Prey-catching behaviour and echolocation in the Australian Ghost Bat, Macroderma gigas (Microchiroptera: Megadermatidae).

Abstract

The prey-catching behaviour of Macroderma gigas was investigated under laboratory conditions using Mice. The echolocation pulses were very short, broad-banded and downwardly modulated with four harmonics, the first of which was usually weak and the second and third strong. These pulses were emitted either singly or in groups. Sounds from live Mice (vocalisations or sounds made by their movements) caused the hanging bats to direct their pinnae at the sound source and to move them backwards and forwards. These movements were usually not accompanied by echolocation pulses. The ultrasonic cries of infant Mice produced these responses with minimum delay. After listening to the sounds of the prey for varying periods, depending on the amount of noise the prey made, the bat emitted echolocation pulses that reached a peak frequency just before take-off on a varying number of reconnoitre flight s past the prey and back to the perch. The final attack was made from the perch or from a hover during a reconnoitre flight. The captured Mice were taken back to the perch to be eaten. Macroderma gigas was able to locate live Mice placed in: 1, one of two to eight tubs in dim light; 2, in one of two tubs covered with nylon gauze so that the Mice could not be seen; and 3, in one of two tubs covered by gauze and wood so that they could not be seen or echolocated. They also differentiated between noises from live Mice and replayed recordings of these noises. Silent and motionless Mice were not detected. The evidence presented suggests that passive acoustic localisation is an important part of prey-catching in M. gigas.