Science. Communication. Community.
One of the world’s greatest music exchanges isn’t underground. It’s underwater. Humpback whale songs ride waves of popularity across oceans – and sometimes beyond. After years of speculation, a team of biologists may have discovered how these exchanges work.
Like all good pop tunes, whale songs are repetitive numbers. A handful of sound units (e.g. ‘ascending cry’, ‘moan’, ‘purr’) strung together make a phrase. These phrases, when repeated a few times, become a theme. And a series of themes make up a song.
Whale song “sharing” is a well-known phenomenon. Two years ago, a group of scientists led by University of Queensland biologists Ellen Garland and Michael Noad made a splash with the graphic below. It shows the eastward progression of 10 humpback whale songs, over as many years, in the South Pacific.
Yet, as Garland and Noad point out in a recent follow-up study in PLoS ONE, even close communities in this chart are still 1500 kilometers apart. So how exactly do whales spread the joy?
Speculation has centered on two basic theories, say Garland, Noad and their co-authors. Perhaps, individual whales move between groups, bringing their tunes in tow. Or whales lift tunes as they share summer feeding grounds off Antarctica and related migratory routes. There’s only one hitch with this latter theory. No one has reported whales performing their songs – which may be territorial displays – during their summer forays. Until now.
While cruising through a feeding area off the coast of Antarctica known as Area V, two other team-members, Nick Gales and Jason Gedamke, dropped “opportunistic” sonobuoys – buoys equipped with recording equipment – hoping to pick up whales songs. Though their recordings were faint, Gales and Gedamke got lucky. Together with their colleagues, they identified ten whale song themes, typically sung in the same order.
The team then compared these themes to songs popular at two nearby breeding areas: one off the eastern coast of Australia and a second, further east, near New Calodonia (see image below). The team recruited three “naïve” listeners – a bowhead whale song specialist, a killer whale call specialist, and fin whale call specialist – to compare the themes as well. Each identified four themes that were first popular in 2009 in eastern Australia, then showed up in Area V, and then hit New Caldonia in 2010.
At last, the authors say, the “summer feeding ground theory” has some empirical weight behind it. But, this is just the beginning. They hope to create an international compendium of recordings, so that the true reach of this “BlueTube” can be discovered.