It’s a question that’s puzzled amphibian enthusiasts for some time: why can certain species of frog appear to walk on water, or even leap from its surface as if jumping from land? New research published in The Journal of Experimental Biology may hold the answer.
According to the researchers—from Virginia Tech and Mount Holyoke College in the U.S.—frog species in the Ranidae family, including cricket frogs, appear to “skitter,” insect-like, across the surface of the water, moving in a side-to-side motion. Stranger still, they have the apparent ability to jump from the surface of the water and land again without sinking. How? Do certain species of frogs have specialized leg anatomy that prevents them from sinking while in motion?
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To get to the bottom of this mystery, researchers studied northern cricket frogs. One of the smallest frogs in North America, these amphibians are found in most areas of the U.S. and in small pockets of Canada. The scientists used high speed videography to film frogs, released in a 20-gallon tank, below and above the water. (High speed videography records an event at a high-frame rate, but slows it down on playback. In this case, the cameras shot up to 500 frames per second.)
The researchers watched the recordings—slowed down to a fraction of their original speed—hoping they could illuminate how the frogs’ leg movements allowed them to travel across water like a stone that’s been skipped across a lake. Except…the videos didn’t show that at all. The reality? Instead of skittering like a bug, the frogs were “porpoising” like a dolphin. “Contrary to expectations based on anecdotal knowledge, we found that cricket frogs do not maintain an above-surface position throughout the locomotor cycle,” said the researchers. “Instead, the frogs are completely submerged during both the launching and landing phase of a jump cycle.”
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So, turns out, if you see a cricket frog running and jumping on the surface of the lake, it’s all a skillful deception, a little like a magic trick. The frogs are moving so fast that your eyes can’t correctly identify what’s happening.
Huh. That’s disappointing. Well, not really. The cricket frogs in the study were able to perform as many as eight jumps in a row, with each complete jump cycle taking less than one second. This is impressive. And it’s a discovery that has implications for science—the robotics field, in particular.
So, cricket frogs can’t walk on water. But they can kind of…belly flop through it. That’s still cool, right?
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