Stealth Cockroaches Surprise Scientists

A team of researchers at University of California in Berkeley has found that cockroaches can disappear in the blink of an eye by flinging themselves at full speed under a ledge.

American cockroach under ledge (Jean-Michel Mongeau / Pauline Jennings / PolyPEDAL Lab UC Berkeley)

The newly spotted cockroach behavior secures the insect’s reputation as one of nature’s top escape artists, able to skitter away and disappear from sight before any human can swat it.

In addition to its lightning speed, quick maneuvers and ability to squeeze through the tiniest cracks, the cockroach also can flip under a ledge and disappear in the blink of an eye, the team reports in the journal PloS-ONE. It does this by grabbing the edge with grappling hook-like claws on its back legs and swinging like a pendulum 180 degrees to land firmly underneath, upside down.

Always eager to mimic animal behaviors in robots, the researchers teamed up with robotics experts to recreate the behavior in a six-legged robot by adding Velcro strips.

The researchers first noticed the roaches’ newly-identified behavior while studying how they use their antennae to sense and cross gaps.

“As we made the gap wider, they would end up on the underside of the ramp,” said lead author Jean-Michel Mongeau. “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.”

“Cockroaches continue to surprise us,” said co-author Robert Full, a professor of integrative biology who 15 years ago discovered that when cockroaches run rapidly, they rear up on their two hind legs like bipedal humans. “They have fast relay systems that allow them to dart away quickly in response to light or motion at speeds up to 50 body lengths per second, which is equivalent to a couple hundred miles per hour, if you scale up to the size of humans. This makes them incredibly good at escaping predators.”

Surprisingly, the researchers discovered a similar behavior in lizards, animals that have hook-like toenails, and also documented geckos using this escape technique in the jungle at the Wildlife Reserves near Singapore.

“This behavior is probably pretty widespread, because it is an effective way to quickly move out of sight for small animals,” Prof Full said.

_______

Bibliographic information: Mongeau J-M, McRae B, Jusufi A, Birkmeyer P, Hoover AM, et al. 2012. Rapid Inversion: Running Animals and Robots Swing like a Pendulum under Ledges. PloS-ONE 7(6): e38003; doi:10.1371/ journal.pone.0038003