We've heard of army ants, but that attribution comes mainly from their raiding and foraging behavior. The African Matabele ant (Megaponera) is soldierly in a different manner: it rescues its wounded, carries the capable back to their nests, and administers treatment.
A Matabele ant treats the wounds of a mate whose limbs were bitten off during a fight with termite soldiers. Credit: Erik T Frank (source)
This amazing instinct has not been seen in any other animal species. It was recently discovered by Erik T. Frank, Marten Wehrhan, and Karl Eduard Linsenmair from Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany.
Matabele ants are termite eaters in Sub-Saharan Africa. They are named after the Mantabele (Ndebele) tribe of South Africa, known for their fierceness. The Matabele ants hunt a ferocious tribe of termites who fight the ants by biting off their legs with their strong jaws.
Generally, if the wounded soldiers have one or two legs missing, his mates will try to rescue him, but if there are 4 or 5 legs missing, the wounded will be left to die.
The most interesting part of this study is how the rescue ants, "the Red Cross," know which ants to rescue.
The wounded ants alert their colonies by releasing a scent. The scent actually tells the tribe that an ant is salvageable and only those ants which can stand by themselves release this scent as a cue to their tribe.
Here's how the scenario plays out:
If an ant is wounded, its first step is to try to get up. If he can get up, he will release the scent and he will walk very slowly, alerting his colony that he is injured. When found, he will fold his legs into his body so that he is easier to carry. Once back in the nest, the other ants will lick the wounds repeatedly.
"We suppose that they do this to clean the wounds and maybe even apply antimicrobial substances with their saliva to reduce the risk of bacterial or fungal infection," researcher Frank explains.
But when an injured ant is too injured to be rescued, it will not release the special scent. Instead it will signal to his army buddies to leave him alone. He will thrash around and "lash out wildly" if another ant tries to help him... So this ant will be left to die.
It's nature's way of allocating resources.