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 language | English |
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Pages (from-to) | 2731-2736.e3 |
Number of pages | 10 |
Journal | Current Biology |
Volume | 29 |
Issue number | 16 |
Early online date | 1 Aug 2019 |
DOIs | |
Publication status | Published - 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.
Funders | Funder number |
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Smithsonian Tropical Research Institute | 215370, FP7-ICT-2007-1 |
Keywords
- acoustic masking
- active gleaning
- bats
- clutter echoes
- echolocation
- foraging strategies
- Micronycteris microtis
- Phyllostomidae
- prey approach
- specular effect