A new study from Brown University sheds light on the big power of little tongues that have been overlooked in smaller species of chameleons.
Chameleons are well known for their sticky long tongues, but until a recent study from Brown University, the true power of this awesome ability had been largely overlooked in smaller species of chameleon, which have been found to pack a much more powerful punch than their larger relatives.
"Smaller species have higher performance than larger species," said Christopher Anderson, a postdoctoral research associate in the Department of Ecology and Evolutionary Biology at Brown University.
In the online journal Scientific Reports, Anderson shows that the ballistic tongue projection in a chameleon small enough to fit on a human 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.
According to the university, the study suggests that chameleons have the highest acceleration and power output produced per kilogram of muscle mass by any reptile, bird, or mammal — the second most powerful among any kind of vertebrate (only a salamander outdoes it). The Rhampholeon spinosus is among the most impressive chameleon species, with a tongue that produces a total power output of 14,040 watts per kilogram.
Chameleons 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 and the recoil of those tissues greatly augments what muscle is capable of.
Trioceros hoehnelii was one of the 20 chameleon species in the study. Here tongue extension is shown in very slow motion. Photo credit: Christopher Anderson
Using high-speed photography, Anderson measured the tongue performance of 20 species of chameleon of widely varying sizes. He found 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, Rhampholeon.
The results make physical and evolutionary sense, Anderson said. All of the chameleons have the same catapult-like apparatus for launching the tongue, but proportional to their size, smaller chameleons have a bigger one than larger chameleons.
The evolutionary reason why tiny chameleons are proportionately better equipped for feeding is presumed to be because, like all small animals, they need to consume more energy per body weight to survive. So little chameleons must be especially good at catching their insect meals because their tongues have to burst out unusually fast, far, and often to compete for all their needed nutrition.
For these reasons, Anderson said, it will often benefit researchers to look at the little guys when studying physical performance. Prior studies of chameleon tongue acceleration had measured much lower peak values because they only looked at much larger chameleons.
Based on materials provided by Brown University.