Hunt Like a Chameleon

Scientists unravel the secrets of a perfect reptilian predator

January 16, 2017

By Katherine Tweed

When a chameleon spots a tasty cricket nearby, it doesn’t race over to grab it. Instead, it shoots its tongue out faster than a fighter jet taking off. Scientists have known about the incredible speed of a chameleon’s tongue for a long time. But how the tongue actually holds on to the prey in order to reel it in has been the real mystery—until now.

Chameleons live in many parts of the world, from Spain and Sudan to Madagascar. Most species hunt insects up to one-third their size. The largest ones can capture small birds.

“This is probably the ultimate predator,” says Pascal Damman, a physicist at the University of Mons in Belgium. Not only are their tongues well designed for catching dinner, chameleons also have an incredibly strong grip and eyes that swivel to see in any direction. Of course, they can also change color to hide as they lie in wait for their next meal.

A team of physicists and biologists recently discovered that the secret to the chameleon’s success is its saliva. The chameleon uses a tiny bit of its incredibly sticky spit at the tip of its tongue to capture prey. It’s about 400 times stickier than human saliva, and thicker than honey. The sticky saliva grabs on to prey and slows it down, says Damman.

Before making this discovery, Damman had never studied chameleons or done any research on animals. He spends most of his time on physics problems involving how soft, squishy objects like plastic ribbons move. One day, a biologist came by his lab to ask for his thoughts on the chameleon conundrum, and Damman was suddenly hooked.

Because chameleons use such a small amount of saliva for hunting, it was impossible to collect large amounts of it for testing. Instead, the scientists measured just a little bit of it, then used mathematical models to understand its sticky force. “Without math, you can’t solve anything,” says Damman.

Chameleons may have been Damman’s first foray into animal research, but it’s not his last. He’s now investigating how bees are able to capture a flower’s nectar.

SOLVING A SYSTEM BY GRAPHING

Two or more linear equations are called a system of linear equations. The solution to a system of equations is the point where the lines intersect. You can solve a system of equations several ways. One method is to graph both lines and find the coordinates where they intersect.

The questions below show the linear equations representing the path of the tongues of different chameleon species and the path of each one’s prey. Solve each system on its own graph to see where the chameleons snag their meals. Then check your solutions.