Ants learn and change colony scent ^{CEFR B2}

Researchers report in Current Biology that ant recognition systems are more adaptable than assumed, revealing how social scent and experience interact. The team studied clonal raider ants (Ooceraea biroi). Because these ants reproduce asexually, the scientists could produce genetically identical lines and mix them to form controlled experimental colonies.

Chemical analyses showed colonies share the same set of waxy compounds but create distinct colony scents by varying the ratios of those compounds. Baseline behaviour tests confirmed that ants typically act aggressively toward foreign genotypes. To probe flexibility, researchers placed young ants with faint chemical profiles into foreign colonies. After one month of sustained exposure, those ants’ chemical profiles shifted to resemble their foster colony, and they no longer faced aggression when tested separately.

There were limits: ants separated from their genetic kin at the egg stage still accepted individuals of their own genotype, indicating an intrinsic sense of self that experience did not erase. Learned tolerance proved fragile: when contact with the foster colony stopped, aggression returned in about a week as chemical profiles drifted back. At the same time, brief, occasional encounters were sufficient to maintain tolerance, and tolerance persisted even after five days of complete separation, consistent with longer-lasting olfactory memory rather than short-term sensory desensitization.

The authors compare this pattern to immune tolerance, where repeated low-level exposure can dampen defensive responses, while noting that the molecular mechanisms differ. "Now we can combine the neurobiological tools with this behavioral system and image neural activity while an ant encounters a nestmate or a non-nestmate," says Daniel Kronauer. The work aims to show where learning and adaptation occur in the ant brain.