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Common pesticides change odds in ant fights

Species’ combat success can rise or fall after repeated exposure to a nicotine-related insecticide

DOSED  The southern ant, which is native to New Zealand, can fight ferociously. But chronic exposure to a common neonicotinoid pesticide can alter its aggression and even some battle outcomes.

Repeated nonlethal doses of a widely used pesticide can change the outcomes of fights between ant species.

Repetitive exposure to traces of nicotine-related pesticides called neonicotinoids may alter who wins when invasive species clash with natives, says entomologist Rafael Barbieri of Victoria University of Wellington in New Zealand.

In small battles that he and his colleagues staged in the lab, New Zealand’s native southern ant could exterminate an equal force of invasive Argentine ants in about 16 hours, if the invaders had been repeatedly exposed to neonicotinoids. Yet if the natives were contaminated too, they failed to wipe out opponents as quickly. Some of the invaders were still alive at the end of the experiment, after 32 hours, Barbieri and his colleagues report October 23 in the Proceedings of the Royal Society B.

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