Are ant colonies like human brains?
An ant queen lives for 10 or 30 years. All the other ants live only a year or two. But scientists are finding that colonies seem to remember things for generations, even after all the individual ants in a generation have died off.
Redwood ants in Europe forage in the trees for aphids, following the same set of trails every year. They live in massive pine needle nets for generations. During the winter, the ants huddle together underneath the snow. When the snow melts in the spring and the ants emerge, an older ant and a younger ant team up, the younger one following the older one down a trail. The old ant dies, but the young one learns the new trail, securing the knowledge for the next generation.
“Every morning, the shape of the colony’s foraging area changes, like an amoeba that expands and contracts. No individual ant remembers the colony’s current place in this pattern,” wrote Gordon. “On each forager’s first trip, it tends to go out beyond the rest of the other ants traveling in the same direction. The result is in effect a wave that reaches further as the day progresses. Gradually the wave recedes, as the ants making short trips to sites near the nest seem to be the last to give up.”
Gordon conducted a number of experiments to figure out how ant colony memories work. She put things in the way of colonies — she blocked trails and scattered toothpicks that worker ants had to move. Even though she only affected a group of worker ants, the whole colony adjusted to account for the additional work that had to be done in the area.
“After just a few days repeating the experiment, the colonies continued to behave as they did while they were disturbed, even after the perturbations stopped,” Gordon continued. “Ants had switched tasks and positions in the nest, and so the patterns of encounter took a while to shift back to the undisturbed state. No individual ant remembered anything but, in some sense, the colony did.”
Gordon also found that older colonies seemed to understand the world better than younger colonies, even though the ants themselves were the same ages.
“The larger the magnitude of the disturbance, the more likely older colonies were to focus on foraging than on responding to the hassles I had created; while, the worse it got, the more the younger colonies reacted,” she explained. “In short, older, larger colonies grow up to act more wisely than younger smaller ones, even though the older colony does not have older, wiser ants.”