Echolocation calls of emballonurid bats from Panama

Abstract

Saccopteryx bilineata, Cormura brevirostris and two other species tentatively identified as emballonurid bats, were recorded in the field in Panama. The search and approach phase calls of all the species began with a rise in frequency followed by a constant frequency (CF) portion and a terminal drop in frequency.S. bilineata and one of the unknown species produced pairs of calls, the first 2–3 kHz lower in CF frequency than the second. This has been suggested as associated with Doppler shifts of echoes caused by the bats' flight and bats' beaming calls towards different targets. However, a second unidentified species produced call triplets with the total difference in CF frequencies too great to be explained by this hypothesis. Increased bandwidth and integration of echo information, or social communication may be alternative functions. Terminal phase calls of three of the species were typical frequency modulated signals.C. brevirostris terminal calls, however, were CF in nature, a form not believed to be suitable for tasks requiring high resolution such as prey pursuit. The characteristics of these bats' signals are more complex than previously suggested and bring into question their supposed ‘primitive’ nature.