SAN FRANCISCO (August 15, 2006) – A new record has just been set in the category of fastest self-powered strike—and it doesn’t belong to a cheetah, a lizard tongue, or a Nolan Ryan fast ball. According to new research by California Academy of Sciences entomologist Brian Fisher, trap-jaw ants in the species Odontomachus bauri can make all three of these speed demons seem sluggish by moving their mandibles at speeds of up to 64 meters per second, or 145 miles per hour. These remarkably rapid movements help them to capture prey, eject enemies, and catapult themselves to safety. Fisher’s findings, which will be published in the August 21 issue of the Proceedings of the National Academy of Sciences, will be posted online this week at www.pnas.org. High-resolution images are available at here.
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| Photos courtesy Alex Wild/myrmecos.net |
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Fisher first encountered the phenomenally fast ants in October of 2004 at La Selva Biological Station in Costa Rica, where he was collecting a colony of army ants for the Academy’s exhibit, ANTS: Hidden Worlds Revealed. “I traveled to Costa Rica to study army ants, which build nests out of their own bodies and are fascinating in their own center,” says Fisher, who has collected over 900 new species of ants during his career. “But when I witnessed the remarkable behaviors of the trap-jaw ants, I knew I had just found the icing for the expedition’s cake.” He collected seven trap-jaw ants and brought them back to California, where he worked with Sheila Patek from the University of California, Berkeley and Andrew Suarez from the University of Illinois to study the speedy insects.
The team used a high-speed video camera filming at 50,000 frames per second to visualize the ants’ mandible movements. Motion pictures, by comparison, are typically shot at 24 frames per second. The average duration of a trap-jaw mandible strike was a mere 0.13 milliseconds, or over 2,000 times faster than the blink of an eye. “Ants are similar to human societies in many ways, but they have mastered rapid motion in a way we never can,” says Fisher. “Without the invention of the new technology used in the high speed camera, we never would have discovered the fast world of ballistic jaw propulsion.”
Trap-jaw ants are able to achieve unprecedented strike speeds by utilizing a latch system to release stored energy. Their mandibles are held in a cocked position by a pair of large, contracting muscles in the head. The muscles are sprung when their corresponding latches are triggered. These rapid motions do not simply help the ants capture prey; the extreme accelerations also create strike forces that can exceed 500 times the ant’s body weight, allowing the ants to launch themselves into the air. Simply by snapping their jaws against the ground or the body of an intruder, the ants can catapult themselves out of harm’s way, achieving heights of up to 8.3 centimeters and horizontal distances of up to 39.6 centimeters. If an average human were to travel along a comparable aerial trajectory, these numbers would translate to roughly 44 feet high and 132 feet long.
Fisher and his colleagues identified two different types of defensive propulsion among trap-jaw ants: “bouncer defense” strikes and “escape jump” strikes. In a bouncer defense strike, an ant swipes a large intruding object with its jaws, simultaneously propelling itself away from the intruder. In an escape jump, the ant fires its mandibles directly against the ground, launching itself into the air and remaining airborne for up to 0.27 seconds—long enough to avoid the average lizard’s predatory strike. Bouncer defense jumps tend to cover more horizontal distance, while escape jumps have a more vertical trajectory. “These propulsive behaviors may be especially important given that O. bauri builds nests in leaf litter, rather than below ground,” the researchers write. “Without the subterranean strongholds typical of many ants, temporary escape from predators and ejection of intruders may be essential for this species.”
“One of the most amazing things about these trap-jaw ants is the way they can work together to stay safe,” says Fisher, who documented the cooperative behavior of an O. bauri colony in Costa Rica. “A group of ants can confuse predators by performing multiple, simultaneous escape jumps, creating what I call the ‘popcorn effect.’ The ants can also team up to perform group bouncer defense attacks on large intruders.”
The trap-jaw system in O. bauri ants probably originally evolved simply for high-speed predatory strikes. Now, the versatility of trap-jaw strike functions offers an excellent example of co-option in evolutionary origins.
Fisher is currently studying similar behaviors in other lineages of long-mandibled ants, many of which occur in Madagascar.
If trap-jaw ants take the gold medal for the fastest moving body part in the animal kingdom, who stands below them on the podium? Mantis shrimp, the previous record-holders, can strike at 23 meters per second, while jellyfish can eject stinging spines called stylets at 18.6 meters per second.