Frog’s Tongue is Sticky due to Saliva that Switches from Thin and Watery to Thick and Sticky to Catch the Prey

The most amazing feature of a frog’s tongue is its stickiness, which allows the amphibian to catch passing insects without moving an inch towards them. There are more than 4,000 species of frogs and toads which can catch their prey faster than a human can blink. The tongues of frogs are so sticky that they can catch prey heavier than their own weight. Now, a new study has now revealed the reason why frog’s tongue is so sticky.

According to researchers, frog’s tongue is sticky due to the saliva that can switch between thin and watery (when the tongue hits the prey) to thick and sticky to create an inescapable trap for the insect.

“For frogs, saliva seeps easily when it hits the insect, then thickens up during retraction. It’s really an incredible process,” explains Alexis Noel, the first author of the paper. Noel is currently pursuing a mechanical engineering PhD program at the Georgia Institute of Technology in Altlanta.

According to Noel, frog’s saliva displays the unique feature due to shearing forces working in unaligned directions, thus making the saliva a non-Newtonian fluid, similar to custard. Researchers found that a globule of frog spit, when stationary on a surface, has a thick snotty consistency. However, it becomes thick when the frog lashes its tongue at high speed against its prey, filling all the insect’s crevices.

“Then, when the tongue snaps back, the saliva changes and becomes more viscous –thicker than honey, actually – gripping the insect for the ride back,” said Noel.

The frog then rubs its tongue on the inside of its mouth and swallows the insect.

The study also reveals that frog’s tongue is extremely soft, about 10 times softer than a human tongue, and as soft as brain tissue. This softness of tongue further enhances the stickiness of the tongue.

The researchers believe practical applications for the discovery may be found in near future, such as drones fitted with artificial frog tongues to grab objects in flight.

“We’re hoping to look into reversible adhesives,” said Noel.

The detailed findings of the study have been published in the Journal of the Royal Society Interface.