No abstract

Although the songs of humpback whales have been extensively studied, other vocalizations and percussive sounds, referred to as "social sounds," have received little attention. This study presents the social vocalization repertoire of migrating east Australian humpback whales from a sample of 660 sounds recorded from 61 groups of varying composition, over three years. The social vocalization repertoire of humpback whales was much larger than previously described with a total of 34 separate call types classified aurally and by spectrographic analysis as well as statistically. Of these, 21 call types were the same as units of the song current at the time of recording but used individually instead of as part of the song sequence, while the other 13 calls were stable over the three years of the study and were not part of the song. This study provides a catalog of sounds that can be used as a basis for future studies. It is an essential first step in determining the function, contextual use and cultural transmission of humpback social vocalizations.

Humpback whales are renowned for the complex structured songs produced by males. A second, relatively understudied area of humpback acoustic communication concerns un‐patterned sounds known as “social sounds,” produced by both males and females. These include vocalizations as well as sounds produced at the surface of the water as a result of surface behaviors (e.g., breaching, pectoral slapping). This study describes a portion of the non‐song social sound repertoire of southward migrating humpbacks in Australian waters, and explores the social relevance of these sounds. On migration, humpback whales travel in social groups of varying compositions. These social groups are not stable in that humpback whales continually change group composition by splitting from, or joining with, other groups. The results of this study suggest that “breaching” and “slapping” have a communicative function. Other sounds such as “underwater blows” and “cries” were heard mainly in competitive groups while other low‐frequency sounds such as “grumbles,”“snorts,”“thwops,” and “wops” may function in intra‐ or inter‐group communication. Particular sounds (“grunts,”“groans,” and “barks”) were almost exclusive to joining pods suggesting a role in social integration. Social sounds in humpbacks may have specific social and behavioral functions relating to social group composition, and the mediation of interactions between these social groups.