During humpback whale breeding season (July to October in the south), males all sing the same song. That song can evolve rapidly, and before long all the whales are singing the new tune. When scientists analyzed the songs sung by whales in the southern Pacific Ocean, they made a curious discovery—the new tune almost always originated in the west, near Australia, before traveling east. (They report their findings in Current Biology.)
Researchers at the University of Queensland in Australia and elsewhere studied songs from southern Pacific whales recorded over a period of 11 years. They were able to group the tunes into "lineages," hearing bits of a song change over time, eventually being completely overwritten with new phrases and themes. "It would be like splicing an old Beatles song with U2," said lead researcher Ellen Garland of the University of Queensland. "Occasionally they completely throw the current song out the window and start singing a brand new song."
The changes seem to originate with whales off the east coast of Australia and then spread east to New Caledonia, Tonga, American Samoa, the Cook Islands and finally French Polynesia. Only once did a song spread to the west, from French Polynesia to the Cook Islands.
The researchers don't know why the Australian whales seem to be the songwriters, but that population is the largest in that region. A small number of whales may move from that population to the east and take the songs with them, or whales from other populations may learn them while traveling along shared migration routes.
It's just the latest mystery to add to the puzzle of the humpback whale. Scientists still aren't even sure about why the males sing those haunting songs, though they hypothesize that they do so to either attract females or repel potential rivals.