Severe and widespread reductions in night-time activity of nocturnal moths under modern artificial lighting spectra

Artificial lighting has many negative impacts on nocturnal insects, from harmful phototaxis to disruption of feeding and reproduction. Although comparatively poorly explored, many detrimental outcomes could be associated with changes in activity. We investigated the effects of different types of light-emitting diode (LED) lighting on activity in multiple wild-caught moth species in three different families. While behaviour under natural conditions varied among species, artificial lighting strongly and largely consistently suppressed activity. In our main experiment, testing 843 moths of 23 species, we found that white LEDs at 10 lx illuminance depressed activity by 85% on average relative to natural night-time illumination, and even purportedly less harmful amber lighting had similar impacts at the same intensity. There were no differences between the effects of broad-spectrum LEDs and combinations of narrowband LEDs that produce equivalent light for human vision. Collection methods, using light traps or hand-catching with nets, did affect activity in some species, with implications for future research. Finally, further experiments found significant activity suppression overall under lighting at 1 lx, for white LEDs especially, with some species affected even by skyglow levels of white light. Substantial inhibition of activity under multiple streetlight-relevant LEDs suggests potential for widespread impacts on moth populations.