Last year, Harvard biologist Andrew A. Biewener and then-grad student Monica A. Daley made seven helmeted guinea fowl—birds similar to pheasants—dash down a 20-foot-long plywood runway. Not just any old plywood runway, mind you, but one equipped with a device that measures force and a high-speed digital video camera.

The team discovered that a spring-like mechanism in the birds’ legs helped them keep their balance on uneven ground. The findings, published last week in the Proceedings of the National Academy of Sciences, have profound implications for developing legs for robots—and, eventually, more mobile prosthetic ones for humans.

Running on the plywood track, the fowl had to traverse a hidden 8.5-centimeter-deep pothole camouflaged by tissue paper.

“The birds fell down only once in 77 times,” said Biewener, the chair of the organismic and evolutionary biology department. “We were surprised by the fact that one of the responses was fairly simple, pretty well explained by the mass-spring model.”

The team’s discoveries are already proving useful in robotics. According to Biewener, Boston Dynamics, a company that works on human simulation, will use the findings in its push to create a legged robot.

And the results of the study—which is titled “Running over rough terrain reveals limb control for intrinsic stability”—could inform efforts to design more lifelike prosthetic legs.

To gauge how the guinea fowl reacted to an unexpected pothole, Biewener and Daley set up a force plate, which measures quick changes in force, under tissue paper in the middle of the runway.

According to Biewener, another surprise came when he and Daley removed the tissue paper to let the guinea fowl see the hole. The birds slowed down and couldn’t maintain their stability as well.

The experiments were carried out in Biewener’s lab at the Concord Field Station, a Harvard research facility in Bedford, Mass.

Daley, who finished her doctorate in biology at Harvard this past spring, is now a fellow at the University of Michigan. She could not be reached for comment.