Why do whales sing?

Nobody is completely certain, and that is part of what makes it worth wondering about. What we do know is that humpback whales sing in long, patterned songs, some of them twenty minutes from beginning to end, repeated over and over for hours.

Every whale in the same stretch of ocean sings more or less the same song, and across a season that song slowly changes, the way a tune shifts as it gets passed from one singer to the next. Because low notes carry so well through water, a single one of those notes can cross more ocean than any voice could ever cross in air.

So a whale singing in the dark is further from alone than it sounds.