If you're an unwary fly, here's a tongue-lashing you won't see coming. A study of chameleons' stretchy tongues has found that smaller species, some the size of your thumb, can hurl their sticky lickers with blazing-fast accelerations – up to 264 times the force of gravity.
That, for the record, is roughly five times as fast as larger-bodied chameleons. The findings, published in Scientific Reports, sheds light on how these animals seem to surpass the limitations of their muscle cells – and why they might need to be so speedy.
While chameleons may be best known for their color-changing abilities, they're also skilled ambush hunters, lying quietly in wait until an unsuspecting bug comes within spitting distance. Then – flick! – its long, sticky tongue flashes out, latches onto the insect and reels the hapless prey straight into its open mouth.
“Personally I’ve been interested in chameleons since I was a kid and always found them fascinating,” said study author Christopher Anderson, a functional morphologist at
Scientists have measured the acceleration of chameleons' tongues before, but they've tended to focus on the larger species, Anderson pointed out. That's partly because it's easier to handle the larger animals, to keep them alive and to measure their movements.
But research has consistently shown that at smaller scales, animals seem to get a bigger energetic bang for their buck – think of tiny planthopper insects that can leap with accelerations of 719 times the force of gravity (719 G) – and Anderson wanted to see if this was the case for chameleons as well.
"Small organisms tend to be capable of greater performance than larger species performing similar movements," he wrote in the paper.
So during the course of various research experiments, the biologist gathered high-speed video of 20 different chameleon species, filming them during feeding events and capturing their lethal tongues in action.
Previous results had found that larger chameleons' tongues could stretch up to twice the length of their bodies, with an acceleration of 486 meters per second squared, or 50 G. But his measurements showed that the smallest species performed best – some could actually stretch their tongues up to 2.5 times their body length and shoot their tongues out at accelerations of 2,590 meters per second squared, or 264 G.
"I expected to find that these smaller species would have higher accelerations and higher power outputs … but I really had no idea how high it would be," he said.
Of course, the animal has a certain advantage in relative tongue length over its more massive peers; for one thing, it simply has more tongue relative to its body length than larger chameleons. But the smaller animals' tongues were actually speedier because they could take advantage of the elastic recoil of their muscle tissue, not just the capability of the muscle cells alone.
"By using elastic tissues like tendons or other tissues that have elastic properties, these animals are able to amplify the performance that they produce during movement," Anderson said. "And that's what's happening during tongue projection in chameleons: They get such high performance because the muscles are loading energy into elastic tissues before they actually project the tongue."
Plenty of animals use these mechanical properties to their advantage, he pointed out – kangaroos, for example, execute their impressive hops thanks in part to their highly elastic tendons.
Why would tinier tongues need to be so lickety-split? It might be tied to the fact that tinier animals actually tend to have relatively higher metabolic rates and need to eat more often than larger peers, Anderson said.
Compared with larger animals, "small animals need to consume a proportionately larger amount of food for their body size to be able to survive," Anderson said. Thus, a snappier and stretchier tongue might be just the evolutionary edge that they need.
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