INSECT PURSUIT, PREY CAPTURE AND ECHOLOCATION IN PIPISTRELLE BATS (MICROCHIROPTERA)

The foraging and echolocation behaviour of three European pipistrelles (Pipistrellus pipistrellus, P. nathusii and P. kuhlii) was studied un der natural conditions. The pipistrelles were photographed with two 35 mm cameras under stroboscopic illumination, and their echolocation si gnals were recorded simultaneously. This permits a three-dimensional r econstruction of the flight paths of bat and prey, and allows the deta ils of echolocation behaviour to be studied in the context of natural foraging behaviour. The general relationships between foraging and ech olocation behaviour were consistent among the three species. Foraging behaviour consisted of four stages: search flight (before detection of prey), approach flight (pursuit after detection of prey), capture and retrieval of prey. These stages correlated with phases in echolocatio n behaviour: search, approach, and terminal phase followed by a pause. Detection of prey occurred at distances of 1.14-2.20 m. The search co ne extending from the bat's mouth was up to 150 degrees wide. The pipi strelles caught prey in mid-air, either with the tail membrane alone o r by funnelling it with a wing onto the tail membrane. Except for some intra- and interspecific differences in sound duration, pulse interva l, bandwidth and terminal frequency in search phase, the structure and pattern of the echolocation signals were similar in the three pipistr elles. In the approach and terminal phases, pulse duration and pulse i nterval decreased with the approach to the target, while bandwidth and sweeprate increased. While pursuing insects, the pipistrelles precise ly avoided an overlap between outgoing signal and the echo returning f rom the prey. Furthermore, the bats stopped emitting signals several c entimetres before they reached the insect. (C) 1995 The Association fo r the Study of Animal Behaviour