The hearing of barn owls is unaffected by age, new research into the bird's behaviour has found.
While humans usually lose more than 30 dB in sensitivity at high frequencies around the age of 65, old birds will experience almost no loss at all. This is due to their evolved ability to regenerate sensory cells in the inner ear, something mammals, including humans, lack.
If we can learn more about the biological mechanisms behind the bird's ability to retain its hearing sensitivity, we may be able to develop new treatments for people with hearing loss.
Barn owls, in particular, have incredibly sensitive hearing, 10 times as powerful as the most sensitive human ears. So precise in fact that "they can capture prey in total darkness", George Klump, one of the authors of the study from the University of Oldenburg, told IBTimes UK.
Some of the trained owls that were tested for the research, published in the journal Proceedings of the Royal Society B, were even older than the oldest recorded wild barn owl in Britain, which reached 15 years of age. But even these birds had very minimal hearing loss. In fact, the birds in the experiment were some of the oldest birds ever tested for their hearing.
"It's a nice demonstration that in birds, hearing is preserved much better than in mammals and humans with age and one could make the hypothesis that this is correlated with the bird's ability to repair the damage in their ears," Klump said.
"Humans cannot do this. If you go to a rock concert you may lose some hearing sensitivity, or if you work in noisy environments, a disc jockey in a club is a typical example. They will lose hearing sensitivity due to overstimulation and that's related to the inability of humans to repair damage in their ears."
To test the owls' hearing, the birds were trained to sit and wait on a perch for a sound to turn on, which signalled to them that if they flew to another perch where a feeder was present, they would be rewarded with food. If they flew to the feeding perch when the sound wasn't turned on, they received no reward.
Studying the hearing of birds could provide solutions to treating humans who lose their hearing with age.
Understanding the biological process that underpins hearing regeneration in birds "will definitely have a large implication for the treatment of hearing loss in humans", Klump said.
In the past few years birds have been the focus of much research in an attempt by scientists to shed light on the question of why mammals and humans no longer have this ability to regenerate the cells in their ear, something which may have been possible at past stages in our evolution.
"In the vestibular system – which is for balance – we can actually do it, so it's interesting why this ability has been switched off, we don't know why. But people are looking at the differences between birds and mammals and if they find out which 'switch' has been turned off in the development of the cells in the mammals, it might be possible to turn it on."
This will enable us to truly cure hearing loss rather than simply giving people hearing aids, Klump added.