Researchers study impact, adhesive forces of frog tongues

Every predator needs to catch its prey. We humans use our hands, sharks and wolves use their jaws, but a few animals like frogs use something much stranger: their tongues.

To understand just how frogs snatch their snacks, scientists made the first direct measurements of the amphibians’ tongues in action, according to a study published this week in the journal Scientific Reports.

For the experiment, the researchers recruited the horned frog, a rotund South American amphibian. Horned frogs prefer to hunker down and wait for their prey to wander by before snagging their victims with powerful tongues. Their stationary habits make them easy subjects to use in studies.

Just before mealtimes, the scientists inserted glass plates fitted with pressure sensors into the frogs’ quarters about an inch from their faces. Then they offered up tantalizing grasshoppers behind the glass. When the hungry frogs fired their ballistic tongues (yes, that’s an actual scientific term), the sensors measured the impact force. The tongue prints they left behind gave scientists an indication of the contact area and the amount of mucus on the tongue.

The researchers found that, on average, the adhesive force of the frogs’ tongues exceeded their body mass by 50 percent.

“I knew these frogs could eat large things,” said Thomas Kleinteich, lead author of the study and a zoologist at Kiel University in Germany, “but I didn’t really expect that the forces would be that high.”