title: Behavior of bats at wind turbines.
abstract: Wind turbines are causing unprecedented numbers of bat fatalities. Many fatalities involve tree-roosting bats, but reasons for this higher susceptibility remain unknown. To better understand behaviors associated with risk, we monitored bats at three experimentally manipulated wind turbines in Indiana, United States, from July 29 to October 1, 2012, using thermal cameras and other methods. We observed bats on 993 occasions and saw many behaviors, including close approaches, flight loops and dives, hovering, and chases. Most bats altered course toward turbines during observation. Based on these new observations, we tested the hypotheses that wind speed and blade rotation speed influenced the way that bats interacted with turbines. We found that bats were detected more frequently at lower wind speeds and typically approached turbines on the leeward (downwind) side. The proportion of leeward approaches increased with wind speed when blades were prevented from turning, yet decreased when blades could turn. Bats were observed more frequently at turbines on moonlit nights. Taken together, these observations suggest that bats may orient toward turbines by sensing air currents and using vision, and that air turbulence caused by fast-moving blades creates conditions that are less attractive to bats passing in close proximity. Tree bats may respond to streams of air flowing downwind from trees at night while searching for roosts, conspecifics, and nocturnal insect prey that could accumulate in such flows. Fatalities of tree bats at turbines may be the consequence of behaviors that evolved to provide selective advantages when elicited by tall trees, but are now maladaptive when elicited by wind turbines.
authors.affiliation: Fort Collins Science Center, United States Geological Survey (USGS), Fort Collins, CO 80526; cryanp@usgs.gov.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Cryan
authors.affiliation: Hawaii Cooperative Studies Unit, University of Hawaii, Hilo, HI 96720;
authors.forename: P Marcos
authors.initials: PM
authors.lastname: Gorresen
authors.affiliation: Bat Conservation International, Austin, TX 78716;
authors.forename: Cris D
authors.initials: CD
authors.lastname: Hein
authors.affiliation: Bat Conservation International, Austin, TX 78716;
authors.forename: Michael R
authors.initials: MR
authors.lastname: Schirmacher
authors.affiliation: Northern Rocky Mountain Science Center, USGS, Bozeman, MT 59715;
authors.forename: Robert H
authors.initials: RH
authors.lastname: Diehl
authors.affiliation: Forest and Rangeland Ecosystem Science Center, USGS, Corvallis, OR 97330;
authors.forename: Manuela M
authors.initials: MM
authors.lastname: Huso
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, CO 80523; Department of Biology, University of Florida, Gainesville, FL 32611;
authors.forename: David T S
authors.initials: DT
authors.lastname: Hayman
authors.affiliation: The MathWorks, Inc., Natick, MA 01760;
authors.forename: Paul D
authors.initials: PD
authors.lastname: Fricker
authors.affiliation: Pacific Island Ecosystems Research Center, USGS, Hawaii National Park, HI 96718;
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Bonaccorso
authors.affiliation: Northern Prairie Wildlife Research Center, USGS, Saint Paul, MN 55108;
authors.forename: Douglas H
authors.initials: DH
authors.lastname: Johnson
authors.affiliation: Conservation Biology Graduate Program, University of Minnesota, Saint Paul, MN 55108; and.
authors.forename: Kevin
authors.initials: K
authors.lastname: Heist
authors.affiliation: Wildlife Engineering, Tucson, AZ 85745.
authors.forename: David C
authors.initials: DC
authors.lastname: Dalton
mesh_terms: D025041:Animal Migration; D000818:Animals; D001522:Behavior, Animal; D002685:Chiroptera / Q000502:physiology*; D007196:Indiana; D010465:Perception; D012621:Seasons; D013696:Temperature; D014197:Trees; D014481:United States; D014741:Video Recording; D014919:Wind
keywords: energy development; sensory perception; video surveillance; wildlife; wind energy