Synthetic communication signals influence wild harbour porpoise (Phocoena phocoena) behaviour

We used our novel and programmable Porpoise Alarm (PAL, patd.) to synthesize lifelike, electronic harbour porpoise communication signals based on those described for captive animals. In the Little Belt, Denmark, we employed PAL (source level 158 ^ 1 dB p–p re 1mPa@1 m; centroid frequency 133 ^ 8.5 k...

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Bibliographic Details
Published in:Bioacoustics
Main Authors: Culik, Boris, Dorrien, Christian von, Müller, Vailett, Conrad, Matthias
Format: Article in Journal/Newspaper
Language:English
Published: 2015
Subjects:
Text
harbour porpoise
Phocoena phocoena
click communication
field experiments
by-catch mitigation
acoustic surveys
instrumentation
Harbour porpoise
Online Access:https://doi.org/10.1080/09524622.2015.1023848
https://www.openagrar.de/receive/timport_mods_00038146
https://www.openagrar.de/servlets/MCRFileNodeServlet/timport_derivate_00038146/dn055453.pdf
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Summary:We used our novel and programmable Porpoise Alarm (PAL, patd.) to synthesize lifelike, electronic harbour porpoise communication signals based on those described for captive animals. In the Little Belt, Denmark, we employed PAL (source level 158 ^ 1 dB p–p re 1mPa@1 m; centroid frequency 133 ^ 8.5 kHz) to synthesize three aggressive click train types termed “A”, “F3” and “M1” to naive, free-living harbour porpoises. Via theodolite tracking (372 h of total visual effort spread over 10 expeditions) we found that, depending on signal type, porpoises either avoid or become attracted to PAL: Signal types “A” and “F3” are slight deterrents, porpoises increasing minimum range (þ23 to 32 m, respectively), whereas “M1” attracts porpoises, reducing range (by 229 m). As determined via archival acoustic detectors (AADs), both signals “F3” and “M1” led the animals to significantly intensify their click rate (by þ10% and 68%, respectively) while signal “A” led to a significant reduction (259%). We propose that equipping fishing gear with PAL emitting signal “F3” could potentially reduce porpoise by-catch by increasing (1) awareness through enhanced echolocation and (2) distance to the nets. Detection probability and radius of PAL/AAD tandems could be improved by emitting signal “M1” to focus porpoise echolocation signals on the AAD. The signal may also be useful in luring animals away from hazards, which may be helpful for conservation measures prior to the onset of harmful acoustic activities such as pile-driving, seismic exploration or ammunition clearance.

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