Vespertilionid bats control the width of their biosonar sound beam dynamically during prey pursuit

Lasse Jakobsen, Annemarie Surlykke

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Animals using sound for communication emit directional signals, focusing most acoustic energy in one direction. Echolocating bats are listening for soft echoes from insects. Therefore, a directional biosonar sound beam greatly increases detection probability in the forward direction and decreases off-axis echoes. However, high directionality has context-specific disadvantages: at close range the detection space will be vastly reduced, making a broad beam favorable. Hence, a flexible system would be very advantageous. We investigated whether bats can dynamically change directionality of their biosonar during aerial pursuit of insects. We trained five Myotis daubentonii and one Eptesicus serotinus to capture tethered mealworms and recorded their echolocation signals with a multimicrophone array. The results show that the bats broaden the echolocation beam drastically in the terminal phase of prey pursuit. M. daubentonii increased the half-amplitude angle from approximately 40 degrees to approximately 90 degrees horizontally and from approximately 45 degrees to more than 90 degrees vertically. The increase in beam width is achieved by lowering the frequency by roughly one octave from approximately 55 kHz to approximately 27.5 kHz. The E. serotinus showed beam broadening remarkably similar to that of M. daubentonii. Our results demonstrate dynamic control of beam width in both species. Hence, we propose directionality as an explanation for the frequency decrease observed in the buzz of aerial hawking vespertilionid bats. We predict that future studies will reveal dynamic control of beam width in a broad range of acoustically communicating animals.
Original languageEnglish
JournalPNAS
Volume107
Issue number31
Pages (from-to)13930-5
Number of pages6
ISSN0027-8424
DOIs
Publication statusPublished - 3. Aug 2010

Keywords

  • Acoustics
  • Animals
  • Chiroptera
  • Echolocation
  • Predatory Behavior

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