With increasing age, all humans eventually become hard of hearing. However, it is known from birds that the cells in the inner ear can regenerate well. Oldenburg researchers have now shown that barn owls can still hear well in old age.
By the age of around 65, five out of ten people have already lost so much hearing sensitivity that speech intelligibility and enjoyment of music can be impaired. This is because the hair cells and nerve connections in the inner ear are irretrievably lost. Such age-related hearing loss is also known to occur in other mammals. Birds, on the other hand, have retained the ability over the course of evolution to form new hair cells in the inner ear or to replace hair cells that have been lost following damage.
In order to better treat hearing loss in humans in our ageing society, scientists want to understand which regeneration mechanisms birds possess. However, little research has been carried out into whether this type of regeneration in animals is maintained with advancing age and whether birds can therefore continue to hear well, i.e. have "eternally young ears". A team led by zoologist Dr Ulrike Langemann from the University of Oldenburg has now shown that barn owls do not become hard of hearing with increasing age. The researchers have published their findings in the journal "Proceedings of the Royal Society B".
For a songbird, the native starling, the team led by Prof Dr Georg Klump and Dr Ulrike Langemann from the Department for Neuroscience was able to show some time ago that it does not become hard of hearing with age. Now they have been able to confirm this finding with a study funded by the German Research Foundation: the scientists trained barn owls of different ages with the help of food rewards and compared their hearing ability. They found that the hearing sensitivity of very old and young birds does not differ. "The ability to regenerate functional hair cells throughout life is probably a general, robust characteristic of birds," concludes Klump.
Barn owls have extremely good hearing sensitivity due to their eponymous facial veil. They can also locate sound sources more accurately than any other animal. Both of these abilities help barn owls to localise and catch their prey - mainly mice. The hair cells in the inner ear of these birds are particularly specialised. The star of the Oldenburg study is the old owl "Weiss", who has been accompanying the scientists for 24 years. "She is now very sluggish," says researcher Bianca Krumm, who handles the animal on a daily basis, "but she still has excellent hearing".