Animals

Deadly Snake Lures Frogs With Its Forked Tongue

The venomous puff adder tricks amphibians into thinking its tongue is food, as researchers document the first instance of "lingual luring" in a terrestrial snake.

Africa's deadly puff adder is a serious ambush predator, with fierce fangs and powerful venom. However, it turns out the striking reptile has another weapon. Its tongue is a forked instrument of deception, if you're a frog.

That was the discovery made by a pair of University of the Witwatersrand (Wits) researchers, who recorded and then pored over thousands of hours of video of puff adders hunting. The footage revealed a bit of trickery the snakes were using to draw frogs closer to them – just close enough to strike and snare the poor amphibians.

In a process called "lingual luring," the snakes were essentially fooling frogs into thinking their tongues were something the frog would like to eat - a tasty invertebrate such as a worm. Curious, and hungry, the frogs hopped too close, and then it was too late for them to beat a retreat.

"We know that snakes use their tongues to pick up scent cues in their environment," explained Wits researcher Xavier Glaudas, in a statement. "But these snakes were extending their tongues out of their mouths for up to 30 seconds, which is dramatically longer to what they do when they are just using their tongues to 'smell' their environment."

Although other animals – some wading birds, aquatic snakes and alligator snapping turtles – use tongue luring, "this is the first time that it is reported in a terrestrial snake," Glaudas said.

What's more, only frogs got the lingual luring treatment. Glaudas and research partner Graham Alexander never caught the snakes using the hunting maneuver on other kinds of prey, such as small mammals. That told the scientists that the snakes were making foraging decisions based on the type of potential food within view, which indicated that snakes might have more going on upstairs than typically thought.

"Our study reveals the diverse predatory strategies and complex decision-making process used by 'sit-and-wait' predators, such as ambush-foraging snakes, to catch prey, and indicates that snakes may have higher cognitive abilities than those usually afforded to them," Glaudas and Alexander wrote, in a paper on their findings published in the journal Behavioral Ecology and Social Biology.

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The discovery was "complete luck," according to the humble Glaudas, but it was hard-won luck, as he and Alexander watched the equivalent of nearly 200 days of footage of puff adders stalking prey on the Dinokeng Game Reserve in South Africa. That came after tagging and tracking the reptiles and leaving cameras in place overnight to study the snakes at work.

"We really wanted to have a closer look into the secretive lives of these fascinating animals, and specifically study their foraging ecology," said Glaudas.

Another secret-life behavior the researchers noticed in their study involved the puff adder's tail, which waved and appeared to Glaudas and Alexander to be another luring technique. But, the tail-waving didn't win the snakes any food during filming.

"We suspect that this behavior is also used to attract prey, as it is pretty common in snakes, including adders, but we weren't able to observe prey capture with the videos," Glaudas said.

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