Humpback whales living in the waters of the Great Barrier Reef have astonished scientists by learning a new melody sung by visitors from a distant ocean.
Australian marine biologists believe the males copied the songs of the migrants to stop potential female suitors from losing interest. And they think it is an unprecedented example of a "cultural revolution" in whale songs.
Moonlight serenade
Male humpback whales sing on their way to and from their mating grounds in the waters of the Great Barrier Reef off the east coast of Australia.
Normally, whales in different ocean basins sing unrelated songs. Like birds, their melodies can change over time, but usually this is a slow, gradual process.
So Dr Michael Noad of the University of Sydney, New South Wales, and colleagues, were surprised to find that the whales they were studying had suddenly picked up a new tune.
Dr Noad told the BBC: "All of a sudden, a few dozen whales have come across from the west coast population and mixed in with the east coast population.
"In 1996, when we were recording the whales we picked up a small number of whales that were singing this completely different song. Literally, within a period of a few months, the east coast singers have all changed their song and adopted the west coast song."
'Cultural novelty'
The marine biologists found that at first only two of 82 east coast whales were singing the new tune.
But over a period of less than two years, all the males had switched songs.
The finding is intriguing because it suggests that whales may be attracted to the cultural novelty of a song and then adopt it themselves.
Reporting their findings in the scientific journal Nature, the team said: "Such a revolutionary change is unprecedented in animal cultural vocal traditions and suggests that novelty may stimulate change in humpback whale songs."