The Loudest Sound In The Ocean May Be A Sperm Whale Flirting

Scientists Just Found the Loudest Known Sound Any Mammal Makes

Somewhere in the dark of the open ocean, a male sperm whale is making a sound louder than a jet engine at takeoff, and doing it on purpose. The clicks come slow and steady, like a heartbeat stretched to inhuman lengths, one every few seconds instead of dozens per second. A new study suggests these sounds could potentially be heard tens of kilometers away, far enough that a whale calling from one end of a small country might, under the right conditions, reach the other.

Published in the Annals of the New York Academy of Sciences, the study focused on a signal called the slow click and found it to be the loudest known communication sound made by any mammal on Earth, measured at over 200 underwater decibels. Underwater decibels are not directly comparable to decibels in air, but the takeaway is simple: this is exceptionally loud. What makes the discovery stand out isn’t just the volume, though. It’s the rhythm, landing with a regularity researchers had never documented at such a slow pace in any animal, roughly one click every three to 10 seconds, like clockwork. Researchers believe volume and timing together could let males send messages across staggering distances, though whether any whale hears and responds to one from that far away remains unconfirmed.

Slow Clicks Are a Male-Only Sperm Whale Signal

Sperm whales already own one biological superlative: the largest sound-making structure in the animal kingdom, taking up roughly a third of the body in mature males and weighing more than five tons, packed with a waxy substance called spermaceti oil. That structure produces a handful of distinct click types, each doing different work.

Most people picture the clicks sperm whales use to hunt, blasting sound into the depths and listening for the echo off prey below. Females and young whales swap shorter, patterned clicks called codas, like conversational chatter, though that only carries a few kilometers. Slow clicks work differently: only males produce them, at a much slower pace, built to travel far beyond a coda’s reach. They had barely been studied before now, so researchers measured how loud they are, how far they might carry, and how steady their rhythm really is.

How Researchers Measured Loudness and Rhythm at Sea

To gauge how loud slow clicks are at the source, researchers tracked a mature male off the Seychelles, picking up 65 usable slow clicks within 200 meters of him. For the rhythm side, the team assembled a bigger haul: 1,839 slow clicks from six sites in Norway, Sri Lanka, Scotland, and the Seychelles, gathered from listening stations and suction-cup tags on whales. To estimate how far a click might travel, researchers modeled sound propagation through the ocean, factoring in depth, temperature, and the seafloor, rather than tracking actual whale-to-whale conversations.

The Rhythm Is Stranger Than the Volume

Loudness alone would be impressive. Rhythm is what stopped researchers in their tracks. Slow clicks kept an almost metronomic beat across every recording. Most rhythmic animal sounds, birdsong, primate calls, tend to land at a beat or faster per second. Slow clicks crawl along at a tenth to a third of that pace, yet hold their timing with a precision no other animal has matched. When the beat shifted, it shifted in tidy, musical fractions, doubling or halving cleanly rather than drifting randomly.

That kind of consistency raises an odd puzzle: how does an animal keep time that well, that slowly. Humans lose the ability to feel a steady beat once the gap stretches past three-quarters of a second, yet sperm whales manage gaps of two seconds to more than twenty. Researchers have two competing guesses, both speculative. One is that whales track their own heartbeat, which during a deep dive may slow to roughly the pace of the clicks. The other involves the ocean itself: a loud click bounces off the seafloor and surface and returns as an echo, and if a whale fires the next click right when that echo arrives, the seafloor’s geometry would lock the rhythm in place. One old account describes a whale seemingly syncing its clicks to a research ship’s sonar.

What Are the Whales Actually Saying

Perhaps the most tantalizing question here is who is meant to hear all this, and why. Females may be within earshot of a slow click from far away, but cannot answer back over that distance, so researchers suspect slow clicks are mostly males talking to other males, sizing each other up before crossing paths. The gap between pulses inside a click seems to depend on the size of a whale’s nose, so up close, that timing could hint at how big the sender is. Farther out, that detail gets lost, but the overall rhythm might still carry some version of the message. That would matter, because male sperm whales fight, sometimes brutally: scarred heads and broken jaws are not uncommon among older males. A signal that lets two whales size each other up from a distance could mean fewer encounters.

Whether slow clicks are about mating, rivalry, or something else, and whether any whale actually catches one from 70 kilometers away, remain questions only future fieldwork can answer. What’s clear is that male sperm whales shout across an ocean and keep near-perfect time doing it.

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