Pay no attention to people who claim to feel things “in their bones.” But do listen to whales who say as much.
Researchers have discovered that the skulls of baleen whales—the suborder of whales that comprise all toothless variations, including blue whales, gray whales, and humpback whales—have acoustic properties that allow them to detect low-frequency waves. In other words, they hear with their bones.
When baleen whales, which are the largest animals on Earth, intercept the deep murmuring noises that they send across the ocean, their skulls begins to slightly vibrate. This nearly undetectable quivering is directed to their ear bones and is interpreted as sound.
This discovery, made by biologist Ted W. Cranford of San Diego State University and engineer Petr Krysl of the University of California-San Diego, is unprecedented. Whale noise is a notoriously elusive subject for scientists. (No one yet knows what whales are communicating—if at all—with their deep, low frequency calls.)
Some whales emit sounds with a wave length about 75 meters long—measuring three times as long as their bodies. How this whale is hearing that noise—how their little ears detect these long, low-frequency sounds—has previously been a complete mystery. While this discovery doesn’t paint the full picture, it adds a piece to a complex puzzle.
When baleen whales, which are the largest animals on Earth, intercept the deep murmuring noises that they send across the ocean, their skulls begins to slightly vibrate. This nearly undetectable quivering is directed to their ear bones and is interpreted as sound.
“For the first time ever, we have some idea about which two mechanisms they hear by: pressure and bone mechanisms,” Cranford says.
Using a baby sperm whale’s head (found dead on an Orange County beach) and a military grade CAT scanner, the researchers spent years employing a technique called finite element modeling, whereby they digitally separated the skull into a million little pieces, which Cranford described as very complex LEGO blocks, and observed how every component responded when subjected to simulated sound waves.
This discovery could help us to understand how artificially created noise is affecting these animals. With four times as many ships in the ocean than there were just 20 years ago—the majority of them large cargo shipping vessels—there has never been more noise pollution at sea. The fact that these ships emit a sound in the same frequency as the baleen whale call is especially concerning.
“This makes you wonder how much we’re interfering with whale communication sounds—or whatever they’re using the sounds for,” Cranford says. “Do we have some sort of effect? Can they not find a mate? Can they not find a food source?”
Cranford cautions, however, against making any sweeping claim about our harmful effect on these creatures. Their research sheds some light on a previously shadowed issue, but the next step will be trying to discover just how sensitive they are to these noises.
“We’re just at the beginning of this,” Cranford says. “We never knew before how they hear, we couldn’t even make guesses about how sensitive they might. But we’re getting closer to the truth.”
