Researchers from France and Belgium discovered the mystery hidden in chameleon’s adhesive tongue: sticky mucus.

Chameleons “magic” tongue has inspired several hypotheses about its great skill to haunt with the tongue. The study entitled Dynamics Of Prey Prehension By Chameleons Through Viscous Adhesion tested chameleons system to project and capture large preys with its tongue. Finally, researchers came out with the answer to the mystery.

Chameleon's tongue
Researchers found that sticky mucus is key for the chameleon’s high specialized hunting system. Credit:

Scientists examined the mechanism of the reptile to capture its prey successfully once it gets in contact with the tongue. The team evaluated the viscosity of chameleon saliva by the use of a magnifying glass plate containing an insect. Once the chameleon was pretty sure it could easily get the prey, it flicked the glass with its tongue, leaving some spit behind.

Researchers tested the spit sample with some rolling beads on the thin layer of mucus. The finding pointed out that the viscosity of the chameleon’s secretion is 1,000 times larger than human saliva.

“We were surprised to find that the liquid is very viscous, about 1,000 times more so than (human) saliva,” according to the co-author of the study, Pascal Damman of the University of Mons in Belgium.

Then, researchers incorporated the reptile’s viscosity into a dynamical model for viscous adhesion. They wanted to determine the retraction phase of the tongue’s motion while capturing the prey. They found out that a strong adhesion in chameleon’s tongue tip is required to hold on the prey while snapping it back towards to the mouth. The study showed that the size of the captured prey is not a limit to the viscous adhesion of chameleon’s tongue tip. 

“Contrary to what many thought, the viscous adhesion is more than sufficient to allow the chameleon to haul in such big prey,” said Damman.

Previous hypotheses linked chameleon’s hunting mechanism to stickiness, suction, even a velcro-like bond between the reptile’s tongue tip and its prey was suggested. This study proved that all that is needed to hunt as fast and accurate as chameleons is a very sticky mucus.

This is the very first research of its kind. Even if chameleons characteristics have been thoroughly studied by scientists, the spit of this reptile had not ever been examined. The findings were published on Monday in the journal Nature Physics.

Chameleons: opportunistic predators

Chameleons are widely known for its successful ability to capture no matter what variety of invertebrate or vertebrate animals. They are very patient predators. They remain hidden and motionless while waiting for the best opportunity to make contact with its prey.

These lizards use all biological features they have on their own to develop a high specialized feeding system based on a fast, accurate tongue shoot. It is the viscosity of the mucus of the tongue tip what allows chameleons to snatch insects and bugs that weigh up to 30 percent of their body mass.

Source: Nature