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The Evolving Songambience, humpback whalesHeres a program from our archives.One of the remarkable things about the songs of humpback whales is that they're changing, evolving all the time, and these changes are uniformly picked up by all the whales across an entire ocean. I'm Jim Metzner and this is the Pulse of the Planet.Payne: You go to a singing ground where humpback whales are singing. You lower a hydrophone into the water, and then you listen and you record everybody singing the same song around you. Then you go back next year and you lower a hydrophone and it is the same whales, you know them as individuals, they have distinct markings on their tails, but now the song has changed. And at the end of five years, it's all completely different from what you heard five years ago, and everybody's singing exactly the same song."Roger Payne is president of the Whale and Dolphin Conservation Society. Payne: The question, of course, is how does this whole process work? Who's the leader? Who's the conductor? Nobody knows the answer to it fully, but I suspect that what's going on is that these whales are actually copying changes that they hear around them. Changes which are successful in whatever it is that the function of the song serves. I believe that what the function of the song is is a means of males, it's sung only by males, attracting females and it's sung principally during the breeding season. But there is no direct, compelling, useful evidence that would tell you why it is that the animals are actually singing and changing their songs.Another mystery is how do groups of whales communicate changes in their song across the ocean. The high frequencies don't travel that far, and yet, somehow all the humpback whales in the North Pacific for example, sing the same slowly evolving song. This archival program is part of our thirtieth anniversary celebration. Im Jim Metzner and this is the Pulse of the Planet.