Tag Archives: Owls

Barn owl.

Owls’ ears are always in tip-top shape because they’re self-repairing

Mammal ears, including those of humans, tend to deteriorate over time. By contrast, barn owls’ hearing appears to suffer no ill effects from aging, a new paper reports. This comes down to a genetic switch allowing the birds to continuously regenerate their ears as they age — a switch locked in the ‘off’ setting in mammals.

Barn owl.

Image via Pixabay.

No matter how quiet your life is, by the time you grow old and grey, your ears simply won’t be as good as the day you got them. Past research has shown that by age 65, most people lose over 30 decibels of sensitivity in the high-frequency range due to age-related deterioration known as presbycusis. Naturally, your mileage may vary and you can lose a lot more, mostly based on lifestyle and genetics.

Not so with barn owls (Tyto alba). Hogwarts’ mailbirds seem to possess a natural regenerative mechanism that ensures they always hear at peak performance. For all intents and purposes, their ears are ageless.

Eearly problems

The team, led by Bianca Krumm from the University of Oldenburg’s animal physiology and behavior group, worked with seven barn owls named Weiss, Grün, Rot, Lisa, Bart, Ugle, and Sova. All of the birds were hatched in captivity and lived in aviaries. The researchers divided them into two age groups — those less than 2 years old, and those between 13 and 17 years old.

What they wanted to test is how well the owls could hear frequencies of 0.5, 1, 2, 4, 6.3, 10, and 12 kHz (kiloherz). To this end, they trained the birds to fly between two perches when hearing a short sound tone. After successfully completing the task, the owls would receive a food reward. To minimize training effects (false positives) the owls were trained separately, using a specific sequence of frequencies for each bird. The team also specifically tracked Weiss’ auditory sensitivity throughout his lifetime. The bird reached an impressive (for an own) 23 years old, far above the species’ typical lifespan in the wild of just 4 years old.

Overall, the paper reports that at test frequencies of 0.5, 1.0, and 6.3 kHz, the old owls performed slightly better than their younger counterparts (with mean differences in hearing thresholds between 0.1 and 3.1 dB). Younger owls fared better in the remaining frequency range (mean thresholds between 0.9 and 9.6 dB). However, the team notes that these differences are not significant, saying the results varied between individuals but “without any relation to age.”

Barn Owl pose.

Can you hear that? Can you hear adventure calling? Oh, sorry, I forgot you’re just a mammal.
Image credits Karen Arnold.

The results are consistent with previous research showing that birds, fish, and amphibians can regenerate lost hair cells in their equivalent of an ear, an organ known as the basilar papilla. These ‘hairs’ are actually very long and flexible organelles (organs, but for cells) which turn sound vibrations into an electrical signal that’s passed onto auditory nerves and the brain.

“The regeneration mechanisms, and therefore their benefits, are likely present in all bird species,” said senior author Ulrike Langemann in an interview for Seeker.

“The amazing thing is that the majority of small bird species are rather short-lived, and thus will never really benefit from a preservation of auditory sensitivity at old age.”

Humans and our fellow mammals have some regenerative capability in this direction, but it’s a far cry from what owls can pull off. We can’t replace hairs lost by injury, disease, not even old age — which is why we get presbycusis. The team believes that mammals lost the full scope of these regenerative abilities sometime during their evolution. Which is a shame, really, because according to the National Institutes of Health, over 90% “of hearing loss occurs when either hair cells or auditory nerve cells are destroyed.”

It’s not clear why we lost this very desirable trait, but “unfortunately, the genetic switch for the inner ear of mammals is in the off mode,” the team says. Barn owls however, being auditory hunters par excellence, stood to benefit a lot from such a regenerative system.

“Scientists have shown that a tame barn owl will catch a prey item in complete darkness,” Krumm explains

As such, their evolution selected heavily in favor of keeping the switch “on.” The team is now looking into how pathologies affect mammalian inner ears, and how barn owls use their hearing to accurately locate prey. We can’t yet copy these regenerative mechanisms into humans, the team notes, so for the time being you should take care of your hearing as much as possible.

“Listening to very loud music plays a role in hearing loss because it may damage sensory hair cells and the connecting nerve fibers immediately,” Langemann said. “However, the impact from constant and work-related noise is as serious. These are some of the reasons why wearing ear protection for specific types of work are nowadays standard in the professional world.”

The paper “Barn owls have ageless ears” has been published in the journal Proceedings of the Royal Society B.

Flying owl

Owl wings may inspire stealthier aircraft

Flying owl

While the owl is commonly associated with wisdom, make no mistake  – it’s a vicious predator of the night. It’s main weapon is its stealth, as it silently dashes through pitch black catching pray off-guard. This remarkable ability  of noiseless flight has intrigued scientists who are looking to develop aircraft inspired by the owl.

The owl has a special plumage that allows is to fly on sly. When air airfoils travel through a shape, be it the wing of a bird or a plane, turbulence is created. The turbulence is significantly amplified towards the trailing edge of the wing, which also causes noise to occur.

Aircraft wings have hard and relatively rigid trailing edges, which coupled with extremely high speeds, causes loud noise to be generated. Researchers are now studying the wing structure of the owl to better understand how it mitigates noise so they can apply that information to the design of aircraft.

“Many owl species have developed specialized plumage to effectively eliminate the aerodynamic noise from their wings, which allows them to hunt and capture their prey using their ears alone,” Cambridge researcher Justin Jaworski said.

“No one knows exactly how owls achieve this acoustic stealth, and the reasons for this feat are largely speculative based on comparisons of owl feathers and physiology to other not-so-quiet birds such as pigeons.”

So far, the Cambridge researchers have identified three aspects that have been liked with owl silent flight: a comb of stiff feathers along the leading edge of the wing; a soft downy material on top of the wing; and a flexible fringe at the trailing edge of the wing.

With these preliminary findings, the researchers created a computer model of wing trailing edge with elastic and porous properties and learned, indeed, that this kind of design would allow for a better noise mitigation.

“This implied that the dominant noise source for conventional wings could be eliminated,” researcher Nigel Peake said.

The findings were presented Sunday at a meeting of the American Physical Society‘s Division of Fluid Dynamics in San Diego.

 

The giants with piercing yellow eyes and 5-foot wingspans have adapted so well to snow that they can dive face-first through up to a foot of it to catch the voles they hear creeping underneath.

Ornithologists remotely tracks endangered Yosemite Great Gray Owls with sound tech

The Great Gray Owls of Yosemite are a unique species, after they separated from their cousins some 30,000 years ago when an ice age forced them into isolation. Though similar to the Great Gray Owls, commonly encountered through out North America and the Asian taiga forests, the Yosemite branch is genetically distinct, but unfortunately also endangered with only 200 specimens left in the wild.

The giants with piercing yellow eyes and 5-foot wingspans have adapted so well to snow that they can dive face-first through up to a foot of it to catch the voles they hear creeping underneath.

The giants with piercing yellow eyes and 5-foot wingspans have adapted so well to snow that they can dive face-first through up to a foot of it to catch the voles they hear creeping underneath. (c) Joe Medley / U.S. Forest Service

With such a fragile population, every measure of precaution must be taken. Tracking and tagging, indispensable to conservation efforts, is extremely difficult in such situations since it traumatizes the birds, disrupting matting cycles and nesting in the process. So, this summer researchers decided to tackle the situation with a different, more innovative approach – they used remote audio recording, coupled with complex software, to track and recognize individual Great Gray Owls through out the national park.

“Even if it takes only 15 minutes to trap a bird, it’s traumatic for them in the long term,” said Joe Medley, a PhD candidate in ecology at UC Davis who perfected computer voice recognition software to track the largest of North America’s owls. “With a population this small, we want to err on the side of caution in terms of the methods we use to get data.”

Thus,  40 data-compression digital audio recorders with high gain were placed in key areas of Yosemite,  around the mid-elevation meadows typically favored by the owl known as Strix nebulosa Yosemitensis. By the end of the high tech owl spy experiment, Davis garnered some 50 terrabytes of recording – enough for seven years of continuous playing. Owl howls weren’t the only thing he ended up with though; all kinds of environmental sounds were picked up as well, from airplanes, to frogs, to shivering trees.

To solve this, Medley along with scientists at  Cornell University Laboratory of Ornithology, developed a specialized software called Rave Pro. The program was able to recognize and filter the  Great Gray Owls’ low-pitched hoot from the massive data, and discern males and females from juveniles. The software was even able to identify nesting females calling for food to help determine reproduction success.

“It’s capable of searching a week’s worth of data in an hour. What I was left with was owls and a host of other things that fell in the same bandwidth,” Medley said.

The researchers involved in the study hope that the same technique might be applied to observing other endangered species that are particularly sensitive to human interaction.

“These (owls) exist nowhere else in the world, and where they do occur is a pretty amazing location,” said Joshua Hull, a researcher with the U.S. Fish and Wildlife Service and adjunct professor at the University of California, Davis. “These are going in a different evolutionary direction than the others, and we don’t know where that is right now.”