Chameleons Use Super Sticky Spit to Nab Heavy Food

A hunting chameleon is a sight to behold. The color-changing reptile’s long, powerful tongue can extend more than twice its body length, capturing prey that can weigh as much as a third of its body weight. A new study out in Nature Physics today illuminates just how chameleons are able to whip their heavy prey back into their awaiting mouths: Their spit is incredibly sticky.

Chameleons lie in wait while hunting, keeping still to stay hidden from their own predators. When a tasty morsel gets within range, they shoot their tongue out like a missile. When they make contact, spit that’s 400 times more viscous than human saliva brings their dinner back to them, as the study led by researchers from the University of Mons in Belgium finds.

The researchers collected mucus from five different chameleons using microscope slides. They recorded images of the spit rolling down the angled slide to measure its viscosity, as well as taking video of chameleons hunting crickets. Based on how sticky the mucus was, they created a model for how adhesion might function in chameleon hunting mechanisms, taking into account the tongue’s surface area and roughness.

“This unexpectedly large mucus viscosity strongly suggests that the prey sticks to the chameleon’s tongue through viscous adhesion,” the authors write of the sticky spit.

Previously, scientists hypothesized that the chameleon tongue might utilize suction to bring prey back to the reptile. This adds another layer to our understanding of how the chameleon’s powerful mouth works.