Humpback whales (Megaptera novaeangliae) are famous for their complex song, produced by males which changes over time and is culturally transmitted. Moreover, both sexes produce social and feeding sounds used during several interactions and are likely to be involved in coordinating behavior. This study investigated the acoustic behavior of feeding ‘super groups’ of humpback whales (e.g. aggregations of over 20 animals observed in tight formation on the west coast of South Africa as well acoustic data collected from smaller groups during opportunistic encounters. Four distinct and structurally stable call types were identified, based on aural and spectrographic features and supported by Classification and Regression Trees (CART). Common sound types such as ‘wop’ and ‘grumble’ contributed to a large proportion (> 30%) of the repertoire. Stereotyped sounds were arranged into sequences and repeated within encounters and over years, adding extra complexity to the repertoire. However, to date the function of these calls is ambiguous. Average sound production rate from super groups was 9 (±SD 13.68) sounds per minute. Over recent years, the inter-annual occurrence of these ‘super groups’ has become predictable providing future opportunity to study acoustic communication in this species.
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