Navy helps track suspected blue whale
By HARRY EAGAR, Staff Writer
WOODS HOLE, Mass. – For the past 15 years, the Navy has been eavesdropping on an odd beast that wanders the North Pacific Ocean.
It’s a whale, of the baleen group that includes the humpbacks, and it may be some kind of blue whale. Nobody knows, but he (or she) has an unusual voice, which allows Navy hydrophones to pick it out from all the thousands of other whales in millions of square miles of empty ocean and follow its wanderings.
And wander it does. Passive hydrophone tracking has been used to monitor sea mammals for a long time, but usually the recordings have lasted for minutes, perhaps a few hours.
This whale has been recorded for months at a time.
Not continuously, of course, but the voice is so distinctive that Navy locators are able to fix its position closely enough to reconstruct its path. One year’s track was followed for more than 11,000 kilometers, nearly 6,000 miles.
The whale with a voice but no name is called the “52-Hz Whale” by researchers at Woods Hole Oceanographic Institution. A research paper on “52-Hz” was published in Deep-Sea Research recently.
One of the authors, Mary Ann Daher, said Tuesday in a telephone interview that one of the main insights from tracking “52-Hz” was to learn how much we do not know about what whales are capable of.
“Do we really know what blue whales do out there?”
The answer is, not much.
The Navy’s Sound Surveillance System, designed to detect submarines, has hydrophone listening posts on the ocean floor. For years, the data collected were secret, but in 1992 part of the information was declassified.
“52-Hz” could be singled out because his call was within the range of blue whales but lacked the 17-Hz fundamental tone that goes along with it in other blues.
Nobody knows why. It could be a “developmental problem,” or possibly “52-Hz” is a hybrid.
It’s hard to imagine what other whale might mate with a blue, which is twice as big as the next biggest animal, the fin whale; but hybrids are known among the cetaceans.
In 1985 at Sea Life Park in Honolulu, a “wholphin,” half bottlenose dolphin, half false killer whale, was born, to the surprise of the animal keepers there.
Daher says propositions about the source of the voice track of “52-Hz” are “just speculation,” since no one has ever sighted the whale.
If it could be done, using hydrophones to track individual whales would be a great help to researchers. The 5,000 humpback whales that winter in Hawaii are studied by at least a dozen researchers, but once they pass over the horizon on their way back to Alaska, little is known about them.
The Navy sound surveillance and similar records have been used to track populations, but Daher says finding an individual animal in a group of animals that sound alike is probably beyond practical possibilities.
“It’s very hard to distinguish one from the masses.”
“52-Hz” has been deepening his voice over the years, almost like a teenage boy; it’s down to 49 Hz now.
Most of the time, “52-Hz” travels north and south, which is what is expected of a blue whale in the North Pacific. However, from time to time, the track is east-west, and at other times the path seems truly aimless.
However, he calls only about half the year (August to February, with December to January the peak); so nothing is known about his behavior at other times.
Daher says the Navy’s hydrophone array is “a beautiful system for working on baleen whales,” because their deeper voices are easy for Navy experts to pull out of the buzz of noise in the ocean.
Smaller whales, with higher-pitched voices, are less easy to deal with acoustically.
Trying to track whales visually is wearisome and subject to bad weather.
“52-Hz” spends most of his time above 50 degrees north latitude, although he has been heard as far south as 22 degrees – the latitude of Maui.
However, he hangs out far to the east of us.
No one has ever sighted a blue whale in Hawaiian waters, according to Naomi McIntosh, the director of the Hawaiian Islands Humpback Whale National Marine Sanctuary.
However, from 1978 to 1981, Navy scientists Paul Thompson and William Friedl recorded undersea noises off Oahu, and they identified a “long pulse” noise from blue whales, presumably migrating past the islands.
The low-register rumble travels a long way in the water, and it was not possible to pinpoint the location.
The other authors of the “52-Hz” research paper, all associated with Woods Hole, were the late William Watkins, Joseph George and David Rodriguez.