Matabele ants, which are native to sub-Saharan Africa, send out several raiding parties every day to hunt down their favorite meal: termites. But with their powerful jaws that can easily tear off tiny ant limbs, termites make for a dangerous snack. Matabele ants regularly sustain injuries during raids, and as Jasmin Fox-Skelly reports for New Scientist, a new study has found that wounded critters are often given life-saving treatment by other members of their colony.
In 2017, myrmecologist Erik Frank observed matabele ants carrying their injured comrades off the battle field and back to the nest. He wanted to know what happened once the ants moved underground, so, as Christie Wilcox writes for National Geographic, he and a team of researchers at the Comoé National Park Research Station in Côte d'Ivoire created artificial nests topped with a clear cover that allowed them to peer inside the dwellings. As the researchers report in Proceedings of the Royal Society B, they observed a veritable ant hospital—and were able to record the first evidence of a non-human animal giving medical care to others.
According to the study, healthy Matabele ants held the injured limbs of their nest-mates and intensely licked at their wounds for up to four minutes at a time. Scientists aren’t quite sure why the ants do this. “We don’t know if they are just removing dirt from the wound or applying an antimicrobial substance to fight off an infection,” Frank tells Ian Sample of the Guardian. Even so, the behavior appears to be life-saving. Eighty percent of ants injured deliberately by researchers died when they were kept on their own. But 90 percent of ants that received just an hour of care from their nest-mates survived.
Frank’s earlier research revealed that when Matabele ants are wounded, they release a “help pheromone” that signals their distress. But the more recent study found that matabele ants have other ways of letting their buddies know that they need help. If they were on their own, many wounded ants proved capable of getting up by themselves and speeding toward the nest. When other ants were around, however, the injured moved slowly and stumbled, possibly in the hopes of being picked up.
Mortally wounded ants—which had five of their limbs crushed, as opposed to one or two—were not picked up by their nest-mates, even when the researchers covered them in the "help pheromone." But this wasn't because their nest-mates didn’t try. When healthy ants arrived on the scene to rescue their dying comrades, the wounded ants flailed around, making it impossible for them to be picked up.
“In humans in cases were a triage system is necessary, the decision [about] who will receive help is made by the doctor: a top-down regulated system,” Frank, who is now a postdoctoral fellow at Switzerland’s University of Lausanne, tells Wilcox of National Geographic. “In the ants it's exactly the opposite.”
The way that ants “triage” is pretty logical, if a bit mercenary. There’s no use wasting time and energy on nest-mates that will not survive their injuries. But with assistance and treatment, lightly-wounded ants can recover and continue to assist on raids. In fact, Frank and his team discovered that one-fifth of the ants’ raiding parties were comprised of ants that had lost a few limbs.
The new research raises plenty of questions about Matabele ants: How do the critters locate their nest-mates’ injuries? How do they know when to stop treating wounds? Do other ants engage in similar rescuing behaviors? Researchers hope to conduct further investigations, but for now, the study offers a glimpse into the complicated workings of social insect colonies. As Frank tells Sample of the Guardian, “you can get very complex and sophisticated behavior without any need of cognition or knowledge of what you are doing.”