A thunderhead loomed to the south of the island of Culebra, in Puerto Rico, threatening to drench Paul Knapp Jr. and the three passengers of his 18-foot inflatable dinghy, the Little Compass. The sticker at the helm of his boat read: “I Speak Whale.” A sun-swept couple from Michigan waited toward the bow, while I sat beneath the Bimini top. As we exited the harbor, Knapp punched the engine and headed northwest, the wind to our stern. The Little Compass skimmed across the blue swells like a well-skipped stone.
After 20 minutes, we reached Knapp’s most reliable listening location, an indistinctive stretch of open water just west of a peninsula. Knapp cut the engine, plugged a hydrophone into a pair of boat speakers, and dropped the device into the water. “OK,” he said as the cable ran through his fingers, falling to 50 feet below the surface. “Let’s see if we hear anything.”
Within seconds, a chorus of cetacean song filled the air—humpbacks emanating a series of elevated chirps and bellows and downward-spiraling moans. I’d listened to countless whale recordings in preparation for the trip, but they failed to convey how haunting the songs are in person. Knapp fell silent for a few minutes before rattling off guesses at the whales’ numbers and distance from us—two or three of them, maybe three or four miles away.
For more than 30 years, Knapp has guided some 4,000 people on such listening trips in the Caribbean Sea, where many Atlantic humpbacks spend winter and spring, the males crooning in competition and the mothers nursing calves, before migrating north in search of fish and krill. Whale-watching attracts millions of visitors to hot spots like Hawaii, Alaska, and Puerto Rico annually. On Puerto Rico’s main island, tourists flock to the west-coast town of Rincón each spring for the annual Festival de la Ballena (Whale Festival), embarking on day trips with one of the numerous outfitters that line the streets. Despite the guaranteed business, Knapp prefers the aural experience.
“As far as I know, I’m the only person who’s just listening,” he said. “I’m not interested in seeing them at all.”
Few people were listening to whales until 50 years ago, when biologists Katy and Roger Payne released the album Songs of the Humpback Whale, which featured little more than the calls against a backdrop of waves. It became an unexpected hit, selling more than 100,000 copies. In the years that followed, the album was part of a rise in international activism to protect marine mammals like whales, dolphins, and porpoises, inspiring people like Knapp to explore their vibrant vocal world. When the album was added to the National Recording Registry in 2010, it was called “probably the most famous nature album in American history.”
Within seconds, a chorus of cetacean song filled the air—humpbacks emanating a series of elevated chirps and bellows and downward-spiraling moans.
But with the discovery of whale songs and the critical nature of their submarine communications came revelations about an urgent threat from noise pollution. As anthropogenic activity floods the ocean with mechanical sounds, whales have been forced to compete with human-made noise in order to communicate.
Some 50,000 merchant ships traverse the ocean, their engines and propellers generating a din that can be heard from hundreds of miles away. And that’s nothing compared with the intensity of the sound created by seismic air guns used by many oil and gas companies at offshore sites across the globe. These blasts take place every ten to twelve seconds, can travel up to 2,500 miles, and can be as loud as 260 decibels—louder than a rocket launch. Whales migrating along the Atlantic coast of the United States have been spared from this disturbance since the 1980s, the last time seismic surveys occurred in this area. But in 2017, the Trump administration sought to lift Obama-era bans and open up the Atlantic, a move that’s been in limbo ever since.
Though scientists think that singing plays a role in breeding displays, a lot remains unknown about humpback songs. Experts aren’t sure how the male’s ballad functions—it might be meant to show off for females or to communicate with other males during mating season. (While female humpbacks also use sound for communication, they haven’t been observed singing like the males.) What we do know is that underwater noise pollution has been shown to increase stress hormones and disrupt migration patterns among many marine animals, including Atlantic humpbacks. Additionally, it’s been found that zooplankton—including krill, a main food source for whales—are especially susceptible to loud blasts. An impact study published in 2014 by the Bureau of Ocean Energy Management found that hundreds of humpbacks could be negatively affected each year if seismic surveys were permitted in South and mid-Atlantic waters.
It disturbs terrestrial creatures attempting to listen in, too—since Knapp started his work, he has sometimes strained to hear and record whale songs amid the increased racket of boat traffic. As we drifted off the coast of the island, it wasn’t long before the whir of a yacht engine drowned out the sound of the calls.
Knapp reached over to turn off the speaker. “Let’s wait until this one passes,” he said.