Well-coordinated cooperative transport in the invasive ant Anoplolepis gracilipes

Abstract

Cooperative transport, defined as the coordinated effort of multiple individuals to move a single item, enables social animals to retrieve resources more efficiently and reduces the risk of exploitation by competitors. In this study, we provide the first detailed description of such a coordinated prey retrieval behavior in the invasive ant Anoplolepis gracilipes. We examined the influence of prey and colony size on the success of cooperative transport and investigated whether chemical cues, such as footprints of nestmates or workers of competing Diacamma rugosum ants, affected foraging decisions. Our results, using a Y-maze experimental setup, revealed that A. gracilipes does not modify its foraging behavior based on the presence or absence of chemical footprints. However, colonies exhibited fine-tuned cooperative transport, only once exhibiting a deadlock in 144 transport processes. The ants adjusted the number of workers involved according to prey weight, increasing retrieval speed. Nevertheless, lighter prey was still transported faster than heavier prey, even though fewer workers were involved in the transport. Lighter prey items and those carried by larger groups were more likely to be transported successfully, with most failures caused by navigation errors rather than insufficient workforce. Workers joined a transport typically positioning themselves at the front, aligned with the nest, rather than at alternative locations. Our findings highlight the efficiency and plasticity of cooperative transport, a coordinated behavior that likely confers the invasive A. gracilipes a significant competitive advantage over species lacking such sophisticated cooperative strategies.