Superheroes of the Sea: Baleen Whales and Their Hearing Powers
They may not wear capes or fly through the skies, but you might say baleen whales have a superpower that rivals some comic book heroes: they possess extraordinary hearing. Thanks to two recent studies — one carried out in the chilly waters off Stamsund, Norway1 and the other conducted along the Sunshine Coast of Australia2 — we’re beginning to understand just how sensitive baleen whale hearing is. The hope is that this new understanding will further benefit conservation efforts, protecting whales from the negative impacts of noise in the ocean.
Superhero Snapshot: 5 Unique Traits of Baleen Whales
1. Baleen – Instead of teeth, baleen whales use comb-like plates made of keratin to filter small prey, like krill and plankton, from seawater.
2. Two blowholes – Positioned on top of the head, their paired blowholes allow for efficient breathing and quick surfacing.
3 . Large size – Baleen whales are among the largest animals on Earth, with the blue whale holding the record as the largest animal to have ever lived.
4. Long-distance migrations – Many baleen whale species migrate thousands of miles annually between nutrient-rich feeding areas and warmer breeding grounds.
5. Lack of echolocation (reliance on low-frequency sounds) – Unlike toothed whales, baleen whales do not echolocate. Instead, they use low-frequency vocalizations that can travel vast distances through the ocean.
Why Whale Hearing Matters
Baleen whales, or mysticeti, are among the largest animals on Earth. Yet, despite their size and importance in marine ecosystems, and their reliance on sound for communication, we know very little about the frequencies of sound they hear.
To illustrate a whale’s hearing ability, researchers develop audiograms. Audiograms are graphs that give a visual depiction of hearing range and sensitivity. Until recently, no audiograms have been available for baleen whales, except those predicted based on the anatomy of the whale’s ear. By contrast, many audiograms exist for toothed whales, like those of killer whales or belugas.
Knowing how whales hear is essential. Why? Because many parts of the ocean are getting noisier. Human-made, or anthropogenic, noise — generated by ships, sonar, oil drilling, and construction — fills the water with sound pollution that can disrupt whale behaviors like feeding, breeding, navigating, and migrating. It can also interfere with communication and, in some cases, lead to hearing damage, chronic stress, or injury.
Before we can protect whales from these threats, we need to understand exactly how well they hear and how they react to sound.
To illustrate a whale’s hearing ability, researchers develop audiograms. Audiograms are graphs that give a visual depiction of hearing range and sensitivity. Until recently, no audiograms have been available for baleen whales, except those predicted based on the anatomy of the whale’s ear. By contrast, many audiograms exist for toothed whales, like those of killer whales or belugas.
How Do You Test the Hearing of a Whale?
Unlike dolphins or seals, baleen whales are more challenging to perform studies on due to their large size, and the difficult logistics of gaining access to them. So how do you test their hearing in the wild?
These latest studies show how it is possible with some fascinating insights. One study employed Auditory Evoked Potential (AEP) testing while the other used a modified version of Behavioral Observation Audiometry (BOA).
The Norway Study: Measuring Brainwaves in Minke Whales
In 2023, a team of researchers in Norway used AEP testing to study the hearing of adolescent minke whales during their summer migration. The National Marine Mammal Foundation’s Director of Conservation Biology, Dr. Dorian Houser, served as primary investigator on this study. AEP tests measure the brain’s electrical responses to sound via small, noninvasive EEG electrodes placed on the whale’s skin.
This marked the first time a baleen whale species successfully underwent an electrophysiological hearing test.
Using a temporary catch-and-release site, the scientists exposed the whales to a series of chirps and tone bursts and recorded their neural responses. Once testing was complete, the whales were released. They quickly resumed normal diving behaviors, displayed no signs of stress or harm after release, and through the use of satellite telemetry, were observed being normal whales weeks and months later.
The findings proved remarkable. The whales responded to frequencies between 45 and 90 kilohertz (kHz). To put that in perspective, the upper limit of human hearing is about 20 kHz, and that’s only for people with exceptionally sharp ears. Most of us wouldn’t detect such a high-pitched tone.
This implies these whales possess the capacity for ultrasonic hearing, a “superpower” previously unconfirmed in baleen whales.
The Australia Study: Watching Humpback Respond
While the Norway study focused on electrical signals in the brain, the research team in Australia took a behavioral observation approach. Dr. Houser acted as co-investigator on this study, and this time the focus was on humpback whales.
Because humpbacks follow predictable migratory patterns and appear in large numbers off Peregian Beach, this provided scientists with an ideal location and opportunity for collecting data on their hearing.
Using BOA techniques, researchers tracked migrating humpback whales and recorded how their behavior changed in response to specific sounds. Behavior changes included alterations in swim speed, direction, diving, startle responses, and fluke movements.
Their findings were equally exciting: some humpbacks responded to sounds as high as 16 kHz, and as low as 0.25 kHz. These results demonstrated hearing in noise across an expected frequency range of hearing, but also highlighted the utility of the method, which could be used to study the upper frequency limits of hearing in humpbacks.
