Dr. Brian Fisher of the California Academy of Sciences finds
Trap-jaw ants in Costa Rica, clocks mandibles at 145 miles per hour
|A trap-jaw ant about to strike. (High-resolution images are available here.)|
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 right,” 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.”
|A trap-jaw ant captures its prey. (High-resolution images are available here.)|
The Need For Speed
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.
Dr. Brian L. Fisher
Brian L. Fisher, Chairman of Entomology at the California Academy of Sciences, is an ant systematist who specializes in the large-scale discovery, description and naming of African and Malagasy ants. In the past few years, he has discovered over 900 new species of ants in Madagascar alone, including the Madagascar Dracula Ant – a find that is helping scientists to understand the evolution of ants from wasps. Fisher also maps diversity patterns and uses them to instruct land management and conservation decisions. His inventory work in Africa and Madagascar demonstrates the feasibility and challenges of conducting global biodiversity inventories. He is currently developing technologies for collaborative taxonomy, which will accelerate the process of identification and description of new species with products accessible across a broad community of users (see www.antweb.org). He also has particular interest in the evolution of the early lineages of ants and is dedicated to instructing the next generation of ant systematists.
Education and Research at The California Academy of Sciences
The Academy is an international center for scientific education and research and is at the forefront of efforts to understand and protect the diversity of Earth's living things. The Academy has a staff of over 50 professional educators and Ph.D.-level scientists, supported by more than 100 Research and Field Associates and over 300 Fellows. It hosts ten scientific research departments in the fields of anthropology, aquatic biology, botany, entomology, geology, herpetology, ichthyology, invertebrate zoology, mammalogy and ornithology.
Mandible Strike Video: Trap-jaw ants, Odontomachus bauri, 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. The mandibles of a trap-jaw ant are filmed at 50,000 frames per second in this clip. The video is being shown 1,667 times slower than real time.
Escape Jump Video: When trap-jaw ants fire their speedy mandibles, the forces generated are strong enough to propel their bodies through the air. In an "escape jump," shown here, the ant's trajectory is directed upward. In a "bouncer defense jump," by comparison, the ant clears a greater horizontal distance. The video is being shown 100 times slower than real time.
Bouncer Defense Video: In a bouncer defense strike, shown here, the trap-jaw ant swipes a large intruding object with its jaws, simultaneously propelling itself away from the intruder. The video is being shown 100 times slower than real time.
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The California Academy of Sciences is home to Steinhart Aquarium, Morrison Planetarium and the Kimball Natural History Museum. The Academy is in the midst of an extensive rebuilding project in Golden Gate Park. Pritzker prize-winning architect Renzo Piano is designing the new Academy, which is scheduled to open on September 27, 2008. www.calacademy.org (415) 379-8000.