Arousal-based physiological changes influence acoustic features of vocalizations in mammals. In particular, nonlinear phenomena are thought to convey information about the caller’s arousal state. This hypothesis was tested in the infant African elephant (Loxodonta africana) roar, a call type produced in situations of arousal and distress. Ninety-two percent of roars exhibited nonlinear phenomena, with chaos being the most common type. Acoustic irregularities were strongly associated with elevated fundamental frequency values. Roars produced in situations of highest urgency, based on the occurrence of behavioral indicators of arousal, were characterized by the lowest harmonics-to-noise ratio; this indicates low tonality. In addition, roars produced in these situations lasted longer than those produced in contexts of lower presumed urgency. Testing the infant roars for individual distinctiveness revealed only a moderate classification result. Combined, these findings indicate that infant African elephant roars primarily function to signal the caller’s arousal state. The effective communication of this type of information may allow mothers to respond differentially based on their infant’s degree of need and may be crucial for the survival of infant African elephants in their natural environment.
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September 2011
September 02 2011
Vocal cues indicate level of arousal in infant African elephant roars
Angela S. Stoeger;
Angela S. Stoeger
a)
University of Vienna
, Department of Cognitive Biology, Althanstrasse 14, A-1090 Vienna, Austria
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Benjamin D. Charlton;
Benjamin D. Charlton
University of Vienna
, Department of Cognitive Biology, Althanstrasse 14, A-1090 Vienna, Austria
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Helmut Kratochvil;
Helmut Kratochvil
University of Vienna
, Department of Evolutionary Biology, Althanstrasse 14, A-1090 Vienna, Austria
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W. Tecumseh Fitch
W. Tecumseh Fitch
University of Vienna
, Department of Cognitive Biology, Althanstrasse 14, A-1090 Vienna, Austria
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a)
Author to whom correspondence should be addressed. Electronic mail: [email protected]
J. Acoust. Soc. Am. 130, 1700–1710 (2011)
Article history
Received:
July 24 2010
Accepted:
May 27 2011
Citation
Angela S. Stoeger, Benjamin D. Charlton, Helmut Kratochvil, W. Tecumseh Fitch; Vocal cues indicate level of arousal in infant African elephant roars. J. Acoust. Soc. Am. 1 September 2011; 130 (3): 1700–1710. https://doi.org/10.1121/1.3605538
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