A Recording Studio Found Under the Pacific

Several genetically different groups of humpbacks, separate populations with little interchange among them, live in the South Pacific. Researchers recorded 11 different song types in the region from 1998 to 2008.

Their study, published online Thursday in Current Biology, found that each year, songs spread from one group to another, moving east from Australia to French Polynesia. They believe that this is the first observation of a cultural change transmitted repeatedly on such a large geographic scale.

Why this happens is unclear, but the lead author, Ellen C. Garland, a doctoral student at the University of Queensland in Australia, said the reasons probably have to do with sex. Only male humpbacks sing, and each group of whales sings its own tune. “If you change your song, you stand out,” she said. “We could speculate that that could be more attractive to the females.”

The consistent eastward movement of the songs is another puzzle, but the scientists speculate that the larger population near eastern Australia might have greater influence.

Although sounds travel only a few miles, it is possible that some individuals get close enough to be heard. This minimal contact could be enough for males from another group to pick up the new melody.

The changes happen rapidly, Ms. Garland said, usually within two to three months, and the male humpbacks are enthusiastic singers. “When the new song types come in,” she said, “it’s a chance for them to really go for it.”