How Is It Possible?
Morning Wake Up
We have all, at some point, experienced the ear piercingly loud wake-up call of a rooster in a neighbouring field. Roosters crowing is exceptionally loud, considering the proximity of the rooster from the typical bedroom. It’s a wonder how roosters don’t suffer from damage to their hearing. So, how is this possible? Why don’t roosters suffer from hearing loss?
Research, undertaken by the University of Antwerp and the University of Ghent in Belgium, wanted to find out what’s ‘the secret’ to how roosters can avoid damage to their hearing.
Human ears are comparatively very sensitive; a sound above 120dB (the approximate volume of a chain saw), even in short exposures, can cause permanent damage to our hearing. The intensity of the sound waves (volume and frequency), along with the air pressure created from the sound, can cause harm to the cells within our ears (inner hair cells). If these hair cells are damaged, or killed, they cannot convert the sound waves into signals that our brain can process.
Roosters can crow as loud as 100dB (the approximate volume of a jackhammer), so you would expect them to have some form of hearing loss over the course of their life. Research suggests that this is not the case.
For the research, microphones were attached to the head of three different roosters, with the receiving end of the microphone pointed at their ears. By doing this, it meant that they were able to measure the sound level that the roosters would be exposed to during their crows.
The decibel levels were all in excess of 100db, proving that the levels of noise generated by a rooster’s crow would, in humans, be sufficiently loud enough to cause hearing damage. One of the roosters even produced a craw at 140dB (equivalent to the sound level on an aircraft carrier deck).
Roosters keep themselves safe from their crows by an anatomical adaptation. When they open their beaks to crow, a quarter of the ear canal closes, and soft tissue covers approximately 50% of their eardrum. Roosters have their own built in noise protection plugs, which protects them from much of the risk of damage. Hens also have this same protections. Not only do roosters and hens possess this useful feature, it has since been discovered that all birds regrow damaged cochlea hair cells in as fast as a couple of days.