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Characteristics of Lasiurus intermedius (Northern Yellow Bat) Roosts on Sapelo Island, Georgia
Laci S. Coleman, Katrina M. Morris, and Steven B. Castleberry

Southeastern Naturalist, Volume 11, Issue 3 (2012): 534–536

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534 Southeastern Naturalist Vol. 11, No. 3 Characteristics of Lasiurus intermedius (Northern Yellow Bat) Roosts on Sapelo Island, Georgia Laci S. Coleman1,2, Katrina M. Morris3, and Steven B. Castleberry1,* Abstract - We radio-tracked 3 male and 1 female Lasiurus intermedius (Northern Yellow Bat) to 16 unique roosts on Sapelo Island, GA in summer 2010. All bats roosted in Tillandsia usneoides (Spanish Moss) hanging in hardwood trees. Trees used as roosts were similar in height as surrounding trees but were larger in diameter. Mature hardwood stands appear to be important roosting habitats for Northern Yellow Bats in areas where Pinus (pine) and mixed-pine hardwood habitats dominate the landscape. Lasiurus intermedius Allen (Northern Yellow Bat) occurs in the Coastal Plain of the southeastern United States from Virginia to Texas, and south throughout much of Mexico into Honduras (Webster et al. 1980). Although Northern Yellow Bats have been documented roosting in a variety of structures throughout the range, in the southeastern US the species most commonly roosts in Tillandsia usneoides L. (Spanish Moss) hanging in hardwood trees (Constantine 1958, Hutchinson 2006, Jennings 1958, Menzel et al. 1999). Most roosts of Northern Yellow Bats have been described from anecdotal observations (Constantine 1958, Jennings 1958) or systematic searches from the ground (Hutchinson 2006). Menzel et al. (1999) used radiotelemetry to locate 5 roosts of 1 male on Sapelo Island, GA. Herein, we describe characteristics of additional Northern Yellow Bat roosts on Sapelo Island located using radiotelemetry. Sapelo Island is a 6677-ha barrier island located approximately 5.5 km off the coast of Darien, GA. Forest cover primarily is Pinus (Pine) and mixed pine-hardwood with interspersed patches of mature hardwood forest dominated by Quercus virginiana Miller (Live Oak). We used mist nets set over fresh water to capture Northern Yellow Bats from 18 May–2 June 2010. Radio transmitters (0.33 g; Blackburn Transmitters, Nacogdoches, TX) were attached to the interscapular region using surgical adhesive. Transmitters averaged 1.6% (range = 1.5–1.8%) of bat body mass. We tracked bats to their roost trees during the day and attempted to identify the specific roost location within the tree by visually searching from the ground. For a subset of bats not observed during the day, we attempted to locate the roost as the bat emerged at dusk. Roost trees were characterized by recording species, diameter at breast height (dbh), height, and a description of the roost (foliage, moss, bark, etc.). We also recorded species, dbh, and height of all overstory trees (≥10 cm dbh) within a 0.04-ha plot centered on each roost tree. We compared height and dbh of roost trees to surrounding trees using Wilcoxon Sign-Rank Tests. We accepted statistical significance at P < 0.05. We captured and radiotagged 4 Northern Yellow Bats, 3 non-reproductive males and 1 pregnant female, and identified 16 unique roosts. We tracked all bats to at least one roost. We did not document multiple bats using the same Spanish Moss clump. Individuals were often found at the same roost for multiple days or returned to previously used roosts after switching. The female was located for 14 days at 10 unique 1Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602. 2Current address - Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0321. 3Georgia Department of Natural Resources, Nongame Conservation Section, Social Circle, GA 30025. *Corresponding author - scastle@uga.edu. Notes of the Southeastern Nat u ral ist, Issue 11/3, 2012 534 2012 Southeastern Naturalist Notes 535 roosts, switching roosts 10 times. Males switched roosts a mean of 4.3 times (range = 2–9). One male was located for 14 days at 3 unique roosts, while the other two were located for 2 days at 2 roosts and 1 day at 1 roost, respectively. Similar to previous observations, bats always roosted in Spanish Moss hanging on live hardwood trees. Although it is unknown why Northern Yellow Bats roost in Spanish Moss, Hutchinson (2006) noted that Spanish Moss appeared to protect roosting Northern Yellow Bats from intense rainfall. Bats roosting in Spanish Moss also may be less visible to predators. As previously noted (Constantine 1958, Hutchinson 2006), we observed that clumps of Spanish Moss used as roosts typically were suspended underneath branches with no clutter below, providing a clear flight path when entering and leaving the roost. All roosts were in hardwood trees within hardwood-dominated stands. Menzel et al. (1999) similarly reported that all 5 roosts of a single male Northern Yellow Bat on Sapelo Island were in Live Oak-dominated habitats. Live Oaks have been noted as the primary roost tree in previous studies (Constantine 1958, Jennings 1958, Menzel et al. 1999), but we found roosts in Live Oaks (n = 7), as well as Q. laurifolia Michaux (Laurel Oak; n = 5), Q. nigra L. (Water Oak; n = 3), and Nyssa sylvatica Marshall (Blackgum; n = 1). Given the preference of Northern Yellow Bats to roost in Spanish Moss, it is unclear whether selection of hardwood trees as roosts is related to tree characteristics or the presence of Spanish Moss, which occurs more frequently on hardwood trees (Garth 1964). Previous studies have shown that forest bats typically select roost trees that are taller and have a larger diameter than surrounding trees (Kalcounis-Rüppell et al. 2005). Although mean height of roost trees (15.4 ± 3.2 m) and surrounding trees (14.2 ± 1.3 m) were similar (P > 0.05), mean dbh of roost trees (45.5 ± 3.0 cm) was larger (Z = 109.0, P = 0.034) than surrounding trees (33.2 ± 1.2 cm). Many hardwood species, particularly Live Oaks, tend to allocate growth to large horizontal branches as they mature rather than growing upward, resulting in a relatively uniform canopy height within these stands. Although the height of roost trees was relatively uniform, Northern Yellow Bats selected trees with larger diameters than surrounding trees. Authors have suggested that trees extending above the general crown serve as a visual reference and are more easily located by bats returning to the roost (Hein et al. 2008, Vonhof and Barclay 1996). For Northern Yellow Bats, the larger diameter of roost trees may serve as the reference that allows them to locate the roost tree. Our observations support previous findings that hardwood stands are important roosting habitats for Northern Yellow Bats. Use of hardwood trees as roosts may coincide with the preference of the species to roost in Spanish Moss which grows most frequently on hardwoods. To benefit the Northern Yellow Bat, management that promotes retention of mature hardwood stands should be considered in areas of the southeastern US where pine and mixed pine-hardwood stands dominate the landscape. Acknowledgments. We thank E.L. Oxford and B. Knight for field assistance. N.P. Nibbelink provided GIS assistance and an early review of the manuscript. We thank the Georgia Department of Natural Resources for housing, field transportation, and logistical support. Literature Cited Constantine, D.G. 1958. Ecological observations on lasiurine bats in Georgia. Journal of Mammalogy 39:64–70. Garth, R.E. 1964. Ecology of Spanish moss (Tillandsia usneoides): Its growth and distribution. Ecology 45:470–481. Hein, C.D., S.B. Castleberry, and K.V. Miller. 2008. Sex-specific summer roost-site selection by Seminole Bats in response to landscape-level forest management. Journal of Mammalogy 89:964–972. 536 Southeastern Naturalist Vol. 11, No. 3 Hutchinson, J.T. 2006. Bats of Archbold Biological Station and notes on some roost sites. Florida Field Naturalist 34:48–51. Jennings, W.L. 1958. The ecological distribution of bats in Florida. Ph.D. Dissertation. University of Florida, Gainesville, FL. 126 pp. Kalcounis-Rüppell, M.C., J.M. Psyllakis, and R.M. Brigham. 2005. Tree roost selection by bats: An empirical synthesis using meta-analysis. Wildlife Society Bulletin 33:1123–1132. Menzel, M.A., D.M. Krishon, T.C. Carter, and J. Laerm. 1999. Notes on tree-roost characteristics of the Northern Yellow Bat (Lasiurus intermedius), the Seminole Bat (L. seminolus), the Evening Bat (Nycticeius humeralis), and the Eastern Pipistrelle (Pipistrellus subflavus). Florida Scientist 62:185–193. Vonhof, M.J., and R.M.R. Barclay. 1996. Roost-site selection and roosting ecology of forestdwelling bats in southern British Columbia. Canadian Journal of Zoology 74:1797–1805. Webster, W.D., J.K. Jones, Jr., and R.J. Baker. 1980. Lasiurus intermedius. Mammalian Species No. 132:1–3.