‘Cultural revolution' sees humpback whale song change every few years
Populations of male humpback whales undergo a “cultural revolution” every few years when they change their song anthem, research has shown.
A study of whale song patterns spanning 13 years found that the signature song of individual groups evolves gradually over time.
But every few years, a population’s song is completely replaced in an event described as a “cultural revolution”.
When the revolutions occur, the new song is always simpler than the one that preceded it.
Humpback whales are famed for having “dialects” unique to different populations. In addition, groups of male whales have their own “anthems”, with each member of the population singing the same sequence of the same sounds.
The new research, which focused on 95 humpback whale “singers” from east Australia, found evidence that gradual song changes are due to embellishments introduced by individuals that are then learned by the rest of the group.
Songs introduced by revolutions may be simpler because the singers find it harder to learn completely new material, say the scientists.
Lead researcher Dr Jenny Allen, from the University of Queensland, Australia, said: “We examined two measures of song structure, complexity and entropy [a tendency to become more disordered] in the eastern Australian population over 13 consecutive years.
“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.”
The research, which also involved UK scientists at the University of St Andrews, is reported in the journal Royal Society Proceedings B.