| Summary: | Humpback whales produce a complex sequence of vocalisations, called songs, while on migration paths and breeding grounds. While its function remains unclear, the association between song and its production during the breeding season has lead to the hypothesis that song may be an acoustic display used by males to attract potential mates and repel rival males. If so, significant differences in the song between singers might be expected. Here we describe the structure of the song off east Australia in 1998 and present a quantitative comparison of the acoustical characteristics of two sound types between six individual singers to determine the extent that these provided discrimination between individuals. The song was found to consist of five themes produced in a fixed order, consistent with other observations of humpback whale song. Multivariate and univariate tests showed significant measurable differences between individuals for all acoustical parameters included in the analysis. However, for any parameter, the differences were accounted for by one or two individuals and there was no observable pattern or consistent differences between individuals. Canonical analysis showed substantial overlap between clusters suggesting poor discrimination between individuals. The frequency of different units of the same sound type varied by less than two semi-tones for an individual and no more than three semi-tones between individuals, suggesting that humpback whales have a well refined perception of pitch. We conclude that while there were differences between individuals in the characteristics of the two sounds analysed, these did not provide useful discrimination between individuals.
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