Scientists Keep Finding the Same Mysterious Beat Across the Animal Kingdom, From Fireflies to Sea Lions

From fireflies to mammals, evolution may have tuned communication to the rhythm of neurons.

Fireflies flash, crickets chirp, and sea lions bark. Three examples with signals so radically different that they seem to have little in common. Yet strip away the pitch, the sound-making organ, and even the sensory channel, and a curious pattern appears: many animals seem to communicate at roughly the same tempo.

Two independent research teams have now arrived at that conclusion using strikingly different approaches. One found that repetitive animal signals often cluster between about 0.5 and 4 times per second. The other analyzed recordings from 98 species and calculated an evolutionary optimum of 2.7 times per second (2.7 Hz). Both teams landed on the same provocative conclusion, namely that the tempo may suit something animals share despite their enormous differences—neurons.

That’s not to say every animal marches to a universal metronome. Bats and bush crickets provide conspicuous counterexamples. But the convergence suggests animals may communicate in very different ways, yet many of their signals still unfold at a similar rhythm.

A Strange Coincidence

The first clue came almost accidentally.

In 2022, Northwestern University biophysicist Guy Amichay traveled to Thailand to film Pteroptyx malaccae fireflies flashing together. As he watched, nearby crickets seemed to chirp alongside the insects’ lights.

“At some point, I thought that the flashing of the fireflies and the chirping of the nearby crickets were in sync with each other,” Amichay said. “My colleagues noticed it too, and we thought that it was crazy that these two unrelated species would interact in such a way.”

They weren’t actually synchronizing. Both simply happened to signal at about 2.4 hertz, or 2.4 pulses per second—roughly 144 bpm.

Amichay and his colleagues then surveyed research on fireflies, crickets, frogs, fish, birds, crustaceans, and mammals. They also checked wildlife recordings from Xeno-canto, screening 124 recordings to obtain 50 examples that met their definition of regularly repeated communication. Again, signals piled up in the 0.5-to-4-hertz range.

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Then another team independently found nearly the same thing.

Convergent Pattern

Researchers led by Théophane Piette at the University of Geneva approached the problem from a different direction.

They collected acoustic sequences from 98 species and analyzed them with a standardized method designed to detect slow rhythmic changes in signal amplitude.

Because birds and mammals dominated the dataset, the researchers restricted their main evolutionary analysis to 58 bird and 28 mammal species. Other animals, including insects, amphibians, reptiles, and fish, were included in exploratory supplementary analyses.

The researchers first looked for more obvious explanations.

Perhaps large animals communicate more slowly. Perhaps there’s something about the habitat. Maybe chewing constrains the rhythm of vocalizations. Or perhaps socially complex species need to pack information into signals at different rates.

None provided a decisive explanation when confronted with data.

Instead, evolutionary models favored a process that repeatedly pulls communication rhythms toward an optimum. The estimated value was about 2.7 Hz, with a broad 95% interval extending from 0.45 to 4.99 Hz.

That lands remarkably close to the tempo hotspot identified independently by Amichay’s team.

A PLOS Biology commentary accompanying the two studies highlighted exactly this convergence. Two groups, using comparative evolutionary analysis on one hand and broad surveys plus computational neuroscience on the other, had independently arrived at both a similar pattern and a similar possible explanation.

The answer might be in the receiver’s brain.

Different Instruments, Same Tempo

Pitch behaves very differently. Larger mammals generally produce lower-frequency voices because larger vocal folds and vocal tracts favor lower frequencies, as a 2017 study of 91 mammal species found. The study led by Théophane Piette likewise found that body size helped explain dominant sound frequency while failing to explain communication rhythm.

That distinction may hold the key. A whale and a sparrow may produce very different sounds, but their brains could still be especially responsive to signals arriving at a similar pace.

The researchers point to delta brain rhythms, slow neural oscillations around 1 to 4 hertz that occur across many animals. Amichay’s team modeled tiny neural circuits and found that circuits with neural circuits tuned near 2 hertz responded most strongly to signals arriving at about the same pace.

“There’s a somewhat subtle point here: we suspect that getting the ‘carrier’ signal in the right tempo range is key to communicating efficiently,” said Daniel M. Abrams, senior author of the Northwestern-led Amichay et al. study. “It might not be that the tempo itself conveys any information, but it just serves as a baseline for getting attention, with actual content sent on top of it like musical notes following along with the beat in a song.”

Previously, a 2022 experiment with rats found particularly strong auditory-cortex responses and spontaneous movement synchronization with music at around 120 to 140 beats per minute. And a 2025 analysis of 48 human languages found that intonation units recur at a slow rhythm peaking around 0.6 hertz.

None of this yet proves that delta rhythms caused animal communication to evolve this way. Researchers still need direct neural experiments across species.

Taken together, the two studies suggest that animals may differ enormously in how they produce signals, while sharing a similar preferred tempo for communication. If that pattern holds up, the reason may lie in how nervous systems process it.