The Biologist and the Birds
If you’re looking for research assistants willing to work hard—and cheap—you could do worse than Terry Takahashi’s barn owls.
Every time the biology professor walks into his laboratory, they snap to attention. Wide-eyed, they closely watch his every move. He can feel the intensity of their laser-like stare even when his back is turned to them. Tireless workers, they spring into action to run every test, over and over and over.
All they ask in return? Maybe a dead mouse to eat.
Takahashi, co-director of the Institute of Neuroscience, has worked closely with barn owls for more than 30 years, examining their magnificent hearing ability to better understand how we process sounds ourselves. Takahashi teaches the raptors to cooperate with numerous tests that help unlock how humans hear—and what causes our hearing to fail.
“Helen Keller said that if you are blind, you are cut off from objects, but if you are deaf, you are cut off from your fellow human beings,” Takahashi said. “Humans rely on their hearing to stay in contact with other people.”
Distinguishable by its ghostly visage and piercing black eyes, the barn owl hears with such precision that it can strike prey in total darkness. In 2000, Takahashi and his team were examining the raptor’s auditory mechanics when they stumbled across a discovery that has paid off for humans.
A research associate was assessing an owl’s response to sounds by observing its physical reactions—in this case, movement of the eyelids. But after a few runs, the only response in the owl was dilation of its pupils.
The light bulb went off. Takahashi and his team hadn’t been considering this behavior—they theorized that humans, too, might have this involuntary hearing response. That’s exactly what they found: Our eyes dilate when we pick up soft sounds in a controlled environment. The lab team’s observation contributed to the development of testing for people unable to take part in a traditional hearing exam, including infants too young to respond to questions and those with disabilities.
Such breakthroughs are the reward for the countless hours that go into training owls to cooperate in a research setting. As astounding as their hearing is, Takahashi jokes, the birds aren’t good at listening to instructions.
Testing takes place in a soundproof room within a soundproof room, to eliminate all other noise. The birds perch on a stand in complete darkness, wearing earphones (yes, a barn owl can be trained to wear earphones). A sound is played—a “hiss”—at various volumes, all below what we can hear. Takahashi and his team observe the owl’s movements with infrared cameras.
Before any of this can happen, though, these feisty fliers must be taught to sit still and to accept being handled by Takahashi and his graduate students.
Working with three to six birds at a time, Takahashi and his team raise the owls from hatchlings, feeding them on an hourly basis for the first week. The infant birds bond with the person who raises them—the process is called imprinting—which can lead to some interesting twists on the idea of “workplace relations.”
Takahashi recalled a young owl that strongly connected with a female student. It saw a particular male assistant as a threat, and would propel itself in feathered fury at the unsuspecting student’s head whenever he entered the lab. They had to keep the owl in its cage to keep the peace.
Of these strong-willed creatures, Takahashi said, “it’s probably as easy to train them as it is training cats.”
Takahashi was first drawn to studying the barn owl after learning that their brains process sounds the way that our brains process sights. He has circled back to this physiological phenomenon for his latest work.
In the owl brain, neurons that capture sound are arranged topographically—like a map—so that each represents a particular “auditory point” in the physical landscape around the bird. This serves the barn owl not only in hearing, but also in pinpointing, the location of a field mouse scurrying across the forest floor in the dead of night. It also prompts interesting questions regarding humans and noisy environments.
About two-thirds of people over the age of 65 struggle to hear conversations amid the din of a crowded room, Takahashi said.
He is studying which part of our auditory system fails in these environments, preventing us from distinguishing the location of different sounds among many competing ones. In the barn owl, Takahashi can analyze how the auditory system identifies and “visualizes” sounds from a particular source, in the presence of noise.
The scientist says he still has much to learn from his feathered friends, including how they avoid crashing into trees while plunging down toward their next meal on a moonless evening.
“How they do it,” Takahashi said, “we’d love to know.”
Photo credit: Studio McDermott