Ants have been seen healing wounded trees in Panama—behavior that is believed to have never been observed before.
When holes were drilled into Cecropia tree trunks, the ants emerged from their homes to patch up the wounds, significantly reducing the size of the holes within 2 1/2 hours and leaving them completely healed within 24 hours.
Details of this newly discovered behavior were published in the Journal of Hymenoptera Research. Azteca ants and Cecropia trees are known to have a symbiotic relationship, with the ants using the trees as their homes.
The trunk is like an ant apartment, with more floors added as the tree grows. Inside there are passages, allowing the ants to move around, with small openings letting them go outside. In exchange for their home, the ants defend the Cecropia leaves from herbivores.
William Wcislo, a senior scientist at the Smithsonian Tropical Research Institute, was at home during the pandemic when his twin sons and their friends were out playing with a slingshot and a clay ball. One of them was aiming for the leaves of a Cecropia tree but accidentally hit the trunk, leaving a hole in it.
Wcislo had been tending to the tree as a project. I watched as the clay ball tore gaping holes in the trunk near the top of a small Cecropia tree that I was keeping as a pet during the pandemic, and wondered if the queen ant was injured," he told Newsweek. "I feared my Cecropia-Azteca association suffered a mortal wound. I was flabbergasted the next day when we learned the holes were all patched up."
To work out what had happened, Wcislo, his sons and their friends carried out an experiment. They went around the local area drilling holes into Cecropia trees and charting the response of the Azteca ants. The ants would emerge from the trees, run to the wounded area and start patching it up. The workforce would consist of between seven and 10 ants and they would work from outside the tree and within. They patched the holes with plant fibres that were bound by a liquid, believed to be tree sap.
"Once the hole was sealed they continued to apply plant materials to fill it in completely," the team wrote. "Eventually the plant formed its own scar tissue, which differs in color, texture, and durability. The initial diameter of the opening was significantly reduced by the ants after 2.5 hrs. After 24 hrs ants further reduced the diameter of the opening or these holes were completely sealed."
Wcislo said that while there are many examples of insects and other animals repairing their homes if damaged, only a few of these use other living species as housing. "To my knowledge, this is the first time home repair behavior has been shown to fix living partners," he said.
Not all Azteca ants were found to fix their Cecropia trees and the reason for that isn't known, but it looks like they will repair damage to their plant when it "threatens their brood," Wcislo said. "So my colleagues and I speculate that there were two likely reasons why some did not respond within 24 hours.
"In some cases the holes were drilled into an internode (chamber) near the base of a large tree, while the chambers being occupied by the ants were far up in the top of the tree, so such a wound was less of an immediate threat to the ants. If so, we would predict that if we had given them more time, such colonies would have eventually gotten around to fixing the damage."
Many ants synthesize chemicals with antimicrobial properties. Wcislo said the next step in the research is working out whether they are secreting those chemicals when carrying out their repairs.
"If so, it would be a major benefit to the plant, and then flip from being completely self-serving to an example of mutual aid!"