ky. U.S. Dep. Agric. Soil Conserv. Serv. and For. Serv., Washington, D.C. 87 p.

Ross, A. 1967. Ecological aspects of the food habits of insectivorous bats. Proc. Western Found. Vertebr. Zool., 1:205-264.

SAMPLE, B. E. AND R. C. WHITMORE. 1993. Food habits of the endangered Virginia big-cared bat in West Virginia. J. Mammal., 74:428-435.

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WHITAKER, J. O., JR., C. MASER AND L. E. KELLER. 1977. Food habits of bats of western Oregon. Northwest Sci., 51:46-55.

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Author:Burford, Laura S.; Lacki, Michael J.
Publication:The American Midland Naturalist
Date:Jan 1, 1998
Words:2142
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