Ants Double Survival Rate with Impressive Jaw Jumps

Ants are pretty clever insects, with researchers recently finding that certain species can even double their survival rate using impressive jaw jumps.

According to a new study published in the journal PLOS ONE, some species of trap-jaw ants use their spring-loaded mandibles to hurl themselves out of harm's way when an ant-trapping predator is stalking nearby. When all other escape methods fail, this trick significantly increases their chances of living to see another day.

The mandibles of the trap-jaw ant, Odontomachus brunneus, can slam shut at speeds over 40 meters per second (144 kilometers per hour, or 89 mph), instantaneously marring a prey insect or enemy ant. They also are used for more routine tasks, such as digging nests or tending to eggs and larvae.

Previous studies have reported that trap-jaw ants sometimes jump with their jaws, "but it was unknown whether this behavior was meant to help them get away from a predator, and it wasn't clear that it actually improved their odds of surviving an encounter with a predator," graduate student Fredrick Larabee from the University of Illinois, who led the study, said in a statement.

But this time around, researchers were finally able to verify that the high-powered mandibles do in fact aid the ants' survival by allowing them to eject themselves from a dangerous dilemma.

Pit-building antilions (predator ants) are one such species that may try to devour trap-ants. The first part of their strategy is to dig cone-shaped pits in the sand and bury themselves at the bottom, anxiously waiting for a victim to fall in.

"If an ant falls into the pit, it tries to run away, but the sand crumbles beneath its feet," Larabee explained. "This pulls it closer to the center of the pit where the antlion is waiting."

Here, the antilion sometimes employs its second strategy, which involves hurling the sand to cause a tiny avalanche, further destabilizing its target. If its prey tumbles to the bottom of the pit, it's doomed, as the antilion can grab it with its strong mandibles.

But, to see how trap-jaw ants fared in this situation, they dropped several of them into antlion pits in the lab to see if, and how often, the ants used the jaw-jumping maneuver to escape from an actual predator. The ants usually tried to run out of the pit, and sometimes were successful. If that strategy failed, they sometimes jumped with their jaws.

"The ants were able to jump out of the pits about 15 percent of the time in their encounters with antlions," Larabee said. "But when we glued their mandibles shut before dropping them in the pits, they couldn't jump at all. It cut their survival rate in half."

Previous research has showed that O. brunneus sometimes adopts an unusual body posture just before jumping, according to the study. It lowers its head, making contact with the ground, and occasionally raises a leg before deploying its mandibles to hurl itself into the air.

"Based on our earlier studies, if the ant was striking a prey object, the distance between the ant and the prey was about the length of the trigger hairs that come off the mandibles," said entomology professor Andrew Suarez, who helped conduct the study. "But when they were jumping off a surface, you would often see the ants put their entire face against the surface, and it was more of a pushing behavior than a striking behavior."

The study shows researchers how a trait or capability that evolved for one purpose can be adapted for different uses.

"In this case, a tool that is very good for capturing fast or dangerous prey also is good for another function, which is escape," Larabee added.

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