Whale 'Pop Songs' Spread Across the Ocean
Music mania is sweeping the ocean, and all the young male humpback whales are in on the latest trend. A new study reveals that, just like humans, humpback whales in the South Pacific follow musical trends that change by the season. Moreover, these songs always move from west to east across thousands of miles of ocean—from the east coast of Australia to French Polynesia—over the course of a year or two. The authors say it's one of the most complex and rapid patterns of cultural evolution across a region ever observed in a nonhuman species.
The findings are based on 11 years of recordings from underwater microphones slung over the sides of boats, which were collected by marine biologist Ellen Garland of the University of Queensland in Australia and colleagues. Picking out the patterns took a while; the team had to listen to 745 songs in total from six whale populations across the South Pacific over the 11-year period. The researchers identified 11 distinctly different styles (audio). Sometimes the "hit song" contained snippets from previous seasons, sometimes it was entirely revolutionary. But at any given time and place, there was only one song. What's more, the popular song switched incredibly rapidly; it took only 2 to 3 months for whales in a given region to entirely change their tune, the team reports online today in Current Biology.
For male whales, singing is known to be a mating behavior, and Garland calls the results a "weird interaction of constrained novelty" where each whale wants to one-up the whale next to it but still feels pressure to conform enough that it doesn't stand out as an oddball. But whether a whale primarily intends its song to impress females or to intimidate other males with its swanky style remains unclear. Peter Tyack, a marine biologist at Woods Hole Oceanographic Institution in Massachusetts, who was not involved in the research, says that to understand this, behavioral biologists "need to dive in a little more deeply to understand subtle details of how males respond to males and how females choose an animal for mating."
This is extremely difficult to do, as humpbacks are too large to be put in captivity for study, and no good methods for tracking individual mating patterns exist. For instance, it's currently impossible to tell how a female swimming through a group of males singing the same song picks out one animal from the rest. Garland says she'd love to study which aspects of a song are important for helping males mate and whether nonconformists are less successful at mating.
Garland says it's also not clear why the song spreads in one direction only. She guesses that the high density of whales off the east coast of Australia affords more opportunity for new songs to arise than in a sparsely populated region such as French Polynesia.
Most of all, the researchers would like to understand why humpback whales, of all species, resemble humans in their love for ever-changing yet conformist fashion. "There's something about these songs; if it were just novelty, then everyone would just do their own thing," Tyack says. Maybe whales, he thinks, have "a sense of aesthetic judgment."