Bats Actively Use Leaves as Specular Reflectors to Detect Acoustically Camouflaged Prey

Inga Geipel*, Jan Steckel, Marco Tschapka, Dieter Vanderelst, Hans Ulrich Schnitzler, Elisabeth K.V. Kalko, Herbert Peremans, Ralph Simon

*Corresponding author for this work

    Research output: Contribution to JournalArticleAcademicpeer-review

    Abstract

    Filtering relevant signals from noisy sensory input is a crucial challenge for animals [1, 2]. Many bats are acoustic specialists relying on sound to find prey. They discern salient acoustic signals from irrelevant background masking noise. It has long been considered a sensory impossibility for bats to use solely echolocation for the detection of silent and motionless prey resting directly on foliage due to the masking effects of background echoes [3, 4]. Some bats, however, do successfully perform this seemingly impossible task [5], raising the question-what underlying acoustic and behavioral mechanisms do bats use to solve this conundrum? To address this question, we used biomimetic sonar to record high-resolution measurements of echoes from insects resting on leaves. Based on our echo recordings, we predicted optimal approach angles from which masking echoes can best be avoided. In behavioral experiments, we put these predictions to test. We recorded the prey approach behavior of wild bats in a flight cage equipped with an ultrasonic microphone synchronized with two high-speed cameras for 3D flightpath reconstructions. Bats approached prey from our predicted optimal oblique angles, using the leaf as a specular reflector to uncover previously acoustically hidden prey. Our findings disclose key behavioral and acoustic mechanisms enabling the detection of prey echoes that background clutter would otherwise mask. This work adds to the fundamental understanding of how bat echolocation strategies can override acoustic camouflage by silent, motionless prey, thus providing new insights into the evolutionary arms race between predators and their prey.

    Original languageEnglish
    Pages (from-to)2731-2736.e3
    Number of pages10
    JournalCurrent Biology
    Volume29
    Issue number16
    Early online date1 Aug 2019
    DOIs
    Publication statusPublished - 19 Aug 2019

    Bibliographical note

    Copyright © 2019 Elsevier Ltd. All rights reserved.

    Funding

    We thank Rachel Page, Wouter Halfwerk, Annette Denzinger, and Kirsten Jung for discussions; Rachel Page, Egbert G. Leigh, Jr. Gerald Carter, Florian Maderspacher, and two anonymous reviewers for comments on the manuscript; and Damond Kyllo for the drawing of the bat head. The Smithsonian Tropical Research Institute, especially the Biological Station BCI, provided excellent logistic and technical support. This study was funded by the EU-Project ChiRoPing, FP7-ICT-2007-1, STREP project 215370, and the Wissenschaftskolleg zu Berlin, Germany to I.G. This article is dedicated to Elisabeth K.V. Kalko, who initiated this work and brought us together before her all-too-early death. Her passion and intuition about nature, specifically bats, and her inexhaustible enthusiasm were an inspiration to us. I.G. and E.K.V.K. conceived the original idea of the study. I.G. J.S. D.V. E.K.V.K. H.P. and R.S. designed the study. I.G. collected behavioral data. R.S. collected ensonification data. D.V. assisted with initial key elements of analysis. M.T. and H.-U.S. contributed ideas to the manuscript. I.G. J.S. H.P. and R.S. performed data analysis and wrote the manuscript. The authors declare no competing interests.

    FundersFunder number
    Smithsonian Tropical Research Institute215370, FP7-ICT-2007-1

      Keywords

      • acoustic masking
      • active gleaning
      • bats
      • clutter echoes
      • echolocation
      • foraging strategies
      • Micronycteris microtis
      • Phyllostomidae
      • prey approach
      • specular effect

      Fingerprint

      Dive into the research topics of 'Bats Actively Use Leaves as Specular Reflectors to Detect Acoustically Camouflaged Prey'. Together they form a unique fingerprint.

      Cite this