Wednesday, August 10

Fast or slow? Study Reveals Differences in How Humpback Whales Change Their Tone | Whales

From Abba’s Mamma Mia, who steals Queen’s Bohemian Rhapsody’s crown, to Rihanna’s Diamonds, who knocks Psy’s Gangnam Style off the top of the charts, even the catchiest song is eventually replaced by a new number.

But the phenomenon is not unique to humans: male humpback whales also sing and change their pitch.

Now researchers say they have uncovered the mystery of why humpback whales in the southern hemisphere suddenly change their songs, while those in the northern hemisphere tend to change theirs more gradually.

The key, they suggest, is that different populations of humpback whales in the Northern Hemisphere come into contact with each other during the feeding season, and in the process, males can exchange settings in their songbooks. The result is that all populations sing from the same score, and the piece evolves slowly over time.

However, in the southern hemisphere, the different populations are dispersed and not all of them gather in the feeding season, but their interactions are limited to neighboring populations.

This means that not only can different populations sing different songs, but these are not struck during the feeding season in a uniform melody. Instead, each town learns the song that its neighbor to the west sings, passing its own melody to the east.

“This 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 says, is likely due to the songs being passed down from larger populations to smaller ones. “They won’t learn their neighbor’s song to the east, because it’s probably their old song from the year before,” Zandberg said.

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Over time, a song can be expected to return to its origin. But Zandberg pointed out that by then it would probably have accumulated so many small changes that it would be a completely new song.

Writing in the diary Philosophical Transactions of the Royal Society B, Zandberg and his colleagues report how they reached their conclusions by creating computer models of how songs might change based on how humpback whale populations interact and assumptions including that whales remember old songs and are eager to learn new ones.

They then compared the results of the model with recordings of songs from different populations in the southern hemisphere collected between 1998 and 2008.

The model showed that, as in the real world, whale populations changed their song rapidly, with the new melodies shifting from west to east.

The team then changed the model to reflect how whales behave in the Northern Hemisphere.

“We found that if we used the same model, but we just changed the size of the population and how they interact, we found that we got that very slowly evolving song instead of those revolutions,” Zandberg said.

He added that the model gave the team the opportunity to study whale culture, something difficult to do in the real world, especially given the creatures’ sheer size and staggeringly long migratory routes.

“This shows us that even with the same way of learning, having a preference for new and unfamiliar songs, due to the way populations interact in the two hemispheres, completely changes how those song patterns are shared and how they move between populations “. she said.

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