COUPLING OF SOUND EMISSION AND WINGBEAT IN NATURALLY FORAGING EUROPEAN PIPISTRELLE BATS (MICROCHIROPTERA, VESPERTILIONIDAE)

Owing largely to technical difficulties, there are few field studies l inking sound emission and wingbeat of aerial insectivorous bats in fli ght. I accomplished the linkage by simultaneously photographing three species of naturally foraging European pipistrelle bats (Vespertilioni dae: Pipistrellus pipistrellus, P. kuhlii, and P. nathusii) under stro boscopic illumination and recording their echolocation signals. I foun d sound emission in straight search flight to be intimately coupled wi th wingbeat. Mostly, the pipistrelles produced one signal per wingbeat . In some cases, they either skipped a signal during a wingbeat cycle or performed short gliding flights (100-200 ms) without sound emission . During turns and insect pursuits pipistrelles produced groups of at least two signals per wingbeat. Just before capturing insects, they of ten emitted groups of 10-15 signals per wingbeat. During insect pursui ts involving steep dives coupled with sharp turns, pipistrelles freque ntly glided for as long as 300-700 ms. In these instances, in contrast to the gliding flights observed in straight search flight, the bats c ontinued to emit signals. Recent studies demonstrate that it is energe tically most economical for flying bats to couple sound emission with wingbeat. I discuss possible implications of the observed coupling of sound emission and wingbeat on the energy budget and of feeding ecolog y of pipistrelles.