Researchers Shed Light On Cockroaches' Vanishing Act

UC Berkeley Researchers Say Bugs Use 'Pendulum Maneuver' To Disappear Quickly

You've seen it and begrudgingly admired it: the speed and swiftness with which a cockroach vanishes as you enter a room.

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Now, researchers at UC Berkeley have figured out how these indomitable and repugnant little critters disappear so quickly. It’s a feat of gymnastic ability.

The bugs hurl themselves, full speed, toward a crack or ledge, grabbing hold with their hind claws and swinging themselves like a pendulum a full 180 degrees to land upside down in the protective darkness.

The researchers say cockroaches are not the only animals capable of such dynamic maneuverability. Lizards, such as geckos, may use it, too.

The paper appears this week in the journal of the Public Library of Science.

"This behavior is probably pretty widespread, because it is an effective way to quickly move out of sight for small animals," said Robert Full, a professor of integrative biology at UC Berkeley.

Fifteen years ago, Full discovered that when cockroaches run really fast, they rear up on their two hind legs and run like people.

"Animals, even those as disgusting as cockroaches, have special secrets," Full said. And sometimes, understanding those secrets allows us to understand more general principles about how animals move, evade predation and attack.

The researchers discovered the pendulum maneuver while studying how the roaches use their antennae to sense gaps in a surface.

Full said his undergraduates started coming back to him reporting that as the roaches crossed some of the gaps, they disappeared.

"Disappeared?" Full said. "I said that was impossible. They couldn't have just disappeared. I told them to film it on a high-speed camera and see what was happening."

They did.

"As we made the gap wider, they (the roaches) would end up on the underside of the ramp," said Jean-Michel Mongeau of UC Berkeley's Biophysics Graduate Group. "To the naked eye, it wasn’t clear what was happening, but when we filmed them with a high-speed camera and slowed it down, we were amazed to see that it was the cockroach's hind legs grabbing the surface that allowed it to swing around under the ledge."

Full figured this move was unlikely unique to the American cockroach, so he and his team looked at geckos. They did the same thing.

To better understand the mechanics and physics of the pendulum maneuver, the biologists teamed up with UC Berkeley robotics experts to build a six-legged robot that could re-create the behavior.

They discovered the pendulum maneuver subjects the animal to forces three to five times the force of gravity – kind of like what a human feels when bungee jumping.

Full said the research lends itself to robotics development. For instance, it will allow engineers to create robots that could be used to quickly survey and comb through the debris caused by tornadoes, hurricanes or earthquakes, looking for survivors.

"This started from basic, curiosity-based research," Full said. "It's an example of how you never know where basic research will lead you. But it often leads to amazing things."

He also added that the work should underscore the importance of conservation.

"Every animal has its own secret," he said. "And if you destroy their habitat or pave over them, you’ll have lost those secrets forever – even those animals as disgusting as cockroaches."

Story by Susanne Rust California Watch

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