Victorious ant colonies admit turncoat losers


With jaws powerful enough to annoy elephants, the African acacia ant is an aggressive little insect. But when they do battle with other colonies, they stop short of slaughtering all their enemies. Amy Middleton reports.


230316 ants 1.jpg?ixlib=rails 2.1
Unrelated ants fight, but the losers don't have to die. Instead, they can become part of the victors' colony.
Patrick Landmann / Getty Images

When ant colonies fight each other, the victorious recruit turncoats from their opponents, a new study has revealed.

In Africa, a species of acacia ant (Crematogaster mimosae) battles within its species, as well as taking on elephants, giraffes and baboons, in an attempt to keep hold of its acacia tree home.

The battles between ant colonies are vast and violent, and the casualties high for both winners and losers.

In this study, published this week in Behavioral Ecology, researchers from the University of Florida studied the ants’ environment at the Mpala Research Centre in Laikipia, in Kenya, to find out how colonies bounce back after such costly battles.

To track the colonies, researchers analysed the genetic makeup of groups before and after battle, observed the behaviour of winning colonies, and set up tarps beneath the trees to count casualties.

The ants use vicious bites to ward off their enemies. “They really seem to have a knack for finding your soft tissue,” says lead researcher Kathleen Rudolph. “It’s a nasty business.”

The findings show that following a battle, which generally last less than 12 hours and results in thousands of casualties, ant armies are depleted, and the patrolling of their quarters drops off significantly.

'Physical combat not only yields biological winners and losers, it can alter the identity of its combatants.'

To combat this inevitable drain on their resources, victorious ant colonies may replenish their workers by recruiting from the losing side.

Analysing the DNA of more than 800 ants, the study revealed that the genetic make-up of the winning colony can changes following a battle, and begins to incorporate members of the losing side.

This is particularly surprising given that ant colonies are thought to be giant family operations, in which relatives of the queen work to support her.

However, of the winning colonies analysed during the study, 56% later contained workers that once fought for the losing side.

"Physical combat not only yields biological winners and losers, it can alter the identity of its combatants,” Rudolph says.

The paper suggests that a colony’s newfound tolerance for outsiders could be because loser ants mimic the chemistry of the winning colony, effectively becoming ‘spoils of war’.

In other instances, battles didn’t draw a clear winner, and instead the colonies called it quits and joined together under two queens – a blended family dynamic that was still going strong eight months after the battle had taken place.

“It’s pretty remarkable,” Rudolph says. “Colonies are battling so aggressively that many individuals die, but then they are able to just stop fighting and form a lasting truce.”

The findings could provide support for the theory that animals become more biologically similar through combat, which may have interesting applications across the animal world.

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  1. http://beheco.oxfordjournals.org/content/early/2015/12/14/beheco.arv219.full
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