Dim ultraviolet light as a means of deterring activity by the Hawaiian hoary bat Lasiurus cinereus semotus

Abstract

Widespread bat fatalities at industrial wind turbines are a conservation issue with the potential to inhibit efficient use of an abundant source of energy. Bat fatalities can be reduced by altering turbine operations, but such curtailment decreases turbine efficiency. If additional ways of reducing bat fatalities at wind turbines were available such tradeoffs might not be needed. Based on the facts that bats perceive distant objects primarily through vision and can see in very dim lighting conditions, and the possibility that bats might interact with turbines after approaching them as they would trees, we propose a novel method of reducing bat activity at wind turbines: illumination of the structure with dim light. As a first step toward assessing this approach, we illuminated trees with dim flickering ultraviolet (UV) light in areas frequented by Hawaiian hoary bats Lasiurus cinereus semotus, an endangered subspecies affected by wind turbines. We used a repeated-measures design to quantify bat activity near trees with acoustic detectors and thermal video cameras in the presence and absence of UV illumination, while concurrently monitoring insect numbers. Results indicate that dim UV reduces bat activity despite an increase in insect numbers. Experimental treatment did not completely inhibit bat activity near trees, nor did all measures of bat activity show statistically significant differences due to high variance in bat activity among sites. However, the observed decreases in bat activity with dim UV illumination justify further testing of this method as a means to reduce bat fatalities at wind turbines.

A smart curtailment approach for reducing bat fatalities and curtailment time at wind energy facilities

“…However, application of statistical risk models across larger geographic areas (such as at the regional and continental scales) and among a variety of bat species assemblages may be much more challenging, and may require many years of data to sufficiently train models, even within a given ecoregion (Voigt et al 2015. Other approaches to reducing bat fatalities at wind energy facilities have focused on technological advances in realtime acoustic and video monitoring of bats and birds at these facilities (Willmott et al 2015) and using electromagnetic and ultrasonic signals and deterrents to reduce bat activity near turbines (Nicholls and Racey 2007, Szewczak and Arnett 2007, Gorresen et al 2015). These technological advances also suggest substantial promise, but may not always be applicable across species assemblages in a variety of ecoregions (Arnett et al 2016).…”

Comparing acoustic and radar deterrence methods as mitigation measures to reduce human-bat impacts and conservation conflicts

“…Potential deterrence methods for bats include light, radar and sound [12,16,18,[33][34][35]. Some bat species are deterred by certain types of lighting, for example streetlights or flood-lights [33,[36][37][38].…”

Do you hear what I see? Vocalization relative to visual detection rates of Hawaiian hoary bats (Lasiurus cinereus semotus)

“…The site studied by Belwood and Fullard (1984) on Kaua'i was surrounded by dense native forest and located among several buildings illuminated by incandescent lights where bats foraged on concentrations of insects; as such, call parameters may have reflected echolocation targeting nearrange prey. In contrast, the relatively sparse insect prey available at our study site (see Gorresen, Cryan, Dalton, et al, 2015) and the openspace setting above the orchard may have influenced foraging bats to use lower pulse rates, and correspondingly longer interpulse intervals.…”

“…The resulting airspace available to foraging or commuting bats was a mix of edge‐space and open‐space settings above the orchard. Twenty nights of time‐synchronized video and acoustic samples were collected as part of a study of bat response to dim ultraviolet illumination (Gorresen, Cryan, Dalton, et al., ). The dataset analyzed herein was derived from the “control” sample of nights, that is, the subset of nights at 10 orchard sites prior to application of ultraviolet illumination.…”

“…The resulting airspace available to foraging or commuting bats was a mix of edge-space and open-space settings above the orchard. Twenty nights of time-synchronized video and acoustic samples were collected as part of a study of bat response to dim ultraviolet illumination (Gorresen, Cryan, Dalton, et al, 2015).…”