A frog found in South America has a tongue so strong, and so sticky, that it can reel in prey up to three times its own weight. Researchers believed frogs used the thick mucus coating on their tongues to seize prey, but a recent study contradicts the idea, suggesting that the slimy organ is actually hard-wired for adhesive contact.
Meet the Ceratophrys, otherwise known as the South American horned frog. Known for preying on organisms of large sizes (in comparison to itself), such as lizards, snakes and rodents, the horned frog can be found in Argentina, Bolivia, Brazil and Paraguay.
To understand exactly how strong the adhesive forces on these frogs' tongues are, researchers collected a few and placed them in front of various prey. Between each frog and its lunch was a glass slide with a transducer that measured the force of the frog's tongue, as well as the speed. Everything about the results was surprising.
Scientists studying biomechanics at the University of Kiel, Germany, published the unexpected results in Scientific Reports on June 12. On average, the adhesive forces of the frogs' tongues were as much as three times the weights of the frogs. One frog even displayed a force of up to six times its own weight, shocking the authors of the study, Thomas Kleinteich and Stanislav Gorb.
Many frogs have a sticky layer of mucus on their tongues, which was previously thought to be the adhesive mechanism by which they preyed. Kleinteich and Gorb found that the strongest adhesive contact between the frog tongue and the glass slide occurred where mucus levels were actually the lowest. This discovery, coupled with the fact that the average tongue impact was less than 40 milliseconds, lead the scientists to believe that the horned frog's tongue contains mysterious gripping mechanics worth studying.
"The experimental data shows that frog tongues can be best compared to pressure-sensitive adhesives that are of common technical use as adhesive tapes or labels," says Kleinteich and Gorb in their published study.
The University of Kiel group plans to push studies into a bioengineering phase to find more efficient ways of making useful adhesive products. Thus far they have studied beetle feet and gecko skin to unravel nature's sticky secrets. As the first researchers to ever measure the stickiness of frog tongues, Kleinteich and Gorb are confident their future findings will be exciting and beneficial.
