Sound and Fury
Whale deaths blamed on sonar have triggered a heated debate about man-made noise in the sea
Whale biologist Ken Balcomb always gave what he calls the "standard disclaimer" to the Earthwatch volunteers who would come to the Bahamas to help him and his collaborator and wife, Diane Claridge, study Cuvier's beaked whales. The animals are elusive, he would warn them, usually over morning coffee at the beach house he and Claridge rented each season. The odds were pretty slim that they would spot one of these small whales during their 10-day visit. But on March 15, 2000, before the new crew had even heard the disclaimer, they'd seen their first beaked whale.
"Ken, come quick!" shouted a research assistant who'd gone out for an early-morning walk. As Balcomb and Claridge ran down to the beach they could see a young whale stuck in the sand around its midsection, still sweeping its tail up and down, as if to complete its suicide run up onto dry land. The tide was dropping, so Balcomb, Claridge, and their Earthwatch crew got to work quickly, pivoting the 16-foot creature and then, with each wave, nudging it deeper into the water. Once freed, it swam strongly out to sea. But before they could raise a cheer, the whale turned and headed back to the beach. Balcomb and his team had plunged back in the water to try to herd the whale out to sea again when a local fisherman came by with the news that another whale had beached itself a mile and a half down the shore. Then a frantic neighbor called, asking to borrow a sea kayak--he, too, had been trying to keep a disoriented whale off the sand. And so it went all day long.
In the end, a total of 14 beaked whales, along with two minke whales and a spotted dolphin, ran aground across a hundred miles of Bahamas coast. Seven are known to have died. The shy, deep-diving beaked whales have met similar sad ends on beaches worldwide, from the Galapagos Islands and the Lesser Antilles to Corsica and Greece. In September, a pair of beaked whales came ashore in the Gulf of California, and 15 in the Canary Islands, off northwest Africa. And while so-called strandings of other kinds of whales are common, they are usually blamed on disorientation and illness. In this case, the cause is suspected to be man-made noise.
In the Bahamas, the whales flopped up onto Balcomb's doorstep while, offshore, the U.S. Navy was conducting exercises with powerful sonars. In the Canaries, a multinational fleet comprising at least 58 boats and six submarines was engaged in maneuvers when the whales began fleeing the sea. In the Gulf of California, a seismic research vessel towing an array of air guns was probing the Earth's crust with powerful pulses of low-frequency sound. In fact, many mass strandings involving beaked whales in recent decades appear to be linked to sources of loud sound in the ocean, says Charlie Potter, an expert on marine mammal strandings at the Smithsonian Institution in Washington, D.C. The incidents have fed an increasingly raucous debate about the threat posed to whales and other marine mammals by all sorts of noisy machines at work in the oceans--from supertankers and cruise ships to oil rigs.
Quiet, please. The Navy itself has acknowledged that the earsplitting, 235-decibel-plus screeches emitted by its sonar played a role in the Bahamas strandings. But the Navy and others who inject loud sounds into the ocean now face wider concerns that could mute their equipment, at least for now.
Last October, an environmental organization filed suit against the National Science Foundation, which funds the seismic research vessel that was operating in the Gulf of California, for failing to conduct a review of the blasts' impact on marine mammals. A judge issued a restraining order halting research with the towed array until the analysis could be completed. The Navy has come under fire from environmentalists over a low-frequency sonar system it is developing to detect a new generation of quiet, diesel-electric submarines. The Navy says the system has never harmed whales, but last month a judge limited tests of the system to a 1 million-square-mile zone of the Pacific off the Philippines and Japan pending a trial. Noise, it seems, has joined toxics, oil spills, and overfishing as a recognized threat to sea life, even though the extent of the danger is still unclear.
Ken Balcomb's quick action on March 15 helped pin down the link, long suspected, between sonar and strandings. After getting word of a third beached whale that day, Balcomb put in a call to Bob Gisiner, manager of marine mammal science and technology programs at the Office of Naval Research in Washington. To document the sounds that the whales had been exposed to, Balcomb urged him to save acoustic records from Navy hydrophones positioned in local waters. When Balcomb said he would try to freeze the ears of whales that died, Gisiner suggested that he cut off whole heads instead. More detailed dissections could be conducted, Gisiner said, by other whale-acoustics scientists.
The upshot of the investigation was a report issued by the Navy and the Department of Commerce that described hemorrhages "consistent with acoustic trauma" in and around the ears of the dead beaked whales. The report concluded that while "intensive active use of multiple sonar units" was the most reasonable explanation for the injuries, the sounds the animals heard were not intense enough to have killed them directly. Instead, the pings drove the whales up onto beaches, where they died from overheating and cardiovascular collapse.
Few scientists dispute that it was the whales' response to the noise that did them in, not the noise itself. The Smithsonian's Potter points out that a lethal blast would have caused all kinds of animals--from fish to pygmy whales--to wash ashore. Darlene Ketten, a biologist with the Harvard Medical School and Woods Hole Oceanographic Institution, performed three-dimensional CT scans on the whales' heads to look for trauma. She says that had the pings been at deadly levels she would have seen "blowouts of membranes in the inner and middle ear," among other injuries. If the whales hadn't beached themselves, she says, "I would have expected them to recover."
Some scientists take issue, however, with what they argue is the report's implication that the Bahamas strandings were a rare misfortune. The report suggests, for example, that unusual water conditions that day may have channeled the pings and that beaked whales are especially sensitive to sonar. Narrowing the focus of concern in that way is unwarranted, asserts Lindy Weilgart of Dalhousie University in Nova Scotia, who studies sperm whales. It "really oversteps what we know about whale hearing and behavior."
The din below. Indeed, scientists concur, there's a lot that isn't known about whale acoustics. Giving a whale a hearing test, says Ketten, "is not a trivial problem." So they have had to make assumptions. One of them is reassuring: Whales' ears cannot be preternaturally fragile because the environment in which they evolved is a naturally noisy one. Winds riffling the surface, raindrops, and snapping shrimp all contribute noise beneath the waves. Lightning strikes produce the loudest sounds in the ocean, as high as 260 decibels at the source. Many of the big whales themselves produce astonishingly loud noises. Some baleen whales produce low-frequency calls that can reach 180 decibels or more, intense enough at close range to bruise human lung tissue.
Yet whale biologists also assume that most cetaceans can hear--and thus can potentially be harmed by--midfrequency sonars like the one used in the Bahamas. That's because it's generally thought that animals' hearing is tuned to the same frequency range at which they vocalize, and most cetaceans, from great whales to dolphins, emit at least some midrange sound. Indeed, whalers have long known that midrange pings can impel frightened whales to run at the surface instead of diving. By the same argument, blue, finback, humpback, and other baleen whales, which make low-frequency sounds, might be most vulnerable to the very low "booms" emitted by the Navy's new, long-range sonar system, called SURTASS LFA, for "surveillance towed array sensor system low frequency active."
The Navy, however, says it is encouraged by studies it funded in 1997 and 1998, which exposed blue, finback, humpback, and gray whales off the coasts of California and Hawaii to signals from a test array. The sonar has a remarkable range. Under the right water conditions, its signal will travel hundreds of miles before dropping below 120 decibels, which many scientists thought might be the threshold at which the sound would begin disrupting whale behavior. Yet the whales turned out to be relatively tolerant of the signals.
In one experiment, the array was placed a mile and a quarter from the shore, in the middle of the whales' historical migration corridor. When the sonar began broadcasting at 180 decibels, the whales deviated from their path, but by only a mile or so. When the test array was placed outside the corridor, about 3 miles from the shore, the whales stayed right on track. In another study, singing humpbacks exposed to signals between 120 and 150 decibels sang longer songs instead of quitting the area. "Yes, we saw reactions," says Christopher Clark, director of the bioacoustics lab at Cornell University, "but not all the time. And when we did see them, the animals seemed to resume their normal activities within tens of minutes and a couple of miles [of the signal source]."
To Clark, what's known so far suggests sonar will not be the "death knell of the oceans." But the problem of noise is bigger than sonar, he says. Sonar is part of a man-made "acoustic smog" that could be threatening marine mammals in ways that are not fully understood. One major contributor is the air guns and drilling rigs of the offshore oil industry. "I can't hear blue whales off the Grand Banks anymore because there's so much seismic exploration in Canadian waters," Clark says, "It's `ka-bam, ka-bam, ka-bam' every 11 seconds, 24 hours a day, for days on end."
Shipping is another big source of acoustic smog. Supertankers, icebreakers, cruise ships, even tugboats and ferries have helped boost the level of ambient noise 10-fold in the past 40 years in the frequency band that whales use to communicate, says John Hildebrand of the University of California-San Diego and the Scripps Institution of Oceanography. Many scientists suspect that the noise has shrunk the range over which the big whales can hear one another from about 1,000 miles to 100.
Many industries that inject a lot of noise into the ocean have gotten used to operating in an out-of-sight, out-of-mind fashion, says Cornell's Clark. But he's not entirely despairing. Now that regulators are coming to grips with the idea that noise can be a pollutant, innovative people will begin devising ways to quiet the cacophony under the seas.
Depth charge
Potent beams of sound from Navy sonar, used to detect submarines, apparently injured and confused beaked whales, leading these small cetaceans to beach themselves and die. Beaked whales can dive to depths of almost a mile to feed on squid; no one knows how deep they were when they were injured.
In this 3-D image, hemorrhages (red) are evident in the head of an injured whale.
Collateral damage?
Dozens of multiple strandings of beaked whales have been reported in recent decades. At least nine occurred when naval or other ships were said to be maneuvering nearby:
DATE LOCATION NUMBER
April 1974 Bonaire 4
Dec. 1974 Corsica 3
Feb. 1985 Canary Islands 13
Nov. 1988 Canary Islands 3
Oct. 1989 Canary Islands 25
May 1996 Greece 12
March 2000 Bahamas 14
Sept. 2002 Canary Islands 15
Sept. 2002 Mexico 2
This story appears in the December 23, 2002 print edition of U.S. News & World Report.