Data from: Transition from conventional to light-emitting diode street lighting changes activity of urban bats

Light pollution is rapidly increasing and can have deleterious effects on
biodiversity, yet light types differ in their effect on wildlife. Among
the light types used for street lamps, light-emitting diodes (LEDs) are
expected to become globally predominant within the next few years. In a
large-scale field experiment, we recorded bat activity at 46 street lights
for 12 nights each and investigated how the widespread replacement of
conventional illuminants by LEDs affects urban bats: we compared bat
activity at municipal mercury vapour (MV) street lamps that were replaced
by LEDs with control sites that were not changed. Pipistrellus
pipistrellus was the most frequently recorded species; it was 45% less
active at LEDs than at MV street lamps, but the activity did not depend on
illuminance level. Light type did not affect the activity of Pipistrellus
nathusii, Pipistrellus pygmaeus or bats in the
Nyctalus/Eptesicus/Vespertilio (NEV) group, yet the activity of P.
nathusii increased with illuminance level. Bats of the genus Myotis
increased activity 4·5-fold at LEDs compared with MV lights, but
illuminance level had no effect. Decreased activity of P. pipistrellus,
which are considered light tolerant, probably paralleled insect densities
around lights. Further, our results suggest that LEDs may be less
repelling for light-averse Myotis spp. than MV lights. Accordingly, the
transition from conventional lighting techniques to LEDs may greatly alter
the anthropogenic impact of artificial light on urban bats and might
eventually affect the resilience of urban bat populations. Synthesis and
applications. At light-emitting diodes (LEDs), the competitive advantage –
the exclusive ability to forage on insect aggregations at lights – is
reduced for light-tolerant bats. Thus, the global spread of LED street
lamps might lead to a more natural level of competition between
light-tolerant and light-averse bats. This effect could be reinforced if
the potential advantages of LEDs over conventional illuminants are applied
in practice: choice of spectra with relatively little energy in the short
wavelength range; reduced spillover by precisely directing light; dimming
during low human activity times; and control by motion sensors. Yet, the
potential benefits of LEDs could be negated if low costs foster an overall
increase in artificial lighting.