The best chance most of us have to see a Cuvier’s beaked whale is if it is in trouble. The species (Ziphius cavirostris) was scientifically described only in 1823, and even then, the description was made on the basis of a skull collected in 1803.
But with the increasing use by the U.S. Navy of mid-frequency sonar as part of submarine detection exercises, strandings of Cuvier’s beaked whales may well be on the increase in Hawai`i. On July 28, a young male stranded on a Moloka`i beach and later died within a day of the Navy concluding Rim of the Pacific exercises in nearby waters. According to the National Marine Fisheries Service, only five instances of Cuvier’s beaked whale strandings had been reported in Hawai`i before that date: in 1950, 1970, 1980, 1996, and 1998.
The Navy has denied any culpability in connection with the stranding last July. While it concedes that high-frequency mid-frequency active sonar can have an impact on deep-diving marine mammals, which rely on a highly developed sense of hearing to locate prey and navigate in sunless environments, it maintains that the sonar signals only cause harm in combination with other factors beyond the Navy’s control.
Whale experts disagree, noting repeated incidences of whale strandings that occur in connection with military sonar exercises.
In the Bahamas, for example, in 2000, 16 marine mammals stranded, including 10 beaked whales. Seven died, with NMFS finding that the “most likely cause of the observed trauma was either acoustic or impulse injuries.” (Since then, the ocean around the Bahamas has been virtually depopulated of Cuvier’s beaked whales.) Investigations showed later that the level of sonar that the whales had been exposed to was far less than the Navy had initially claimed.
In 2004, about 200 melon-headed whales stranded in Hanalei Bay, Kaua`i, during Rim of the Pacific exercises. One calf died.
In April 2007, right after the conclusion of two undersea warfare exercises concluded, a dead male pygmy sperm whale washed up on Maui, while a pregnant pygmy sperm whale was found on a remote beach on Lana`i.
In the last two decades alone, mass whale strandings have been associated with naval exercises off the coasts of the Canary Islands, Spain, Greece, Madeira, and Puerto Rico, and in waters off Washington state, California, and North Carolina.
Experts speculate that the loud “pings” emitted at mid-range frequencies by the Navy during undersea warfare exercises can affect deep-diving beaked whales in a couple of different ways. The high pressure of the sound blasts may cause hemorrhaging in the whales’ ears. This can cause disorientation, leading the whales to beach themselves. Also, the sonar may interfere with behavior, leading whales to surface rapidly instead of more gradually and bringing about a condition similar to the “bends” experienced when human divers ascend too rapidly.
Whatever the cause, the Navy itself has estimated that over the course of two years, its planned undersea warfare exercises in waters around Hawai`i will result in more than 61,000 exposures of whales to sounds at or exceeding 173 decibels, with 22,598 “takes” of whales federally listed as endangered.
The lawsuit filed by Ocean Mammal Institute and other conservation groups in Hawai`i argues that while these are high numbers, they are not high enough. The Navy’s 173dB thresholds “are far too high, [so] its estimate of the range at which animals may be affected is far too low.” The plaintiffs’ experts challenged also the Navy’s estimates of the distances over which the sound would be attenuated, with whales’ behavior being disrupted miles from a mid-frequency sonar source.
— Patricia Tummons
Volume 19, Number 4 October 2008
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