This Frog Escapes Danger by Running Toward It
Sometimes the best, or even only, solution to a problem is a counterintuitive one. Firefighter Wagner Dodge, for example, once saved himself from a wildfire by starting another fire. A change in the wind had sent the wildfire moving towards him and cut off his escape route, so Dodge lit a match, burned off a large area of vegetation and laid down in the middle of it. When the wildfire reached him, there was no fuel in the patch where his “escape fire” had burned, and it parted around him. Of the 15 smokejumpers in Dodge’s crew who went in to fight the fire, he was one of only three that walked out alive.
The túngara frog, a tiny amphibian found throughout Central America, is no Wagner Dodge, but it too does something pretty surprising when faced with danger: It runs toward the very thing that wants to eat it.
Male túngaras seem to invite trouble. When they’re ready to breed, they get together in groups in ponds or puddles and produce whining calls to advertise themselves to nearby females. The racket naturally also draws the attention of predators like snakes, possums, crabs, spiders, and bats. Túngaras aren’t toxic or camouflaged, and they have no defensive weaponry to use in a fight with a predator, so the only option they have when their mating choruses draw unwanted attention is to flee. Given the range of animals that want to make meals of the frogs, Australian ecologist Matthew Bulbert (whose research we’ve covered before) wanted to know if túngaras use different escape tactics for different predators.
In Panama, Bulbert and his team set up an experiment. They found groups of male túngaras sitting in puddles and got them to start choruses by playing recordings of the frog’s mating call. Once the frogs were singing, the scientists singled one out in each group and faked an attack by a predator. A researcher hiding nearby either pulled a rubber snake towards the targeted frog using fishing line or sent a model of a bat flying over it on a zip line.
When confronted with the snake, the frogs did what the researchers predicted and moved away from the threat, either fleeing in the same direction that the snake was moving or away at an angle. When the fake bat swooped over them, though, the frogs used an escape tactic that surprised the researchers. Bulbert had thought that the frogs would move away from bat like they did with the snake or move perpendicular to its path (as mice often do when escaping from owls). Instead, except for a handful that dove under nearby shelters, all of the frogs moved toward the attacking bat.
Moving toward a predator is a risky move for an animal, but Bulbert thinks that in this case, it may be the túngara’s safest option. A túngara can’t outpace a flying bat, but by hopping toward it, it can out-maneuver the bat. If the frog times its jump right and moves toward a bat as it swoops in to attack, the bat overshoots its target and has to turn around. That lets the frog put plenty of distance between itself and the bat without having to cover a lot of ground. In the time the bat takes to correct its course and come in for another attack, the túngara can escape or find someplace to hide. Bulbert says that the frogs can just freeze and stay silent after the near-miss, too. The bats that hunt túngaras rely on the frogs’ noises to find them because the dense forests they live in cause too much sonic clutter to use echolocation. After making daring leaps at bats, the túngaras can hide from them simply by sitting still and shutting up.