Map of the ant colony's route and my set.
I set up shop with the one local colony that's large enough to film. Much farther into the forest are two enormous colonies but they're beyond reach of my 100 meter extension cord. Filming at night is hard enough, never mind without power. So I'm working with what I have. This modest, mid-sized colony lives on a hillside and has two main highways. I chose the larger of the two. Selecting the only partially-level area available, one that's nestled in a stand of bamboo, I raked it clean to facilitate spotting snakes and scorpions in the dark and dug a six-foot, rectangular trench big enough for me that runs parallel to the line of ants. I like to be low to position the camera at their level.
It's curious this colony's main highway takes such a long, meandering route to reach the mango tree from which it's harvesting. Emerging from their underground home, the ants cross into the bamboo, through scrub bush, out into a clover field, then back in the scrub and up the tree. It would be more efficient for them to simply walk down the hill. It's a straight shot, relatively open and less than half the distance. Instead they make a grand, circular detour through the clover field. It would be like going from midtown to downtown by taking the Lincoln Tunnel, wandering around Jersey and returning in the Holland. At first I was hesitant to build my set on a line that made no sense. I thought one evening I would come to work and find no ants. Collectively they are smart and surely soon they would figure out the shortest route to the tree and bypass my encampment.
The more I thought about it, though, I begin to see something else at work. Perhaps their highways are like any organic system, the structure of which gives clues to its evolutionary past. Life doesn't make things from scratch. Evolution works with what it has at hand. This is the dry season and the clover is shriveled and brown, but earlier in the year, in the rainy season, this area would have been lush and green. The ants love this clover plant. When it's healthy and flowering colonies from all around make super-highways to harvest from it. I've seen seven different colonies, who risk war by passing so close, target the same field. It's like a giant salad bowl and they all dig in.
My guess is this colony created the route in the wet season specifically to harvest clover. But, once the season changed, the ground cover withered and tender mango leaves sprouted, the ants extended their existing highway to the tree. The shortest route to the mango tree from the clover field is the exact route they are taking.
I had looked at their highway as if it was designed for its current purpose. Making super-highways are an expensive investment of energy and once constructed colonies tend to use them for years. It reminds me of what Neil Shubin talked about in his fabulous book, Your Inner Fish, which unfortunately I don't have with me to quote. He said our bodies have pathways linking vital organs that loop around and take odd, indirect routes. Just like the ant's trail, they too were not specifically designed to make the connections they do now, but evolved over time from other things with different objectives.