I have mentioned Argentine Ants before, because I have found it fascinating to learn about this phenomenon of nature. Argentine ants are the most common nuisance ant in Southern California. They’re small (about 1/8″), uniformly brown, and travel in long, steady trails. They’re hard to eliminate because they don’t form separate colonies. Instead they build huge “supercolonies” with many queens, so killing the ants you can see does almost nothing. They tend to move indoors during hot, dry spells and after heavy rain. It has been said that the colony is so big out here that it extends all the way from Argentina to Alaska. I’m not sure that’s accurate, but it makes for a dramatic story. Argentine ants act as one enormous cooperative network instead of many rival colonies, which makes them unusually good at invading new areas and hard to get rid of. Their social structure is centered around supercolonies. Ants from nests miles apart treat each other as nestmates. In California, one supercolony certainly stretches roughly 600 miles along the coast, and they share workers, food, and queens. There are many queens as a single nest can hold dozens of queens, so wiping out one nest barely makes a difference. These ants don’t have mating flights. Queens mate inside the nest, then walk off with a group of workers to start a new nest nearby. This is why an infestation keeps creeping outward. Scouts leave a pheromone trail, and within minutes hundreds of workers are following it. That explains how a single crumb can turn into a steady stream of ants. They prefer sugars. Much of what they eat is honeydew from aphids and scale insects, and they actively protect those insects from ladybugs and other predators. These ants swarm and push out native ant species. This has knock-on effects on wildlife, such as coast horned lizards, which depend on native ants for food.
The nesting and movement habits are very different for these buggers. They make shallow, temporary nests. They set up under mulch, stones, potted plants, and cracks in walls, and they relocate quickly when disturbed. In winter they gather into a few large, warm nests. In spring and summer they spread out across many small nests. Heat, drought, or heavy rain drives them inside in search of water, food, or dry ground. That’s why they seem to show up in the kitchen suddenly. An odd detail of this species is that each spring the workers kill off a large share of the queens, with some studies putting it as high as 90%. Scientists still don’t fully understand why they do it but its good to remember that as we consider other aspects of the colonies.
Today, the Washington Post put up an interesting article about these ants. They explained that a world war is raging among them at this very moment, with millions dying each week along battlefronts that have never made front-page news. The combatants in this war aren’t people but Argentine Ants, whose supercolonies have for decades been locked in ferocious combat across six continents. It’s a fight that is far larger than any human war has ever been…so the thought is that they may be an example worth our study. The logic that drives this warfare feels uncannily like humans are responding to the growing population of the world as we approach 9 billion. The Argentine Ant is an invasive species originally from northern Argentina and adjacent regions. After a century-plus of hitchhiking on human transportation, the species has reached far-flung parts of the world, where it is organized into at least a dozen massive supercolonies that have expanded over huge areas and often bump into each other with savagely violent consequences.
In the United States, the article said that the war rages prominently around none other than Escondido, California. So, this hilltop turns out to be Ground Zero. It is said that a yard like ours can harbor a million of the two-to-three-millimeter-long workers. The species is superabundant enough to cause environmental damage that includes wiping out native ants (which are, contrary to popular opinion, often beneficial). Members of a supercolony recognize each other by scent, their version of a “national flag,” and the ones in San Francisco and Mexico and Escondido in between are part of the same ant nation. The entire state is inhabited mile after mile by ant citizens in the billions. But supposedly Southern California is occupied by four warring Argentine ant supercolonies, each controlling tracts that converge around this very hilltop. The battle lines meander year after year as the fortunes of the colonies shift during unceasing engagements that may well have been going on for more than a century, ever since this species first arrived here. Standing in my yard I have been tempted to feel above it all, but Kim certainly does not feel that way in the kitchen.
Biologists have noted that the patterns of aggression among ant colonies of the same species are similar to those seen within the human species. In both human and ant societies, the nature of violent conflict tends to depend on population. Small societies generally avoid head-on assaults. When our long-ago ancestors lived as hunter-gatherers, their dispersed bands simply moved away from confrontations when they could. They had little to lose by leaving, having no elaborate homes or larders to defend. When hunter-gatherers did attack, they generally sneaked in and out quickly to avoid casualties on their side. As humans accumulated wealth there was more to defend and this is what changed the nature of conflict, shifting things from skirmishes to outright large-scale warfare.
The same pattern is generally true for ants living in small colonies. But warfare is another business entirely. Warfare, in the sense of fighting that puts both sides at risk of mass destruction and comes to the fore as societies grow large and become rooted in a place with resources. The greater numbers, in both human and ant societies, tip the scales. So, does dividing up the world among enduring, clearly membered groups inherently lead to conflicts? This is doubtless so for the ant…and probably equally so for humans. No colonies of the same species get along. Either they avoid each other or they attack. That’s also true among our fellow vertebrates. Species such as wolves, lions and some bats, birds and fish also live in enduring, territory-holding societies. Tolerance, let alone collaboration between the societies of most vertebrates seems to be virtually nonexistent. Perhaps the convivial bonobos (the example all peace-loving people like to make), close kin to the chimpanzee, and hence to us, might be an exception. While chimps are notorious for aggression between societies (largely carried out in sneaky raids), some bonobo communities do socialize. It’s often suggested that a key to bonobo sociability is the limited competition they show for resources worth fighting over. Still, as observations on this so-called hippie ape increase, primatologists have been witnessing more examples of tension, and at times violence, between communities. As with human nations, it seems good relations between bonobo societies can be fragile.
Thus viewed in the context of nature, the warlike tendencies of ants and humans are no anomaly. The mystery, then, is the emergence not of war but of peace. I have asked Kim to consider alternative ways to hold peace talks with the ants, but she says she’d rather just kill them all. Sigh…. We humans are no more than one big ant farm after all.