Old barn owls hear as well as the younger ones, according to scientists


It’s common for humans to progressively lose their ability to hear through the pass of the years. In fact, it happens to all mammals and a lot of other animals. However, there are some birds whose ears seem to have the same quality as in their earliest ages. According to German scientists, barn owls are one of those birds that don’t suffer from the age-related hearing loss.

It was already known that some birds experience the minimum of loss as they get old and that barns owls usually have an excellent and sensitive hearing ability that they use to locate their prey and hunt them in the dark. Now, according to a study published in Proceedings of the Royal Society B: Biological Sciences, we know these birds don’t only hear extremely well, but also that their ears are unaffected by their age.

Image credit: IntoConnection Youtube Channel
Image credit: IntoConnection Youtube Channel

When people reach the age of 65, the average of lost in sensitivity at high frequencies is more than 30 decibels. These new findings could hopefully represent the beginning of studies to develop advanced medicines to treat human hearing problems caused by the age – or maybe even other critical issues.

“Barn owls have ageless ears,” Dr. Ulrike Langemann, a study researcher from the University of Oldenburg in Germany, said. “Evolution has favored birds to benefit from regeneration in the inner ear that is absent in mammals. Mammals, including humans, commonly suffer from a serious hearing loss at old age… If we could learn how birds can retain their sensitivity, this may lead to new treatment options for humans.”

Birds appear to be the only animals whose ears don’t get affected by the age because some of these can regenerate cells in their inner ears. According to the study, this regenerative ability is something that humans might have in the past but lost it while evolving. However, scientists plan to do more research to verify and prove this hypothesis.

Age-related hearing loss, or presbycusis as experts call it, is one of the most common conditions that affect older and elderly adults. According to the National Institute on Deafness and Other Communication Disorders, around one out of three American citizens between the ages of 65 and 74 suffer from hearing loss, and approximately one out of two people in the United States that are older than 75 have difficulties when hearing.

Hearing loss often affects both ears equally, making people not notice if they are suffering from it. This deficiency might influence the life of a person in many manners – like keeping them from hearing their phones or even smoke alarms. Sometimes, these hearing problems might push the individual to depression and isolation.

“To truly utilize this knowledge, we need to conduct comparative studies of birds and mammals that aim to find the differences in regenerative capacity,” said Dr. Stefan Heller of Stanford University School of Medicine, who is willing to understand the difference between birds and mammals. “A topic that is actively pursued by a number of laboratories worldwide,” the BBC reported.

Birds of more than 20 years with the same ability to hear

From the youngest to the oldest, the experts trained seven barn owls to study their responses to a sound in exchange for food as a reward.

Although these birds have an average of life from four to five years in the wild, they reached way more years living in the free-predators zone where the experts studied them. Out of the seven, four of them were just two years old – considering them the youngest -, and the others were between 13 and 17. All of them were submitted to a series of tests to compare the responses in front of the experts’ callings.

Image credit: Ecologysurveyors.co.uk
Image credit: Ecologysurveyors.co.uk

Inside of sound chambers, scientists put a loudspeaker on the opposite to the owls’ perch and reproduced pure tones that lasted around 300 milliseconds, varying in a frequency ranging from 0.5 to 12 kHz. Impressively, no differences were found between the two groups. Not even the oldest responded nor better or worst.

However, the scientists left the oldest owl aside to study it individually and corroborate if their finding was entirely correct. With 23 years old, which is a lot for a barn owl, the bird was tested three times during its lifetime, but the experts didn’t find any deterioration.

Dr. Langemann also tested the European starlings before, which is another type of birds. The results were pretty the same: none of them presented age-related hearing loss. She said that the birds regenerate the ear’s cochlea, which is a structure in the inner ear that transmit the sound waves to the auditory nerve, leading them to have the exact hearing ability for life.

“This suggests the innate capacity for hair-cell regeneration to protect birds from age-related hearing loss,” Dr Langemann said. “The hope and interesting question remains whether, someday, our knowledge on preservation of sensitive hearing in birds will provide for new treatment options that could counteract human sensory deficits,” the Daily Mail reported.

Source: Proceedings of the Royal Society B: Biological Sciences


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