leaf cutter ants from costa rica - june 15, 2024
Beneath my feet lies a vast underground network larger than my one bedroom apartment. The only above ground evidence of this network is enormous piles of excavated soil, and the winding road of workers. They carry fragments of leaves, berries, caterpillar droppings, and other plant materials in a mostly single file line as long as 500 meters (2000 feet). Once they reach an opening, they disappear into expertly constructed tunnels (with air vents built in because of how deep in the ground they go) leading to a large body of fungus at which they drop off the plant material. It can only be compared to a pilgrimage, a divine duty to sustain an entity that quite literally feeds them. These workers are Atta cephalotes, leaf cutter ants native to Central and South America. They construct intricate nests that sometimes required scientists up to 10 tons of cement to cast and several months to remove from the ground. But their complex societies and roles rival these nests in intricacy. The population of the colony is divided into four castes, each with specialized jobs that aid in the farming of the fungus and the prosperity of the colony.
Among these jobs is the humble forager, an ant who cuts leaves and brings them back to the nest. These ants come into direct contact with the fungus inside of the nest, as well as a host of all kinds of pathogens along the way. A war rages on everyday with a particular parasitic fungus that greatly alters ant behavior, ultimately leading to fatality.
Last week, in Pejibaye, Costa Rica, I saw a forager ant afflicted with the cordyceps (or zombie) fungus. It was exhibiting all of the usual behavior - she kept dropping her leaf, she was sluggish and disoriented (I say she because all worker ants are female - the males are used for mating and then discarded). It all culminated to the final death walk. She wandered off the path, heading towards nowhere in particular. Normally, ants let the injured or diseased go - in fact, the garbage workers usher the bodies themselves to the graveyard. But for the first time observed, a fellow (clearly lucid) forager ant followed the diseased one. Quickly, she caught up to the ant and crossed her path multiple times. She’d get the zombie ant to follow her back towards the path, but the ant would once again become void of the self determination it once possessed and wander off. The lucid ant tried over and over again, seemingly pleading with the sick ant to return to the colony, but her efforts were fruitless. I thought about trying to reroute the ant myself. But ultimately I continued my hike, wondering somewhat anthropomorphically why even the most instinctive creatures will occasionally show allegiance to the pitiful.