An amazing new finding by scientists about frogs could totally change how we think about these creatures, and amphibians in general.
Frogs have always been fascinating because of their ability to grab a fly with lightning speed, but it’s the saliva that is the focus of new research. A study has found that the sticky frog saliva is a non-Newtonian fluid, meaning it can remarkably behave as both a liquid and a solid, an unusual combination that enables frogs to catch insects or even small animals incredibly fast.
Frogs grab their prey in mid-air often with this snot-like spit, and then pull it back into their mouth at a force that is 12 times greater than gravity. It enables the frog to catch prey up to 1.4 times its own body weight, which is something no man-made device has ever achieved.
Corn starch is a good example of a non-Newtonian fluid is corn starch mixed with water, which flows like a liquid but turns into a solid when you push on it. Frog saliva is the opposite: the saliva turns to a liquid when the tongue makes contact with the prey, and becomes solid as it fills the cracks and crevices of the creature that has been snared.
“Frogs can capture insects, mice and even birds using only their tongue, with a speed and versatility unmatched in the world of synthetic materials,” the paper’s abstract states. “How can the frog tongue be so sticky? In this combined experimental and theoretical study, we perform a series of high-speed films, material tests on the tongue, and rheological tests of the frog saliva. We show that the tongue’s unique stickiness results from a combination of a soft, viscoelastic tongue coupled with non-Newtonian saliva. The tongue acts like a car’s shock absorber during insect capture, absorbing energy and so preventing separation from the insect. The shear-thinning saliva spreads over the insect during impact, grips it firmly during tongue retraction, and slides off during swallowing. This combination of properties gives the tongue 50 times greater work of adhesion than known synthetic polymer materials such as the sticky-hand toy. These principles may inspire the design of reversible adhesives for high-speed application.”