Listening to Giants: A New Tag Could Reveal How Humpback Whales Hear
By Rachel Plunkett
September 8, 2026
Scientists have spent decades listening to humpback whales (Megaptera novaeangliae). Now, a new tag that can be attached noninvasively by suction cups and dropped from a drone may help them understand how humpbacks hear.
Each winter, koholā (humpback whales) in Hawaiʻi, return to the islands to breed, give birth, and nurse their calves. Their songs are among the most recognizable sounds in the ocean, traveling through the water in long, complex patterns that have fascinated scientists and the public for generations. Hydrophones allow researchers to record those songs, monitor whale presence, and study the acoustic environment these animals move through.
While scientists can listen to humpback whales, understanding how and what humpbacks hear in the ocean around them is far more difficult.
"Large baleen whale hearing is something that's still poorly understood. We just don't know very well what their hearing sensitivities are, or even the frequency ranges that they hear," said Hawaiian Islands Humpback Whale National Marine Sanctuary Research Ecologist Dr. Marc Lammers. That information matters because sound is central to whale life — and because human activity is changing the ocean's acoustic environment.
At Hawaiian Islands Humpback Whale National Marine Sanctuary, researchers and partners are working to close that gap. In collaboration with Ocean Alliance and Dr. Adam Smith of the University of Southern Denmark, Lammers and his team are helping test a first-of-its-kind electrophysiological tag designed to study hearing and physiological responses in free-swimming whales.
The tag, placed by drone on humpback whales in the wild under a scientific research permit, represents an important step toward a long-term goal: collecting direct, empirical information about how large whales perceive and respond to sound.
Why Hearing Matters in a Noisy Ocean
In Hawaiʻi, humpback whales share their breeding grounds with vessels, human activity, and an increasingly noisy ocean. Vessel noise is one of the most widespread sources of human-made sound underwater, and humpbacks routinely use shallow, nearshore areas where vessel activity is common. While in Hawaiʻi, whales may be resting, socializing, breeding, nursing calves, or conserving energy for the long migration back to their feeding grounds.
To understand how human-made sound may affect them, scientists first need to answer a deceptively simple question: What can humpback whales hear?
Noise impacts can be difficult to detect because they are not always visible. A vessel strike or entanglement can leave an obvious injury on an individual whale. Sound, by contrast, can affect whales in different ways depending on the source, intensity, duration, and context. Some sounds, such as sonar or seismic surveys, may be more episodic or impulsive. Others, such as vessel noise, can be more persistent.
For humpback whales in Hawaiʻi, vessel noise is one of the most widespread sources of human-made sound they are likely to encounter. "Noise is often a chronic pressure at the population level, compared to an acute stressor at the individual level," Lammers said.
Those pressures matter because they can add up, affecting a whale's overall energy budget.
"If whales change their behavior in response to vessel noise or other sounds, they may spend time and energy responding to disturbance instead of doing what they would otherwise be doing," Lammers said.
Those energetic costs may matter even more when combined with other stressors. Humpback whales generally do not feed while they are in their Hawaiian breeding grounds. They rely on energy reserves built up in higher-latitude feeding areas. During climate-driven events such as El Niño, prey availability can shift, and whales may arrive in Hawaiʻi with fewer reserves or face a harder time replenishing them after migration. In that context, even small additional energy costs can become part of a larger picture of stress.
That is one reason better hearing data could be so valuable. Many guidelines and models used to assess ocean noise impacts rely on assumptions about what whales can hear (e.g., NOAA Technical Guidance for Assessing the Effects of Anthropogenic Noise on Marine Mammals). Direct measurements could help scientists refine those assumptions and give managers better tools for evaluating when, where, and how sound may affect whales.
A New Way to Study Whale Hearing
Measuring hearing in a humpback whale is not like giving a hearing test to a person — or even a dolphin or a sea lion, which can be trained to respond to sounds under controlled conditions or temporarily restrained for physiological testing. A free-swimming humpback whale cannot be brought into a laboratory, asked to press a paddle, or held still for a conventional hearing test.
For decades, scientists have had to rely on anatomical studies, modeling, and indirect evidence to estimate baleen whale hearing. In a 2018 study, researchers developed a model of the humpback whale middle ear to estimate how acoustic energy may be transmitted to the cochlea. In 2026, another study observed behavioral responses of humpback whales to generate a predicted hearing curve. Those methods are useful, but still leave uncertainty.
The new project grew out of a conversation between Lammers and Smith at a biologging conference in Tokyo in 2023. Smith and engineering colleagues had modified a biologging tag to measure auditory brainstem responses in free-swimming harbor porpoises. Lammers, meanwhile, was studying humpback whale behavioral responses to sound playback in Hawaiʻi. Together, they saw the potential to combine those approaches: If a tag could measure a small cetacean's neural response to sound, could a similar method be adapted for a much larger, free-swimming baleen whale?
Unlike many biologging tags that measure pressure, acceleration, and underwater sound, Smith said this tag also has "little metal-disk electrodes embedded in suction cups" that attach to the whale's skin and measure electrophysiological signals, including cardiac signals and the much smaller neural signals associated with hearing.
An auditory brainstem response, or ABR, is one of those signals. It is produced when the nervous system responds to sound.
"You can think of the ABR as a series of short brainwaves, or neural signals, that are generated by specific areas of the auditory system in response to the detection of a sound," Smith said.
By comparing those brainwaves with the sounds that produced them, researchers can begin to derive information about an animal's hearing abilities. For this study, scientists use short, repeated sound pulses and then look for corresponding patterns in the physiological data recorded by the tag. If the whale's nervous system responds in time with the sound, that response may indicate the sound was received. If the response disappears at certain frequencies, researchers may eventually be able to learn more about the limits of what the whale can detect.
But detecting those signals in a 25- to 40-ton animal swimming freely in the ocean is an extraordinary technical challenge.
"We have little data on their hearing simply due to their sheer size and the fact that they will rarely be available for the types of laboratory-style hearing measurements that we can do with smaller species like porpoises or dolphins," Smith said. "By developing this tag-ABR method further, we are effectively trying to bring the laboratory to them."
Precision is Key
The tag does not just need to be attached to a whale; it needs to stick onto the right place.
For many biologging studies, suction-cup tags can be placed on different parts of a whale's body and still collect valuable information about movement, diving, acceleration, or sound. This project requires more precision. To increase the chance of detecting an auditory brainstem response, researchers need to place the tag behind the blowhole, near where they think the signal may be strongest.
That is where Ocean Alliance became an essential partner. The organization has been helping develop drone-based tagging methods with sanctuary staff and partners, including helping Hawaiian Islands Humpback Whale National Marine Sanctuary's Natural Resource Specialist Ed Lyman test drone-based approaches to free entangled whales. For this project, Ocean Alliance developed a system that allows researchers to drop the specialized tag onto a surfacing whale from above.
"This electrophysiological tag needs to be much more accurately placed on the whale than what we're used to with more typical suction-cup biologging tags," said Chris Zadra of Ocean Alliance. "We want to place the tags very close to the blowhole so it's ideally over where we think the brain is. You only get one chance to drop the tag in the right spot, so as the pilot I want to be as patient as possible to make extra sure we're in the right place at the right time and take advantage of the best opportunities."
The fieldwork requires careful timing, steady conditions, and a whale at the surface. From the drone pilot's perspective, Zadra said the team approaches the whale from behind, tilts the camera down to look directly at the animal, lowers the drone to the right altitude, and follows the whale underwater while waiting for the moment it surfaces to breathe.
During recent field efforts, the team successfully deployed tags on humpback whales and demonstrated that they could place the tag near the area needed for this type of research.
That achievement alone is significant. Before scientists can measure hearing in a free-swimming humpback, they first have to prove they can safely and reliably place the right equipment on the animal in the right location. The pilot deployments showed that the approach has promise and gave the team critical information for improving future work.
The project also depends on a broader partnership. In addition to Lammers, Smith, and Ocean Alliance, the work involves NOAA National Marine Fisheries Service Endangered Species Act/Marine Mammal Protection Act permitting support from Dr. Adam Pack at the University of Hawaiʻi at Hilo. The combination of sanctuary expertise, tag development, drone deployment, and permitted field operations is what makes this type of experimental research possible.
Building a Knowledge Base
The work is still in its early stages, and the team does not yet have confirmed humpback whale auditory brainstem response results. Researchers are still working to improve signal strength, refine tag placement, and process the complex data required to detect such small neural signals.
But the pilot work has already produced an important result.
"One of the things that we found was that we were able to measure the whale's heart rate," said Lammers.
Heart rate is especially important in diving mammals. When marine mammals dive, their heart rate slows as part of the dive response, helping them conserve oxygen while underwater. Measuring heart rate can help—scientists understand how whales manage their oxygen reserves during dives and how that balance may change when they respond to a sound.
If a whale's heart rate increases in response to an unexpected or meaningful sound, it may use oxygen more quickly. That response could offer another way to study whether and how a whale perceives sound, even when the neural signal is difficult to detect.
The team is now thinking about the tag as part of a three-pronged approach. The first pathway is the auditory brainstem response—the direct neural signal related to hearing. The second is heart rate, which may reveal how sound affects oxygen use and other physiological responses. The third is behavior. Because tags can record fine-scale movement, researchers can look for subtle changes, such as a whale turning toward a sound source or shifting its activity.
Together, those signals could eventually help scientists build a more complete picture of how whales detect, process, and respond to sound in their environment.
From Pilot Effort to Three-Year Study
The promising pilot work has now grown into a larger research effort. Lammers and Smith were recently awarded $604,712 from the Office of Naval Research Marine Biology Program for their proposal, "Tag-based measurement of Auditory Brainstem Responses and electrocardiograms in free-ranging cetaceans."
The award will support three years of work, through 2028, with an optional fourth year in 2029. The project will be administered by the University of Southern Denmark and the National Marine Sanctuary Foundation, with funds supporting operations, equipment, and non-federal labor.
The investment gives the team time to refine the tag, improve deployment methods, strengthen signal detection, and collect more data. It also reflects the broader importance of the question. Agencies and industries involved in assessing and mitigating underwater sound need better information about how marine mammals perceive sound. For baleen whales, those data have long been difficult to obtain, although recently researchers developed a catch-and-release method to assess hearing in a small baleen, the minke whale (Balaenoptera acutorostrata).
Although this work focuses on humpback whales in Hawaiʻi, its implications could extend beyond one species or one geography. Large whales are among the most challenging animals to study, and methods developed here may help advance future research on other cetaceans.
For Hawaiian Islands Humpback Whale National Marine Sanctuary, the work supports a core management need: understanding the pressures whales experience in their breeding grounds and identifying where science can inform adaptive management. Some challenges faced by the whales, such as changes in prey availability, are difficult to address at the sanctuary scale. Noise is different. It is persistent, but it is also something people may be able to reduce, manage, or mitigate.
Scientists have spent decades listening to humpback whales. With this new tag, they are opening up a window into understanding how humpbacks listen to the world around them.
Rachel Plunkett is the content manager and senior writer/editor for NOAA’s office of National Marine Sanctuaries
Jennifer Crawford is the media coordinator for the Pacific Islands Region of NOAA's Office of National Marine Sanctuaries