2008 NORTHEASTERN NATURALIST 15(3):453–460 Spring Migration and Roost Selection of Female Myotis leibii in Maryland Joshua B. Johnson1,2,* and J. Edward Gates1 Abstract - Many aspects of the ecology of Myotis leibii (Eastern Small-footed Myotis) are unknown due to the rarity of the species throughout its range in the eastern United States. Few studies have examined Eastern Small-footed Myotis migration and roosting behavior. Until a recent discovery of a population of Eastern Small-footed Myotis using an abandoned railroad tunnel in western Maryland, most observations from the state were limited to records of a few individuals at scattered caves, mines, and tunnels. We used harp traps to capture Eastern Small-footed Myotis at an abandoned railroad tunnel located in Allegany County, in spring 2007. We captured 47 Eastern Small-footed Myotis and equipped four females with radio transmitters. Telemetry revealed that female Eastern Small-footed Myotis migrated ≤1.1 km to nearby shale barrens and roosted in rock outcrops of various sizes during spring. Females moved <50 m between successive diurnal roosts, which did not differ from random sites located within the shale barrens in terms of site characteristics. Migratory distances and, consequently, geographic ranges of female Eastern Smallfooted Myotis probably are influenced by the availability of hibernacula and roosting sites across the landscape. Introduction Myotis leibii Audubon and Bachman (Eastern Small-footed Myotis) is one of the rarest bats in North America and is considered vulnerable to extinction throughout its range (Best and Jennings 1997). Because of its small size (<6 g), rarity, and elusive behavior, it has received relatively little research focus compared to other North American bat species. Eastern Small-footed Myotis infrequently are documented hibernating in caves, mines, and tunnels, presumably because they are difficult to observe roosting beneath rock slabs or in narrow rock crevices near hibernacula entrances (Martin et al. 1966, Mohr 1936). Colder temperatures at these hibernacula may result in low overwinter survival (Hitchcock et al. 1984). Few reports exist of Eastern Small-footed Myotis roosting behavior during summer, and most records are limited to anecdotal observations and unpublished research. During summer, Eastern Small-footed Myotis have been observed roosting in rock crevices and under rock slabs in rock outcrops and have even been associated with buildings (Best and Jennings 1997; Hitchcock 1955; Roble 2004; C. Stihler, West Virginia Division of Natural Resources, Elkins, WV, pers. comm.). No published information documenting migration distances 1University of Maryland Center for Environmental Science, Appalachian Laboratory, 301 Braddock Road, Frostburg, MD 21532. 2Current address - Wildlife and Fisheries Resources Program, Division of Forestry and Natural Resources, West Virginia University, Morgantown, WV 26506. *Corresponding author - jjohns21@mix.wvu.edu. 454 Northeastern Naturalist Vol. 15, No. 3 between winter and summer ranges exists, with the exception of an observation of two Eastern Small-footed Myotis in Ontario, Canada that migrated <20 km (Hitchcock 1955). In Garrett County, MD, there is a historical record of a maternity colony of Eastern Small-footed Myotis roosting in rock outcrops <6 km from a known hibernaculum (D. Feller, Maryland Department of Natural Resources, Frostburg, MD, pers. comm.). In Maryland, the Eastern Small-footed Myotis is listed as state-endangered because of its limited range and few records within the state (J. McCann, Maryland Department of Natural Resources, Frostburg, MD, pers. comm.). Records mostly are restricted to the western third of the state, with exception of one account near Washington, DC. (D. Feller, pers. comm.; Gates et al. 1984; Marsh 1998; Nelson 1913; Paradiso 1969). The majority of accounts are from surveys conducted during autumn, winter, and spring at caves, mines, and tunnels in the karst and shale-barren areas of the Ridge and Valley and Appalachian Plateau provinces (D. Feller, pers. comm.; Gates et al. 1984, Johnson and Gates 2005, Marsh 1998). There is only one record of an Eastern Small-footed Myotis maternity colony roost: an account in the Appalachian Plateau physiographic province (D. Feller, pers. comm.). Relatively few Eastern Small-footed Myotis have been documented at any single hibernaculum (Gates et al. 1984, Marsh 1998). However, a population of Eastern Small-footed Myotis was recently discovered at an abandoned railroad tunnel in Allegany County, MD. Capture rates of Eastern Small-footed Myotis at the tunnel were higher than at any other hibernacula in Maryland (J.E. Gates, unpubl. data). Our objective was to determine movements and roost selection of female Eastern Small-footed Myotis following emergence from hibernation. Study Area and Methods The abandoned railroad tunnel is located within the Chesapeake and Ohio Canal National Historical Park (CHOH) in Allegany County, MD. Still largely intact, the tunnel was constructed in 1904 and used until 1975. The tunnel is oriented in a northeast–southwest direction and is approximately 1.3 km in length between entrances. The tunnel wall surfaces are exposed bedrock and the ceiling is deteriorated brick. Wooden cribbing, supported by vertical creosoted timbers spaced approximately 1.2 m apart, contains the ceiling. Historically, most surveys conducted at the tunnel have been of hibernating bats during winter. Prior to this study, only Eptesicus fuscus Beauvois (Big Brown Bat), Myotis lucifugus LeConte (Little Brown Myotis), and Pipistrellus subflavus Cuvier (Eastern Pipistrelles) have been documented hibernating in the tunnel (D. Feller, pers. comm.; Gates et al. 1984). However, in recent years, bat species other than the aforementioned have been reported during spring emergence and autumn swarming, including Lasionycteris noctivagans LeConte (Silver-haired Bat), Lasiurus borealis Müller (Eastern Red Bat), Eastern Small-footed Myotis, Myotis septentrionalis Trouessart (Northern Myotis), and Myotis sodalis Miller and Allen (Indiana Myotis) (J.E. Gates, unpubl. data). 2008 J.B. Johnson and J.E. Gates 455 The tunnel is <200 m from the Potomac River in an area of the Ridge and Valley province characterized by shale-barren communities consisting of steep talus slopes and rock outcrops sparsely vegetated by Pinus virginiana Mill. (Virginia pine), Quercus ilicifolia Wang. (Scrub Oak), and Juniperus virginiana Linnaeus (Eastern Red Cedar). The talus slopes and rock outcrops in the area largely are concentrated along the Potomac River gorge in the Hampshire and Foreknobs formations, which mostly consist of shale and sandstone (Schmidt 1993). Upland forests are dominated by Quercus spp. (oak) and Carya spp. (hickory). Some small areas of pasture and row crops exist on the hilltops. Liriodendron tulipifera Linnaeus (Yellow-poplar), Platanus occidentalis Linnaeus (American Sycamore), Acer spp. (maples), and Betula nigra Linnaeus (River Birch) occur along the Potomac River banks and adjacent CHOH. Ephemeral standing water occurs in some sections of the canal. Elevation at the tunnel is approximately 150 m, whereas the immediate area ranges from approximately 130 m on the Potomac River to approximately 275 m on the hilltops. We used harp traps to capture bats at the tunnel during spring (mid- March–mid-May) 2007. We placed 2 harp traps (1.8 m × 2.3 m; Bat Conservation and Management, Carlisle, PA) side by side in the east and west entrances to capture bats entering or exiting the tunnel. Our harp traps were completely surrounded with tarpaulin and/or bird netting to prevent bats from bypassing traps. Sampling was conducted 3 nights/week for 4 hours following sunset. Each captured bat was identified to species, and weight (g), forearm length (mm), sex, and age were determined before release (Menzel et al. 2002, Racey 1988). 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 (Gannon et al. 2007). We marked bats with non-toxic paint pens to facilitate identification of recaptures. We also wing-banded Eastern Small-footed Myotis for long-term monitoring of their activity (48.5 mg; Porzana Ltd., Icklesham, East Sussex, UK). Males and females were banded on their right and left forearms, respectively. We did not band females that were part of the radio-telemetry study. We examined spring migration and roost selection of female Eastern Small-footed Myotis using radio-telemetry methods. We used surgical cement (Torbot Group, Cranston, RI) to affix a 0.35-g radio transmitter (Model LB-2N; Holohil Systems Ltd., Carp, ON, Canada) between the scapulae of captured females. Transmitter weight to animal body weight ratio (mean = 8.0% ± 0.2%) was similar to ratios in other bat studies, including eastern pipistrelles, which are similar in body weight to Eastern Small-footed Myotis (Best and Jennings 1997, Carter et al. 1999, Leput 2004, Perry and Thill 2007, Veilleux et al. 2003). We used radio receivers and 3-element Yagi antennae (Advanced Telemetry Systems, Inc., Isanti, MN) to locate diurnal roosts three times per week until the transmitter failed. Migration distance 456 Northeastern Naturalist Vol. 15, No. 3 for each bat was calculated as the mean distance from its roosts to the tunnel entrance at which it was captured. Within a 10-m radius centered on the roost, we determined degree of slope using a clinometer, slope aspect using a compass, percent canopy cover using a densiometer, width of rock outcrop as measured parallel with the contour, height of rock outcrop as measured perpendicular to the contour and parallel with the slope, distance to nearest potential roost rock outcrop, tree species diversity (Simpson’s 1-D), tree species evenness (Simpson’s E 1/D), tree species richness (number of tree species), number of trees, number of snags, and mean diameter at breast height of all trees within the plot. We located one random site (i.e., rock outcrop) approximately 100 m from each known roost in a random direction. A distance of 100 m, as measured parallel with the slope, bounded the maximum distance any individual bat moved between successive known roosts. We examined random sites for roosting bats. We measured the same variables in random plots as in roost plots. We used Wilcoxon tests to compare ranked means of variables between known roosts and random sites (SAS Institute, Inc. 2004; PROC NPAR1WAY). To determine if spatial arrangement of roost sites was similar to rock outcrops distributed across the area, we established five 100-m transects aligned parallel with the contour. We measured the width of each rock outcrop encountered and distances between each rock outcrop. We compared these rock outcrop widths and distances to nearest rock outcrops to known roost rock outcrop widths and distances to nearest rock outcrops using a Wilcoxon test. Statistical significance for all analyses was set at P ≤ 0.05. Results We conducted surveys at the tunnel for 31 nights from 12 March through 16 May 2007, spanning 248 hours. We captured 47 Eastern Small-footed Myotis (33 males, 13 females, and 1 escaped). We banded 41 Eastern Smallfooted Myotis, and recaptured eight of them within 64 days after initial banding; no females were recaptured. We conducted radio telemetry on four female Eastern Small-footed Myotis from 13 March to 4 April. We were able to maintain contact with all but one of the tagged bats until the transmitters failed or detached from the bats (mean = 8 days). We were unable to acquire a signal from one bat after it crossed the Potomac River during its 7th night of activity. Transmittered females migrated 0.1–1.1 km (0.4 ± 0.2; n = 4) from the tunnel to south-facing slopes where they day-roosted in crevices in small (less than 3 m x 3 m) to large (greater than 10 m x 10 m) rock outcrops within the shale barrens. We only observed bats roosting singly in crevices of rock outcrops, and did not observe any bats roosting in rock outcrops that were chosen as random sites. Telemetered females moved <50 m between successive diurnal roosts and typically switched roosts every day unless inclement weather prevented foraging (Table 1). Characteristics of roost sites were similar to those of random sites (P > 0.178). Rock outcrops in which females roosted and those sampled 2008 J.B. Johnson and J.E. Gates 457 along transects in the area were similar in terms of their widths (P = 0.135), and distances between rock outcrops (P = 0.629) (Table 2). Discussion The prevalence of Eastern Small-footed Myotis at the tunnel, relative to other hibernacula in Maryland, may indicate that this site contains the largest known hibernating population of the species in the state (Gates et al. 1984, Johnson and Gates 2005). Eastern Small-footed Myotis have been captured at other abandoned railroad tunnels in the area during spring 2007, but in fewer numbers than at the tunnel we surveyed (J.E. Gates, unpubl. data). Recaptures of banded males and the short distances travelled by radio-tagged females indicate that at least some Eastern Small-footed Myotis remain in the vicinity of the tunnel during spring. The short migration distances we recorded for Eastern Small-footed Myotis may result from the proximity of the tunnel to shale barrens and other rock outcrop types. Migration distances may have been greater if the tunnel was located farther from the shale barrens. It is unknown if, before the tunnel was constructed, Eastern Smallfooted Myotis occurred at the shale barrens year-round (hibernating in the Table 1. Distance (m) between successive diurnal roosts of telemetered female Myotis leibii captured at an abandoned railroad tunnel in Allegany County, MD, March–April 2007. Number of roosts Mean SE Range 4 41.8 5.0 32.6–49.8 2 22.2 - - 2 37.0 - - 2 8.2 - - Table 2. Characteristics of diurnal roosts (n = 10) used by female Myotis leibii (n = 4) captured at an abandoned railroad tunnel in Allegany County, MD, March–April 2007. RoostC Random Variable Mean SE Mean SE U P Elevation (m) 182.1 7.4 195.9 6.7 87.5 0.213 Slope (°) 37.7 1.4 33.0 2.7 117.0 0.393 Aspect (°) 175.8 11.9 182.9 11.8 98.0 0.629 Canopy cover (%) 85.4 2.0 83.3 4.7 104.5 1.000 Rock outcrop width (m)A 85.8 68.4 84.1 69.0 112.5 0.603 Rock outcrop height (m)B 7.1 2.5 6.9 2.1 43.0 0.949 Distance to nearest rock outcrop (m) 9.1 2.2 10.9 2.0 99.5 0.709 Tree species diversity 0.7 0.1 0.6 0.1 121.0 0.256 Tree species evenness 0.6 0.1 0.5 0.1 120.0 0.287 Tree species richness 5.2 0.4 5.3 0.4 103.0 0.909 Number of trees/ha 779.8 102.8 967.6 64.2 86.0 0.178 Mean diameter at breast height (cm) 12.4 0.5 12.6 0.5 106.0 0.970 Number of snags/ha 70.0 16.3 127.3 33.6 92.5 0.367 AWidth of rock outcrop, measured parallel with contour. BHeight of rock outcrop, measured perpendicular to contour and parallel with slope. CDifferences were analyzed with ranked data, but actual means are presented. 458 Northeastern Naturalist Vol. 15, No. 3 rock outcrops), or migrated to the shale barrens from more distant natural hibernacula, or did not occur in the area because of relatively long distances to natural hibernacula. A historical summer record of an Eastern Smallfooted Myotis on a Potomac River island near the fall line and Washington, DC, indicates that this bat either migrated a relatively long distance from a natural cave or hibernated in the cliffs adjacent to the river (Nelson 1913). It is unknown if the summer distribution of Eastern Small-footed Myotis in Maryland is limited to areas within some unknown maximum migrating distance to hibernacula, i.e., caves, mines, or tunnels, within the Ridge and Valley and Appalachian Plateau provinces, or if they are able to use rock outcrops year-round in the Blue Ridge and Piedmont, where caves occur more sparsely. Although landscape-scale distributions of Eastern Small-footed Myotis in Maryland remain to be determined, we hypothesize that they may concentrate in areas with favorable geology, i.e., talus slopes or limestone outcrops, such as those that occur in the Ridge and Valley and Appalachian Plateau provinces where the majority of hibernacula in Maryland occur (Franz and Slifer 1976). If they are able to use the same rock outcrops as hibernacula and summer roost sites, then their distribution in Maryland may extend to the fall line, but their densities probably would be lower in areas farther east due to a rarity of favorable geology in the area (Schmidt 1993). The short migration distances we documented also may be a consequence of few hibernating bats within the tunnel and abundant rock outcrops in the vicinity, which may result in reduced intraspecific competition for resources, e.g., roosts in rock outcrops, when bats emerge from hibernation and migrate to their summer ranges. Wing morphology also may dictate migration behavior in part. The low wing loading of Eastern Small-footed Myotis is consistent with other bat species considered sedentary in migration distance (Farney and Fleharty 1969, Fleming and Eby 2003). However, we suggest caution in applying our results elsewhere because the bat with which we lost radio contact may have migrated out of the area, therefore making migration distances minima for our sample population. All Eastern Small-footed Myotis roosted in rock outcrops similar to those that have been observed in other parts of their range (Roble 2004; C. Stihler, pers. comm.), and did not exhibit selection for specific roost sites, i.e., rock outcrops within talus slopes in the shale barrens. The sparsely forested shale barrens likely were selected over adjacent, densely forested hilltops, because of increased solar exposure and abundance of rock outcrops, i.e., potential roost sites. We conducted our study before leaf-out in spring. As leaf-out progresses, some rock outcrops may receive less solar exposure than others. Eastern Small-footed Myotis may select certain rock outcrops within the shale barrens during the summer maternity season when rock outcrops with higher solar exposure may be less plentiful, if indeed this is a selected attribute of summer roost sites. In the George Washington National Forest in western Virginia, an Eastern Small-footed Myotis was observed roosting in a crevice between two rocks in a boulder field with partially open forest 2008 J.B. Johnson and J.E. Gates 459 canopy (Roble 2004). Similarly, most Eastern Small-footed Myotis roosts on North Fork Mountain, WV, were in talus slopes that received full or nearly full solar exposure (C. Stihler, pers. comm.). 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