The Science Behind the Flamingo’s One-Legged Stance
The New York Times by JOANNA KLEIN
Credit DeAgostini/Getty Images
“Usually as humans we take the standing behavior for granted until we lose that ability,” she said. Simplicity may be for the birds, but we complicated humans can appreciate its lessons.
Credit DeAgostini/Getty Images
Squat down as if you’re going to sit in a chair. Make sure to keep your back straight, use your hips as a hinge and push your butt backward. Try not to lean forward. Maintain your knees and ankles at 90-degree angles. Now try it on just one leg, and then swap that one with the other. To make it even harder, stand on a foam mat — and close your eyes.
You may feel your body wobbling, or you may fall over. If only you were a flamingo.
Flamingos can stand on one leg for a really long time. They even do it while sleeping. And according to a study published Tuesday in Biology Letters, flamingos may not even need to use their muscles for the task.
“It’s not tiring for them to stand on one leg and they can achieve it with very little effort,” said Lena Ting, a biomedical engineer at Emory University and the Georgia Institute of Technology who co-led the study. “It might even be easier for them to stand on one leg than to stand on two.”
Plenty of birds adopt a one-legged posture, often while sleeping, but the flamingo provides an extreme example. The prevailing hypotheses say the birds do it either to reduce muscle fatigue caused by switching legs, or to conserve heat. But both assume it takes muscles to stand this way, and that hadn’t actually been tested.
Dr. Ting and her colleague, Young-Hui Chang, a neuromachinist at Georgia Tech who works with prosthetics, analyzed the behavior of flamingos in a zoo and examined the joints of flamingo cadavers.
With the help of zoo keepers, the researchers coaxed eight young flamingos who had just eaten and were getting sleepy onto a device called a force plate to measure their postural sway, or the movements of an unsteady body as it tries to stabilize itself.
“Remarkably, when they’re falling asleep, the motion and the speed of the body was very, very low,” said Dr. Ting. “That’s counterintuitive because when you and I stand on one leg and close our eyes, we generally have more postural sway.”
That’s because our response is complicated. The nervous system senses instability and sends messages to muscles to tell them to contract to stabilize the body. But the steady zoo flamingos appeared to use some kind of passive strategy that relied less on muscles and nerves, and more on the simple mechanics of how their bodies fit together.
The researchers used flamingo cadavers, which obviously lack active muscles, to see if muscles were necessary for this stability.
Dr. Chang stood the cadavers up in a one-legged position. Rather than flopping over as expected, the bird settled into a stable, one-legged posture that stayed put even when the top of its body was tilted backward and forward. On two legs, or if the foot was not right below the body, the cadaver was far less stable.
The joints were easily unfolded also, suggesting that a flamingo can transition out of this position without much effort, either to switch legs, respond to wind or muddy water, or escape a threat.
The birds showed that “it’s possible to maintain what we’d consider very difficult posture without having to activate muscles,” said Dr. Ting. The birds might, she added, rely on gravity and some interaction between joints and ligaments to keep everything in place.
Because moving in and out of the one-legged stance appears to use little energy, flamingos could inspire improvements for robotics and powered prosthetics, said Dr. Ting, who studies the process of recovering movement after an injury.