Fast or slow? Study reveals differences in how humpback whales change tune
Researchers solve mystery of why southern hemisphere whales switch suddenly but in north it is gradual
From Abba’s Mamma Mia stealing the crown from Queen’s Bohemian Rhapsody to Rihanna’s Diamonds knocking Psy’s Gangnam Style off the top of the charts – even the catchiest song eventually becomes superseded by a new number.
But the phenomenon is not unique to humans: male humpback whales also sing – and change their tunes.
Now researchers say they have unpicked the mystery of why humpback whales in the southern hemisphere suddenly switch their songs, while those in the northern hemisphere tend to change theirs more gradually.
The key, they suggest, is that different humpback whale populations in the northern hemisphere all come into contact with each other during the feeding season – and in the process males can exchange tweaks to their ditties. The upshot is that all the populations sing from the same song sheet, with the piece evolving slowly over time.
However, in the southern hemisphere the different populations are spread out and do not all gather together in the feeding season – instead their interactions are limited to neighbouring populations.
This means that not only may different populations sing different songs, but these are not bashed out during feeding season into a uniform tune. Instead, each population learns the song being sung by its westerly neighbour, passing its own tune eastwards.
“This just shows how variable culture can be in the natural world and how the environment affects that,” said Dr Lies Zandberg, the first author of the research from Royal Holloway, University of London.
The shift from west to east, the team say, is probably down to the songs being passed from larger to smaller populations. “They won’t learn the song from their eastern neighbour, because that is likely to be their old song from the previous year,” said Zandberg.
Eventually, a song may be expected to loop back to where it originated. But Zandberg noted that by then it would probably have accumulated so many small changes it would be a completely new song.
Writing in the journal Philosophical Transactions of the Royal Society B, Zandberg and colleagues report how they came to their conclusions by creating computer models of how songs might change based on how humpback whale populations interact, and assumptions including that the whales remember old songs and are keen to learn new ones.
They then compared the outcomes of the model with recordings of songs from different populations in the southern hemisphere collected from 1998 to 2008.
The model showed that, as in the real world, the whale populations changed their song rapidly, with the new tunes passed from west to east.
The team then changed the model to reflect how whales behave in the northern hemisphere.
“We found that if we use the same model, but only change population sizes and how they interact, we find that we got that very slowly evolving song rather than those revolutions,” said Zandberg.
She added that the model allowed the team the chance to study whale culture – something difficult to do in the real world, not least because of the creatures’ enormous size and staggeringly long migration routes.
“This shows us that even with the same way of learning, so having a preference for unfamiliar and new songs, due to how populations interact in the two hemispheres that completely changes how those patterns of songs are shared and how they move between populations,” she said.