Ant With Lightning Jaws Makes World's Fastest Strike
for National Geographic News
|August 21, 2006|
A new speed record has been set in the animal kingdom, scientists say.
A species of tropical ant snaps its jaws together at an astonishing 145 miles (233 kilometers) an hour, using the force of that motion not only to capture prey but also to catapult to safety, according to a new study.
The study establishes that the ants have adapted a structure normally used for feeding for a completely different purpose: propulsion.
Trap-jaw ants have the fastest self-powered strike in the animal kingdom, outpacing speed demons like the whip-fast chameleon.
(Read "'Catapults' Give Chameleon Tongues Superspeed, Study Says" [May 2004].)
"In terms of basic engineering, ants have solved this incredible problem of producing force using very simple structures at a very small scale," said Brian Fisher, co-author of the study and curator of entomology at the California Academy of Sciences in San Francisco.
"They use their mandibles [jaws] to feed, of course, but they've also turned this feeding mechanism into a mechanism to escape predators," he added.
Fisher and his colleagues published the study today in the early online edition of the Proceedings of the National Academy of Sciences.
The study clears up a basic question about this species: Why do these ants have jaws that can generate such extremes of force and acceleration?
"It's not like they're trying to catch a cricket that's so fast they need this high speed, so there's a conundrum there," Fisher said.
"Now we've found there's a dual function. It may be that a very important aspect of their life history is escaping from an enemy."
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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