Researchers recently discovered that whales can actually hear through their bones.
Using computer simulations of a fin whale head, researchers from San Diego State University (SDSU) and University of California, San Diego (UCSD) determined that the skulls of at least some baleen whales (mysticetes) capture the energy of low frequencies and direct it, amplified, to their ear bones.
Baleen whales, a group that includes blue, minke, fin, right, and gray whales, emit extremely low frequency vocalizations that can travel huge distances underwater. They use these sounds to communicate and to find food. However, this makes baleen whales susceptible to the potentially dangerous effects of increasing man-made noises in the oceans.
Commercial shipping, energy exploration, and military exercises can be incredibly loud activities that could limit the distance over which the vocalizations can travel. This will make it harder for whales communicate about important things like finding food and mating. These risks have led some government officials to attempt to limit the amount of man-made noise that baleen whales can be exposed to.
No laws have been enacted yet, though, partly because the government lacks adequate information about how baleen whales actually hear. Most information is based on recordings of vocalizations and anatomic studies of ears.
SDSU biologist Ted W. Cranford and UCSD engineer Petr Krysl wanted to take a different approach. They built a three-dimensional computer model of a fin whale head that included the skull, skin, eyes, ears, tongue, brain, muscles, and jaws. Using this incredibly complex model, they were able to perform simulations of how sound would travel through it and see how each component responded.
Whales’ ear bones are rigidly attached to their skull. Sound can reach it in one of two ways: the pressure waves can travel through to the whale’s soft tissue, or it can vibrate along the skull. The researchers found that the second process, called bone conduction, was approximately four times more sensitive to low frequency sounds than the first pressure mechanism.
Humans experience something similar to this when we submerge entirely in a pool, Krysl explained in a news release.
“Our ears are useless, but we still hear something because our head shakes under the pushing and pulling of the sound waves carried by the water.”
These findings may help legislators put limits on man-made noise in the ocean.
To learn more:
- Read the SDSU news release: Baleen Whales Hear Through Their Bones.
- Read the full study: Fin Whale Sound Reception Mechanisms: Skull Vibration Enables Low-Frequency Hearing.
Copyright © 2015 by Marine Science Today, a publication of Marine Science Today LLC.