Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world
Species: Odontomachus bauri
Habitat: forests of Central and South America, in the trees, on the ground – and sometimes in water
If you're an insect, don't mess with the trap-jaw ant Odontomachus bauri. Like other Odontomachus, it uses its massive jaws to attack prey and defend against predators. The jaws are slowly drawn back and held open by catches in its head, springing forward when the catches are released at speeds exceeding 60 metres a second. This is faster even than the fearsome claw strikes of mantis shrimps
"They can literally toss invaders out of the nest with their jaws," says Joseph Spagna of William Paterson University in Wayne, New Jersey.
By striking against the ground, the jaws can also propel the ants through the air. Spagna says the vertical leaps – which, scaled up, would propel a human more than 10 metres into the air – are an escape response. However, sometimes the ants jump unintentionally when their jaws hit the ground.
Spring-loaded gnashers would be enough of a novelty for most creatures. But it now turns out that O. bauri is also a champion swimmer.
Not quite butterfly stroke
Ants have many claims to fame. They are strong, they form super-smart colonies and they make great farmers. One thing ants are not generally renowned for is their swimming.
At least, until recently. In the last decade, biologists have found some ants are surprisingly at home in water. One Australian species, for example, seems to be happy to nest underwater, hiding out in air pockets in mangroves. Fire ants, meanwhile, cope with rising water levels by teaming up to form unsinkable rafts
In the forests of Central and Southern America, though, swimming seems to come naturally to many ant species. Here, there are plenty of rivers and floods are frequent, making death by drowning or predatory fish a threat for any ant that loses its footing as is scurries through the canopy.
Wet behind the antennae
Conservation biologist Steve Yanoviak at the University of Louisville in Kentucky and his student Dana Frederick collected ants belonging to 35 local species and dropped them into water to see how they deal with this occupational hazard.
Ten of them proved to be surprisingly strong swimmers, able to propel themselves along at more than three times their body length per second. For comparison, when Michael Phelps set the Olympic 200 metres freestyle record in Beijing, he was covering almost exactly his standing height each second.
Odontomachus bauri was one of the champions. These ants are around 1 centimetre in length on average, but can swim at speeds exceeding 10 centimetres a second.
Aquatic prowess seems to have evolved multiple times in different lineages of ants, say Yanoviak and Frederick – perhaps to provide an escape route for frequent but unintentional dives into the water. O. bauri will swim towards dark poles rising vertically from the water, which provide a path back to dry land, suggesting they are keen to get out of the water.
You might think that the ants would simply "walk on water", rather than really swimming. But high-speed video shows that the ants do adopt an unusual swimming stroke when they fall into the wet stuff. Their back legs, which provide forwards movement on dry land, are simply held behind the body, apparently to provide stability (see video, above).
They can also steer, by sweeping one set of legs harder than the other. It's "just like you'd steer a rowboat," says Yanoviak.
Journal reference: Journal of Experimental Biology, DOI: 10.1242/jeb.101600
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