Sounding Out Whales for Clues to Sonar's Effects
Monday, October 15, 2007
Twenty-two varieties of beaked whales roam the seas, diving as deep as a mile to feed on bottom-dwelling squid and small fish on the dark ocean floor. Shy and seldom seen by man, they are among the least understood large creatures on Earth.
But in recent years, these deepest-diving whales have sent out an unexpected distress signal, alerting researchers and marine mammal advocates, through their confused behavior and beachings, to an environmental hazard that until 10 years ago was not known to exist. The threat comes from very loud noises, especially from Navy sonar, that on at least several occasions have proved fatal to the whales.
The realization that sonar can disorient or frighten whales sufficiently to leave them beached and dying has spurred protests and lawsuits, and has given the Navy a problem that it first denied but now, to some extent, acknowledges. Navy officials, however, have strenuously resisted efforts to limit testing of their sonar, saying it is essential to national security.
In response to angry protests, as well as some pressure from Congress and the marine mammal scientific community, the Navy has now funded an ambitious, $6 million project to learn more about beaked whales and their response to sonar and other loud ocean noises. The research began in earnest last month in the Bahamas under the leadership of the National Oceanic and Atmospheric Administration (NOAA), not far from the spot where, in 2000, the stranding of 17 beaked whales after a Navy sonar exercise first brought the issue to public attention. At least six of those animals died.
The goal is to learn about beaked whales by attaching sophisticated motion detectors to the very few that can be spotted and approached during their brief stays on the surface. The instruments are being used to record the timing, depth and angles of their dives and ascents and to see how the animals react when exposed to sounds approaching (but never reaching) the intensity of sonar signals. It is a clinical trial of sorts, trying to scientifically determine how very loud, man-made sounds may be affecting the elusive creatures.
"The Navy and we as regulator have been really struggling with this issue," said NOAA ocean acoustics specialist Brandon Southall, a principal investigator. "So far, we've been able to make only educated guesses about what might be going on from the whales that come ashore. We really want some direct measurements from live beaked whales to finally get hard data about their reactions to sound."
Peter Tyack, a senior scientist at Woods Hole Oceanographic Institution who is co-investigator, said that "this project starts with the acknowledgment that there is an association between sonar exercises and atypical mass strandings of beaked whales but that we have no idea of what the causal chain of events is."
There are an estimated 22 species of the small whales in the family Ziphiidae. They are probably the least-known family of large mammals: Several species were only described in the last two decades. Beaked whales were once thought to be rare, but now researchers believe there are hundreds of thousands.
Named for the distinctive structures extending from their skulls, beaked whales can dive for extraordinarily long periods. They are commonly underwater for 30 minutes at a time, and one dive of 85 minutes has been recorded, making them the deepest diving air-breathing animals known. Because it is entirely dark on the ocean bottom where they feed, they use their own form of sonar, a narrow "flashlight" of clicking sounds, to find their prey. They range in size from the 30-foot northern bottlenose whale to the 10-to-14-foot-long Blainville's beaked whale.
It is precisely because beaked whales are such deep divers that researchers believe they are at greater risk from sonar. Necropsies of several stranded whales in the Canary Islands found nitrogen gas bubbles in the animals' veins and some organs, suggesting that the whales rose too quickly from the ocean depths and developed a version of the bends.
In one month of work off the Bahamas' Andros Island, at the Navy's Atlantic Undersea Test and Evaluation Center, the team succeeded in placing the data sensors on six beaked whales and four pilot whales. Two of the tags stayed attached long enough to monitor several deep dives -- some lasting as long as an hour -- as well as many shallow "bounce" dives that the animals may use to decompress when they rise from the depths.
The two whales bearing those tags were then exposed to sonar-like sounds, as well as the recorded sound of an approaching killer whale, with little apparent change in behavior.
Southall describes the September work as basically a proof-of-concept effort, rather than serious data collecting, and says he plans to continue it next year.
The project, expected to run at least two more years, has been generally welcomed by other researchers and advocates for whales, who say virtually any information about the mysterious beaked whales will be valuable.
But some are concerned that the built-in limitations of the research could allow the Navy to declare that sonar is not harming the whales, when the project's protocols do not allow the scientists to expose whales to sounds as loud as those produced by sonar. With numerous lawsuits pending, as well as regulatory issues that could affect many Navy sonar programs, there is potentially a great deal at stake.
"We're definitely concerned the findings from this research could be misused by the Navy," said Michael Jasny of the National Resources Defense Council, which has sued the Navy on sonar-related issues. "It's great to learn more about beaked whales, but we can't see how this research could properly be used to set future policy."
NOAA's Southall says he understands the concerns and has taken them into account. "Five years ago, this kind of research would have been impossible because the technology just wasn't there," he said. "Now we have the monitors and an extensive set of hydrophones on the . . . seabed that can follow the movement of the whales.
"So we've gone from facing a task that was impossible to one that is very, very difficult. We're learning a lot about the physiologically amazing dives these whales take, and we hope the knowledge can some day help reduce any danger to them from sonar or any other loud sound source."