Abstract: Ant colonies operate without central control and resemble large distributed systems. An ant’s behavior depends on its recent experience of brief interactions with other ants. In the course of a brief antennal contact, one ant can assess the task of the other using odor cues. A long-term study of the behavior and ecology of harvester ants in the Arizona desert shows how colonies regulate foraging to balance the tradeoff imposed by spending water, while foraging in the desert sun, to obtain water, which is metaboized from seeds. The goal is not to send out more ants than are justified by the current food supply. The ants collect seeds that are widely scattered, each retrieved by a single ant without the use of pheromone trails. The duration of a foraging trip depends mostly on how long the forager had to search to find a seed. A forager leaves the nest on its next trip in response to the rate at which it meets foragers returning to the nest with food. Thus foraging activity is adjusted to food availability without any information about the location of food. I will discuss a model of the algorithm colonies use to regulate foraging, and the ecological and evolutionary consequences of variation among colonies.
Deborah M Gordon is a Professor in the Department of Biology at Stanford. Her research on the collective organization of ant colonies includes studies of the long-term demography and behavior of harvester ant colonies in Arizona; the factors that determine the spread of the invasive Argentine ant in northern California; and the ecology of ant-plant mutualisms in tropical forests in Central America. She is the author of two books, Ants at Work (2000) and Ant Encounters:Interaction Networks and Colony Behavior (2010). She has been awarded fellowships from the Guggenheim Foundation and the Center for Advanced Study in Behavioral Sciences. She is interested in analogies between ant colonies and other distributed networks, and has given talks at TED, Xerox Park, Google Tech, Dagstuhl seminar on distributed algorithms, and at robotics and artificial intelligence conferences.