2007 NORTHEASTERN NATURALIST 14(3):317–322 Food Habits of Myotis leibii during Fall Swarming in West Virginia Joshua B. Johnson1,* and J. Edward Gates1 Abstract - The ecology of Myotis leibii (eastern small-footed myotis) remains largely unclear, including its foraging behavior. During fall, cavernicolous bats must accumulate enough fat reserves to sustain them during winter hibernation. We examined the food habits of eastern small-footed myotis captured at abandoned coal mines at New River Gorge National River in West Virginia during fall 2005. Based on fecal samples from 44 bats, we found that eastern small-footed myotis diets were diverse, containing 9 families within 7 orders of insects. Lepidoptera were consumed by all but one bat and represented the largest average percent volume among insect orders. This study elucidates an important component of the foraging ecology of this rare bat species. Introduction Myotis leibii Audubon and Bachman (eastern small-footed myotis) is considered rare throughout its range, which includes northern Arkansas and southern Missouri, east to the Appalachian Mountains and Ohio River basin, and north into New England, southern Ontario, and Quebec (Barbour and Davis 1969, Best and Jennings 1997). Although the causes of its rarity are unclear, it is suspected that low over-winter survival rates may be a factor (Hitchcock et al. 1984). During winter, eastern small-footed myotis hibernate in colder portions of mines and caves, where they sometimes are found in crevices and under rock slabs (Davis and Lidicker 1955, Gates et al. 1984, Martin et al. 1966). Anecdotal observations indicate eastern small-footed myotis roost in mines, caves, and rock outcrops during summer (Best and Jennings 1997, Hall and Brenner 1968), and are rarely associated with buildings (Hitchcock 1955). In late summer and early fall, eastern smallfooted myotis and sympatric cavernicolous bat species arrive at cave and mine entrances and exhibit swarming behavior. Swarming is thought to fulfill particular life-history requirements such as mate selection, breeding, and hibernacula selection (Cope and Humphrey 1977, Fenton 1969, Schowalter 1980). During this time period, bats accumulate fat reserves vital to surviving hibernation (Ewing et al. 1970, Fleming and Eby 2003, Krulin and Sealander 1972, Tuttle 1976). Little is known about the food habits of eastern small-footed myotis. To our knowledge, the only published record of food habits of eastern small-footed myotis examined fecal samples of 4 individuals captured at caves in western Maryland (McDowell-Griffith 1983). We examined the food habits of eastern 1University of Maryland Center for Environmental Science, Appalachian Laboratory, 301 Braddock Road, Frostburg, MD 21532. *Corresponding author - jjohnson@al.umces.edu. 318 Northeastern Naturalist Vol. 14, No. 3 small-footed myotis during fall swarming because little is known about this aspect of its ecology, despite the importance of preparing for hibernation. Study Area and Methods We conducted bat surveys at abandoned coal mines at New River Gorge National River (NERI) in Fayette County, WV. NERI contains approximately 28,329 ha located in the Appalachian Plateau physiographic province (Fenneman 1938) and is characterized by steep slopes and exposed rock cliffs ascending 300 m above the river to plateau-like ridge tops. The New River courses through NERI and is provisioned by high-gradient streams that incise the steep slopes of the gorge. Quercus spp. (oaks) dominate the forest overstory, while the understory mainly consists of Rhododendron maximum Linnaeus (rhododendron). The abandoned mine portals at NERI are used by many bat species, including Corynorhinus rafinesquii Lesson (Rafinesque’s big-eared bat), C. townsendii virginianus Cooper (Virginia big-eared bat), Eptesicus fuscus Beauvois (big brown bat), eastern small-footed myotis, M. lucifugus LeConte (little brown myotis), M. sodalis Miller and Allen (Indiana myotis), M. septentrionalis Trouessart (northern myotis), and Perimyotis subflavus Cuvier (eastern pipistrelle) (Johnson et al. 2005, 2006). We surveyed for bats at 19 NERI mine entrances during fall 2005 (22 August to 29 September). We used 1-m2 harp traps (Bat Conservation and Management, Carlisle, PA) and/or mist nets (6 x 2.8 m or 9 x 2.8 m, depending on entrance size; Avinet, Dryden, NY) to capture bats entering or exiting the mines or swarming around mine entrances. Harp traps were positioned in mine entrances and were surrounded with tarpaulin to prevent bats from bypassing the harp trap. We positioned mist nets 1–2 m from mine entrances, if harp traps were not used. Depending on their proximity, 1–3 mine entrances were sampled each night. We sampled each mine entrance 3 nights (once in August, early September, and late September, respectively) between sunset and 0000 hours, with at least 9 nights separating consecutive samples. Data collected from each captured bat included species (Menzel et al. 2002), sex, age, and reproductive condition (Anthony 1988, Racey 1988). The reproductive condition of females and the ages of all bats were difficult to determine during fall sampling and were not considered during analyses. We uniquely marked their wings with non-toxic paint markers to facilitate identification of recaptures within the same night (Barclay and Bell 1988). Bat recaptures at caves or mines during fall swarming are typically less than 5% within the season (Fenton 1969, Marsh 1998). We placed captured eastern small-footed myotis in plastic containers for 􀂔10 minutes or until fecal samples were obtained. Sampled bats and those that did not void feces within 10 minutes were released unharmed. Fecal samples were frozen until analysis. Bat capture and handling protocols were approved by the Institutional Animal Care and Use Committee of the University of Maryland Center for Environmental Science (Protocol Number F-AL-05-06) and followed the guidelines of the American Society of Mammalogists (Animal Care and Use Committee 1998). 2007 J.B. Johnson and J.E. Gates 319 We used a 20–40x dissection microscope to examine fecal samples, which were placed in a petri dish and teased apart into a uniform layer in 70% isopropyl alcohol (Whitaker 1988). To facilitate insect identification, we used a reference insect collection and referred to dichotomous keys and figures in texts (e.g., Triplehorn and Johnson 2005, Whitaker 1988). We identified insects to order, and superfamily or family when possible. We followed the insect taxonomic classification system in Triplehorn and Johnson (2005). We visually estimated percent volume of each insect order in each sample by backlighting a transparent 1-mm2 grid beneath the petri dish (Whitaker 1988). We estimated percent volume of Lepidoptera according to Whitaker (1988) and a bat food-habits study in West Virginia (Carter et al. 2003). We calculated average percent volume and percent frequency of prey items for the dataset. The average percent volume was the average percentage by volume of each insect type in the total sample. This measure is useful for determining if, on average, certain insect types comprise a large portion of bat species’ diets. The percent frequency was the number of bats consuming each insect type divided by the total number of sampled bats (Whitaker 1988). This measure determines if consumption of a certain insect type is widespread among individuals of a bat species. Together, average percent volume and percent frequency can be used to examine if few individuals of a bat species are consuming a particular insect type or if they are more general in their prey preference. Results We captured 84 eastern small-footed myotis, including 66 males and 17 females, at 18 mine entrances throughout the sampling period. One eastern small-footed myotis escaped before sex was determined. Fecal samples were obtained from 44 eastern small-footed myotis, including 39 males and 5 females. We identified 7 insect orders, 1 superfamily, and 9 families in the fecal samples. Lepidoptera (moths) were the most frequently consumed insect order and were more abundant, on average, than any other consumed insect order (Table 1). Other insect orders (superfamilies or families) we identified included Hymenoptera (Chalcidoidea and Ichneumonidae, parasitic wasps), Coleoptera (Curculionidae, snout beetles; and Scarabaeidae, scarab beetles), Diptera (Mycetophilidae, fungus gnats; Psychodidae, moth flies; and Tipulidae, crane flies), Psocoptera (Psocidae, common barklice), Hemiptera (Cercopidae, froghoppers), and Neuroptera (Hemerobiidae, brown lacewings). We observed soil particles or small gravel from 3 bats. Table 1. Insect orders found in fecal samples of Myotis leibii (n = 44) at New River Gorge National River, WV, 2005. Lep = Lepidoptera, Dip = Diptera, Col = Coleoptera, Hym = Hymenoptera, Pso = Psocoptera, Neu = Neuroptera, and Hem = Hemiptera. Insect order Lep Dip Col Hym Pso Neu Hem Percent volume 58.5 24.7 5.5 5.4 3.4 1.6 1.0 Percent frequency 97.7 65.9 45.5 27.3 15.9 6.8 4.5 320 Northeastern Naturalist Vol. 14, No. 3 Discussion Eastern small-footed myotis consumed a variety of insects at NERI, and consumed more Lepidoptera, by volume and frequency, than other insect orders. These results were similar to data collected in fecal samples from eastern small-footed myotis captured during a study of food habits of bats in western Maryland (McDowell-Griffith 1983). Other myotine bats, including little brown myotis and northern myotis, in West Virginia also are known to consume a variety of insects (Burke 2002, Carter et al. 2003). Burke (2002) found that little brown myotis and northern myotis consumed mostly Lepidoptera, in volume and frequency. Carter et al. (2003) determined that little brown myotis consumed mostly Lepidoptera, and northern myotis consumed mostly Coleoptera. Differential digestion of different insect orders by bats may introduce some error into fecal analysis results (Kunz and Whitaker 1983). For example, although Lepidoptera apparently are an important food source for eastern small-footed myotis, scales from Lepidoptera may persist in the bat’s digestive system for several days, increasing the frequency of occurrence compared to other insects whose undigested parts may be voided within hours after consumption (Buchler 1975, Whitaker 1988). Moreover, comparing percent-by-volume may overestimate the importance of Lepidoptera because small, hard-bodied prey items contribute little to the total volume (Griffith and Gates 1985, Kunz and Whitaker 1983). For example, although Coleoptera were present in >45% of our samples, they represented <6% of the total volume. Lepidoptera often comprised the remainder of the sample volume not occupied by identifiable hard-bodied insect parts. However, among all the insect orders, only Lepidoptera ever comprised 100% of a sample, which we observed five times, supporting the suggested importance of Lepidoptera to eastern small-footed myotis. It is unclear why soil particles or small gravel were ingested by 3 bats in our study. Soil has been found in fecal samples collected from big brown bats, little brown myotis, northern myotis, and eastern pipistrelles in western Maryland and New York (Buchler 1976, McDowell-Griffith 1983). The authors suggested that these bats ingested soil with insect prey captured from the ground. The high-frequency, broadband, frequency-modulated echolocation call of eastern small-footed myotis may be suited for gleaning prey from substrates (Mukhida et al. 2004). Eastern small-footed myotis have been observed foraging near the forest floor (van Zyll de Jong 1985). Perhaps eastern small-footed myotis in our study consumed soil when capturing insect prey from the ground or during grooming while roosting in the mines. It is unknown if consumed soil particles provide any nutritional benefit to the bats or aid in mechanical digestion of chitin. Our study reveals an important component of the foraging ecology of eastern small-footed myotis. Food habits of eastern small-footed myotis were poorly documented prior to our study. We found that eastern smallfooted myotis consumes a variety of insects, but may specialize in preying upon Lepidoptera. It is unclear if our results are representative of food 2007 J.B. Johnson and J.E. Gates 321 habits of eastern small-footed myotis in other areas of its range or during other seasons because of the paucity of existing data. Many important aspects of eastern small-footed myotis ecology remain undetermined. 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