It's no surprise that the mother and calf humpback whales that wandered many miles up the Sacramento River, but that yesterday disappeared, presumably into the Pacific, did not respond as hoped to attempts to lure them downstream by playing recordings of whale noises. When it comes to sounds and songs, these animals behave in mysterious ways.
Consider the beautiful music that whales make, which became known to us 37 years ago when “Songs of the Humpback Whale” was released — and went on to become one of the best-selling nature recordings of all time. The whales’ long, drawn-out melodies thunder on, loudly enough to be heard underwater for a distance of at least 10 miles. Five- to 20-minute songs — marked by repeating phrases, rhythm and even rhyme — are sung over and over for hours on end.
Because only the males sing, scientists long assumed that their songs were mating calls directed at females — like bird song in spring. But observation of humpback whale behavior has revealed that females actually pay no attention to the males’ singing.
Other explanations have been proposed: that males sing to warn other males away, for example, or that the songs act as some kind of beacon to help migrating whales navigate.
The most recent theory on why whales sing comes from James Darling, a researcher who for many years has carefully observed the interactions of singing humpback whales near Maui, Hawaii. Mr. Darling has observed that males singing alone usually will join up with another male for a brief but almost always friendly, or at least conflict-free, interaction. And so he thinks it is likely that male whales sing to one another. During breeding, their songs somehow may help them to cooperate, and to recognize their closest male associates.
Whale song has another unexplained aspect that no bird song possesses. Across a single breeding ground, and in some cases across the reach of an ocean basin as large as the North Pacific, the whales all sing essentially the same tune. And as the season progresses, they collectively revise it, adding new melodies and taking others away. Over several mating seasons, songs are entirely changed. (Today’s humpbacks would not recognize the music on “Songs of the Humpback Whale” from 1970.)
The whales evolve their common songs simultaneously even though some of them are much too far apart from one another to hear the changes at the same time.
How do they know what new notes to choose? What guides the changes they make? Scientists don’t know, and hardly know how to find out.
Because the whales that were in the Sacramento River are females, whale songs probably would not have lured them downstream. So marine biologists tried playing feeding calls. This strategy worked 22 years ago when Humphrey, another humpback, was stuck in the same river. This time, it didn’t work.
It’s not easy to tell great whales what to do; it is even harder to figure out what drives them. But it is encouraging to see how many people have rallied round the cause of this stranded family.
There may be a reason whales have been drawn more than once to swim miles up this particular river. The more we observe them, the more we may learn.
David Rothenberg, a professor of philosophy and music at the New Jersey Institute of Technology. He's the author of Why Birds Sing and the forthcoming Thousand Mile Song: Whale Music in a Sea of Sound.