Groups of humpback whales all sing the same song at any one time – and they keep singing it until it gets too complicated, according to new research by Scottish scientists.
St Andrews University experts who looked at song patterns over 13 years found that the song gradually changes each year – and every few years it is completely replaced in what the scientists call “a cultural revolution”.
When such “revolution” events occurred, the new song was always simpler than the one it replaced.
The St Andrews scientists, whose study is published today, suggest that gradual song changes may be “embellishments” by individual singing whales – and that revolutions are simpler because the tuneful marine mammals may have limited ability to learn new material.
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Cetacean ecologist Dr Ellen Garland, of St Andrews University, led the studies, conducted in east Australia and focusing on male humpbacks, together with Dr Jenny Allen of University of Queensland.
Dr Allen said: “Much evidence for non-human culture comes from vocally learned displays, such as the vocal dialects and song displays of birds and cetaceans. While many oscine birds use song complexity to assess male fitness, the role of complexity in humpback whale song is uncertain due to population-wide conformity to one song pattern.
“We examined two measures of song structure, complexity and entropy, in the eastern Australian population over 13 consecutive years. These measures aimed to identify the role of complexity and information content in the vocal learning processes of humpback whales.
“Complexity was quantified at two hierarchical levels: the entire sequence of individual sound units and the stereotyped arrangements of units which comprise a theme. Complexity increased as songs evolved over time but decreased when revolutions occurred.
“No correlation between complexity and entropy estimates suggests that changes to complexity may represent embellishment to the song which could allow males to stand out amidst population-wide conformity. The consistent reduction in complexity during song revolutions suggests a potential limit to the social learning capacity of novel material in humpback whales.”
