Elastic Tongues and Sticky Spit

Frogs are often overlooked when people talk about well-equipped hunters. Their long sticky tongues are a deadly tool for hunting prey. Even people might think having a tongue similar to frogs might be helpful.

The biomechanics behind the frog’s tongue are fascinating. Starting with the tongue’s texture, it feels much like a piece of chewed gum. If a person tried to pull their finger back, the bond is sticky enough to follow the path of the finger, at least for a little while. That stickiness is there partially because of the tongues texture, but mostly it is there due to the frog’s saliva.


When it comes to hunting prey, the frogs catch insects by wrapping their long sticky tongues around the insect’s body. This is where their tongues are entirely different from that of a human which can only ever stretch so far because of their stiffness.

Interestingly enough, a frog’s tongue is one of the softest bio tissues known to man. When it comes to squishiness, it is very similar to brain tissue. And if we compare a frog and a human tongue, the human tongue is about 10 times harder.

When it comes into contact with its prey, the frog tongue works similarly to a car bumper as it absorbs most of the force that hits the insect. This is where the saliva comes into play. As it hits the insect, the saliva becomes watery. Because of this, it can penetrate and fill every crevice of the insect’s body. The grip on the insect improves as the amount of saliva covering its body increases. This is similar to a basketball player or football player that handles the ball. Larger hands improve the player’s control of the ball.

When the frog begins reeling the meal back into its mouth, the saliva becomes stickier. When scientists tested different frog saliva, they concluded that it becomes almost as viscous as honey to stick to the prey. This ensures that the insect goes straight into the frog’s mouth. Another interesting fact is that their saliva behaves like a reversible adhesive. The thickness of the saliva also dictates the speed at which it travels to and from the frog’s mouth. This means that frog saliva is a non-Newtonian fluid. Some other members of this exclusive group are soap solutions, butter, jam, ketchup, magma, lava, and many others. A non-Newtonian fluid is one that does not abide by the Newtons’ law of viscosity according to which constant viscosity needs to be independent of stress.

An excellent example of a non-Newtonian fluid is paint. It is wet and thin while it is in a bucket, but as soon as it hits a wall, it thickens up and does not run, but remains wet.

To test these theories, a team of scientists helmed by Alexis Noel observed and filmed a large number of frogs. To check the viscosity of frog saliva, the scientists scrapped the tongues of more than a dozen frogs. This gave them enough saliva to test and examine underneath a microscope. They later compared their findings to earlier research which was done on frogs and even chameleons.

This research also revealed how frogs consume their food. To swallow their food quickly, they have to generate enough speed to make the saliva watery again. They achieve this by pushing their eyeballs back into their heads and into their tongue. The spit “relaxes” because of this eye-popping movement.

The scientists hope that they might be able to create new kinds of adhesives by using this research. The ability to quickly grab items without damaging them is of great use when working with microchips for example. The issue with the frog method is that they might be covered in saliva in the process.

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