We were motoring in towards the southwest shore of Maui, having completed our first dive in Molokini crater, when Andy slowed the boat and craned his neck, peering out over the bow at the water ahead.
Divers, divemaster, and deckhand all lunged to our feet and peered in that direction; this was my second day with the crew, and I knew by now that slowing down probably meant he had spotted whale activity of some sort.
“I think it’s a singer,” he said, pointing ahead of us as he slowed the boat to a dead stop and cut the engine. “I just saw it dive, and I’m pretty sure it’s alone. If I’m right, he’s hanging motionless underwater, with his head lower than his tail, and he’s signing. If we’re quiet, we may be able to hear him.”
We all stood silent as the boat drifted in the direction Andy had seen the whale submerge. At first the predominant noise was the slap of waves on the metal hull, but after a couple of minutes the boat found her groove and the slapping vanished. I heard a phrase of faint, deep moaning that lasted just a few seconds. When I looked around, wondering if my imagination was running away with me – I’d heard recorded whale songs dozens of times in my life – I was pleased to see that others heard it, too.
Andy was nodding excitedly. “Everybody put an ear on the railing,” he said, demonstrating the pose himself.
Somewhat skeptical, I set my ear against one of the round metal pipes that formed a cage-like railing system all around the boat – and heard more moaning, higher-pitched and very distinct. The metal hull of the boat amplified the sound like the body of an acoustic guitar and transmitted it through the railing to our ears. “Hey, Andy, pull the string tighter, I can’t hear so well,” deckhand Jeff joked, referring to the tin-can-and-string “phones” we had all played with as kids.
The sounds were fascinating:
- Long, drawn-out moans at high, medium, and low pitches. The low-pitched ones really reverberated through the boat and into your flesh and bones.
- Short, deep “huh” sounds that made me thing of punctuation marks.
- Short and long squeals that reminded me a bit of recordings of dolphins, but seemed a bit lower-pitched and more drawn out to my untrained ear.
- Noises I can only describe as “bubbly” – the sort of “glub glub” effect you get if you try to speak with your mouth underwater in a swimming pool.
The sounds got louder as we drifted over the singer, then started to fade as we drifted past him and away. When Andy was sure we were a safe distance past the singer, he started the boat and motored slowly away. We had listened for about fifteen minutes, and the song would go on for another five to ten minutes.
Although female humpbacks issue short vocalizations, only the males of the species sing, and they only do it when they are here in their Hawaiian islands breeding waters. Researchers don’t know if every male of breeding age does it, but many do. They also don’t know what prompts them to start, or why they sometimes sing over and over again and other times take breaks in between.
Remember singing “Row Row Row Your Boat” in school when you were a kid? The teacher would divide up the class into three groups, and group one would start whie group two would wait and start with “Row, row, row” as the first group began “Merrily, merrily…”, and then group three would join in later stil? The whale singing is like that, but far less organized!
Being underwater or listening through a hydrophone, you often hear several males singing simultaneously. They are all singing the same song, but in a “round,” so that the first phrases of one singer overlay the second chorus of another and the fifth of yet another.
There is one song for the season, and all males sing that song, with one of them occasionally making a change that all the other singers then immediately pick up on and incorporate into their songs. Nobody knows why they introduce these changes. The changes accumulate over the season, which runs from January through May, and by the time the whales leave the Hawaiian islands to go feed in the waters off Alaska, the song has changed considerably. When the first hydrophone picks up the first singer next year, he’ll be singing exactly the song that they left off with at the end of the 2008 season, and over the course of the season, other males will introduce changes so that it’s a different song by the end of the 2009 season.
The noise carries for miles; other whales, with their highly attuned hearing, can hear it for at least 25 miles around, while we mere humans, when submerged, can pick up the tune broadcast my a male some five to seven miles away. Scientists are sure it has to do with breeding, but they have yet to fully explain the meanings of the songs. It could be anything from advertising his presence to showing off his fitness for mating – we may never know the true meaning to another whale.
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