Ants recall nearby rivals by their stink

U. MELBOURNE (AUS) — Weaver ants share a collective memory for the odor of ants in rival nests, and use that information to identify them and compete.

An ant colony’s collective memory gives them an edge in a competitive world by priming all nest mates with information about rivals before they encounter them, says study leader Mark Elgar, zoology professor at the University of Melbourne.

“This communication highlights the impressive nature of ant societies because the colonies of some species, like weaver ants, can consist of networks of nests containing millions of workers,” Elgar says.

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The research is published in the current issue of the journal Naturwissenschaften (The Science of Nature) and includes zoologists as well as researchers from the department of mathematics and statistics.

The research team conducted experiments with colonies of weaver ants (Oecophylla smaragdina), which are more aggressive to ants from nearby rival nests, just as sports rivalries are greater between teams from the same city, like the New York Yankees and the Mets.

The scientists took ants from 12 colonies of weaver ants and challenged them with intruders from other colonies that were either familiar or unfamiliar to them, based on previous experimental challenges. Weaver ants build intricate nests in trees and are found in northern Australia, India, and Africa.

“We find that once an ant has had an encounter with a rival, it can go back to its colony and pass on information about the rival’s smell and about how aggressive the interaction was.

“When a colony was exposed to intruders from the same rival nest repeatedly, we saw the encounters were increasingly aggressive, suggesting that ants were passing on information about the frequency of interaction to their nest mates as well as information about their identity.”

The next step for the research team is to understand what chemical and behavioral cues the ants use to communicate this complex information.

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