Wind power is one of the fastest growing renewable energy sources and is expected to continue to increase globally (Wiser et al. 2015). Nonetheless, there are concerns over the potential threats that wind facilities pose to wildlife populations. For example, large numbers of bats are killed at wind turbines annually across North America, and just 3 species of migratory tree bats comprise 78% of these fatalities: hoary (Lasiurus cinereus), eastern red (Lasiurus borealis), and silver-haired bats (Lasionycteris noctivagans; Arnett et al. 2008, Arnett and Baerwald 2013). The period of peak fatality at wind turbines for these species occurs from July through September coinciding with fall migration, and it has been estimated that up to 90% of annual fatalities occur during this time (Rydell et al. 2010). Many studies have been undertaken to better understand fatality rates (e.g., Huso 2011, Strickland et al. 2011, Korner-Nievergelt et al. 2013), patterns of fatality (e.g., Arnett et al. 2008, Baerwald and Barclay 2008, Korstian et al. 2013), and the proximate causes of fatality (e.g., Baerwald et al. 2008, Horn et al. 2008, Rollins et al. 2012); however, we still do not entirely understand why bats are coming into contact with wind turbines.
Researchers have proposed 3 broad explanations for the ultimate causes of bat fatalities at wind turbines: 1) fatalities are random events that reflect local bat abundance; 2) fatalities are coincidental as wind turbines are located in close proximity to existing resources where bat activity may be concentrated; and 3) fatalities occur because bats are attracted to wind turbines (Cryan and Barclay 2009). Note that these proposed explanations are not mutually exclusive and may vary among species. Previous studies at wind facilities have shown that bats approach both rotating and non-rotating blades and investigate various parts of wind turbines, providing evidence that bats are attracted to wind turbines (Horn et al. 2008, McAlexander 2013). Three general hypotheses of attraction have been proposed: 1) bats are interested or intrigued by the sound, motion, or lights associated with wind turbines; 2) turbines provide a resource for bats (i.e., foraging, mating, or roosting sites; Kunz et al. 2007, Horn et al. 2008, Cryan et al. 2014); and 3) turbines are misperceived to provide one or more resources (Cryan and Barclay 2009, Cryan et al. 2014, McAlexander 2013).
The objectives of this project were to 1) determine if bats in a flight facility would attempt to drink from smooth painted surfaces similar to wind turbine towers, and 2) identify a surface texture that bats show little or no interest in approaching. To accomplish these objectives, we captured local bats (including species that are frequently killed at wind turbines) and conducted a behavioral experiment in a flight facility at Texas Christian University. We created smooth and textured surfaces of varying types and grade and recorded how these wildcaught bats behaved towards each surface. The ultimate goal of the behavioral experiment was to inform the development of a cost-effective texture coating that could be applied to existing wind turbine towers or towers in the manufacturing stage as a mitigation strategy for bat fatalities at wind farms.