Particle Motion May Play a Role in Humpback Whale Songs

A team of researchers has discovered that humpback whales can potentially project their songs farther than previously believed. The whales use particle motion, a phenomenon that was overlooked in other whale song studies. The details are in a paper that was just published in the journal Biology Letters.

Whale songs have been studied extensively yet their exact functions mostly remain a mystery. Humpback whale (Megaptera novaeangliae) songs are generally associated with mating though scientists have speculated that the songs also play a role in feeding, competition, and cooperative behaviors. When whale songs have been studied, researchers have always focused on the pressure waves, the sounds we could hear. Particle motion, the vibrations of any substances the sounds are passing through, has been ignored in previous studies. Scientists believed that any particle motion wouldn’t carry the songs much farther. Pressure waves can also be picked up by simple hydrophones, making them easy to measure. Measuring particle motion requires more advanced equipment.

Researchers from the Woods Hole Oceanographic Institution studied wild humpback whales in Hawaii. They were surprised to learn that particle motion was carrying sounds from the whale songs farther than previous research had suggested. Particle motion was detected 200 meters from where the songs had originated. The team notes that the sounds could probably cover even more distance. They aren’t sure if whales can sense these vibrations but it seems likely based on their anatomy. Humpback whales have ear bones fused to their skull and may sense the vibrations in a similar way to hippopotamuses and elephants.

The team’s findings add to our understanding of whale communication. Acoustic particle motion had never been considered a major component of whale songs. The authors point out that this brings up conservation concerns. If humpback whales are sensitive to particle motion vibrations, human activity may be more disruptive to their communication than previously thought. The team emphasizes the need for future research on how the whales might utilize acoustic particle motion in their songs.

REFERENCE

Mooney AT, Kaplan MB, Lammers MO. Singing whales generate high levels of particle motion: implications for acoustic communication and hearing? Biology Letters (2016).

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