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A dragonfly buzzes through the air, stopping to rest on a branch. All of a sudden, SPLAT! A chameleon snatches the bug with its long, sticky tongue. 

Chameleons are some of nature’s most effective predators. Their tongues unfurl at lightning speed and can stretch twice the length of their bodies to help them capture insects, other lizards, and even small birds to eat.

Pascal Damman, a physicist at the University of Mons in Belgium, knew scientists had studied how a chameleon’s tongue moves. But Damman was interested in another question: Does mucus, a slimy substance in a chameleon’s spit, also help it catch its prey? Damman and his team set up an experiment to find out.

A dragonfly buzzes through the air. It stops to rest on a branch. All of a sudden, SPLAT! A chameleon grabs the bug with its long, sticky tongue. 

Chameleons are some of nature’s best predators. Their tongues whip out at lightning speed. They stretch twice the length of the animals’ bodies. Chameleons use their tongues to catch and eat insects, other lizards, and even small birds.

Pascal Damman is a physicist in Belgium. He knew scientists had studied how a chameleon’s tongue moves. But Damman had another question. Does a chameleon’s spit also help it catch its prey? He set up an experiment to find out.

A chameleon’s tongue can grab an animal that weighs up to one-third of the chameleon’s body weight. But the tongue doesn’t wrap around its prey, so how does it grip these supersized meals? Damman suspected the answer had to do with the spit on the end of a chameleon’s tongue. “When you touch the tip of their tongue with your finger, you can feel how sticky it is,” he says. 

To study the spit, Damman first had to collect it. He and his team placed a chameleon in a tank with a cricket. A glass slide separated the predator from its prey. When the chameleon attacked, its tongue smacked the glass, leaving its spit behind. 

A chameleon’s tongue can grab an animal that weighs one-third as much as the chameleon. But the tongue doesn’t wrap around its prey. So how does it grip these big meals? Damman thought the answer had to do with the spit on the end of a chameleon’s tongue. It contains a slimy substance called mucus. “When you touch the tip of their tongue with your finger, you can feel how sticky it is,” says Damman. 

Damman first had to collect the spit to study it. He and his team placed a chameleon in a tank with a cricket. A glass slide separated the predator from its prey. The chameleon attacked. Its tongue smacked the glass and left spit behind. 

Next Damman measured how sticky the spit was. He had to work quickly so the water in the spit wouldn’t evaporate, or turn to gas. That would change the properties of the mucus—and the results of the test.

Seconds after the chameleon struck, Damman’s team grabbed the mucus-covered slide. They immediately held it at an angle and rolled a small steel ball down the glass, using slow-motion cameras to measure how fast the ball moved. The stickier the mucus, the more it would slow the ball down. 

Damman repeated the experiment several times. He calculated that chameleon spit is about 400 times stickier than human spit. The mucus, he concluded, plays a big role in snagging the chameleon’s prey. 

But spit isn’t the only factor, says Damman. The cameras also showed that the tip of the chameleon’s tongue spreads out when it hits its prey. Damman suspects this makes it even harder to escape the predator’s grasp. 

Next Damman measured how sticky the spit was. He had to work quickly. Otherwise, the water in the spit would evaporate. It would turn from a liquid to a gas. That would change the properties of the mucus. It would also affect the results of the test.

Damman’s team grabbed the spit-covered slide seconds after the chameleon struck. They quickly held it at an angle. The scientists rolled a small steel ball down the glass. They used slow-motion cameras to measure how fast the ball moved. The stickier the mucus, the more it would slow the ball down. 

Damman repeated the test several times. He found that chameleon spit is about 400 times stickier than human spit. He concluded that gooey mucus plays a big role in snagging chameleons’ prey. 

But spit isn’t the only factor, says Damman. The cameras showed something else. The tip of a chameleon’s tongue spreads out when it hits its prey. Damman suspects this makes it even harder to escape the predator’s grasp.