Some talented humans can fold their tongues into a three-leaf clover, but some bats accomplish an even greater feat: Hair-like structures on their tongue tips stand to attention when they lap up nectar, allowing them to collect more.
This "nectar mop," described in the Proceedings of the National Academy of Sciences, could become a useful model for future medical devices, researchers said.
Scientists have seen many methods of nectar collection. Butterflies suck liquid with a straw-like proboscis, and hummingbirds have forked tongues that help them 'grab' droplets during feeding.
But nectar-drinking bats' secrets remained something of a mystery. More than 500 hairs crowd the tongue tip of Glossophaga soricina, known commonly as Pallas' long-tongued bat. Researchers had figured they served as a way to pick up more nectar, but didn't know exactly how the hairs worked their magic.
"Previously people thought that they were just passive structures," said lead author Cally Harper, a biomechanist at Brown University.
To watch the hairs in action, the researchers filmed the winged mammals drinking artificial nectar from a feeder and watched the playback in slow motion. They found that, as the tongue muscle contracted and lengthened, it would push blood into networks of vessels around each hair, causing it to stand erect. Nectar would get trapped in the gaps between each stiff bristle.
"It just loads nectar into each one of those spaces," Harper said.
This is a blindingly fast process. Blood fills the tongue tip in 40 milliseconds as the bat extends its tongue. It will do this several times over a feeding session lasting 300 milliseconds. That's about the time it takes to blink, Harper said.
Because it's so flexible and it works so quickly, the researchers think this could be useful in making medical devices that work inside the body, Harper said — perhaps, for example, to make a modified endoscope that a doctor could use to look for plaque buildup or cancerous cells.