When catching crickets, small chameleons can project their tongues farther than the bigger guys (at least proportionately), achieving projection distances of two-and-a-half body lengths from their mouth. And at peak accelerations of 2,590 meters (8,500 feet) per second per second and power outputs of 14,040 watts per kilogram, these tiny lizards demonstrate some of the highest accelerations and power output values for any animal movement known, according to findings published in Scientific Reports this week.
By stretching and rapidly recoiling elastic tissues, animals can release energy more quickly than by contracting muscles directly. This amplifies their power output. While chameleons are famous for sticking out their tongues, the smallest species have often been overlooked. Until now, most studies of chameleon tongue projection examined those with a snout-to-vent length (or SVL, which excludes the tail) that exceeds 100 millimeters.
To see if small chameleon species outperform larger ones during ballistic tongue projections, Brown University’s Christopher Anderson gathered up chameleons of 20 species with varying sizes. Some of the smallest chameleons he examined were the brown leaf chameleon (Brookesia superciliaris) with a 40-millimeter SVL, the bearded leaf chameleon (Rieppeleon brevicaudatus) with a 45-millimeter SVL, and the rosette-nosed pygmy chameleon (Rhampholeon spinosus) with a 47-millimeter SVL. He placed them in front of a camera that shoots 3,000 frames a second, then hung a cricket off a dangling mesh contraption. In total, he analyzed 279 feeding events with 55 different individuals. Turns out, smaller species have a higher performance than larger ones.
The smaller the chameleon, the higher the peak acceleration, relative power, and distance of tongue extension relative to body size. The rosette-nosed pygmy chameleon, for example, stuck out its tongue to 2.5 times its body length. Furthermore, the maximum peak power required to generate these observed accelerations ranged from 1,410 to 14,040 watts per kilogram.
The results make physical and evolutionary sense, Anderson explains in a statement. Like all small animals, tiny chameleons need to consume more energy per body weight in order to survive.
The tongue of a rosette-nosed pygmy chameleon (Rhampholeon spinosus) can reach a peak acceleration that's 264 times greater than the acceleration due to gravity. Christopher Anderson
