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Monday, March 12, 2012

Male whales try to entice mates with the latest songs

During a voyage last week off Puerto Vallarta, Mexico, the wind grew light, and Honu's speed dropped to 3 mph. That's slow even for a sailboat, but because Banderas Bay is famous for humpback whales, Craig and I left the engine off.

We sat back in the cockpit, each facing opposite directions. The gurgle of small waves hitting the hull was like a mantra, and for hours we stared at the water. I enjoy these peaceful times, but my true reason for sailing is to see wildlife. As usual, the whales came through.

Well, whale, singular. We saw only one, but others were clearly about because this humpback whale whacked his tail, or fluke, hard on the surface. We counted the explosions out loud … 15, 16, 17. Then the spray, splashes and slapping stopped. Whatever had been happening was over.

Tail slaps are a sign of aggression among male humpbacks. Often the whale strikes its flukes on the surface repeatedly to tell other males to back off, sometimes even hitting another male on the head.

This grouchiness is understandable. Male humpbacks migrate thousands of miles each winter for only one reason, and that's to mate. But breeding grounds contain far more sexually mature males than receptive females. This gives females lots of choices — but, oh, those poor males. Not only does each one have to outmaneuver dozens of others courting a particular female, but he then has to face what must be enormous frustration if the hard-won female won't accept him.

Like some of their human counterparts, though, these males have figured out what gets the girls. They are remarkable vocalists, and hoping to become rock stars, they start bands.

A humpback soloist sings one song for 10 to 15 minutes, repeating it until other males join him. Band membership is brief, usually lasting 10 minutes or less. Some associations among singing males are so short, researchers refer to them as drive-bys.

Biologists never see females joining these singers, suggesting the songfests are male-only gatherings.

But the get-togethers have a purpose. During these encounters males apparently teach each other the latest melody. As a result, all males in the same ocean basin, the North Pacific in the case of Mexico, Hawaii and Japan's winter visitors, end up singing the same song.

Why such conformity? One theory is that if one individual belts out a remarkable rendition, he stands out from his buddies. Another guess is that no male wants to stick out as a weirdo singing a tired old track.

Males might somehow use ballads to compete for females, but they also fight, using fluke force, body blocks and breaches to drive off competitors.

We were impressed with the 17 tail slams we saw, but one whale in Hawaii once performed 70, the slaps occurring as fast as researchers could count.

When commercial whaling ended in the mid-20th century, the North Pacific population of humpback whales numbered a few hundred. Today, estimates are in the 20,000 range and growing. Whatever reason for crooning, the Baleen Boys are getting the job done. Rock on.

Marine biologist Susan Scott writes the newspaper column, "Ocean Watch", for the Honolulu Star-Advertiser,

©2012 Susan Scott