Meet the ant species with a strict “no nestmate left behind” policy.
African Matabele ants regularly risk death and injury while hunting down termites. So when one ant is hurt in the pursuit of prey, its nestmates will carry it to safety, scientists found.
The rescue not only saves the fallen comrade but also helps the entire colony by keeping the population from dwindling, a German research team said in a new study in Science Advances.
While common to nearly every Hollywood war movie, dramatic rescues are extremely rare among predators. Before this study, it wasn’t known that insects even had this rescue reflex, said Erik Frank, a doctoral student University of Würzburg and the study’s co-author.
“We have observed helping behavior vis-à-vis injured animals for the first time in invertebrates,” he said in a news release.
The Matabele ants (Megaponera analis) are common in areas south of the Sahara Desert. Two or four times a day, the ants march from their nests in long lines and raid termites at their foraging sites, killing and hauling their prey back home.
But termites don’t go down easily. Soldier termites fight back, using their powerful jaws to fend off their attackers. They’ll bite off an ant’s leg or antenna if they can, or attach themselves to the ant and weigh it down. It’s truly a fight to the death.
The German researchers found that when a Matabele ant is injured, it will “call” for help by excreting chemicals that alert its mates. The fellow ants scurry to the rescue and carry the wounded ant back to the safety of its nest, where it can recover.
Frank and his colleagues tested this rescue behavior on wild colonies of Matabele ants in the humid savannah woodland of the northern Ivory Coast.
In a series of experiments, they found that ant rescues brought combat mortality down to nearly 0 percent, at no perceived cost to the rescuer. Nearly all rescued ants participated in later termite invasions, sometimes within an hour of the injury. Without the rescues, however, nearly one-third of injured ants died on their way home — most were eaten by spiders.
The German scientists said their experiments can help identify drivers of “selfless” evolutionary behaviors in animals.
Video credit: Frank et al., Science Advances (2017).