“The ants go marching one by one….”
Actually, they don’t. At least not when you’re talking about army ants, or driver ants, as they’re sometimes called. What they do is form marching “columns” that vary from a few ants in width to a wave pouring over everything in their path.
Until fairly recently, everything I knew about army ants came from two childhood sources: a 1938 short story titled “Leiningen Versus the Ants” by Carl Stephenson, and a children’s book, Alonzo and the Army of Ants, written by Murray Goodwin in 1966. In both books, the ants are portrayed as a horrifying, unstoppable force of nature:
“They’re not creatures you can fight—they’re an elemental—an ‘act of God!’ Ten miles long, two miles wide—ants, nothing but ants! And every single one of them a fiend from hell; before you can spit three times they’ll eat a full-grown buffalo to the bones. I tell you if you don’t clear out at once, there’ll be nothing left of you but a skeleton picked as clean as your own plantation.” [“Leiningen Versus the Ants”]
What better to titillate the fertile imagination of a child? Naturally, I was fascinated and frightened in equal measure.
When I began travelling to the tropics as an adult, I somehow believed my chances of seeing these fearsome creatures were about the same as running into a tiger. I mean, if they were that dangerous, surely someone would have got them under control or something. Or there would be fences. Or warnings. In Africa, you see signs about how to act around elephants and hippos. In Australia, there are crocodile warnings. Nowhere do you see signs warnings about army ants.
However, somewhere in my readings about birds, I learned that there are certain species of birds that follow ant armies for a very particular reason.
“During their hunt, many surface-raiding army ants are accompanied by various birds…which devour the insects that are flushed out by the ants, a behavior known as kleptoparasitism.”
Sneaky buggers, eh? But they get their just deserts, because they in turn become dessert for bigger birds—raptors—who also follow the swarms and prey on them.
What this all boils down to is a bird photographer’s dream: a bunch of birds that are too absorbed in lunch to pay much mind to large lenses being poked at them:
“While focused on feeding on these invertebrates, birds at army-ant swarms typically allow very close approach by people—within 1 or 2 meters in many cases—often providing the best opportunities to see [and photograph] many of these species.”
In my case, I did things backwards (as is so often the case), stopping by the roadside in Costa Rica to photograph a roadside hawk (yes, that’s its actual name). After shooting from the car window, I thought I’d try getting out and moving a bit closer, as the hawk seemed absorbed in watching something and disinclined to move. I opened the car door silently and ever-so-slowly reached my foot toward the ground, always keeping my eyes on the bird. Until something moving below me caught my attention. I glanced down and realized we had stopped the car in the middle of an army ant swarm.
Not knowing how many beloved ant citizens we had crushed with our metallic behemoth or what gruesome revenge their comrades would wreak upon us—Were they even at that moment scaling the walls of the engine compartment, breaching the flimsy barriers that stood between the ravening horde and our shrinking flesh, soon to pour forth with gigantic clacking mandibles from vents and other car orifices?—we elected to retreat to a safe distance.
That was a small swarm, just a few square metres in size. And we didn’t really see the kleptoparasites in action that day. Perhaps the presence of the hawk kept the smaller birds in hiding. Our next army ant encounter, however, provided a spectacular example.
We were staying at a small jungle lodge in the Yucatan. There were few guests, just a couple of the cabanas were occupied and the staff were usually nowhere to be found. As we returned to our hut after a walk, we spotted a column of ants moving along the main driveway. This group was about a metre in width and extended back into the jungle farther than we could see. Intrigued, we followed the ants as they marched forward.
They moved along steadily, searching everything in their path methodically and efficiently to find food. They swarmed up each twig of every bush and plant to flush out whatever was there. We could see spiders, grasshoppers, beetles, and other insects frantically leaping or running to escape. Some made it, others were tackled by the ants and quickly disappeared under the onslaught. You could actually hear the rustling of the vegetation as the ants moved through. It was mesmerizing and extremely creepy at the same time.
We began to see the small birds that accompanied the column. They hung in the bushes just off the ground, keeping close watch on the progress of the army. The insects that managed to elude the ants were often snapped up by the birds instead.
I was able to approach as close as I dared to take photos. The antbirds ignored me and the ants seemed to have little interest in us.
Soon the column entered the courtyard in front of the reception office, an open building in the tropical style. There was no one inside. As the ants fanned out to search the clearing, we realized they were also going inside the building. I wondered if this was unusual and if we should tell someone, but we hadn’t seen any staff members for quite some time.
Our main concern was to avoid being encircled ourselves. We figured we could easily outrun the army as long as we had at least one clear path, but didn’t fancy putting our feet down in the midst of those soldiers. We watched and waited as long as possible, with the ants around us on three sides getting ever closer, then we took our leave.
Later, we talked to the manager and he shrugged the whole thing off. The ant armies came through the property regularly. They didn’t bother people. As for them storming the reception building, he said, that happened a lot and was of no concern. In fact, he welcomed the conquering army, because the ants swept in, searched the building thoroughly and hunted down any resident bugs, and then quickly left without disturbing anything else. Sure enough, when we returned to the clearing, there was no trace of the column and no ants in the building.
The fearsome army ant: just a cleaning brigade on the move. If Leiningen only knew.
 An excellent Scrabble word.
 Apparently, there is no existing term to describe raptors that feast on army ant kleptoparasites, so this is your opportunity to coin a word. Uberkleptoparasites?