Dolphins don luminescence to light a bow-riding night

Did you see a lot of bioluminescence?" a friend asked me last week after I returned home from my Mexico voyaging.

I saw twinkles in the water only once, but since a bunch of dolphins were wearing them like sequined wetsuits, I thought that should count as a lot.

This eye-popping sight doesn’t happen often because the circumstances have to be just so. You must be in the cockpit, awake, on a no-moon night in waters loaded with light-making organisms. Also, the boat has to be going fast enough to attract surfers.

Dolphin surfers, that is. Sailboats don’t go fast enough to suit dolphins that can swim 25 mph. But even at 5 or 6 mph, a moving boat pushes water up and forward, creating a force at the front of the boat called a bow wave or pressure wave.

Dolphins love this wave because the force of the water propels the animal forward without it having to beat its tail up and down. It’s a free ride.

Part of the fun of watching dolphins bodysurf is observing the competition. Individuals jostle and shoulder each other to get the choice spot in the wave.

This scene is amazing enough, especially when motoring on a calm day in clear water, as pictured. But at night, in bioluminescent-rich waters, oh, boy. Dolphins rushing to the boat set off the light-makers, which illuminate the dolphins’ paths like green comets, and sometimes, depending on the species, stick to the animals’ skin. The sight is enough to make a sleepy person stand up and cheer.

Dolphins have been riding boat’s bow waves since humans started sailing. The ancient Greeks wrote about dolphins bow-riding in the eastern Mediterranean and the Augean Seas. But dolphins didn’t invent this behavior as a response to boats. Dolphins also ride whales’ bow waves, sometimes swimming back and forth in front of a whale to tease it into a lunge. When the annoyed whale pushes forward, the hecklers fall in for a ride.

Dolphins also ride large ocean waves, their body-surfing technique both elegant and effective.

As for the reason they do it, researchers once proposed that bow-riding might help the dolphins get from point A to point B. Countless observations of the animals swimming back to where they started, however, contradicts this theory. Today most researchers believe that bow-riding is play.

Dolphins just wanna have fun.

On our way to Mazatlan last month, I had just relieved Craig at 2 a.m. for my turn on watch, and was struggling to stay awake, when I heard that familiar chuffing sound of dolphins approaching. Their paths as they raced toward the boat looked like shooting stars, and bioluminescent organisms stuck to the dolphins’ skin. A moment later, in glittering jumpsuits, those acrobats were surfing Honu’s bow wave.

No, on this trip I did not see a lot of bioluminescence. But the one time I did see it made me happy to be alive.

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Reach Susan Scott at www.susanscott.net.