Natures wonders: ant bridge design (Introduction)

by David Turell , Wednesday, November 25, 2015, 02:23 (3285 days ago) @ David Turell

Using army ants it was found that the design of bridges with worker's bodies is very cost effective:-http://www.sciencedaily.com/releases/2015/11/151124143516.htm-"Ants of E. hamatum automatically form living bridges without any oversight from a "lead" ant, the researchers report in the journal Proceedings of the National Academy of the Sciences. The action of each individual coalesces into a group unit that can adapt to the terrain and also operates by a clear cost-benefit ratio. The ants will create a path over an open space up to the point when too many workers are being diverted from collecting food and prey.-"'These ants are performing a collective computation. At the level of the entire colony, they're saying they can afford this many ants locked up in this bridge, but no more than that," said co-first author Matthew Lutz, a graduate student in Princeton's Department of Ecology and Evolutionary Biology.-"'There's no single ant overseeing the decision, they're making that calculation as a colony," Lutz said. "Thinking about this cost-benefit framework might be a new insight that can be applied to other animal structures that people haven't thought of before."-***-"Previous studies have shown that single creatures use "rules of thumb" to weigh cost-and-benefit, said Couzin, who also is Lutz's graduate adviser. This new work shows that in large groups these same individual guidelines can eventually coordinate group-wide, he said -- the ants acted as a unit although each ant only knew its immediate circumstances.-"'They don't know how many other ants are in the bridge, or what the overall traffic situation is. They only know about their local connections to others, and the sense of ants moving over their bodies," Couzin said. "Yet, they have evolved simple rules that allow them to keep reconfiguring until, collectively, they have made a structure of an appropriate size for the prevailing conditions.-***-"Previously, scientists thought that ant bridges were static structures -- their appearance over large gaps that ants clearly could not cross in midair was somewhat of a mystery, Reid said. The researchers found, however, that the ants, when confronted with an open space, start from the narrowest point of the expanse and work toward the widest point, expanding the bridge as they go to shorten the distance their compatriots must travel to get around the expanse.-"'The amazing thing is that a very elegant solution to a colony-level problem arises from the individual interactions of a swarm of simple worker ants, each with only local information," Reid said."-Comment: Group instinctive intelligence. Same old issue: how was it developed?