Bat attacks and moth defensive behaviour around street lights

The defensive behaviour of moths around street lights was examined at a site where bats feed heavily on moths. The lights had a negative effect on moth defensive behaviour, but a combination of observational techniques (recording the outcome of naturally occurring bat-moth interactions) and experimental techniques (deafening moths by puncturing the tympanal organs) indicated that ultrasound-detecting ears still afforded the moths some protection from bat predation. On average, bats captured 69% of the moths they attacked. Moths that exhibited evasive behaviour were caught significantly less often than those that did not (52 vs. 2%). Moths whose tympanic organs had been punctured were significantly easier to catch (requiring fewer attempts) than moths with intact ears, reflecting the fact that significantly more of the eared than the deafened moths showed evasive behaviour (48 vs. 0%). Overall, the number of captures of deafened moths was higher, though not significantly, than the number of captures of eared moths.