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Nonlinear phenomena make animal calls alarming for human listeners
Anna Terrade1,2, Mathilde Massenet1,3,4, Lise Pernel1
1ENES Bioacoustics Research Lab, CRNL, University of Saint-Etienne, CNRS, Inserm, Saint-Etienne, France.
Iscience
|June 11, 2025
Summary
Chaos in animal vocalizations significantly increases their alarming quality for humans. This finding suggests that nonlinear phenomena, particularly chaos, play a key role in alarm calls and potentially in animal intimidation.
Area of Science:
- Bioacoustics
- Animal Communication
- Evolutionary Biology
Background:
- Animal vocalizations exhibit vast diversity, with assumed links between acoustic structure and communicative function.
- Evolutionary studies often posit universal roles for specific acoustic features in animal calls.
Purpose of the Study:
- To investigate if nonlinear phenomena in vocalizations contribute to their alarming quality.
- To determine the specific impact of different nonlinear phenomena on perceived alarm.
Main Methods:
- Resynthesis of 98 bird and mammal calls (18 species) incorporating nonlinear phenomena (frequency jumps, subharmonics, amplitude modulation, chaos).
- Human listener ratings of call alarm levels in an immersive virtual forest environment.
Main Results:
- Chaos consistently increased the perceived alarming quality of animal calls.
- Other tested nonlinear phenomena (frequency jumps, subharmonics, amplitude modulation) did not significantly alter perceived alarm.
- Chaos appears particularly suited for signaling alarm and potentially for intimidation in agonistic contexts.
Conclusions:
- Nonlinear phenomena, especially chaos, are crucial for the alarming nature of vertebrate calls.
- Chaos may serve a broader function in mammalian vocal repertoires beyond alarm signaling.
- Further research is needed to confirm these perceptual effects in non-human receivers.
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