Directionality of nose-emitted echolocation calls from bats without a nose-leaf (Plecotus auritus)

Lasse Jakobsen, John Hallam, Cynthia F Moss, Anders Hedenström

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Abstract

All echolocating bats and whales measured to date emit a directional bio-sonar beam that affords them a number of advantages over an omni-directional beam, i.e. reduced clutter, increased source level and inherent directional information. In this study, we investigated the importance of directional sound emission for navigation through echolocation by measuring the sonar beam of brown long-eared bats, Plecotus auritus. Plecotus auritus emits sound through the nostrils but has no external appendages to readily facilitate a directional sound emission as found in most nose emitters. The study shows that P. auritus, despite lacking an external focusing apparatus, emits a directional echolocation beam (directivity index=13 dB) and that the beam is more directional vertically (-6 dB angle at 22 deg) than horizontally (-6 dB angle at 35 deg). Using a simple numerical model, we found that the recorded emission pattern is achievable if P. auritus emits sound through the nostrils as well as the mouth. The study thus supports the hypothesis that a directional echolocation beam is important for perception through echolocation and we propose that animals with similarly non-directional emitter characteristics may facilitate a directional sound emission by emitting sound through both the nostrils and the mouth.

Original languageEnglish
Article number171926
JournalJournal of Experimental Biology
Volume221
Issue number3
ISSN0022-0949
DOIs
Publication statusPublished - Feb 2018

Keywords

  • Acoustic signals
  • Animal bioacoustics
  • Biosonar
  • Chiroptera
  • Predatory Behavior
  • Animals
  • Chiroptera/anatomy & histology
  • Flight, Animal
  • Sound
  • Nose/anatomy & histology
  • Echolocation

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