Common air pollutants like ozone alter the chemical scents that ants use to identify colony members, causing them to attack their own nest-mates as intruders. Researchers in Germany exposed ants to realistic levels of ozone and observed aggressive responses upon their return to the colony. This discovery highlights hidden ecological costs of pollution beyond human health.
Ants depend on unique chemical scents, composed partly of alkenes, to distinguish friends from foes in their colonies. When exposed to ozone—a pollutant emitted by vehicles and industry—these alkenes break down, subtly shifting the ants' odor profiles. In a study conducted by Markus Knaden and colleagues at the Max Planck Institute for Chemical Ecology in Jena, Germany, scientists tested this effect across six ant species.
They created artificial colonies and isolated individual ants, placing them in chambers with ozone concentrations mirroring those recorded in Jena during summer. Even small changes—altering just 2 to 5 percent of the scent blend—provoked attacks from nest-mates, including biting and potential killing. 'I did not expect it, I have to say,' Knaden remarked, surprised by the intensity of the reactions despite the minor chemical shifts.
The implications extend beyond immediate aggression. Alkenes also play roles in trail-following and interactions between adults and larvae. In experiments with clonal raider ants (Ooceraea biroi), ozone-exposed adults neglected their young, suggesting broader disruptions to colony function. Daniel Kronauer, an ant expert at The Rockefeller University not involved in the research, noted that such scent changes were unsurprising given alkenes' key role in recognition. He emphasized ants' vital ecosystem services: 'If you took the ants out of most terrestrial ecosystems, they would probably collapse.' These include seed dispersal, soil aeration, and symbiotic relationships with other species.
As insect populations decline globally, this work, published in PNAS (DOI: 10.1073/pnas.2520139123), underscores air pollution's role in the crisis. Knaden warned that while ozone levels may not yet harm humans directly, 'we just should know that what we are doing has additional costs that we have maybe not thought about before.' In natural settings, such confusion could reduce colony efficiency, threatening biodiversity.
