Fired with sufficient force, suction arrows stick to any smooth surface. The same goes for a chamelon's characteristic long tongue. Conventional wisdom has it that wet adhesion and surface roughness are responsible for the stickiness of the end of a chameleon's tongue. But stickiness cannot explain how chameleons can capture birds and lizards up to ten per cent of their own body mass. Suction is the answer, Herrel's team announce in the Journal of Experimental Biology 1 .
Chameleons belong to a large group of primitive lizards, the Iguania.
Iguanians use their tongues to capture prey but chameleons have taken this to an extreme, developing a ballistic mechanism in which the tongue is shot at prey at speeds too great for the human eye to follow. Precisely what happens during the actual instant of prey capture has never been securely established. The heavy, gland-rich tongue tip had been thought to splay out on impact, enclosing the prey in adhesive, mucous glue. When the tongue is fired at the prey, the tongue tip is convex. During travel, and particularly just before impact, a pair of muscles called the pouch retractors inside the tongue, contract, turning the tip of the tongue into a concave suction cup.