Sticking your tongue out might seem like child's play, but for chameleons, it's a matter of survival. The color-changing reptiles famously flick their long, sticky tongues to catch insects unawares.
Now, a new study reveals that the tongues of chameleons—particularly the smallest species—can move faster and with more power than anyone thought.
“I didn’t expect to find just how high these values were. It was really a remarkable performance,” said study author Christopher Anderson, a postdoctoral student in vertebrate morphology at Brown University.
The secret to the chameleon’s success, the researchers found, is special elastic tissue in their tongues, which they keep folded up like an accordion. (Read "The Powerful Language of Chameleons.")
When the predators get ready to strike, they contract the muscles in their tongue much as a person pulls back the string of a bow. Scientists call the phenomenon elastic recoil.
Just as the release of the bow string can propel an arrow forward with deadly speed and accuracy, the chameleon releases its tongue muscles, which allows its tongue to spring forward and snare its prey, according to the study, published recently in the journal Scientific Reports.
Anderson, who has been interested in chameleons since childhood, took a closer look at the tiniest chameleon species, which are not as well studied because they're rarer and harder to catch than bigger chameleons.
He wanted to know whether these little guys—which comfortably perch on a human thumb—can propel their tongues as quickly and with as much force as their larger kin. (See pictures: Miniature Chameleons Discovered—Fit on Match Tip.")
On average, a chameleon’s tongue is roughly twice the length of its body. In humans, that would be a tongue about 10 to 12 feet (about 3 to 4 meters) long.
To test his hypothesis, Anderson examined high-speed video of chameleons catching insects. He used previous footage as well as recorded new video of chameleons from zoos, private breeders, and the wild, returning those animals when the experiment was over.
He then took 3000 frames per second—fast enough to measure how quickly the chameleon's tongue accelerated out of its mouth. (Interactive: Explore how chameleon colors can reflect their emotions.)
The results showed that not only did the smaller chameleons perform just as well as their larger counterparts, but in many cases their tongues were actually faster and stronger.
For instance, the tongue of Rhampholeon spinosus, an endangered chameleon from Tanzania and the smallest in the experiment, produced a peak acceleration 264 times greater than the acceleration due to gravity. If it were a car, the chameleon's tongue could accelerate from 0 to 60 miles (97 kilometers) per hour in 1/100th of a second. (See more amazing pictures of chameleons.)
“That’s extremely high. It’s the highest acceleration and power output of all the amniotes, which includes reptiles, birds, and mammals,” Anderson says.
Right on Target
Chameleons also aren't alone in using elastic recoil to their benefit.
Kangaroos use the same principle in their hind legs to hop, and humans unconsciously use it to save energy and prevent physical damage while running. (Also see "Humans Were Born to Run, Fossil Study Suggests.")
Though shooting its tongue out like a bullet takes a fair amount of energy, compared with the cost of moving its whole body to hunt, for a chameleon it’s a good trade-off, Anderson adds.
His many hours spent watching the animals shows that “once they’ve locked onto their prey, they rarely miss.”
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