Dolphins are simplifying their calls to make themselves heard over noisy humans

He just wants to express himself.
He just wants to express himself.
Image: Reuters
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It’s a real sea of noise in the oceans these days. On top of the normal sounds of singing cetaceans, cracking shrimp, and surprisingly rowdy fish, humans have unloaded a veritable cacophony into the water: noises from boats large and small, the sounds of great honking container ships, the dull roar of seafloor mining, and the jackhammering of oil and gas exploration. And because sound travels fast, and far, through water, the noise pollution is magnified, spreading this high-decibel ambient sound all over the seas.

So, what are dolphins to do, if they want to be heard over all that clamor? Well, they adapt, by simplifying their complex calls so they can better understand each other over the fray. That’s according to a study published yesterday (Oct. 24) in the journal Biology Letters, led by University of Maryland marine biologists Helen Bailey and Leila Fouda. “It’s kind of like trying to answer a question in a noisy bar and after repeated attempts to be heard, you just give the shortest answer possible,” Bailey said, in a statement. “Dolphins simplified their calls to counter the masking effects of vessel noise.”

Bailey and Fouda’s team analyzed three months’ worth of recordings of bottlenose dolphin calls, collected using underwater microphones about 20 miles off the coast of Maryland in the Atlantic Ocean. In the noisiest parts of the ocean, dolphins simplified their whistles and made them higher-frequency and more piercing—the dolphin equivalent of shortening their message while shouting it. (They saved the really complicated calls for quieter areas.)

Dolphins aren’t the only ocean creatures changing how they communicate in the face of noise pollution. In a study also published yesterday in Plos One, Japanese researchers found that humpback whales in the Pacific Ocean about 1,000 km (about 625 miles) south of Tokyo stopped singing or shortened their songs whenever noisy ships went by. And above the surface, lovesick Savannah sparrows near Canada’s oil fields are changing their tune to make sure their message gets through. In the case of the birds, a follow-up study suggested that these modified tunes seemed to be no impediment to wooing female Savannah sparrows.

As for the dolphins, it seems they’ve come up with an efficient solution to the problem, though researchers say it’s not yet clear whether it will have a negative impact on how well dolphins can communicate with one another. They are social animals that rely on their calls to keep the group together or tell one another about food sources—they’ll even cry out their own “names” when different groups of dolphins meet. But in the wake of chug-chugging from boats, the heavy grunts of machinery, and the boom of air and gas oil guns, the complexity of those calls flatlines. Going forward, Bailey said, “we need to be working to engineer quieter boats.”