Eavesdropping on the echolocation and social calls of bats

1. Comparisons of original calls and their echoes allow echolocating microchiropteran bats to collect information about their surroundings. Echolocation calls are also a source of information for other animals. A spectacular example is the hearing-based defence of many species of insects that use echolocation calls to detect marauding bats. The role of echolocation calls remains unknown for bats that eat other bats. 2. Other eavesdroppers, biologists, regularly monitor echolocation calls to collect information about the distribution and patterns of habitat use of echolocating bats. People monitoring echolocation calls have discovered cryptic species of bats. 3. Vocal communication in bats involves social calls that serve only in communication, as well as echolocation calls that influence the behaviour of conspecifics and others. There is evidence of individual- and colony-specific social and echolocation calls. 4. The long age-spans of bats and the propensity of some species to roost in groups combine with conspicuousness of echolocation calls to set the stage for the discovery of more behavioural interactions mediated by individual- specific echolocation calls. In the echolocation of microchiropteran bats, signals can serve multiple functions, both for producers and listeners.