Scientists began hearing whale sounds several years ago on a U.S. Navy hydrophone network. The hydrophone system ?called the Sound Surveillance System, or SOSUS ?was used by the Navy during the Cold War to monitor submarine activity in the northern Pacific Ocean. As the Cold War ebbed, these and other military assets were offered to civilian researchers performing environmental studies.
Another Oregon State researcher, Christopher Fox, first received permission from the Navy to use the hydrophones at his laboratory at OSU's Hatfield Marine Science Center to listen for undersea earthquakes ?a program now directed by Robert Dziak.
While listening for earthquakes, the OSU researchers begin picking up sounds of ships, marine landslides ?and whales. An engineer at the center, Haru Matsumoto, then developed an autonomous hydrophone that can be deployed independently and Mellinger's colleagues placed seven of these instruments in the Gulf of Alaska about five years ago. The hydrophones can pick up right whale sounds from about 40 kilometers away ?and even farther, if the waters are shallow and the terrain even.
Using those hydrophones, Mellinger discovered a number of sperm whales living in the Gulf of Alaska in the winter. The hydrophones picked up almost half as many whale sounds as in the summer ?indicating a surprisingly robust "off-season" population.
"There are a handful of records of people spotting sperm whales in the region ?and they're all in the summer," Mellinger said. "Likewise, all of the historic whaling records are from the summer. The Gulf of Alaska is not a place you want to be in the winter. But apparently, sperm whales don't mind."
Other researchers participating in the study include Sue Moore, NOAA's Alaska Fisheries Center in Seattle; Kathleen M. Stafford, an OSU graduate now at the University of Washington; and John A. Hildebrand, Scripps Institution of
Source:Oregon State University