Ants searching for new real estate used the same problem-solving technique regardless of the urgency of the situation.

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SYDNEY: The house-hunting habits of the humble ant might offer insights into the workings of all complex biological systems, according to a new international study.

The study, published in the U.S. journal Proceedings of the National Academy of Sciences, found that ants choosing a new nest use the same algorithm, or set of decision making rules, regardless of whether their move is forced by destruction of their current home or a voluntary search for greener pastures.

According to the researchers, this suggests that ant colonies and other complex biological systems can adapt pre-existing solutions to novel problems, avoiding the hassle of having to devise new problem-solving techniques.

Stephen Pratt, who completed the work while at Princeton University in the U.S., and David Sumpter of Britain's University of Oxford, are part of a growing field of researchers studying the complexity they say characterises "every level of biological hierarchy from genes to ecosystems".

Pratt, who also works with honey bees, is interested in how the interactions of individuals can lead to coherent and adaptive behaviour at the group level, "despite the absence of any well-informed central controller".

Working with the ant species Temnothorax curvispinosus, Pratt and Sumpter derived an algorithm describing their behaviour. They calculated values for the algorithm by making detailed observations of individual ants during forced migrations.

The first step in the algorithm consists of exploratory journeys by scout ants searching for new nest sites. Depending on the quality of a new site, scouts might start recruiting fellow colony members, slowly escorting them on the journey.

Once the new site reaches a population threshold, the ants start recruiting more quickly, bringing the rest of the colony, including passive adults and brood.

To test out the algorithm's flexibility, Pratt and Sumpter set up Temnothorax colonies in nests and placed other empty nests of varying quality in the vicinity. The researchers then destroyed the nests of some colonies, forcing them to search for a new home.

Other nests were left unmolested; however some of these colonies still opted to make the move to a better site. The duo found that the ants used the same key steps to find a new home regardless of the urgency of the decision.

What differed between the two scenarios was the relative weighting given to the different steps. In forced emigrations, more ants engaged in scouting behaviour, and they were more likely to accept inferior real estate than their less rushed counterparts.

The researchers also ran a series of computer simulations based on their algorithm and found they closely matched the ants' actual behaviour.

"These results show that an algorithm originally described in emergency moves can account in detail for the behaviour of colonies in deliberative moves," they said.

The research suggests that ant colonies need not reinvent the wheel each time they face a new problem, rather they can adapt pre-existing solutions to the task at hand. Such 'knob-twiddling', or tunability, could be a common design feature of complex systems found in nature, according to Pratt.

"I think that this kind of algorithm could prove very general, not only in ants and other social insects, but in other kinds of biological collectives, including social mammals, bacterial colonies, and even the collectives of neurons that make up our brains," he said.