Harvester ants may
increase knowledge about networked systems.
Gordon, a Stanford
biology professor who has studied ants for 20 years, found something extraordinarily
sophisticated about the way harvester ants forage for food. She discovered that the ant colonies
regulate their foraging activities based on the amount of food available and the
amount of time it takes for a round trip between the nest and the food.
Harvester ant foragers waiting inside the nest. – photo by Katherine Decktar, one of the researchers
recognized that this particular ant
behavior approximates the way the Internet works, so she invited Stanford Computer Science Professor Balaji Prabhakar to have
a look. Their collaboration is described in a Stanford News story about "the
anternet” and their paper is
published in Plos Computational Biology.
Individual ants leave the
nest looking for the seeds, which they immediately bring back and drop deep
into the nest. The more food they
find, the faster they return. New
foraging trips are initiated based on the rate of return from earlier trips.
There’s no central control or boss ant, and no geographic information on where
the food is located. Some ants leave pheromone trails in their travels, but
these ants don’t. What happens is based on local interactions among the ants in
the nest. New foraging trips are signaled by the rate of contact between the
antennas of returning ants and the antennas of ants available to leave on the
Prabhakar quickly saw the validity of Gordon’s insight. "The algorithm the ants
were using to discover how much food there is available is essentially the same
as that used in the (Internet) Transmission Control Protocol,” he told the
The Transmission Control Protocol, or
TCP, is the way information transmission among networked computers is
regulated. As the Stanford story explains TCP, as a source A sends a file to a
destination B, the file is broken up into numbered packets. Each time B gets a packet, it sends an
acknowledgment, or ack, back to A. Speed of ack return indicates the amount of
bandwidth available. If the ack comes back at a lower speed than it was sent,
it means little bandwidth is available, and transmission traffic is slowed
accordingly. If it returns
quickly, transmission speed can increase. That’s pretty much the same thing the
The researchers found
another similarity: When a data
link is disrupted or broken, the source stops sending packets. If forager ants
don’t get back to the nest in 20 minutes, no more ants leave to forage.
Each ant is limited, but
colonies can achieve some impressively complex computations, and they’ve been
evolving for millions of years, probably doing things humans haven’t thought up
yet. Read Gordon’s wonderful essay "Colonial Studies."
"Ant algorithms have to be
simple, distributed and scalable—the very qualities that we need in engineering
distributed systems,” Gordon said. "I think as we start understanding more about how species of ants regulate their behavior, we
will find many more useful applications for network algorithms.”