Great escape: ant uses spring-loaded jaws to jump away from predators
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Version 0 of 1. They have the fastest bite in the animal kingdom, but the trap-jaw ants’ explosive mandibles also serve a less violent purpose, according to scientists. The insects regularly use their spring-loaded jaws to perform “escape jumps” when face-to-face with a predator. The ant’s jaws open to 180 degrees before snapping shut at more than 60 metres per second (140 miles per hour). The whole action takes place 2,300 times faster than the blink of an eye. Previously, the insects had observed jumping with their jaws, but until now it was not clear whether this was an intentional exit strategy or they were accidentally sending themselves flying while trying to land a snap on an aggressor. Fredrick Larabee, an entomologist who carried out the work at the University of Illinois, said: “It was unknown whether this behaviour 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.” To investigate, Larabee and colleagues placed the trap-jaw ant (Odontomachus brunneus) head-to-head against the pit-building antlion, one of its natural predators. The antlion’s hunting strategy involves digging a conical pit in the sand, burying itself at the bottom and waiting for a victim to fall in. They throw sand at their target, causing tiny landslides, hurrying the progress of their victim to the bottom of the pit, where they are dragged beneath the surface and consumed. Larabee dropped trap-jaw ants into antlion pits in the lab to test whether they used the jaw-jumping manoeuvre to flee. The ants normally tried to run up the sides of the pit – sometimes successfully – but if that strategy failed, they jumped with their jaws. “The ants were able to jump out of the pits about 15% of the time in their encounters with antlions,” Larabee said. When the scientists glued the ant’s mandibles shut before dropping them in the pits, they couldn’t jump at all and it cut their survival rate in half compared to control ants who had glue applied without it closing their jaws. Larabee acknowledges that the experiment belongs to the scientific school of “doing silly things to animals to figure out what they’re doing”. But simple experiments such as these can give real insight into animal traits and why they evolved in the first place, he added. “As an entomologist it’s almost a rite of passage to throw insects into these things [antlion pits] and watch them get eaten,” said Larabee. “They’re such charismatic creatures.” The enormous power of the trap-jaw ant’s mandibles comes from a pair of large, contracting muscles in the head. The muscles work on a latch system, which allows all their stored elastic energy to be released in one go – like a crossbow being fired – generating an explosive force. Other studies by the same team also suggest that the accidental jump is distinct from the “escape jump” because in the latter case the ants adopt a different stance, lowering their head and raising one leg before making the snap to direct more of their movement vertically. Prof Andrew Suarez, a co-author and head of animal biology at the University of Illinois, said: “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 behaviour than a striking behaviour.” The study is published in the journal PLOS One. |