Using a high-speed camera capable of filming at 50,000 frames a second, Fisher and his colleagues tracked every detail of the ants' jaw movements.
They found that a trap-jaw ant uses subtle changes in the angle of its head to capture prey, eject intruders, or leap out of the reach of predators like spiders, frogs, and lizards.
In one behavior, called a bouncer defense, the ant charges toward an intruder with its head angled at the animal, striking it with its jaws and tossing the intruder up to 8 inches (20 centimeters) away.
If the intruder is significantly larger than the ant, the ant may instead bounce itself off the intruder, careering nearly 16 inches (40 centimeters) backward.
If a human were to ricochet off Godzilla with the same acceleration, he or she would sail 132 feet (40 meters) away, the scientists estimate.
In a second defensive move, called an escape jump, the ant angles its head down and snaps its jaws into the ground. The force launches the ant straight into the air up to 3.2 inches (8.3 centimeters).
The human equivalent of that launch would send a 5-foot-6-inch (1.6 meter) person bounding over a 44-foot (13.5-meter) building.
"The ant does some interesting body contortions, wiggles its legs in the air, fires its mandibles against the [ground], and launches itself up in the air," said Sheila Patek, a biologist at the University of California, Berkeley, who filmed the ants' aerial stunts.
"It's one of the most ridiculous things I've ever seen an animal doit looks so silly," she says.
(See related photos of army ants.)
But, she points out, the ants' feats are especially remarkable when imagined on a human scale.
"We cannot as humans generate these kinds of accelerations," she said.
"How much force would we have to apply to the ground to achieve that acceleration? It would be 100,000 times the force of gravitythat's basically what ants are doing. Not even the space shuttle gets that many Gs [units of gravitational force]."
Evolution in Ants
Scientists had previously observed the trap-jaw ant's propensity to launch itself into the air when threatened. Some researchers had also estimated the speed of the ant's jaws.
But this study is the first to accurately record both the speed of a strike and the series of body movements behind it, its authors say.
It's also the first to establish that the high-speed motion had evolved a separate function for evading predators.
"This work is significant in the sense that there's something we've seen for many, many years, but it turns out there's a different explanation for why it's there," said Simon Robson, a tropical biologist at James Cook University in Cairns, Australia, who was not involved in the study.
"It shows that when we get the right technology and ask the right questions, we get a very different answer," he said.
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