Typically, the ants completed the repair work within 24 hours.

Researchers write that in the Journal of Hymenoptera Research. The discovery was made more or less by accident, after student and co-author of the research paper Alex Wcislo shot a 9 millimeter ball through a branch of a large Cecropia tree with a catapult. When he returned to the tree 24 hours later, the hole was completely closed. It turned out to be the work of ants from the Aztecagender and prompted the student to — aided by classmates and a biologist from the Smithsonian Tropical Research Institute in Panama – to start an investigation into this remarkable phenomenon.

Symbiosis

That Azteca-ants and Cecropiatrees have a special bond has been known for much longer. The two completely different organisms live in symbiosis: the tree provides the ants with food and a place to live, and in return the ants protect the trees – or more precisely, their leaves – from herbivores.

filling cavities

But it doesn’t stop there, that’s how the young researchers in the Journal of Hymenoptera Research to conclude. Because even when the tree is seriously injured, the ants come to the rescue. The researchers reached this conclusion after they drilled 22 holes in different Cecropia-bore trees. And 14 of them were killed by ants belonging to the species within 24 hours azteca alfari repaired.

The repair work was actually used almost immediately, the researchers write in their article. Only when the hole was near a brood did the ants first take the time to move that brood. But otherwise they rushed straight to the hole. They then used a mixture of plant fibers and an unidentified liquid — possibly plant sap that drained from the wound — to plug the hole. “Typically, a few to about 10 ants worked to repair the hole,” the researchers write. Some did it from the outside and some from the inside. “Once the hole was closed, they kept adding plant material to fill it in completely.” Usually the holes were quite smaller after 2.5 hours and usually the ants completed the work within 24 hours.

Own sake?

And with that, the researchers seem to have found an additional task that ants perform in the service of their host. But appearances can be deceiving, because the ants probably carry out the repair work mainly for themselves, the researchers say. They point out that the ants themselves naturally make small holes in the hollow twigs or stems in order to then lay their eggs in them. However, those holes are also neatly closed afterwards (see the video below). This may prevent the offspring from having to deal with, for example, predators and pathogens. The same reasons may prompt the ants to plug the holes made in the stems by others; they want to prevent pathogens from reaching the brood through those holes.


The queen ant makes a hole in a hollow stem of the Cecropia tree and then crawls into it to lay eggs. She closes the hole behind her using the spongy material she pulls from the inner wall of the stem. She takes care of the larvae until the first workers see the light of day and the carefully closed hole opens again.

If that hypothesis is correct, it may also partly explain why 8 of the drilled holes were not closed. “We suspect that colonies that didn’t fix quickly had their broods higher up the tree, so minor damage to stems they had long ago left posed minimal risk to them.” As a tree grows, the ants move their broods further and further upwards and the lower stems are no longer inhabited by queens and their broods. In addition, there may also be other factors that help determine whether an ant colony performs repair work or not, such as the size of the colony may also play a role.

Also beneficial for the tree?

The fact that the ants mainly want to save their own skin by closing the holes does not of course mean that the tree is in no way benefited by it. The tree can take care of itself just fine, the researchers write; it can close the hole itself. However, a repair carried out by ants can be beneficial. “We cannot rule out the possibility that the ants add glandular secretions and we know that some ant species may be antimicrobial. If that’s the case, the trees could benefit from the ants’ behavior.”

That leaves the question of how the ants have become such good repairmen. Because the holes that the researchers shot and drilled in the trees are different and are repaired differently than the holes that the ants make in the stems themselves. “Slingshots operated by teenagers are a new threat to the ants’ shelter,” the researchers admit. “But in nature, the Cecropiatrees regularly visited by three-toed sloths and their sharp toenails sometimes penetrate the wood.” The resulting holes are probably smaller than the holes the researchers made, but the ants may have learned the repair work thanks to the sloths and now simply applied it to a different kind of hole.

Either way, it’s fascinating. “The ants not only ensure that their host (by the actions of herbivores, ed.) suffers as little damage as possible,” the researchers say. “But when damage occurs, it is also repaired – albeit for their own benefit.”