Marine research: How do baleen whales hear without external ears?

Baleen whales – some of the largest animals in the world – do not have external ears like humans.

Cal State Fullerton biology graduate student Madison Wilson was intrigued by how these marine mammals hear and communicate over great distances.

For two years, she has been looking for answers, such as whether their jaws work like huge tuning forks to amplify sounds. His research in marine biology focuses on the biomechanics of whale hearing, particularly the impact of the lower jaw, or mandible, on sound reaching the whale’s ears.

“Of the two living suborders of whales, we know a lot about the hearing of toothed whales, like killer whales and dolphins, Wilson said. “These animals have large fatty bodies that are embedded in their lower jaws and connected to their inner ears. Their heads act like antennae, with sound being channeled through these large bodies to their ears.

In toothless baleen whales, such as humpback, gray and common whales, they may use bone conduction as their primary method of hearing, explained Wilson, whose study focuses on the fin whale.

“My research aims to understand if the jaw plays an important role in hearing in baleen whales,” said Wilson, whose research mentor is Misty Paig-Tran, associate professor of biological sciences.

Paig-Tran’s FABB (Functional Anatomy, Biomechanics and Biomaterials) Laboratory uses a blend of anatomy and engineering techniques to answer biological questions about the performance of marine animals. For his study, Wilson is collaborating with marine scientists from San Diego State University and UC San Diego.

“The main question we ask is: do baleen whales amplify sound?” Paig-Tran said. “That might seem like a simple, easy-to-answer question, but when you’re thinking about how to test this, there’s a ton of logistics to sort out.”

madison wilson

Why is this research important?
We don’t understand much about how baleen whales hear and why the differences in anatomy and hearing range developed between the two living suborders of whales. This research helps us better understand how they hear and, possibly, why they developed such different auditory pathways. We use high-level software to accomplish this, and with the help of this software we work to demonstrate the validity of such simulations in biological experimentation.

How did you get interested in this project?
As an undergraduate at the University of Washington, where I earned my bachelor’s degree in oceanography, I led a team building an underwater hydrophone (an underwater device that detects and records sound of the ocean). One of the students had written an article about whale hearing and the different ways they channel sound into their inner ears. I became fascinated.

What is interesting in this research?
Because baleen whales do not have external ears, this sense is modulated internally. Toothed whales, like the orca or killer whale, hear a much wider set of frequencies than baleen whales, which only hear at the lower end of the frequency range. This difference in hearing ability makes their different anatomy even more fascinating as we untangle the functionality.

whale gill bone
This CT image of a baleen whale skull, shown as a mesh, shows the temporomandibular joint, which connects the jaw to the skull (in bright purple).

Do you have any discoveries?
Preliminary results suggest that the jaw does not play an important role in fin whale hearing. However, through this study, I hope to validate the use of software in complex biological modeling and further our understanding of underwater bone conduction and hearing in baleen whales.

How does this project empower you as a researcher?
Dr. Paig-Tran is an incredibly thoughtful mentor who pushes her students towards excellence. She is a tireless advocate for her mentees and uses her many connections and in-depth knowledge of the scientific process to make a good project a success. This research project allowed me to develop expertise in many different fields. I’m a more in-depth writer and editor, more fluent in different coding languages, and expanded my knowledge of the anatomy of my study subjects and mammals as a whole. I feel like the research process made me a more analytical thinker and helped me ask and answer more deliberate questions that get results.

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