Monday February 13, 2017 Q&A

Frogs are remarkably fast and efficient at catching prey with their tongue. What’s their secret?


1 Their saliva changes viscosity in the blink of an eye

2 The tip of their tongue has superfast muscle fibers

3 They hypnotize their prey with their eyes

Question related image
Correct answer: 1, their saliva changes viscosity in the blink of an eye. We’ve all seen it before: armed with only a soft, sticky tongue, frogs achieve a level of accuracy that’s enough to turn any marksman green with envy. It’s their signature move. Flies may, well, fly circles around humans, but they stand no chance against frogs. Recently, a team of researchers from the Georgia Institute of Technology in the United States improved our understanding of this primitive hunting technique. First of all, frogs strike incredibly fast – it takes them only seven hundredths of a second to snatch their prey. That’s five times faster than the blink of an eye. Next, their tongue is composed of one of the most flexible and elastic biological substances in the world. It's like a super shock absorber: when a frog strikes, its tongue engulfs the insect and absorbs the force of the impact. If that didn’t happen, the fly would be flicked away like a football. The tongue’s elasticity also increases the surface area that comes into contact with the fly, which further improves the tongue’s grip. The frogs’ other secret is the saliva on their tongue, which changes viscosity in response to the forces acting on it. The saliva is very thick when frogs launch their attack, liquefies at the moment of impact, and then thickens again once back in their mouth. The researchers liken it to painting a wall: the paint is liquid when applied, so it fills in all the nooks and crannies, but then quickly hardens so that it doesn’t drip, even from the ceiling. But there’s one problem: if the frogs’ saliva gets sticky again back in their mouth, how do they swallow the insects they catch? Lacking a swallowing mechanism, it turns out that they use their eyes, which are located right beside their mouth cavity. By retracting their eyeballs, they exert the pressure needed to liquefy the saliva again. This lets the frogs enjoy their well-earned meal. More information: Article in The Royal Society