Animals such as bats use echolocation as a form of sonar to find food at night, but they might also use it to communicate.
Mirjam Knörnschild at the University of Ulm in Germany and her colleagues recorded and analysed the echolocation calls of a social species of bat, Saccopteryx bilineata (pictured), at three sites in Costa Rica. The researchers found that roosting males seem to detect the echolocation calls of an approaching bat from at least five metres away. In response to an incoming male, the bats emitted aggressive vocalizations suggestive of territorial defence. If the approaching bat was female, however, the males responded with courtship songs.
The males must be using echolocation, the authors conclude, because in low-light conditions at a distance of at least five metres, neither visual nor odour cues could provide the roosting bats with information about the sex of their visitor.
Proc. R. Soc. B http://dx.doi.org/10.1098/rspb.2012.1995 (2012)