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Title: Amazon river dolphins (Inia geoffrensis) modify biosonar output level and directivity during prey interception in the wild
Authors: Ladegaard, Michael
Jensen, Frants H.
Beedholm, Kristian
Silva, Vera Maria Ferreira da
Madsen, Peter Teglberg T.
Keywords: Animals
Sound Detection
Toothed Whale
Predatory Behavior
Sound Spectrography
Issue Date: 2017
metadata.dc.publisher.journal: Journal of Experimental Biology
metadata.dc.relation.ispartof: Volume 220, Número 14, Pags. 2654-2665
Abstract: Toothed whales have evolved to live in extremely different habitats and yet they all rely strongly on echolocation for finding and catching prey. Such biosonar-based foraging involves distinct phases of searching for, approaching and capturing prey, where echolocating animals gradually adjust sonar output to actively shape the flow of sensory information. Measuring those outputs in absolute levels requires hydrophone arrays centred on the biosonar beam axis, but this has never been done for wild toothed whales approaching and capturing prey. Rather, field studies make the assumption that toothed whales will adjust their biosonar in the same manner to arrays as they will when approaching prey. To test this assumption, we recorded wild botos (Inia geoffrensis) as they approached and captured dead fish tethered to a hydrophone in front of a star-shaped seven-hydrophone array. We demonstrate that botos gradually decrease interclick intervals and output levels during prey approaches, using stronger adjustment magnitudes than predicted from previous boto array data. Prey interceptions are characterised by high click rates, but although botos buzz during prey capture, they do so at lower click rates than marine toothed whales, resulting in a much more gradual transition from approach phase to buzzing. We also demonstrate for the first time that wild toothed whales broaden biosonar beamwidth when closing in on prey, as is also seen in captive toothed whales and bats, thus resulting in a larger ensonified volume around the prey, probably aiding prey tracking by decreasing the risk of prey evading ensonification.
metadata.dc.identifier.doi: 10.1242/jeb.159913
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