With a lightning-fast flick of its tongue, a hungry chameleon can fetch dinner. Biologists have long assumed that the rough, sticky nature of its tongue enabled this feat. These mechanisms might suffice for snagging certain small insects, but some chameleons prey on birds and lizards--creatures that can amount to some 10 percent of the hunter¿s own body weight. Even among insects, some are too smooth for the chameleon¿s tongue to lock onto. What, then, is the chameleon¿s secret? According to a report published in this month¿s issue of theJournal of Experimental Biology, it¿s suction.

Because the chameleon fires its tongue at speeds surpassing what the human eye can follow, researchers have not been able to ascertain exactly what happens during prey capture. But with the help of high-speed x-ray videos, Anthony J. Herrel of the University of Antwerp and his colleagues have figured out the sequence of events. When fired, the tongue tip is convex, like a bullet. Just before it reaches the prey, however, muscles inside the tongue called pouch retractors contract, inverting the tip into a suction cup of sorts. Upon contact, the cup clamps onto the prey, resulting in a suction effect. Stickiness does play a significant role in prey capture, but the team found that chameleons whose pouch retractor-controlling nerves had been severed were unable to bring in a meal, suggesting that suction is a critical mechanism.