Tiny chameleons deliver powerful tongue-lashings

Chameleons are known for sticking their tongues out at the world fast and far, but until a new study by Brown University biologist Christopher Anderson, the true extent of this awesome capability had been largely overlooked. That’s because the smallest species hadn’t been measured.
“Smaller species have higher performance than larger species,” said Anderson, a postdoctoral research associate in the Department of Ecology and Evolutionary Biology.
In Scientific Reports, Anderson reports that ballistic tongue projection in a chameleon that would fit on your thumb produced a peak acceleration 264 times greater than the acceleration due to gravity. In automotive terms, the tongue could go from 0 to 60 miles per hour in a hundredth of a second, though it only needs about 20 milliseconds to snag a cricket.

Anderson’s review of the biomechanics literature suggests that the motion has the highest acceleration and power output produced per kilogram of muscle mass by any reptile, bird, or mammal and is the second most powerful among any kind of vertebrate (only a salamander outdoes it). The total power output of the plucky Rhampholeon spinosus chameleon’s tongue was 14,040 watts per kilogram.
The secret of chameleons is that they don’t just use spontaneous muscle power to fling their tongues. They preload most of the motion’s total energy into elastic tissues in their tongue. The recoil of those tissues greatly augments what muscle alone can do on the fly — to catch a fly.
Anderson wanted to find the upper limit of chameleon tongue performance. To do that, he gathered individuals of 20 species of widely varying sizes in his former University of South Florida lab. Then he perched them one by one in front of a camera that shoots 3,000 frames a second. For each measurement, a cricket hung off a small dangling mesh to tempt the tongue to emerge. When it did, he could measure the distance the tongue went, the elapsed time, and the speed and the acceleration at any given time.
What Anderson noticed across all his measurements and analysis was that the smaller the chameleon, the higher the peak acceleration, relative power, and distance of tongue extension relative to body size (Rhampholeon spinosus stuck out its tongue to 2.5 times its body length). Larger chameleons produced impressive motions, too, but not compared to their smaller cousins. For example, a roughly two-foot-long species, Furcifer oustaleti, managed a peak acceleration less than 18 percent that of the tiny champ, Rhamp.