Some species of trap-jaw ants may use their spring-loaded mandibles to hurl themselves out of harm's way when an ant-trapping predator stalks, according to a study published May 13, 2015 in the open-access journal PLOS ONE by Fredrick Larabee and Andrew Suarez from University of Illinois. This dramatic maneuver doubles the ants' survival when other escape methods fail, the researchers found.
The mandibles of the trap-jaw ant Odontomachus brunneus can whip shut at speeds over 40 meters per second, and are used for capturing prey, protection, and more routine tasks, such as digging nests or tending to ant 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," said Fredrick Larabee.
To see if, and how often, the ants used the jaw-jumping maneuver to escape from an actual predator, the authors of the study dropped trap-jaw ants into antlion pits in the lab. Pit-building antlions catch prey by first digging conical pits in the sand and burying themselves at the bottom of the pit to wait for an ant. Then, an antlion might also hurl sand at the ant, causing a tiny avalanche that further destabilizes the ant, causing it to tumble to the bottom of the pit as the antlion grabs it with its mandibles.
"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 in half their survival rate."
This study may show how a trait or capability that evolved for one purpose can be adapted for different uses, Larabee said. "In this case a tool that is very good for capturing fast or dangerous prey also is good for another function, which is escape," he said.
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Citation: Larabee FJ, Suarez AV (2015) MandiblePowered Escape Jumps in Trap-Jaw Ants Increase Survival Rates during Predator-Prey Encounters. PLoS ONE 10(5): e0124871. doi:10.1371/journal. pone.0124871
Funding: Theodore Roosevelt Memorial Grant from the American Museum of Natural History was awarded to FJL richard-gilder-graduate-school/academics-andresearch/fellowship-and-grant-opportunities/researchgrants-and-student-exchange-fellowships); Libbie Hyman Memorial Grant from the Society of Integrative and Comparative Biology was awarded to FJL; Doctoral Dissertation Improvement Grant (Award Number 1407279) from the National Science Foundation was awarded to FJL ; and National Geographic Committee for Research and Exploration (Award Number 9481-14) was awarded to AVS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.