Echolocation and acoustic communication in the Australian Ghost Bat, Macroderma gigas (Microchiroptera: Megadermatidae).

Abstract

The vocal ability of Macroderma gigas can be divided into two sections, social communication and echolocation signals. The echolocation system is characterised by short frequency modulated pulses with an average duration of 0.7 msec at rest and 1.2 msec during indoor flight. The pulses contain 3 or 4 harmonics, with the second and third harmonics having the most energy. The fundamental frequency of the pulse is modulated from 20-15 kHz and is suppressed during sonar emission. Pulse repetition rate varies from 2 pps at rest to 110 pps when approaching objects during flight. An average pulse rate of 32 pps occurs during unrestricted flight. During flight, echolocation pulses are grouped into 3 to 5 pulses with bursts of three being the most common. During the approach to objects sonar pulses become paired, while during landing pulse emission is ungrouped. Two types of social communication sounds are described: audible (to humans) calls which include a commonly used "chirp" and "squabble", and ultrasonic calls. The audible calls have a main energy band between 5-15 kHz. The structure of ultrasonic social calls have similarities to sonar pulses but most of the energy is restricted to the second harmonic.