Challenges of bat biosonar

Research output: Book/anthology/dissertation/reportPh.D. thesis

Abstract

Bat echolocation is undeniably an unfamiliar sense for humans. Since its discovery in 1941, life scientists have formed a solid basic understanding of how these small mammals use their biosonar to hunt and navigate in the dark without too much dependence on vision. However, this sensory system is not a panacea and is associated with certain challenges. The objectives of this thesis are to uncover how bats face two of these challenges, namely noise and escaping prey. To address these, I used microphone arrays and a novel on-animal acoustic and movement tag to record the echolocation calls of bats approaching masked or moveable targets in laboratory settings. Chapter I presents some basic concepts of bat echolocation and reviews and discusses my findings within a broader context of biosonar challenges. Chapter II outlines the biosonar performance of Daubenton’s bats (Myotis daubentonii) tasked with detecting and approaching a landing target during exposure to broadband, ultrasonic masking noise. I show that bats respond to intense acoustic interference by calling louder but that this adjustment only partially compensates for noise. Despite this, I demonstrate that bats can complete the landing task at very low echo-to-noise ratios leading to the proposal that they are extremely resilient to noise masking their echoes. Chapter III shows that despite their vocal flexibility to do so, Daubenton’s
bats do not shift the frequency of their calls in response to noise overlapping spectrally with their biosonar. In Chapter IV, I address how greater mouse-eared bats (Myotis myotis) use their biosonar to track suddenly escaping prey in the wild and during simulated prey escapes in the laboratory. I show that bats use an echo-guided vocal-motor feedback loop by adjusting their call rates within 200 ms of prey maneuvers and by prolonging their fast sonar sampling just before target interception. In conclusion, this thesis explores how echolocating bats adjust their primary sensory modality to overcome noise and evasive prey with the aim of maximising their fitness in an acoustically complex world.
Original languageEnglish
PublisherÅrhus Universitet
Number of pages106
Publication statusPublished - Sept 2022

Keywords

  • Chiroptera
  • bat
  • echolocation
  • biosonar
  • behaviour
  • acoustic interference
  • noise
  • jamming
  • Lombard effect
  • echo-to-noise ratio
  • tracking

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