Presence of single as well as double clicks in the echolocation signals of a fruit bat, Rousettus leschenaulti (Chiroptera: Pteropodidae)

We studied the structure of calls emitted by the echolocating fruit bat Rousettus leschenaulti (Megachiroptera: Pteropodidae) while flying inside a free-flight room. The echolocation sounds consists of both single as well as double clicks, with single clicks emitted either in the beginning or at the end of click sequences. The duration of clicks was brief, about 1.6 ms and most of the acoustic energy is between 18 to 32 kHz. The use of simple, brief impulsive clicks and the reduction of interpulse interval and duration, when approaching the sides of the walls suggest that they have a good capability of obstacle avoidance as similar to microchiropteran bats. Furthermore, the production of both single as well as double clicks like cave swiftlets in orientation flights has an implication for the evolution of echolocation in bats.