Over the last five years, marine scientists developed and deployed a tool called autonomous hydrophones, a device that can recordof whales underwater. The hydrophones can note the unique clicks, pulses and calls of various whale species, including blue, right and sperm whales.
Data collected from the devices in a recent survey, as well as others over the last five years, have shown a surprising difference among whale sounds. For example, blue whales living off the coast of the Pacific Northwest sound different from those in the western Pacific Ocean. Yet both of those are different from species living off Antarctica; and all vary from blue whales off the coast of Chile.
"The whales in the eastern Pacific have a very low-pitched pulsed sound, followed by a tone. Other populations use different combinations of pulses, tones and pitches. The difference is really striking, but we don't know if it is tied to genetics, or some other reason," David Mellinger, an assistant professor at Oregon State University's Hatfield Marine Science Center, said in a statement.
Mellinger added that there are some hybrid sounds that are rare, too. However, it's unclear whether there is a common "language" among various populations of whales, or if the hybrid noises come from confused juveniles that haven't learned the nuances of communicating yet, he said.
The findings were published in January's issue of the journal BioScience.
The listeningwas born out of a hydrophone system called the Sound Surveillance System that was developed by the U.S. Navy. The military used it during the Cold War to track submarine activity, but after the war ended, the government offered it to civilian researchers for use in environmental studies.
Christopher Fox, an Oregon State researcher at the Hatfield Marine Science Center, first used the hydrophones to listen for undersea earthquakes, but the technology began detecting sounds of ships, marine landslides and whales. Haru Matsumoto, an engineer at the center, then developed an autonomous hydrophone to specifically capture the sound of whales.
Mellinger and a team of scientists placed seven of the instruments in the Gulf of Alaska roughly five years ago. The instruments can detect whale sounds from about 40 kilometers away, and sometimes farther in shallow waters.
The technology also helped a team of scientists find a population of rare right whales swimming in the Gulf of Alaska. Right whales were last seen in 1980 in the Gulf. "We picked up the sounds of one whale off Kodiak Island, and several others in deep water, which is also something of a surprise, since most right whale sightings have been near-shore," Mellinger said.