Video: Frog tongues stick like Scotch tape

Frog tongues have starred in thousands of slow-motion scenes, all of which end badly for their insect co-stars. Scientists already know a lot about how frogs launch their tongues from their mouths, but they know much less about how the sticky tongues adhere to their targets. Now, research on horned frogs published today in Royal Society Open Science suggests that their tongues are—in essence—muscular strips of tape that use the pressure of the strike to get a tight seal. To study the tongues in action, scientists played a clever trick. They placed crickets behind a glass plane in the frogs’ terrariums, tricking the amphibians into smacking the transparent barrier with their tongues. High-speed cameras rolled as the fleshy appendages slapped the glass and peeled back off. Even though the strike is almost instantaneous, achieving maximum tongue-to-target surface area in just 20 milliseconds, the process of peeling the tongue off is slower—taking more than a second in many cases. As seen in the video, the frog’s tongue flicks out of its mouth like an unfurling roll of carpet, pinning the insect with its mucus-covered underside. Based on how the muscle fibers roll onto their target, scientists say the tongues are basically pressure-sensitive adhesives, similar to Scotch tape and other sticky materials that work best with a little elbow grease. The tongue then flips back into the mouth, delivering a tasty meal to the frog and a death sentence to the insect.