Humpback whales throughout the entire South Pacific Ocean are connected to each other via shared song, according to new research.
From the east coast of Australia to French Polynesia to breeding grounds off Ecuador – a total distance of more than 14,000 kilometers (8,700 miles) – researchers have heard humpbacks (Megaptera novaeangliae) trading the same viral hits.
Male humpback whales are known to belt out mating songs 'as complex as jazz' during breeding season, and each population has a slightly different chorus of vocalizations that they string together in unique ways.
These multiple repeating phrases are known as 'themes', and each whale song has several.
Yet every once and a while, a breeding population will undergo a song 'revolution', whereby all the themes the males sing are replaced by new ones.
It's not clear why they do this, but previous studies have shown these subtle amendments can turn into smash hits.
Around the turn of the century, humpback populations on the west coast of Australia were found to be sharing themes with populations on the east coast.
Then, years later, breeding populations near French Polynesia were caught singing the same song themes that started on the east coast of Australia, about 6,000 kilometers (3,730 miles) away.
Now, it seems, the songs can spread even further. Researchers have shown whale songs in French Polynesia can migrate right across the Pacific Ocean to South America, another 8,000 kilometers (4,970 miles) east.
Over the course of three years, from 2016 to 2018, the team was able to map a gradual song revolution that was first heard in French Polynesia and then again off South America just a few years later.
"This study demonstrates songs first identified in western populations can be transmitted across the entire South Pacific, supporting the potential for a circumpolar Southern Hemisphere cultural transmission of song and a vocal culture rivaled in its extent only by our own," write the researchers.
It's unclear at this point whether the whale songs can migrate across the Indian Ocean to get back to the coast of Australia.
But according to The New York Times, preliminary results off the coast of Brazil and South Africa suggest a complete circumnavigation of the planet may actually be possible.
By the time a whale song gets back to the original breeding population, however, it's likely to have evolved beyond recognition. With one spin of the planet, it's possible that whales are essentially laying down a whole new track.
"The study of humpback whale song culture not only draws parallels to songbird song characteristics, but sheds light on the underlying mechanisms of social learning and cultural evolution in animals ranging from fish to other cetacean species through to humans," the authors write.
For now, experts can't be sure how these songs are being shared between neighboring whale populations, but they have a leading hypothesis.
Although we don't really know where the humpbacks in French Polynesia usually spend their summer months foraging for food, if they feed in a similar place to Ecuador's whale populations, then it's possible they are sharing tunes while bulking up or migrating through the Pacific.
Male whales, as it turns out, don't only sing during their winter breeding season. Ample evidence suggests they practice during the summer, too. And these tunes may be catchy enough to grab another population's attention.
If this is the case, then the researchers think whale songs can pass around the world in a stepwise fashion. First, a song revolution begins in one population, and then, in the summer, this population migrates to forage, passing it on to a neighboring population. And so on, and so forth.
The researchers hypothesize that the eastward trend is due to differences in population size, with songs moving from larger to smaller groups.
To test that theory, it would be interesting to see if songs created in Australia's large western populations also move in the other direction.
Since the late 1990s, researchers in and around Australia have been gathering evidence that indicates whale songs can morph and migrate within and between populations.
It's taken decades, but scientists are now listening right around the globe.
It won't be long until we know just how far humpback songs can travel.
The study was published in Royal Society Open Science.