Changes in vocal parameters with social context in humpback whales: considering the effect of bystanders

Dunlop, Rebecca A. (2016) Changes in vocal parameters with social context in humpback whales: considering the effect of bystanders. Behavioral Ecology and Sociobiology, 70 6: 857-870. doi:10.1007/s00265-016-2108-0

Author Dunlop, Rebecca A.
Title Changes in vocal parameters with social context in humpback whales: considering the effect of bystanders
Journal name Behavioral Ecology and Sociobiology   Check publisher's open access policy
ISSN 0340-5443
Publication date 2016-06-01
Year available 2016
Sub-type Article (original research)
DOI 10.1007/s00265-016-2108-0
Open Access Status DOI
Volume 70
Issue 6
Start page 857
End page 870
Total pages 14
Place of publication Heidelberg, Germany
Publisher Springer
Collection year 2017
Language eng
Formatted abstract
Many theories and communication models developed from terrestrial studies focus on a simple dyadic exchange between a sender and receiver. During social interactions, the “frequency code” hypothesis suggests that frequency characteristics of vocal signals can simultaneously encode for static signaler attributes (size or sex) and dynamic information, such as motivation or emotional state. However, the additional presence of a bystander may result in a change of signaling behavior if the costs and benefits associated with the presence of this bystander are different from that of a simple dyad. In this study, two common humpback whale social calls (“wops” and “grumbles”) were tested for differences related to group social behavior and the presence of bystanders. “Wop” parameters were stable with group social behavior, but were emitted at lower (14 dB) levels in the presence of a nearby singing whale compared to when a singing whale was not in the area. “Grumbles” were emitted at lower (30–39 Hz) fundamental frequencies in affiliative compared to non-affiliative groups and, in the presence of a nearby singing whale, were also emitted at lower (14 dB) levels. Vocal rates did not significantly change. The results suggest that, in humpbacks, the frequency in certain sound types relates to the social behavior of the vocalizing group, implying a frequency code system. The presence of a nearby audible bystander (a singing whale) had no effect on this frequency code, but by reducing their acoustic level, the signal-to-noise ratio at the singer would have been below 0, making it difficult for the singer to audibly detect the group.

Significance statement: The frequency, duration, and amplitude parameters of humpback whale social vocalizations were tested between different social contexts: group social behavior (affiliating versus non-affiliating), the presence of a nearby singing whale, and the presence of a nearby non-singing group. “Grumbles” (commonly heard low-frequency unmodulated sounds) frequencies were lower in affiliating groups compared to non-affiliating groups, suggesting a change in group motivation (such as levels of aggression). “Wop” (another common sound type) structure (frequency and duration) was similar in affiliating and non-affiliating groups. In the presence of an audible bystander (a singing whale), both sound types were emitted at similar rates, but much lower amplitudes (14 dB), vastly reducing the detectability of these sounds by the singer. This suggests that these groups were acoustically avoiding the singing whale. They did not, however, acoustically respond to the presence of a nearby non-singing group.
Keyword Frequency coding
Signal design
Social group
Source level
Vocal communication
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
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