I live in a fairly dry farming district, and we have many really, really large and complex colonies of meat ants, also called gravel ants, endemic to Australia (Iridomyrmrex purpureus). They are usually in gravel mounds with a foraging path stretching up to half a kilometre from the mound into the surrounding area. Over the last four weeks, a small collection of gravel ants has appeared on our back concrete path, along one edge or in small clusters, apparently just going around in circles and bumping into one another, communicating, then moving on, although remaining in the same self-imposed space. If one is accidentally killed by me or my dogs, it is removed. They aren't particularly interested in anything going on around them or walking or standing near them. They just constantly churn. There is nothing on the path to attract them. As the sun goes down, they disappear and I have not been able to ascertain where they go.

 

I would really like to understand this behaviour, and was wondering if anyone in this forum had any idea about what they could be doing. I have posted a short video clip and a couple of images.

 

Thank you for any thought you can give to this.

Edited by ucaneverdonly1thing, December 5 2018 - 7:28 AM.

G'day,that is a bit weird isn't it? I've seen ants do that before but I've just assumed that something has been there before that they are "smelling" whatever lingers. I wonder if it's where a dog (or person) has peed? Or if something died or was killed there? Weird behaviour for sure.
Two things, it's good to have another Aussie on the forum, and unfortunately you've posted in the wrong section, admin will probably move it I guess.

Hi. Thanks for the reply. I did get a bit confused about where to post and would like to go to the right place!

 

I see that you are also in South Australia. Interesting coincidence.

 

I could understand my ants' behaviour if there were something on the edge of the path, but, even after I've hosed it down, as soon as it dries this little group returns and mills around some more. They are not fighting, but are certainly checking one another out.

There's multiple reasons that could explain this.

The area might be a borderland between two colonies so the colonies present put up guards to enforce their territorial claims - ant species with colonies that frequently clash into each other have often found ways to solve conflicts between rather equaly strong colonies without instantly murdering each other, like antennae duels, counting each others largest workers, "tallness duels" (ants try to erect themselves as high as possible, often climbing on small pebbles to look even taller), ritualized wrestling competitions and similar stuff.

Ants also often forage the poo of other animals (especially bird poo) so this might be something attracting them to the place.

It's also possible that there is some sort of food source (aphids, root aphids) or a water source present at or under the surface.

Edited by Serafine, December 5 2018 - 8:09 AM.

Hi, Serafine.

At the risk of anthropomorphising, it did seem to me as if the ants, when they bumped into one another, were assessing whether they had just met a friend or foe. Those that I watched closely used their antennae to determine who they had just met, disengaged, then moved on until they bumped into the next ant. This bumping and assessing was persistent, and my first thought was that they were two colonies that were perhaps genetically similar, therefore they didn't actually fight, but didn't join one another either. I see you are suggesting that this could be a ritual fight that protects the nests of each group.

 

This made me think of the Linepithema humile from Argentina that now has a global colony, but, as I understand it, the Argentine ants really are all related.

 

Thanks for the feedback. At the rate the ants are nesting on our property, I'm thinking I'll have to get a couple of pangolins, or perhaps a few dozen echidna. That would be cool.

maybe they are doing the ritualized fighting this species does with same species neighbours.

The video does not work for me though