While the bite from a puff adder, one of Africa's deadliest snakes, can eventually take down a rhino, the reptiles can only strike within about 5-10 cm (about 2-4 in) in front of it, which is about two head lengths. Researchers at Wits University have discovered that the snake employs a sneaky tactic called "lingual luring" to get its prey inside that deadly sphere.
Most snakes flick their tongues out continuously to smell their environments, and indeed the puff adder is no different. "Puff adders are a perfect example of an extreme ambush forager," says Wits University herpetologist Xavier Glaudas in the video below about the research. "So what they do is they come out, and they look for chemical traces left by prey. And once they've actually located a good spot where there is evidence that the prey was there not too long ago, they will set themselves up and lie in the bush until prey comes by."
But the snakes had a surprise in store for Glaudas and fellow researcher Graham Alexander, who tracked 86 puff adders using surgically embedded radio transmitters and night vision cameras over the course of three years, collecting over 4600 hours of footage.
The pair discovered that tongue of the puff adder has a special secondary function – as a lingual lure. Apparently, the puff adder's tongue can look like a small worm that would make a tasty snack for a frog. When the reptile is lying in wait, it can leave its tongue out for up to 30 seconds and, when a frog comes close enough to get what it thinks will be a bite to eat, it instead becomes the snake's meal.
The researchers say that other animals like egrets, snapping turtles and a few water-based snakes also use lingual luring to bring their food in close, but that this is the first time such behaviour has been found in terrestrial snakes.
What surprised the researchers even more was that the snakes only exhibited this behavior when they were near aquatic environments like the edge of a pond or lake.
"All the cases of lingual luring that we have observed, occurred with frogs, which suggests that puff adders are able to distinguish between amphibian prey and other prey like small mammals," they say.
What's more, the snakes might also have trick tails. Glaudas and Alexander caught them waving their back ends around in a way that might also have been an attempt to lure prey close. The pair say more research is needed to confirm that theory, however.
"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" says Glaudas.