Friend Or Foe? Ants 'Decode' Other Ants' Odors Before Triggering Aggression

How do socially advanced ants determine which ants are friends and which ants are foes? In a colony, it is important to protect nest mates from intruders and it has been suggested that it is a mismatch in chemical signatures between nest members and non-nest members that give the intruders away.

To test this hypothesis, researchers of a new study gathered Camponotus floridanus ants from nine different ant colonies across Florida and used a specific chemical agent previously discovered by Zwiebel lab that can either over-excite or block the ants’ odorant receptors. They, then, set up a mini dueling arena where they would place two ants, either from the same or different colonies, to interact. Each test was filmed so that they can score the ants’ interactions, specifically the aggressive behaviors.

Interestingly, the researchers found that the ants with unaltered receptors recognized and fought the ants from other colonies, but the ants that had their receptors blocked or over-excited had significantly reduced aggressive behaviors between non-nestmates without affecting aggression levels towards nestmates.

“For years, researchers have hypothesized that ants have specific chemical markers which play key roles in their interactions. What surprised us is that ants not only have these markers, but require these signals be very precisely decoded by specific receptors to trigger aggression,” senior author Laurence Zwiebel said.

Lock And Key

The results of the study suggested that aggressive behaviors in socially advanced ants are not knee-jerk reactions but are, in fact, a result of precise decoding of the chemical signatures of their nestmates. Much like a lock and key mechanism, ants’ aggression is not triggered unless the “key,” which in this case is the chemical marker of an intruder, has been correctly identified.

"Accepting friends and rejecting foes is one of the most important decisions an ant worker must make,” lead author Stephen Ferguson said. “Our study finds that unless there is a clear and unambiguous threat, ants are more likely to be accepting than they are to be aggressive. This process may have contributed to the evolutionary success of these insects, and there may be important lessons about tempering aggression for other social beings such as humans.”

The study is published in the Journal of Experimental Biology.