Study Solves an Animal Locomotion Mystery

November 5, 2013
An illustration shows a glass knifefish and a robotic fish

This illustration depicts a glass knifefish (A) and a robotic fish (B) used in research to study animal locomotion.

A quirk of nature has long baffled biologists: Why do animals push in directions that don’t point toward their goal, like the side-to-side sashaying of a running lizard or cockroach? An engineer building a robot would likely avoid these movements because they seem wasteful. So why do animals behave this way?

A multi-institutional research team, led by Johns Hopkins engineers, says it has solved this intriguing puzzle. In an article published in the Nov. 4-8 online edition of Proceedings of the National Academy of Sciences (PNAS), the team reported that these extra forces are not wasteful after all: they allow animals to increase both stability and maneuverability, a feat that is often described as impossible in engineering textbooks.

“One of the things they teach you in engineering is that you can’t have both stability and maneuverability at the same time,” said Noah Cowan, a Johns Hopkins associate professor of mechanical engineering who supervised the research. “The Wright Brothers figured this out when they built their early airplanes. They made their planes a little unstable to get the maneuverability they needed.”

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