Echolocating bats emit a highly directional sonar sound beam in the field

Annemarie Surlykke, Simon Boel Pedersen, Lasse Jakobsen

Research output: Contribution to journalJournal articleResearchpeer-review


Bats use echolocation or biosonar to navigate and find prey at night. They emit short ultrasonic calls and listen for reflected echoes. The beam width of the calls is central to the function of the sonar, but directionality of echolocation calls has never been measured from bats flying in the wild. We used a microphone array to record sounds and determine horizontal directionality for echolocation calls of the trawling Daubenton's bat, Myotis daubentonii, flying over a pond in its natural habitat. Myotis daubentonii emitted highly directional calls in the field. Directionality increased with frequency. At 40kHz half-amplitude angle was 25 degrees , decreasing to 14 degrees at 75kHz. In the laboratory, M. daubentonii emitted less intense and less directional calls. At 55kHz half-amplitude angle was 40 degrees in the laboratory versus 20 degrees in the field. The relationship between frequency and directionality can be explained by the simple piston model. The model also suggests that the increase in the emitted intensity in the field is caused by the increased directionality, focusing sound energy in the forward direction. The bat may increase directionality by opening the mouth wider to emit a louder, narrower beam in the wild.
Original languageEnglish
JournalProceedings of the Royal Society B
Issue number1658
Pages (from-to)853-860
Number of pages8
Publication statusPublished - 7. Mar 2009


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