The collective route to efficient regulation of carbs

ANTS provide excellent models for the human world because they operate in strong collectives.

ANTS provide excellent models for the human world because they operate in strong collectives.

For example, says biologist Steve Simpson, their way of organising movement in groups has been used in managing vehicle traffic in towns and cities.

Research that Simpson has completed with ant expert Audrey Dussutour at the University of Sydney may offer insights into the regulation of food intake and food supply chains for humans.

"It is important to understand how they control what they eat and how they adjust the nutrients they require in the face of an environment that may challenge them in terms of variable supply," Simpson says.

The research gave rise to a joint paper of which Dussutour was lead author, called "Carbohydrate regulation in relation to colony growth in ants". It recently won the 2008 outstanding paper award from the Journal of Experimental Biology.

In each ant colony, a proportion of 10 per cent or more gather food for the rest. The question was how they altered their practices to cope with varying circumstances. Ant nutrient sources are protein and carbohydrate, and Dussutour opted to tinker with the latter.

Adult Australian green-head ants were offered sucrose solutions of strengths ranging from weak to strong. What emerged was that while some ants initially overfed or underfed on the solutions, eventually they adjusted their feeding patterns to conform to a particular level of carbohydrate intake.

This solved the question of whether they would adjust their foraging to suit changing conditions. But how the larvae made known their needs is a separate issue. "You have a whole lot of larvae -- grubs -- living in the centre of the nest and they need somehow to communicate to the rest of the community what they need to eat," Simpson says.

He is not sure of the complete answer but has a strong theory, a "simple and likely method" that involves the response of the larvae. "If the forager gives the food to another ant to deliver to the larvae, or presents it directly, and they eat it avidly, it means it's worth collecting more of the same," he argues.

But if the larvae reject what is offered, either they have sufficient already or it is the wrong food. "So the forager won't collect it again or will do so in smaller quantities. And this provides feedback that regulates the supply of sugar to the colony."