Urban bats that eat insects may have to find them away from new LED-based streetlights. Apparently, the effect on insects isn’t the only effect on bat behavior from the new lights, according to a recent German study. The findings were published in Journal of Applied Ecology.
Researchers from the Leibniz Institute for Zoo and Wildlife Research (IZW) conducted a large-scale field experiment in which they recorded bat activity at 48 street lights over 12 nights. They compared bat activity around the new LED streetlights with the bat activity around the mercury vapor lights that they replaced.
They found that light sensitive bat species increased their activity around the LED-based streetlights. The team observed that other bat species were opportunistic insect hunters that seek insects that congregated around the mercury vapor lights.
The group found that these opportunistic hunters substantially decreased their activity around the new lights because insects are not attracted to the LEDs that don’t emit UV light.
Pipistrellus pipistrellus was the most frequently recorded species but was 45% less active around LEDs than at MV street lamps. The activity of Pipistrellus pipistrellus did not depend on the intensity of the light.
Other species were unaffected by the light change including Pipistrellus nathusii,Pipistrellus pygmaeus, and bats in theNyctalus/Eptesicus/Vespertilio (NEV) group.
However, the activity of P. nathusii increased with the light intensity level. Bats of the genus Myotis increased activity between four- and five-fold at LEDs compared with MV lights, but light intensity level had no effect.
The group hypothesized that decreased activity of P. pipistrellus, which are considered light tolerant, likely paralleled the decreased insect densities around the new LED-based lights. The results suggested that LEDs may be less repelling for light-averse Myotis spp. than MV lights.
The researchers speculated that LED lighting might help even the playing field for bats competing for food between light tolerant and light averse bats looking to feed on insects.
Lewanzik, D. and Voigt, C. C. (2016), Transition from conventional to light-emitting diode street lighting changes activity of urban bats. J Appl Ecol. doi:10.1111/1365-2664.12758