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Observations of Summer Roosting and Foraging Behavior of a Hoary Bat (Lasiurus cinereus) in Southern New Hampshire
Jacques Pierre Veilleux, Paul R. Moosman, Jr., D. Scott Reynolds, Kirk E. LaGory, and Leroy J. Walston, Jr.

Northeastern Naturalist, Volume 16, Issue 1 (2009): 148–152

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Observations of Summer Roosting and Foraging Behavior of a Hoary Bat (Lasiurus cinereus) in Southern New Hampshire Jacques Pierre Veilleux1,*, Paul R. Moosman, Jr.2, D. Scott Reynolds3, Kirk E. LaGory4, and Leroy J. Walston, Jr. 4 Abstract - Few data are available that describe the roosting and foraging ecology of the Hoary Bat (Lasiurus cinereus), and no such data are available for the northeastern United States. We captured a juvenile Hoary Bat in south-central New Hampshire during July of 2007 and monitored its roosting behavior for ten days and its foraging behavior for one night. The bat roosted with two other bats, which we presumed were its mother and sibling. These bats roosted exclusively in Tsuga canadensis (Eastern Hemlock Tree) and tended to roost near tree tops in the forest canopy. The radiotagged bat used at least six roost trees and changed roost location eight times during the ten-day observation period. Although roost-tree fidelity was low, all roost trees were located within a maximum circular area of 0.5 ha. The bat foraged over an estimated 156-ha area of mostly forest habitat (68%), with additional open habitats (15%) and wetlands (17%). These data are the first observations of roosting and foraging behaviors by the Hoary Bat in the northeastern region of its geographic range. Lasiurus cinereus Beauvois (Hoary Bat) occurs throughout much of North America (Cryan 2003). Although there are exceptions (e.g., Perry and Thill 2007), both sexes of Hoary Bats winter at southern latitudes and appear to migrate to northern latitudes during spring, with males migrating to more western regions and females to more eastern regions (Cryan 2003). Despite the fact that Hoary Bats occur in New Hampshire during summer months (Whitaker and Hamilton 1998), the species is rarely encountered during summer bat surveys. Only five Hoary Bats were observed during a combined 324 nights of mist-netting effort for six recent studies focused on the southern (Chenger 2003, LaGory et al. 2002, Veilleux et al. 2008) and northcentral (Chenger 2004, Krusic 1995, Sasse 1995) regions of the state. Summer roosting habits of the Hoary Bat are not well documented for any region within the species’ geographic range (Whitaker and Hamilton 1998). The only detailed information about summer roosting behavior has been gathered from Arkansas (Perry and Thill 2007) and Saskatchewan, Canada (Willis and Brigham 2005); more limited information is available from Indiana (Sparks et al. 2005) and Iowa (Constantine 1966, McClure 1942). Summer roost sites of Hoary Bats are located almost exclusively in foliage (Shump and Shump 1982). Both adult females and males appear to roost alone throughout the year, except for reproductive females, which roost with their young (Shump and Shump 1982). Because Hoary Bats appear to be rare summer residents in New Hampshire, and since summer roosting and foraging data are lacking for the state (as well as for the entire northeastern United States), we report data on summer roosts and foraging habitat used by a juvenile male Hoary Bat in south-central New Hampshire. The New Boston Air Force Station (NBAFS) is a 1114-ha satellite-tracking facility located in south-central New Hampshire (Hillsborough County; approximately 42°56"N, 71°38"W). Elevation at the NBAFS ranges from approximately 153 m to 390 m above sea level and is dominated by mixed (46% of site), coniferous (25%), and deciduous (19%) forests (LaGory et al. 1997). On 17 July 2007, we captured a juvenile male Hoary Bat during a mist-netting survey at NBAFS. The bat was fitted with a 0.4-g radio-transmitter (Model BD-2N; Holohil Systems, Ltd., ON, Canada), which was glued to the inter-scapular region using a non-toxic surgical adhesive (Skin-Bond; Smith and Nephew, Largo, fl) after clipping a small amount of fur from the area. The bat was released at its point of capture after the glue was allowed to set Notes of the Northeastern Nat u ral ist, Issue 16/1, 2009 148 2009 Northeastern Naturalist Notes 149 for 5 min. Mass of the transmitter was approximately two percent of the bat’s total body mass (24.3 g). Using a radio receiver (Model R-1000; Communications Specialists, Inc., Orange, CA) and a 3-element yagi antenna, the bat was tracked daily to its diurnal roosts for ten days. Once the bat’s position within the tree canopy was estimated with the receiver, canopy foliage was searched with binoculars and a spotting scope to determine the bat’s specific location. Once a roost tree was visually confirmed, the tree’s height, height of the bat in the tree (roost height), and tree diameter at breast height (dbh) were measured. Four randomly selected overstory trees within a 0.1-ha circular plot centered on the roost tree were also measured for height and dbh. Mean canopy height in the roost plot was defined as the mean height of the four randomly selected trees. All trees within the roost plot were identified to species. We tracked the bat during the evening of 18 July 2007 (19:50 to 0:00 EST) to estimate its foraging area and describe its activity patterns. At 5-minute intervals, observers at each of three fixed locations simultaneously recorded the compass bearing to the strongest radio signal. Fast flight of the bat and dense vegetation in the study area prevented accurate triangulation. Therefore, for each bearing taken by each observer, the location of the bat was estimated to be somewhere along a 500-m vector (the estimated range of the transmitter in hilly forested terrain) that projected from the observer’s position toward the strongest signal. We estimated the foraging area of the bat by constructing a minimum convex polygon (Powell 2000) around the points at the end of the 500-m vectors. The bat was tracked to its diurnal roost for ten consecutive days (18–27 July). Six different roost trees (R1 through R6) were used during the ten-day period. The radiotagged bat was visually confirmed at two of the six roost trees (R1 and R4; Table 1). R1 was used on three days, but never on consecutive days, whereas R4 was also used for three days, including two consecutive days (the only observation of consecutive roost use during the ten-day period). The bat changed roosts eight times during the nine-day period when roost switching could be determined (mean residence time per roost = 1.1 d). Mean distance between consecutive roost trees was 42 m. The bat was observed roosting with (presumably) its mother and sibling each day that its location was visually confirmed in a roost (18, 22, 25, and 26 July). The two visually confirmed roosts (R1 and R4), were both Tsuga canadensis (L.) Carr. (Eastern Hemlock). Two trees that were almost certainly roosts based on telemetry data, but for which we could not visually confirm the presence of the bats, were Table 1. Characteristics of two roost trees and four roost plots for a mother/pup Hoary Bat group at the New Boston Air Force Station, NH. Roost/plot number Characteristic R1A R2 R4A R5 Roost-tree height (m) 21.3 ND 24.1 ND Roost height (m) 19.8 ND 22.3 ND Roost-tree dbh (cm) 34.5 ND 25.1 ND Plot canopy height (m) 19.1 18.7 21.0 20.9 Roost height/roost-tree height (%) 92.9 ND 92.3 ND Roost-tree height/plot canopy height (%) 111.1 ND 114.8 ND Roost height/plot canopy height (%) 103.3 ND 106.0 ND ARoosts R1 and R4 were visually confirmed; R2 and R5 were not verified and therefore only plot measurements are reported for R1 and R4. ND = not determined. Tree and plot characteristics were not measured for R3 due to significant overlap with the plot of R1. Although telemetry data indicated a new roost site (i.e., signal not present at a previous roost site), the specific location of R6 was not determined. 150 Northeastern Naturalist Notes Vol. 16, No. 1 also Eastern Hemlock. Eastern Hemlock was the most common tree species in roost plots, accounting for 74% of all identified trees (Table 2). The bats roosted within the live foliage of small (less than 1 cm) diameter branches. Tree heights of R1 and R4 were taller than the mean canopy height of each plot (approximately 111% and 115% of canopy height, respectively). The bats roosted near the top of the roost tree and just above mean canopy height, with both roost locations within 2 m of the tree apex and approximately 1 m above mean plot canopy height. One roost was oriented to the SE (130°) and located 1.5 m from the tree trunk, while the second was oriented to the SSW (204°) and located 1 m from the trunk. All six roost trees were within an approximately 40-m radius, 0.5-ha circular roost area. This roost area was located 0.8 km southwest of the capture site and within 0.4 km of an 18-ha pond. We made a total of 153 observations (51 at each of the three fixed telemetry locations) of foraging activity. We were able to detect a signal for 143 observations, and at least one observer detected a signal at each 5-minute sampling interval. The bat was active for most of the observation period (on the basis of fluctuation in signal strength and bearing), but apparently roosted from 23:40 until observations ceased at 0:00. The area of the minimum convex polygon around the estimated vectors was 156 ha and encompassed mostly forest habitat (38% mixed, 17% coniferous, and 13% deciduous forest), but also included open habitats (e.g., old fields, parkland, and developed areas; 15%) and wetlands (17%; including an 18-ha pond). The estimated foraging area polygon contained all roost locations and the capture location. Our data represent the only information on roosting behavior of the Hoary Bat in the northeastern region of the species’ range. We presume that the roost mates of the juvenile bat we radio-tagged were its mother and sibling, which is consistent with the typical litter size reported in the literature (Constantine 1966, Koehler and Barclay 2000, Perry and Thill 2007, Willis and Brigham 2005). Parturition dates have been observed during mid-June in Arkansas (Perry and Thill 2007), Iowa (McClure 1942), and southern Manitoba, Canada (Koehler and Barclay 2000). In Manitoba, young became volant between 26 and 33 d after birth, but continued to nurse for an additional 16 days, and remained with their mother up to 19 days post-volancy. We were unable to determine if the young Hoary Bat was still nursing, but our data at least indicate that some juveniles remain with their mother through late July in New Hampshire. Assuming a 26- to 33-d growth period to volancy and a capture date near the beginning of volancy, our observations suggest that parturition occurred between approximately 15 and 22 June. This date range is consistent with data from an earlier bat survey at NBAFS, in which a lactating female Hoary Bat was captured on 25 June 2002 (LaGory et al. 2002). The radio-tagged bat changed its roost tree nearly every night. This pattern indicated relatively low roost fidelity compared to that reported for Hoary Bats in a few Table 2. Tree species occurrence within four Hoary Bat roost plots at the New Boston Air Force Station, NH. Total % Tree species occurrence in plots Tsuga canadensis (L.) Carr. (Eastern Hemlock) 74.0 Pinus strobus L. (Eastern White Pine) 6.1 Quercus rubra L. (Northern Red Oak) 5.5 Unidentified snag 4.4 Acer rubrum L. (Red Maple) 3.3 Fagus grandifolia Ehrh. (American Beech) 2.2 Acer saccharum Marsh. (Sugar Maple) 2.2 Betula lenta L. (Sweet Birch) 1.7 Betula populifolia Marsh. (Gray Birch) 0.6 2009 Northeastern Naturalist Notes 151 other studies. For example, Willis and Brigham (2005) reported a mother and two pups that remained at a roost for 14 days, Perry and Thill (2007) reported two mother/ young groups that used a single roost for 23 and 26 consecutive days, respectively, and McClure (1942) reported a mother/young group remaining at a roost for nearly two months. Despite frequent roost switching, roost trees were located within a small forest area (approximately 0.5 ha). Although comparable data on roost area size are not available for Hoary Bats, limited data are available for a sympatric congener, L. borealis Müller (Eastern Red Bat). Hutchinson and Lacki (2000) reported Eastern Red Bats roosting within a mean roost area of less than 40 m2 (0.004 ha), whereas Mager and Nelson (2001) reported a larger mean roost area of 90 ha (range = 2 to 629 ha). The Hoary Bats observed during our study roosted only in coniferous trees (Eastern Hemlock), which was the dominant type of tree in roost plots (80% of available trees). Limited data on roost selection by Hoary Bats indicate that roost trees are used in the approximate proportion of their availability in the forest. For example, Willis and Brigham (2005) observed nearly exclusive use of conifers as roosts in a conifer-dominated forest, while Perry and Thill (2007) reported 57% and 43% of roosts located in coniferous and deciduous trees, respectively, in roost plots containing 63% conifers and 37% deciduous trees (based on basal area reported for each tree category). Although forest composition data were not reported, Constantine (1966) and Sparks et al. (2005) found exclusive use of deciduous trees as roosts. These data suggest that Hoary Bats are flexible in their choice of tree species across their geographic range. The two visually confirmed roosts in our study (R1 and R4) were taller than the mean plot canopy height, and bats roosted at locations in trees that were nearly level with mean plot canopy height. Perry and Thill (2007) reported similar characteristics of Hoary Bat roosts, with mean roost-tree height approximately 2 m above, and mean roost height nearly equal with the mean height of four overstory plot trees. We observed roost locations for the Hoary Bats within 1.5 m of the main trunk and oriented to the SE and SSW. Willis and Brigham (2005) reported that bats roosted at a mean roost orientation of SSE (158°), while Perry and Thill (2007) reported 86% of roosts with an easterly orientation (mean orientation of 66°). Barclay (1985) reported that foraging activity of Hoary Bats occurred mainly in open/edge and marsh habitats, with less foraging activity in forested areas. In our study, nearly 70% of observed foraging activity occurred in forest, with 17% and 15% of foraging observed in open habitats (old field and parkland) and wetland habitats (including an 18-ha pond), respectively. Sparks et al. (2005) determined the foraging patterns of a juvenile Hoary Bat in Indiana during July 2003 and found that it foraged over a much smaller area (21.5 ha) of predominantly old-field habitat. They hypothesized that such a small foraging area was used because roost trees were located at the edge of a large old-field that served as the primary foraging area. Open habitats in our study were not located adjacent to roost sites and were interspersed in the predominantly forested area. Foraging bouts of the Hoary Bat studied by Sparks et al. (2005) ranged from 54 to 155 min during four nights of observation, with the upper range of foraging time being similar to that observed in our study. Our data represent the first observations of roosting and foraging behaviors of Hoary Bats in the northeastern region of the species’ geographic range. Although our data were limited to a single mother/pup group, they shed light on the natural history of a rarely encountered and poorly understood species in the northeastern United States. Acknowledgments. We thank Steve Najjar of the New Boston Air Force Station for his support of the research, field assistance, and access to the base, as well as Chris Andrews, Jocelyn Drexinger, and Gregg Larsen for help in tracking the bat. We also thank Craig Willis for helpful comments on an early draft of this manuscript. 152 Northeastern Naturalist Notes Vol. 16, No. 1 This work was supported under a military interdepartmental purchase request from the US Department of Defense, US Air Force, through US Department of Energy contract DE-AC02-06CH11357. Literature Cited Barclay, R.M.R. 1985. Long- versus short-range foraging strategies of Hoary (Lasiurus cinereus) and Silver-haired (Lasionycteris noctivagans) Bats and the consequences for prey detection. Canadian Journal of Zoology 63:2507–2515. Chenger, J. 2003. Bat inventory for project lands of the upper Connecticut River Basin. Unpublished report. US Army Corps of Engineers, New England District, Concord, MA 109 pp. Chenger, J. 2004. 2004 Woodland bat survey in the White Mountain National Forest. Unpublished report prepared for the US Department of Agriculture, Freeport, IL. 38 pp. Constantine, D.G. 1966. Ecological observations of lasiurine bats in Iowa. Journal of Mammalogy 47:34–41. Cryan, P.M. 2003. Seasonal distribution of migratory tree bats (Lasiurus and Lasionycteris) in North America. Journal of Mammalogy 84:579–593. Hutchinson, J.T., and M.J. Lacki. 2000. Selection of day roosts by red bats in mixed mesophytic forests. Journal of Wildlife Management 64:87–94. Koehler, C.E., and R.M.R. Barclay. 2000. Post-natal growth and breeding biology of the Hoary Bat (Lasiurus cinereus). Journal of Mammalogy 81:234–244. Krusic, R. 1995. Habitat use and identification of bats in the White Mountain National Forest. M. Sc. 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Boitani and T.K. Fuller (Eds.). Research Techniques in Animal Ecology: Controversies and Consequences. Columbia University Press, New York, NY. 442 pp. Sasse, D.B. 1995. Summer roosting ecology of cavity-dwelling bats in the White Mountain National Forest. M. Sc. Thesis. University of New Hampshire, Durham, NH. 65 pp. Shump, K.A., and A.U. Shump. 1982. Lasiurus cinereus. Mammalian Species 185:1–5. Sparks, D.W., C.M. Ritzi, and B.L. Everson. 2005. Nocturnal behavior and roosting ecology of a juvenile Lasiurus cinereus near Indianapolis, Indiana. Proceedings of the Indiana Academic of Science 114:70–72. Veilleux, J.P., H.H. Thomas, and P.R. Moosman. 2008. Bats of Pisgah State Park, Cheshire County, New Hampshire. Northeastern Naturalist 15:25–34. Whitaker, J.O., Jr., and W.J. Hamilton. 1998. Mammals of the Eastern United States. Cornell University Press. Ithaca, NY. 583 pp. Willis, C.K.R., and R.M. Brigham. 2005. Physiological and ecological aspects of roost selection by reproductive female Hoary Bats (Lasiurus cinereus). Journal of Mammalogy 86: 85–94. 1Department of Biology, Franklin Pierce University, Rindge, NH 03461. 2Department of Biology, Virginia Military Institute, Lexington, VA 24450. 3Science Division, St. Paul’s School, 325 Pleasant Street, Concord, NH 03301. 4Environmental Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439. *Corresponding author - veilleuxj@ franklinpierce.edu.