Ants Slack Off for Colony's Greater Good

Sept. 10, 2008 -- They are capable of carrying up to seven times their body weight, but leaf cutter ants are slacking off for the greater good, according to new research.

In a paper published in today's Biology Letters, Martin Burd of Australia's Monash University details how a lower level of productivity by foraging leaf cutter ants improves productivity within the colony.

"What looks inefficient is actually efficiency," Burd, who is attached to the School of Biological Sciences, said.

Burd measured the work done by worker ants tasked with collecting and harvesting leaf fragments in colonies of Atta colombica. He measured the load the ants carried, the time it took to cut leaf fragments and the rate at which fragments were delivered to the colony.

Burd and co-author Jerome Howard at the Department of Biological Sciences at the University of New Orleans found the ants were carrying about half the maximum load they could manage.

Even when the faster delivery time due to the lighter load was taken into account, they were still 35 percent less productive than their optimal performance.

Burd said it was "pretty clear they were underperforming." He added that the inefficiency was explicable only if it improved transportation and processing of the leaf matter inside the nest.

Once the leaf fragment is delivered to the colony, its tissue is processed for use to cultivate fungal gardens that provide feed for the colony's larvae, Burd said.

It is then transported by workers to one of the colony's fungal gardens where it is cleaned and dissected into tiny particles that are then implanted in the gardens.