WHALE SONG 'GPS SYSTEM': PREVIOUSLY UNKNOWN COMPONENT OF WHALE SONGS DISCOVERED

Researchers have known for decades that whales create elaborate songs, sometimes projecting their calls for miles underwater. A new study from the Woods Hole Oceanographic Institution (WHOI), however, has revealed a previously unknown element of whale songs that could aid this mode of communication, and may play a pivotal role in locating other whales in open ocean.

From aboard small research boat, researchers measured two components of the whales' songs -pressure waves (the type of sound wave that pushes on human eardrums, allowing us to hear), and particle motion (the physical vibration of a substance as sound moves through it). Surprisingly, they noted, particle motion in the water propagated much further than expected.

"We threw our gear over the side, and let ourselves drift away from whales while measuring both particle motion and sound pressure. We didn't expect particle motion to be projected much at all -just a few meters away at most. But as we got progressively further away, the particle motion stayed loud and clear," he says the leading author.

The group measured only as far as 200 meters from the whales, but their data shows that this particle motion, especially in lower frequencies of sound, could travel much further than the distance recorded. "It's a whole other avenue of sound that we never knew whales could use," he notes.

Unlike dolphins and toothed whales, humpback whale ear bones are fused to the animals' skull, providing a direct link to any sort of vibration in the water column. "This could mean that their hearing is influenced by the way sound conducts through their bones," he says. "It raises the question: does a whale's lower jaw act like a tuning fork to direct vibrations to their ears? Previous papers have shown this bone conduction might be a viable mode of hearing."

If whales can in fact sense particle motion, similar vibrations caused by humans might interfere with the way the giant animals communicate.

Most human-made noise in the ocean is low frequency, and the level of sound is doubling every decade. There's constantly more shipping, more seismic exploration for oil and gas. Mining and construction, such as pile-driving machinery, is also increasing, contributing low-frequency particle motion that might propagate for miles underwater. We humans don't hear well in water, so we overlook noise in the ocean, but it's very relevant cue for marine animals. This could be a major concern for whales.

Thanks to: sciencedaily.com