Alexis Noel has done something many of us will never do — scrape spit off of frog tongues — 15 frogs to be exact.
“It was pretty disgusting,” Noel, who is a PhD student at Georgia Tech, told NPR.
But this slimy business was worth it because Noel discovered something incredible. Turns out, frog spit has peculiar physical properties that allow it to transform from a sticky, honey-like substance to a watery form in a matter of milliseconds.
The point? Food. Frogs use their sticky tongues to catch prey — but Noel discovered that the second a frog’s tongue flies out of its mouth in search for a tasty treat, that spit goes from sticky to watery.
That way, when the tongue makes contact, all of its watery saliva flows over and on the insect. Within fractions of second, the spit then turns back into its original sticky form, locking the insect in, and ensuring it doesn’t slip away before the frog can eat it.
That’s a sticky situation that’s almost impossible to escape! The idea is that whenever the tongue experiences a force, that force triggers the transformation.
Now, imagine trying to swallow a piece of broccoli with a mouthful of honey — that’s the challenge a frog faces once the prey is wriggling in its mouth. So, once again, the frog transforms its spit to a watery form by pushing its eyeballs back into its head, placing force on the tongue.
That’s why, if you ever watch a frog eating in slow motion, its eyes appear closed.
Noel is the first to study the acute physical properties of frog spit. You can read more about her work in the Journal of the Royal Society Interface.
Video courtesy of Alexis Noel/Georgia Tech.
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