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Elusive whales revealed through underwater acoustics
Researchers are turning to underwater microphones to study beaked whales, a group of deep-diving marine mammals rarely seen by humans. These whales, which can plunge nearly 2 miles (3 km) below the surface, have long evaded scientific observation, but new acoustic techniques are providing unprecedented insights into their behavior and distribution.
A rare encounter off Baja California
In June 2024, bioacoustic scientist Elizabeth Henderson and her team were scanning the waters off Baja California when a pair of juvenile beaked whales unexpectedly surfaced alongside their boat. The sighting defied long-held assumptions that these whales avoid vessels. "They were curious about us," Henderson said, describing the moment as "the coolest thing ever" for a species rarely observed alive in the wild.
The team initially identified the whales by their distinctive echolocation pulses, known as BW43, which were thought to belong to the endangered Perrin's beaked whale. However, genetic analysis later revealed the whales were actually gingko-toothed beaked whales-a species never before seen alive in its natural habitat.
The challenges of studying deep-diving whales
Beaked whales are among the most mysterious marine mammals, with 24 known species making up roughly a quarter of all whale and dolphin species. Some have never been observed alive, known only from stranded carcasses. Their deep, prolonged dives-lasting up to 90 minutes-make them nearly impossible to track using traditional methods.
"Beaked whales have traditionally been overlooked," said Oliver Boisseau, senior research scientist at Marine Conservation Research. "They're offshore, hard to access, and cryptic, which means they're hard to see." Recent discoveries, such as the 2021 identification of Ramari's beaked whale, highlight how little is known about these creatures.
Sound as a window into their world
Because beaked whales rely heavily on acoustics to navigate, forage, and communicate, scientists are using hydrophones-underwater microphones placed at depths ranging from 10 to nearly 5,000 meters (33 to 16,400 feet)-to eavesdrop on their echolocation clicks and buzzes. Each species produces a unique acoustic signature, allowing researchers to distinguish between them without visual confirmation.
"They rely primarily on their acoustics. This is really how they interpret the world around them. So that's an excellent window into their world below the water."
Oliver Boisseau, Marine Conservation Research
Genetic analysis, including skin biopsies and environmental DNA samples, complements acoustic data. However, collecting these samples requires careful ethical considerations due to the potential for injury. Once a species' acoustic profile is matched with its genetic identity, researchers can rely solely on passive acoustic monitoring, eliminating the need for further invasive procedures.
Threats and conservation efforts
Beaked whales face multiple threats, including navy sonar, which has been linked to mass strandings. One theory suggests sonar disorients the whales, causing them to surface too quickly and suffer from decompression sickness, or "the bends." While sonar has been banned in the Canary Islands since 2004-resulting in no further strandings-restrictions in other regions, such as Hawaii and California, remain limited.
Fishing nets and plastic pollution are also emerging concerns. Beaked whales, which primarily feed on squid, often mistake plastic debris for prey due to its similar acoustic properties. Additionally, their role in nutrient cycling-known as the "whale pump"-highlights their broader ecological importance. By transporting carbon and nutrients from the deep ocean to the surface, they support phytoplankton growth, which plays a critical role in carbon sequestration.
Unanswered questions and future research
A key priority for scientists is determining the distribution and population sizes of beaked whale species. "We're just getting a handle on the basic question of who everybody is and where everybody's distributed," Henderson said. For example, the gingko-toothed beaked whale was previously believed to inhabit only the western Pacific, near Japan and New Zealand, making its appearance off California a significant discovery.
Boisseau emphasized the need for caution in conservation efforts due to limited population data. "It's frustrating that we should really be pushing to protect these species in a more robust fashion, but we just don't have the numbers to say, 'this species is at threat of extinction.'"
As oceans warm and plastic pollution spreads, understanding these elusive whales becomes increasingly urgent. "They are just fascinating creatures," Boisseau said. "We really want more people to know about them and care for them."
