DAVID GREENE, HOST:
In war, there's that old saying - leave no man behind.
UNIDENTIFIED SOLDIERS: I'll never quit. I'll never leave a fallen comrade.
GREENE: Those are Army recruits reciting the Soldier's Creed. Well, it turns out that people are not the only ones who pick up their fallen comrades. NPR's Nell Greenfieldboyce reports on the battlefield heroics of ants.
NELL GREENFIELDBOYCE, BYLINE: These ants live in Africa and they eat termites. Scouts will go out, find termites then return to muster the troops. Biologist Erik Frank says hundreds of ants march out in formation.
ERIK FRANK: Like three ants next to each other in a 2-meter long column. It's very peculiar and it looks like a long snake walking on the ground.
GREENFIELDBOYCE: The ants reach their target and the fighting is fierce.
FRANK: And after roughly 20 minutes, the battle is over. You have a lot of termites lying dead on the ground. And the ants start collecting the termites to return.
GREENFIELDBOYCE: Frank is a researcher with the University of Wurzburg in Germany who works at a field station in the Ivory Coast. A few years ago, he noticed that some of the ants marching home weren't carrying termites, they were carrying other ants.
FRANK: And I was wondering what exactly was going on there. Why were they carrying some of the ants?
GREENFIELDBOYCE: It turns out, they were bringing back the injured, like ants that had lost a leg or two. By marking these ants with paint, Frank learned that in nearly all cases, the ants made a full recovery after recuperating at home. With some practice, they learned to walk with fewer limbs.
FRANK: We saw them again participating in hunts the next day.
GREENFIELDBOYCE: He and his colleagues did some experiments to see what would happen to wounded ants that weren't carried home. These poor ants marched slowly. They fell behind and frequently got eaten by predators like spiders. All of this is described in the journal "Science Advances." And Frank thinks it's not so far-fetched to compare it to rescue missions performed by human soldiers.
FRANK: One big difference I would say, though, is that these ants are not doing it out of the goodness of their heart.
GREENFIELDBOYCE: They're just responding to a chemical signal released by the injured. What's more, they'll only respond to this signal after a battle.
PEGGY MASON: If they encounter that same injured ant on the way to the hunt, they ignore it.
GREENFIELDBOYCE: Peggy Mason studies helping behavior in rats at the University of Chicago. She says unlike rats and us, ants don't seem empathetic. Still, they do get a huge payoff from helping the injured fighters.
MASON: The number of ants that are saved by this behavior is about equivalent to the number of ants that are born each day in that colony.
GREENFIELDBOYCE: And more ants means a bigger, more successful army. Nell Greenfieldboyce, NPR News.
(SOUNDBITE OF HIDDEN ORCHESTRA'S "SPOKEN - KRTS REMIX")
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