Whistle variability and social acoustic interactions in bottlenose dolphins

Mustun, F.; Semenzin, C.; Rance, D.; Marachlian, E.; Guillerm, Z.-L.; Mancini, A.; Bouaziz, i.; Fleck, E.; Shashar, N.; de Polavieja, G. G.; Sumbre, G.

doi:10.1101/2024.10.15.618471

bioRxiv · 10.1101/2024.10.15.618471

Whistle variability and social acoustic interactions in bottlenose dolphins

Mustun, F.·Semenzin, C.·Rance, D.·Marachlian, E.·Guillerm, Z.-L.·Mancini, A.·Bouaziz, i.·Fleck, E.·Shashar, N.·de Polavieja, G. G.·Sumbre, G.

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Abstract

Bottlenose dolphins exhibit a sophisticated social structure, known as a fission-fusion society. To sustain this complex system, dolphins rely on a rich vocal repertoire: clicks exclusively used for echolocation, burst-pulse sounds associated with emotions during social interactions, and whistles, including signature whistles that serve as individual-specific identifiers ( names). How dolphins maintain their complex social structure based only on a limited repertoire of sounds remains elusive. Previous studies suggest that contextual information can be transferred by the modulation of the whistles. Here, we investigated the whistle variability using a comprehensive computational approach, and studied the structure of the interactions between the whistle variants. Using a unique large dataset, acquired in a natural environment, we observed that signature whistles exhibit variations in their frequency contours. Unsupervised clustering revealed that signature whistles could be classified into sub-categories (signature whistle variants). The existence of these categories, and their independence on the emitter dolphin, indicate that these variations are not random. Analysis of pairwise interactions between sub-categories revealed a clustered structure similar to that of their social hierarchy. Network analysis of this structure showed that whistle sub-categories had different functional roles: some acted as hubs, others as bridges, and certain were used for turn-taking between the main whistle categories. We also found that the dolphins emit signature whistles of their deceased mothers, a phenomenon only observed in human language. Overall, these findings suggest that dolphins modulate signature whistles to transmit additional information beyond individual identity, and that they engage in "dialogue-like" acoustic interactions.

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Mustun, F., Semenzin, C., Rance, D., Marachlian, E., Guillerm, Z.-L., Mancini, A., Bouaziz, i., Fleck, E., Shashar, N., de Polavieja, G. G., Sumbre, G.. 2024-10-16. Whistle variability and social acoustic interactions in bottlenose dolphins. https://doi.org/10.1101/2024.10.15.618471

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