A systematic examination of learning in the invasive ant Linepithema humile reveals very rapid development of short and long-term memory

The Argentine ant (Linepithema humile) is one of the most damaging and widespread invasive ant species worldwide. However, control attempts often fail due to bait rejection or insufficient bait uptake. Increasing preference for, and consumption of, bait is thus an important requirement for successful control. Learning and within-nest information transfer might be a potential tool for achieving this goal. We conducted a systematic investigation of olfactory learning and route learning in Argentine ants. The ants showed very strong and rapid route learning, choosing the correct arm in a Y-maze 65% of time after just one visit, and 84% correct after two. Odour learning was even more rapid, reaching up to 85% correct choices after just one exposure to flavoured food. Learning is long-lasting, with 73% correct choices after 48h. Food flavour information is transferred efficiently between nestmates in the nest, driving preference: naive ants housed with ants fed on flavoured food show a strong preference (77%) for that odour after 24h. Overall, Linepithema humile are outstanding learners. This, coupled with efficient intranidal information transfer and strong pheromonal recruitment, may help explain their ability to discover and then dominate resources. However, these strengths could potentially be used against them, by exploiting learning and information transfer to increase toxic bait uptake. Steering ant preference by leveraging learning might be an underappreciated tool in invasive alien species control.