Samuel Schratz*, V. Roll...
of 1


Published on: Mar 3, 2016

Transcripts - NASBR_Poster

  • 1. ROOST TREES OF SOUTHEASTERN MYOTIS AND RAFINESQUE’S BIG-EARED BATS IN THE BOTTOMLANDS OF ARKANSAS Samuel Schratz*, V. Rolland, T.S. Risch Department of Biological Sciences, Arkansas State University, P.O. Box 599, State University, AR 72467. Contact:; Presenter* Introduction The Cache River National Wildlife Refuge holds a large continuous tract of bottomland hardwood forest in the Mississippi Alluvial Valley (MAV). The southeastern myotis (Myotis austroriparius, MYAU) and Rafinesque’s big-eared bat (Corynorhinus rafinesquii, CORA) of Arkansas are assumed to be year-round residents of the MAV and primarily roost in trees. Although contact with White-Nose Syndrome is unlikely to impact MYAU or CORA in Arkansas, loss of bottomland habitat remains a threat. Identification of roost-tree characteristics will allow for more informed forest management practices. Methods Bats were captured via mist-netting in closed-canopy flyways and over inundated land. Affixed 0.31g (2014) and 0.27g (2015) LB-2X Holohill transmitters to 32 bats (Fig. 1) and located by homing. Transmitters used in 2015 had a stronger signal output than 2014 models. Located diurnal roosts and characterized trees by measuring diameter at breast height, canopy coverage, basal area, and tree height.1 Random trees were located by generating a number from 0-360 (for directionality) and 40-100 (for distance in meters). Characterized random trees in same manner as roost-trees. Data analysis conducted in Program R. References 1Medlin and Risch (2008). Habitat Associations of Bottomland Bats, with Focus on Rafinesque's Big-Eared Bat and Southeastern Myotis. American Midland Naturalist, 160, 400-412. 2Mirowsky et al. (2013). Distributional Records and Roosts of Southeastern Myotis and Rafinesque's Big-Eared Bat in Eastern Texas. Southwestern Association of Naturalist, 49, 294-298. 3Carver and Ashley (2007). Roost Tree Use by Sympatric Rafinesque's Big-eared Bats (Corynorhinus rafinesquii) and Southeastern Myotis (Myotis austroriparius). American Midland Naturalist, 160, 364-373. 4Dahl, T. E. 1990. Wetlands: Losses in the United States 1780’s to 1980's. Discussion Both MYAU and CORA show affinity towards larger trees with higher basal area than random trees, however species differ in their preferences for tree height and canopy coverage. CORA and MYAU select for similar tree characteristics (canopy coverage, basal area and tree height). However, selection differs between species with tree diameter. Inability to accurately measure DBH of trees with large swellings (buttresses) may make it hard to compare results to other studies. Objective Characterize roost selection of southeastern myotis and Rafinesque’s big-eared bat in Arkansas’ bottomlands. Acknowledgements A special thanks to my field techs, Elizabeth Rush, Megan Wallrichs, Adam Lee, NiKayla Hughes, Alex Gurley, and Megan Buckley for their invaluable field assistance and thanks to Tracy Klotz, Phillip Jordan, Jimmy Gore, Patrick Moore and Daniel Istvanko for their assistance and guidance during my field seasons. An additional thanks to U.S. Fish and Wildlife for funding my project. Fig. 3 – Roost containing over 100 MYAU Results We located roosts of 12 MYAU (7♂,5♀), and 8 CORA (4♂,4♀). CORA selected for larger diameter trees than MYAU (p=0.049), but there were no differences in canopy coverage (p=0.74), basal area (p=0.75), and height (p=0.17) between species. 56% of roost trees had basal openings, 20.5% had chimney openings, 12.8% had neither chimney nor basal openings, 2.5% had both chimney and basal openings, 7.6% had window openings. MYAU CORA % Canopy Coverage MYAU CORA cm MYAU CORA Diameter at Breast Height Basal Area M2/ha MYAU CORA <0.001 0.009 0.019 0.02 0.01 Fig. 2 – Rafinesque’s big-eared bat with aluminum band Fig. 1 – Southeastern myotis with transmitter Abstract: Transmitters were affixed to 23 Myotis austroriparius (13 males; 10 females) and 9 Corynorhinus rafinesquii (5 males; 4 females). Bats were tracked daily to their roost trees for the life of the transmitter. Roosts were discovered from 20 bats with some bats using multiple roosts. Thirty roosts were located in water tupelos (Nyssa aquatica) with large basal hollows and chimney openings, 5 were located in bald cypress (Taxodium distichum). All roost sites were in living trees. Roost trees for both bat species were larger in diameter and in thicker stands than trees selected at random. Relevance to Conservation As wind energy continues to negatively impact tree-roosting bats and WNS continues to cause decline in caverniculous bats, knowledge and preservation of bottomland bat habitat is critical. Arkansas has lost over 70% of its bottomland habitat since colonization.4 Protection and conservation of large roost trees in contiguous habitat is necessary to delay the declining population trend of MYAU and CORA. Tree Height m <0.001 MYAU CORA Fig. 4 – Wilcoxon Rank-signed tests of 4 variables between roost (gray) and random trees (white) for CORA and MYAU, with α=0.05. Species n 𝑁𝑦𝑠𝑠𝑎 𝑎𝑞𝑢𝑎𝑡𝑖𝑐𝑎 water tupelo 30 𝑇𝑎𝑥𝑖𝑑𝑢𝑚 𝑑𝑖𝑠𝑡𝑖𝑐ℎ𝑢𝑚 bald cypress 5 𝑁𝑦𝑠𝑠𝑎 𝑠𝑦𝑙𝑣𝑎𝑡𝑖𝑐𝑎 black tupelo 1 𝐴𝑐𝑒𝑟 𝑟𝑢𝑏𝑟𝑢𝑚 red maple 1 𝐿𝑖𝑞𝑢𝑖𝑑𝑎𝑚𝑏𝑎𝑟 𝑠𝑡𝑦𝑟𝑎𝑐𝑖𝑓𝑙𝑢𝑎 American sweetgum 1 𝐶𝑎𝑟𝑝𝑖𝑛𝑢𝑠 𝑐𝑎𝑟𝑜𝑙𝑖𝑛𝑖𝑎𝑛𝑎 American hornbeam 1 Table 1 – Roost trees by species.

Related Documents