Chameleons have the seemingly impossible ability to capture their prey while remaining motionless simply through the flick of their tongue. This sensationalized predatory ability depends in part on a sophisticated ballistic projection of the chameleon’s tongue. The chameleon is able to extend its tongue as far as two body lengths away during a predatory attack, sending it towards its victim using accelerations that range from 300 to 1500 m/s².

Given the forces involved, what happens next is a bit surprising: the victim sticks to the tongue, even in cases where the prey is up to 30 percent of the chameleon’s own body weight. Recently, a team of scientists investigated how this works.

It all depends on extremely viscous spit. The team characterized the viscosity of the mucus that’s present on the chameleon’s tongue by rolling small steel beads over a thin mucus film. During the rolling, the viscous forces of the mucus produce a drag force on the beads, which can be used to indirectly measure the viscosity. The scientists determined that the mucus viscosity (0.4 ± 0.1 Pa-s) is roughly 400 times larger than that of human saliva (~10^-3 Pa-s).