As they glide through the ocean, mighty humpback whales belt out complex melodies of moans, cries and squeaks. These sing-a-longs can last for hours, and males in a given population are known to transmit tunes to one another; they add their own twists to the song, which are then picked up by other males. (Females don’t appear to sing.) Gradually, the songs spread between populations, so that a tune from an Indian Ocean population, for instance, might crop up among humpbacks of the South Pacific—like an ocean-wide game of telephone.
Now, as Roni Dengler reports for Discover, a new study has found that humpback whale songs don’t stay the same forever. The melodies evolve to become increasingly complex over a period of a few years until, suddenly, the whales drop the tune for a new and simpler song—something that the authors of the study, published in Proceedings of the Royal Society B, deem a “cultural revolution.”
A team led by marine biologist Jenny Allen of the University of Queensland analyzed recordings of eastern Australian humpback whales, taken over the course of 13 consecutive years. In total, according to Virginia Morell of Science, they looked at 412 song cycles from 95 singers, scoring the ditties’ complexity based on the number of sounds, themes and variations.
The researchers found that the songs gradually evolve to become longer and include more parts, possibly due to flourishes that individual males come up with to distinguish themselves from the rest of the chorus. Scientists don’t know precisely why male humpbacks sing, but some have theorized that they are putting on an acoustic performance to attract females—or even to impress their male buddies.
“Since all the males in a population sing the same song, small changes might be an opportunity to stand out from the crowd,” Allen tells Dengler.
Every few years, however, the whales abandon their sophisticated melody in favor of a sparser song. The researchers aren’t sure why, but paring down the tune might give humpbacks a new opportunity to add their own embellishments. In a University of Queensland video, Allen compares the whales’ shifting song preferences to the ebb and flow of fashion trends among humans.
“When a new fashion trend comes in, everybody wants to look new and slightly different,” she says, “so everybody will incorporate that fashion trend until it becomes the norm.”
It is also possible that, after a certain point, the whales just can’t keep up with the increasingly elaborate songs. There may be “a limit to the whales’ capacity to learn new material,” Allen explains.
But make no mistake: humpback whales are highly sophisticated creatures. Their ability to transmit songs, not just within populations, but also between them, “is cultural transmission on a scale comparable to what we find in people,” according to Allen. Having a better understand of what drives cultural and social learning in whales could, therefore, help scientists gain new insight into why these traits have evolved with unparalleled complexity in humans.