Published on Wednesday, March 22, 2000 in the Washington Post
US Navy's Underwater Detonations Are Killing Whales In The Bahamas
by Rick Weiss
|Scientists are trying to understand why about a dozen whales became stranded last week on two beaches in the Bahamas, a highly unusual event that coincided with U.S. Navy operations in the area.
Beachgoers pushed several of the beaked whales back into the waters after the 12-foot to 15-foot toothed mammals mysteriously swam or washed ashore last Thursday, one day after a Navy exercise in which loud noises were propagated through waters in the region. Five of the animals ultimately died ashore.
The mass stranding occurred less than a week after two other whales washed ashore in a different part of the Bahamas during a period of "live fire" naval exercises in that region.
A Navy spokesman in Virginia said yesterday that the Navy had followed all standard procedures to protect wildlife in the area and had concluded there was no connection between the exercises and the strandings.
Nonetheless, the two events have brought fresh attention to a long-standing concern that certain military activities, especially the generation of loud or low-frequency underwater sound waves, may be taking a toll on marine mammals and other kinds of sea life.
The beaked whales involved in the Bahamas incident are in the dolphin family and are related to killer whales. They are not listed as threatened or endangered, but scientists said that is partly a reflection of how little is known about how many of the animals there are. Beaked whales are renowned for their long, deep dives and their secretive behavior.
Beaked whales are relative loners that tend not to swim in pods. That has led some scientists to suspect that each of the few instances in which they have washed ashore in large numbers may have been caused by a short-term, wide-ranging insult, such as a pulse of sound energy, which can cause an intense wave of high pressure.
A 1988 report in the scientific journal Nature found that only seven strandings of more than four beaked whales had been documented worldwide since 1963. The report focused on the most recent of those events, in the Mediterranean Sea during an 18-hour period in May 1997, and found that it corresponded with "sound detecting system trials" of a submarine sensing system conducted by NATO.
That test involved the generation of sound waves of about 230 decibels (a measure of loudness) at wave frequencies ranging from 250 to 3,000 cycles per second, a frequency that deep-diving whales are believed to be "especially affected by," according to the report. The report concluded there was a greater than 99.9 percent chance that the strandings were caused by the military tests.
Last Wednesday the U.S. Navy conducted a test of the Bahamas involving "sonobuoys," devices that generate sound waves in water. The Navy had consulted in advance with the National Marine Fisheries Service, as required by the Endangered Species Act, to devise a plan for ensuring that the tests would not harm endangered or threatened wildlife, including endangered sea turtles in the area. The plan included aerial surveys and acoustical searches for nearby animals, said Kathy Wang, of the fisheries service Southeast regional office in St. Petersburg.
The Navy spokesman would not reveal details of the test, but Wang said the plan called for sounds of about 200 decibels at 6,600 to 9,500 cycles per second. "Two of the whales had eyes that were bleeding," she said, "suggesting acute shock trauma."
Wang said two baleen whales washed ashore dead in the Bahamas the previous week during a period of U.S. Navy live fire. But that was limited to "nonexplosive small-arms fire" that could not have caused harm to whales, said a Navy source who spoke on the condition of anonymity.
Wang said tissue samples obtained from four of last Thursday's dead whales are to be sent to marine fisheries service scientists for analysis and may reveal some details about the cause of death.