Study explains Secret behind Frog's Super-Sticky Tongue
A new study explains how horned frogs use super-sticky tongues to capture large prey.
The horned frogs (Ceratophrys sp.) eat small insects as well as lizards, other frogs and even mice. Zoologists knew that the frog's tongues were good adhesives, but weren't sure how the frog managed to pull large creatures.
In a study, conducted at the Christian-Albrechts-Universität-Kiel in Germany, Thomas Kleinteich - a biologist - and his colleagues made frogs catch prey in a laboratory.
The team placed horned frogs in front of a glass slide and placed a cricket on the other side of the glass, BBC reported. The glass side was attached to a transducer that measured the force with which the frog's tongue attacked the prey.
Researchers then looked at how much mucus the frog left on the glass.
"It's the first time we've ever measured how well frog tongues stick," said Dr Thomas Kleinteich, to BBC reported.
To their surprise, researchers found little mucus on the glass. Previous assumption was that the mucus acts as super-glue that sticks to the prey. The current study found that it is a combination of both strong smack produced by the tongue and mucus that helps the frog hunt large creatures.
"The combination of highly dynamic tongue projection, high adhesive strength, and potentially the versatility to attach to structurally and chemically variable surfaces (e.g. fur, feathers, cuticle, etc.), makes frog's tongue a unique example for biological wet adhesion," the researchers wrote.
Gecko feet, another sticky marvel of the animal kingdom, have more adhesive strength than a frog's tongue. Researchers found that frogs just produced one-fifteenth the adhesive strength generated by gecko feet. However, during meal-time, frogs can generate strong adhesive forces, which are 1.4 times their own body weight, National Geographic reported.
"Translated into human dimensions," Kleinteich said, "that would be an 80-kilogram [176-pound] person lifting 112 kilograms [246 pounds] just by using his or her tongue. And they do this within milliseconds" of making contact, according to National Geographic.
One particular amphibian in the study generated three times stronger adhesive force, BBC reported.
According to researchers, frog's tongue could be described as pressure-sensitive adhesives. These adhesives, such as sticky tape and labels, use a combination of contact surface as well as glue.
Studying sticky systems allows material scientists create better adhesives. Recently, The Defense Advanced Research Projects Agency (DARPA) created a pair of paddles that resemble gecko's feet and allow humans climb walls.
The study is published in the journal Nature.