No soldier left behind: ant armies mirror humans in tending to their injured
ANT armies employ a system of battlefield evacuation and emergency medicine similar to that used by humans, researchers have discovered.
Groundbreaking new observations of mass raids on termite colonies revealed the open wounds of injured ants are swiftly tended by comrades to try to save them for future attacks.
Described in the journal Proceedings of the Royal Society B, the behaviour is the first such example discovered in the animal kingdom.
Entomologists studied more than 200 raids by 16 Matabele ant colonies in Ivory Coast, as well as in laboratories. They witnessed savage battles as 600-strong ant armies carried out coordinated raids on termite settlements in order to drag the insects away for food.
Many were injured in the encounters, yet once carried home, their open wounds were intensively treated by other ants with saliva that may have anti-microbial properties.
Scientists at Wurzburg University calculated that the treatment reduced the injured ants’ chances of dying from 80 to 10 per cent. Last year the same team discovered that injured ants were able to send out distress signals in the form of pheromones, indicating that they need evacuation and treatment.
The new research revealed that only ants capable of rehabilitation and future combat were saved. Those with one or two legs ripped off were routinely carried home, sometimes up to 50m, and often returned to the fray – approximately one third of front-line, or “minor”, ants are amputees. Those who had lost five or six limbs were rarely evacuated. This was not due to the callousness of their comrades, but because the badly injured made it impossible for others to carry them.
The study found that the slightly injured ants were able to tuck in their remaining legs and keep still, whereas those that had lost five or six legs thrashed around wildly.
“They simply don’t cooperate with the helpers and are left behind as a result,” said Dr Erik Frank, who led the research. He told The Daily Telegraph that it was particularly important for Matabele ants to treat their injured because they live in relatively small colonies – roughly 1,000 to 1,500 individuals – and, at ten to 15 ants per day, have quite a low birth rate, meaning that individual ants are valuable.
“Our observations are the first, to our knowledge, to show this type of treatment to be directed towards a high-risk infection zone of an individual open wounds,” said Dr Frank.
“We show organised social wound treatment in insects through a multifaceted help system focused on injured individuals. This was not only limited to selective rescuing of lightly injured individuals by carrying them back, thus reducing predation risk, but, moreover, included a differentiated treatment inside the nest.”
Although not proven, the Wurzburg University team believe the wound healing properties come from the ants’ metapleural and venom glands, which are known to excrete anti-microbial substances.