Somewhere in the deep ocean, a male sperm whale is producing a sound loud enough, in principle, to be heard by another whale 43 miles away, and doing it with the metronomic precision of a drummer keeping an impossibly slow beat. A study published in the Annals of the New York Academy of Sciences, and reported publicly starting in early August 2026, confirms these low-frequency "slow clicks" as the loudest communication signal ever measured in any mammal, while leaving open the more interesting question of exactly what the whales are actually saying.

Not the clicks most people already know about

Sperm whales are already famous among marine biologists for their vocal repertoire. Most attention has historically focused on two distinct click types: rapid echolocation clicks the whales use to hunt squid in total darkness at extreme depths, and shorter, rhythmic click sequences called codas, which function as social communication and have themselves drawn recent scientific interest for containing patterns researchers describe as roughly analogous to vowel sounds in human speech.

Slow clicks are something else entirely. According to the research team, led by Simone Videsen of Aarhus University in Denmark, these signals are produced exclusively by male sperm whales, and they differ from both echolocation clicks and social codas in nearly every measurable way: they are slower, lower-frequency, and considerably more powerful, with anywhere from five to ten seconds separating each individual click.

A sound loud enough to rank among the loudest on Earth

The study's central finding centers on raw acoustic intensity. Researchers measured slow clicks with source levels exceeding 200 decibels re 1 micropascal, peak-to-peak, a threshold that makes them, according to the research team, the loudest communication signal documented in any mammal species. Combining those source-level measurements with sound propagation modeling, the researchers estimated an active space, the maximum distance at which the signal could theoretically still be detected by another whale, of approximately 70 kilometers, or roughly 43 miles, under favorable ocean conditions.

To capture those source-level measurements accurately, researchers tracked a single mature male sperm whale off the Seychelles, recording 65 usable slow clicks from within 200 meters of the animal, close enough to measure the sound's true intensity before it had traveled far enough through water to lose meaningful energy. That direct, close-range measurement approach matters methodologically, since sound intensity naturally degrades with distance, and getting an accurate read on a signal's actual source power requires recording as near to the source as safely and practically possible.

Rhythm precise enough to rival a slow drummer

Beyond sheer volume, the study's second major finding concerns timing. Slow clicks proved highly rhythmic, occurring at rates of roughly 0.1 to 0.3 Hz, meaning an order of magnitude slower than any other known rhythmic communication signal documented among mammals or birds. Despite that extraordinarily slow pace, the whales maintained their click timing with a level of precision the researchers compare directly to a human drummer keeping a very, very slow beat.

To document that rhythmic consistency across a broader population rather than relying solely on the single Seychelles specimen used for source-level measurements, the research team assembled a considerably larger dataset: 1,839 individual slow clicks recorded across six separate geographic sites spanning Norway, Sri Lanka, Scotland, and the Seychelles, gathered using a combination of fixed underwater listening stations and suction-cup tags attached directly to whales.

Two competing theories for how they pull it off

Maintaining rhythmic precision at such an extraordinarily slow tempo, with multiple seconds separating individual clicks, raises a genuine biological puzzle: how does an animal keep accurate time over that kind of extended interval without some kind of internal or external reference point? The research team proposes two competing hypotheses, both of which the study's authors explicitly describe as remaining entirely speculative at this stage.

The first possibility involves the whale's own physiology: during a deep dive, a sperm whale's heart rate can slow dramatically, potentially down to roughly the same pace as the observed click rhythm, raising the possibility that whales are effectively using their own heartbeat as an internal metronome. The second, alternative explanation involves external acoustic feedback, the idea that whales might be using echo information reflecting off the seafloor or other environmental features to help maintain their extreme timing precision over such long intervals between clicks.

Why anyone would evolve to make a sound this loud and this specific

The researchers' leading hypothesis for what slow clicks actually accomplish socially centers on honest signaling, a well-established concept in evolutionary biology describing traits or behaviors that reliably communicate genuine information about an individual's underlying quality or condition, precisely because they would be too costly or physically difficult for a lower-quality individual to convincingly fake. Given that slow clicks are produced exclusively by males, researchers speculate the signal may function as a form of size or fitness advertisement, either broadcasting to potential mates across considerable distances or serving as a competitive signal directed at other males, similar in underlying concept to how many other species use costly, difficult-to-produce vocal or visual displays to advertise genuine competitive strength.

The study's authors frame their overall interpretation of slow clicks as what they describe as a low-entropy, long-range communication signal, one whose value lies precisely in its extreme rhythmic regularity, allowing timing information itself to be reliably transmitted and interpreted correctly even after propagating tens of kilometers through open ocean water.

Real limitations the researchers are careful to acknowledge

The study's authors are notably candid about several limitations in their current findings. Because the precise source-level measurements came from recordings of a single male sperm whale off the Seychelles, the researchers caution against generalizing those specific loudness figures too broadly across the entire species or across different individual whales, whose size and physical condition likely affect how loud their own slow clicks actually register. The apparent source-level calculations also assumed clicks radiate outward evenly in all directions and did not fully account for sound absorption effects at very short distances, meaning the true on-axis loudness at the point of production may differ somewhat from the study's reported estimates.

Perhaps most importantly, the researchers explicitly state that slow clicks' actual social or reproductive communication function cannot be conclusively confirmed without further playback experiments, in which researchers play recorded slow clicks back underwater and directly observe how nearby whales respond, paired with sustained behavioral observation connecting specific click events to specific whale behaviors in real time.

What comes next in solving the puzzle

The research team's stated next step involves exactly that kind of playback experiment: broadcasting recorded slow clicks underwater and documenting how sperm whales in the vicinity actually respond, a methodology that would offer considerably more direct evidence connecting the sound's acoustic properties to its actual behavioral and social meaning than passive recording alone can provide. Until those playback studies are conducted, the honest-signaling and mate-advertisement hypotheses remain scientifically plausible interpretations rather than confirmed conclusions.

Even without a fully settled explanation for their function, the underlying acoustic finding stands on its own as a genuinely notable addition to marine mammal science: a signal loud enough to be classified as the most powerful communication sound documented in any mammal, produced with a rhythmic precision that, at least for now, remains as mysterious as the message it may be carrying across dozens of miles of open ocean.

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*Sources cited in this article include the peer-reviewed study "Extreme Rhythm Keeping in Long-Range Slow Click Communication of Sperm Whales," published in the Annals of the New York Academy of Sciences, and reporting from Phys.org, Live Science, EurekAlert, StudyFinds, and Vice covering research led by Simone Videsen of Aarhus University. All figures reflect reporting available as of August 12, 2026.*