Rooster crows receive a fairly idyllic treatment in children’s books, but in real life they’re so loud they can actually deafen those who come too close. Which presents an interesting question—how do they not go deaf themselves?
To find out, a team of researchers from the University of Antwerp and the University of Ghent, in Belgium, attached microphone recorders to the heads of three roosters to measure the sound at its source, according to Discover.
As it turns out, at point-blank range a rooster crow can pass 130 decibels, which is roughly the same acoustic intensity you’d get from standing 50 feet from a jet as it takes off. One recorded crow reached 143 decibels, comparable to “standing in the middle of an active aircraft carrier,” according to Science.
That’s enough to damage and potentially shatter a human eardrum. The team then conducted micro-computerized tomography scans—tightly focused examples of what are more commonly known as CT scans—to study the features of rooster ears, as well as how they compared to hens'. A paper describing the research was published in the scientific journal Zoology.
The researchers discovered that a rooster’s ear is incredibly technically advanced. When their beaks are fully open, soft tissue moves to cover half their eardrum, while a quarter of the ear canal itself closes off. They also found that the slit which causes their outer ear canal to close doesn’t exist in hens—the hens' ear canals narrows in response to loud sounds like rooster calls, but it doesn't actually close. The roosters don’t deafen all the hens within earshot because the damaging effects diminish significantly with even a few feet of distance, and because birds are capable of regenerating damaged inner ear cells in a way mammals are not, according to Science.
Hens don't get much louder than approximately 70 decibels, so they don't need a similar protective mechanism to avoid being deafened by their own calls, according to Discover. The research points to the idea that rooster crows evolved to become louder over time, and that the shape and characteristics of their ear canals evolved in response; the louder the rooster, the more reproductively successful they stand to be.
Perhaps this is why rooster crows were fatal to the basilisk, a mythical giant snake of which the best-known example is probably in the Harry Potter novels. Snakes don't actually have an eardrum, so they rely on acoustic vibrations to travel from their jawbone to their brain. Aircraft carrier-level crowing might be a bit more than they were built for.
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