One of the most enchanting mysteries about humpback whales is their songs. Only the males are known to sing, although both males and females sound certain social calls while they're feeding, and calves make other calls when they're near their mothers.
The humpback's haunting songs are among the most complex animal vocalizations. They have a hierarchical syntax, one of the basic elements of language, according to recent studies. That is, they sing units of sound that together form a phrase. The phrases are repeated in patterns known as themes. Each song is composed of anywhere from two to nine themes, and the themes are sung in a specific order. Some phrases sound like the low moan of a cello, while others are more like the chirp of a songbird.
Initially, researchers thought the males sang to attract females. When scientists played the songs on underwater speakers, however, other males—not females—showed up. Still, that doesn't mean the females aren't listening. Some people speculate that the whale songs are best compared to those of birds—vocalizations that alert both males and females to a new guy in the neighborhood. Compounding matters, humpbacks sing not only at their breeding grounds but also during their long migrations.
Intriguingly, humpbacks in different populations sing entirely different songs from those elsewhere in the world. And the songs evolve: each year, a few whales in a breeding area add new elements to a song that other males then adopt. "Individuals don't seem to stand out for very long," says Adam Pack of the Dolphin Institute based in Honolulu.
I hear the song late in our whale-watching day. Lou Herman, also of the Dolphin Institute, stops the boat in the middle of a seemingly empty sea and kills the engine. Whale spouts shoot up in the distance. "Listen," he says.
From beneath the boat, a sighing, almost mournful sound rises into the air. It is surprisingly loud and has a yearning edge—a pipe player alone, sounding the plaintive notes of love? Or is he calling for a buddy to join him? Or singing to let all whales in Hawaii know that humpbacks rule?
"The songs fascinate everyone," says Herman. "We know now that all the males here sing the same song, and when they stop the song for this season, they'll pick it up again right where they left off next year. Why and how?" Herman gives a hands-up shrug.