Scientists Discover What Makes Frog Tongues Work So Well – Their Spit

Frog tongues are adept at catching flies and bugs, but what makes them catch these critters so quickly? According to a new study, it all comes down to their sticky spit, and its unusual ability to change from sticky to watery consistency.

The study suggests that frog saliva, which is extremely sticky, is what’s known as a “non-Newtonian fluid,” or a substance that can be both liquid and solid. That consistency makes it easy for frogs to catch their prey with their tongues, and researchers had previously theorized that frogs’ tongues are especially deadly as hunting tools. But in order to prove this, study lead author Alexis Noel had to gather some frog saliva for herself and test the theory.

“I actually got 15 frogs, and scraped their tongues for a couple of hours one night,” said Noel, a Georgia Institute of Technology PhD student, in an interview with NPR, “It was pretty disgusting.”

Quick-switch saliva and squishy tissue combine to help frogs catch prey. https://t.co/VJK0drugfr

— Science News (@ScienceNews) February 3, 2017

Disgusting as it was, it was necessary to prove a theory, and Noel and her fellow researchers then proceeded to analyze the frog spit with high-speed photography and a Rheometer. Innovate Us describes that device as a laboratory tool used to “measure the way in which a liquid, suspension, or slurry flows in response to applied forces.”

The researchers discovered that once a frog’s tongue connects with a fly or a similar small creature, the saliva changes consistency, allowing it to easily catch its prey. Naturally, frog saliva has a thickness akin to honey, but when the tongue catches an insect, the force turns the thick spit into a more liquid, watery form. This liquefied spit then surrounds itself over the bug, trapping it once the saliva thickens once again. That’s when the frog actually begins eating the insect and pulling it into its mouth.

The Los Angeles Times noted that frog tongues, when combined with the animals’ non-Newtonian saliva, are capable of catching insects, or even larger prey such as mice and some smaller birds, five times faster than the average animal. They then take the prey back into their mouths at 12 times greater than gravity – a tremendous amount of force. With all that force, frogs are able to grab prey up to 1.4 times their body weight. According to the L.A. Times, that’s more force than what man-made devices are capable of.

Although saliva is important in helping frogs catch prey, their tongues also do a lot of the work when it comes to holding on to their tiny meals, or big meals, if compared to the size of a frog. The Georgia Tech researchers discovered that frog tongues are among the softest animal tongues out there, and are ten times softer than those of people. That makes them just about as soft as brain tissue, the L.A. Times wrote.

The softness of these tongues make them stretchy enough to extend great distances and catch prey from afar. Taking into account all that her team had learned about frogs, Noel believes that the process is “all very strange” to anyone who’s never watched frogs eat insects.

The discovery may also have some practical applications outside of the animal kingdom. According to Noel, her team’s findings may help researchers develop adhesives that are capable of quickly grabbing microchips and other small and delicate items off conveyor belts without putting them at the risk of damage. Additionally, mechanical frog tongue-inspired tools may be attached to drones, allowing them to catch objects in mid-air, also without risking damage or the chance of the items getting dropped.

[Featured Image by Cameron Spencer/Getty Images]