Migratory bats are attracted by red light but not by warm‐white light: Implications for the protection of nocturnal migrants

Abstract

The replacement of conventional lighting with energy‐saving light emitting diodes (LED) is a worldwide trend, yet its consequences for animals and ecosystems are poorly understood. Strictly nocturnal animals such as bats are particularly sensitive to artificial light at night (ALAN). Past studies have shown that bats, in general, respond to ALAN according to the emitted light color and that migratory bats, in particular, exhibit phototaxis in response to green light. As red and white light is frequently used in outdoor lighting, we asked how migratory bats respond to these wavelength spectra. At a major migration corridor, we recorded the presence of migrating bats based on ultrasonic recorders during 10‐min light‐on/light‐off intervals to red or warm‐white LED, interspersed with dark controls. When the red LED was switched on, we observed an increase in flight activity for Pipistrellus pygmaeus and a trend for a higher activity for Pipistrellus nathusii. As the higher flight activity of bats was not associated with increased feeding, we rule out the possibility that bats foraged at the red LED light. Instead, bats may have flown toward the red LED light source. When exposed to warm‐white LED, general flight activity at the light source did not increase, yet we observed an increased foraging activity directly at the light source compared to the dark control. Our findings highlight a response of migratory bats toward LED light that was dependent on light color. The most parsimonious explanation for the response to red LED is phototaxis and for the response to warm‐white LED foraging. Our findings call for caution in the application of red aviation lighting, particularly at wind turbines, as this light color might attract bats, leading eventually to an increased collision risk of migratory bats at wind turbines.

Orientation and flight behaviour identify the Soprano pipistrelle as a migratory bat species at the Baltic Sea coast

“…Indeed, orientation and takeoff direction were similar to that of P. nathusii , a species with known long‐distance migration across Europe. The seasonal occurrence of P. pygmaeus at our study site in conjunction with orientation towards the south in departing individuals identifies P. pygmaeus as a migratory species, at least for its north‐eastern distribution range (Voigt et al ., , ). Using our novel experimental setup, called the circular release box (CRBox), we here showed (1) initial movements of bats are goal‐oriented on the level of takeoff, that (2) orientations are biologically meaningful, and that (3) the principal methodology enables comparison of different measures between species.…”

“…The observed orientations would lead bats southwards and back to the flyway along the dunes of the shoreline. Based on our findings combined with previous results about population genetics, phenological occurrences and flight behaviour at sea sides, we argue that P. pygmaeus can be considered a true migratory species, at least in northern parts of its distribution range (Ahlén et al ., ; Sztencel‐Jabłonka & Bogdanowicz, ; Rydell et al ., ; Voigt et al ., , ). Quantitative studies based on tagged individuals are now needed to evaluate how regular P. pygmaeus migrate over longer distances and where individuals of northern populations are overwintering.…”

“…Here, we focused on the orientation behaviour of individual P. pygmaeus caught between August and September at Pape Bird Ringing Station (PBRS) at the Latvian Baltic Sea coast. Previous acoustic studies demonstrated a regular occurrence of the species at PBRS during summer migration (Rydell et al ., ; Voigt et al ., , ), yet it is unknown if this reflects the seasonal occurrence of P. pygmaeus in this region without pronounced directional migration flights. Interestingly, similar to other bats passing PBRS on migration, P. pygmaeus only exceptionally displays foraging behaviour (Voigt et al ., , ).…”

“…Previous acoustic studies demonstrated a regular occurrence of the species at PBRS during summer migration (Rydell et al ., ; Voigt et al ., , ), yet it is unknown if this reflects the seasonal occurrence of P. pygmaeus in this region without pronounced directional migration flights. Interestingly, similar to other bats passing PBRS on migration, P. pygmaeus only exceptionally displays foraging behaviour (Voigt et al ., , ). In our study, we aimed to compare directionality of flights, here estimated as the orientation behaviour of departing P. pygmaeus with that of a well‐known European long‐distance migrant, P. nathusii .…”

Potential Factors Influencing Repeated SARS Outbreaks in China

“…It turned out that bats are not only attracted by green lights but also red lights [54]. Along the Yangtze River there are also huge bridges decorated with a massive number of red lights.…”