Secret Messages in the Blue: The Hidden Language of Hawaiian Monk Seals

Arthur here, your monocled reporter from the Pacific trade winds. Today we are listening, not just looking—tuning in to the secret underwater messages of one of the rarest seals on Earth.

Watch & Listen: Monk Seals in Their Blue World

Meet the “Dog That Runs in Rough Water”

In Hawaiian, the monk seal is called ʻīlio holo i ka uaua—“the dog that runs in rough water.” They live only in the Hawaiian Islands and nowhere else on the planet. Imagine a sleek, big-eyed swimmer, part mer-dog, part underwater explorer, snoozing on warm sand between dives for fish, octopus, and lobster.

Their population is still small, only in the low thousands at best, which makes every single seal important. For years, scientists thought these animals mostly grunted and growled in simple ways. Recently, though, a team of researchers decided to listen much more closely.

A Hidden Choir: 25 Underwater Calls and “Seal Sentences”

Researchers set quiet underwater microphones across the Hawaiian archipelago and recorded thousands of hours of monk seal life. When they sorted through the sounds, the result was astonishing: instead of just a handful of noises, they found at least 25 distinct underwater calls.

Some calls were short and sharp, like punctuation. Others were long and sliding, like the bend of a whale note. The real surprise came when the team discovered that seals can link different calls together, creating what scientists call “combinational calls.” To a shark like me, that is basically seal code—little sound-strings that carry more complex messages than single barks or grunts.

One newly described sound was nicknamed the “whine”, a call the seals make while they are actually hunting. Very few seal species use special sounds while they chase prey, so this behavior tells us that monk seals may be “talking” to each other even while they search the sea floor for their next meal.

Why a Quiet Ocean Matters to a Talkative Seal

Monk seals already face a full storm of challenges: shrinking beaches, tangled fishing gear, disease, and rising seas. Now we know that they also rely deeply on sound—on being able to hear, and be heard, in the water.

As boats, engines, and coastal construction add more noise to the ocean, it becomes harder for seals to pick out each other’s calls. Imagine trying to whisper to a friend on the other side of a crowded, echoing gym. The messages are still there, but they get scrambled in the roar.

By carefully mapping out this new “dictionary” of monk seal sounds, scientists are building an acoustic health chart for the species. If certain calls start to disappear from the recordings, it might mean habitats are becoming too noisy or too dangerous for seals to use comfortably.

How Beachcombers Can Be Ocean Listeners Too

You do not need a research submarine to help monk seals. Small, simple choices made by families and kids can keep their soundscape safer:

• Give resting seals space. If you see one on the beach, admire from far away and respect any rope lines or signs. Rest is part of their survival.
• Pack out every scrap. Fishing line, plastic loops, and forgotten snack wrappers can become life-threatening tangles in the surf.
• Choose quieter adventures when you can. Paddles, sails, and slower speeds near wildlife mean less underwater noise.
• Support rescue and research teams. Many organizations in Hawaiʻi care for injured pups and track seal health. Even learning their names and stories helps keep the public eye on their future.

From my vantage point in the blue, I like to imagine the ocean as a vast conversation—whales singing, shrimp crackling, and now, monk seals weaving secret lines of sound between reefs. The next time you hear about Hawaiian monk seals in the news, you will know that somewhere below the waves, they are not just swimming.
They are speaking the language of their survival.

— Arthur, your monocled maritime gent