Ants

Deborah Gordon gave an interesting lecture that covered general principles of ant behavior, as well as findings from her own research on harvester ant colonies in Arizona. The most surprising thing I learned was that at any given time, roughly a third of the colony is simply waiting around in reserve and not working at all. It seems remarkably inefficient– why can’t they do something useful while still being available to switch over to whatever emergency task might need extra workers? The only explanation I could think of relates back to Gordon’s discovery that colonies that don’t forage on exceptionally hot, dry days tend to grow larger and have better reproductive success. The same way the colony succeeds by conserving resources during bad weather, it might be that the reserve ants would consume so much water and energy while foraging that it isn’t worth it for the additional seeds they would bring back.

Gordon told us that the rate at which foragers go out to gather food depends on the rate at which foragers return with food. If ants are coming in more quickly, that means there’s a lot of readily available food, so the colony should send out more ants to take advantage of it. The “go forage” message comes from chemicals on both the returning forager and the food that it’s carrying, so if the food has all been gathered and foragers begin to return empty-handed then more ants won’t go out. This reminded me of feedback inhibition: the colony is like an enzyme, the waiting ants are like substrates, and the returning ants are like products. The analogy doesn’t work perfectly– with the ants, product activates the enzyme instead of inhibiting it– but it’s still a form of self-regulation. These kinds of mechanisms are what allow an ant colony to thrive without a leader giving orders, just as an individual organism survives without something consciously controlling all of its functions.

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