Frog saliva can be like water, then honey, then water again

JC Torres - Feb 1, 2017, 4:45am CST
Frog saliva can be like water, then honey, then water again

Frogs, among their other amphibious relatives, are popular, or notorious, for their rapid tongues that can seem to catch and hold on to any unwitting victim. But if you think its secret weapon is its tongue, you’d only be half right. Working secretly and almost invisibly is the frog’s reversible saliva. “Reversible” because it can switch from watery fluid to viscous honey-like liquid and back to watery form in a blink of an eye. And that is actually the secret of what makes frogs’ tongues so sticky.

Forget what you’ve learned about frog tongues from cartoons. They don’t wrap around their food to keep them from getting away. While the tongues are indeed rolled inside and roll out when stretching towards a prey, that’s not what keeps the food from slipping off the tongue en route to the mouth.

The magic, or science rather, here is the frog’s saliva. Normally like most saliva, the frog’s saliva is initially watery and very fluid. When the tongue makes contact with an insect, the fluidity allows the saliva to flow into the crevices and holes of the insect. Once inside, however, the saliva switches viscosity and becomes as thick and sticky as honey. This is what keeps the insect from escaping. However, the saliva returns to its watery form once food is inside the mouth, allowing the frog to swallow the insect without choking on its own tongue.

That said, the tongue is also special in that it has been measured to be very, very soft. In fact, it is about 10 times softer than our own human tongues. This, combined with the reversible saliva, is what gives frogs such sticky powers.

Georgia Tech researchers who solved the sticky mystery hope that their study will be more than just interesting trivia. To be specific, the study could hopefully provide some inspiration for materials science and engineering in creating adhesives that aren’t so bound to stiff tapes.

SOURCE: Georgia Tech

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