Birds are dumb runners – and maybe dinosaurs were too

Why do birds look silly when they run?

Megan Bartels

When humans want to walk fast (unless they’re in a trotting competition), they lift one foot, but when birds have to hurry somewhere, they tend to keep one foot on the ground at all times, resulting in a strange gait that scientists call “terracing.”

“Very few people have ever seen a bird stomping its feet on the ground,” says Pascha van Bijlert, a doctoral student in evolutionary biomechanics at Utrecht University and the Naturalis Biodiversity Centre in the Netherlands. “When you see a bird walking in a strange way, you know it’s not actually walking, it’s running. You can tell by the hopping.”

Bird ground running has puzzled scientists because if humans were to copy the behavior, it would take significantly more energy to move at the same pace than our habitual airborne flight. But according to a study published September 25 in the journal Nature Communications, Scientific advances A study by van Beylert and his colleagues found that birds may look goofy while running on land, but they’re not stupid.

Supporting science journalism

If you enjoyed this article, please support our award-winning journalism. Subscribe. By purchasing a subscription, you help ensure a future of influential stories about the discoveries and ideas shaping the world today.

This new study shows that common emus (Dromaius novaehollandiae) was studied to show that birds’ posture makes them more efficient at ground running than air running at some speeds. The researchers built this model because they predicted that two factors would affect birds’ movement: their highly elastic leg tendons and their crouched posture, with their hips and knees tucked into their feathered bodies.

Neither factor lends itself to physical experimentation: “You can’t really change a bird’s size and see how that affects the way it runs,” van Bijlert says. “You can’t train an emu to stand upright.” So a simulation approach was employed, which allowed the researchers to tweak the size of the emu’s legs, preventing the tendons from storing energy, while testing which gait was most efficient for moving at a particular speed.

The simulation alone is an impressive feat, says Almita Manafzadeh, a biomechanist at Yale University who was not involved in the study. “Physics-based simulation of movement has come a long way,” she says. “When this kind of methodology first came out, there were so many simplifications, and the algorithms were so simplistic, that the output on the computer didn’t look anything like a living animal.”

The simulation showed two strategies to move faster and use less energy: start with your legs straight, or keep one foot on the ground as long as possible. Humans take the first route, but birds can’t do that, so they take the running route instead. (If humans are asked to run in a crouched position, they’ll instinctively switch to the running route. Want to give it a try? Check this out.)

“When we think about bird locomotion from a human perspective, it seems like a really strange and stupid thing to do because it seems so energy intensive,” Manafzadeh says. “But if you know bird anatomy, it’s actually a pretty clever thing to do.”

While learning more about emus is good, van Beylert hopes the study will also help scientists understand birds’ distant dinosaur ancestors, particularly bird-like dinosaurs like the tiny Velociraptor, which he thinks may have stalked prey like some nightmare agent from the Ministry of Stupid Walking.

But dinosaurs, including the fearsome bipedal dinosaurs, Tyrannosaurus RexManafzadeh said the plane may have also been practicing taxiing.

Dinosaurs aside, she hopes the new study reminds scientists to be curious about how other species live on Earth. “If we try to interpret the diversity of animal migration through a human-centric lens, we’re going to miss out on a lot of really cool and equally viable ways of moving around the world,” Manafzadeh says.