Move over, ant farms -- ant hospitals are where the real action is. Scientists studying the behavior of African Matabele ants in Ivory Coast have found that the insects act like paramedics in a crisis, triaging and treating the wounds of their injured peers.
The discovery, described in the Proceedings of the Royal Society B, documents a surprisingly sophisticated system that helps determine which ants are most likely to survive a combat injury.
Ants are often thought to live in systems where the life or death of an individual worker doesn't matter much. That's because many ant species live in giant colonies whose workers usually have very short life spans relative to the queen, and because the queen can lay eggs for new workers at a fast rate.
"The benefit from helping injured ants in this scenario is small, because replacing them should be easier," the scientists wrote. "At the same time, if injuries were mainly fatal, the benefit of a rescue behavior focused on injured individuals would again be marginal."
That's not the case for ants such as Megaponera analis, which venture out in raiding parties of 200 to 600 individuals, attack termites and carry their unfortunate prey back home. The hard-headed termites don't go without a fight, though. Many invading ants lose legs or end up with termite mandibles dug into their bodies.
Surprisingly, the returning ants don't abandon all their casualties: Before returning home they look for their injured comrades, which send out a "distress signal" pheromone. Within 24 hours of being taken back to the nest and treated, maimed ants can switch to a four-legged or five-legged gait that lets them run almost as fast as their six-legged peers.
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Because these injured ants can still do almost the same things as their healthy peers, it makes sense to bring them home and treat them -- especially since roughly a third of the small-sized ants that run these termite raids have lost a leg at some point in their life.
Gravely injured peers are usually left behind. And open wounds from severed legs could easily become infected and spread disease in the ant nest, given that there's a lot of interaction and very low diversity within a single colony.
So for this paper, scientists from Universitat Wurzburg in Bavaria, Germany, wanted to learn how the ants providing medical aid make decisions about which wounded ants to save -- or whether it's their decision to make at all.
"While the benefit for the colony of leaving behind fatally injured ants is clear, the mechanism that regulates this behavior remains unknown: is the decision to rescue made by the helper or the fatally injured ant?" the study authors wrote.