The role of echolocation in the hunting of terrestrial prey - new evidencefor an underestimated strategy in the gleaning bat, Megaderma lyra

The observation that gleaning bats detect prey by its noises, together with difficulties in recording their faint sonar calls, have led some authors t o conclude that gleaning bats may not use echolocation in certain hunting s ituations. In particular, it is conjectured that echolocation plays no role in the classification and tracking of prey. In the present study, we show that the gleaning bat, Megaderma lyra, is able to find silent and motionles s prey on the ground. The significance of sonar for catching a variety of t errestrial prey is established in a standardized situation. Sonar calls wer e found to be emitted during all stages, i.e. approach, hovering above the prey, and return to the roost, of every hunting flight. The harmonic patter n of the calls differed significantly between these stages, calls with thre e or more prominent components prevailing during hovering. Bats identified prey and rejected dummies while hovering above them. During this stage, inc reased call rates and reduced call durations were found. Echolocation activ ity during, and the duration of, the hovering phase depended on prey type, in particular on prey movement. The prey-dependent shifts in sonar activity , the broadband call structure with an emphasis on higher harmonics, and a systematic shift of the calls' peak frequencies during hovering, are discus sed as adaptations to identifying prey by sonar.