The role of chemical footprints for foraging and competitive interactions in ants

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Many animals sense the presence of other organisms based on cues in the environment. Prey organisms can detect predators from cues like chemical footprints, urine or feces, and change their behaviour to reduce predation risk. The effects of such behavioural responses can be as strong as those of direct predation. In contrast to predator-prey interactions, very little is known on cue-triggered effects in competitive interactions. Here, ants are a particularly suitable model system since they show strong interference competition between members of different colonies. Recently, we showed that they respond to chemical footprints of other colonies, by avoiding them, approaching them or by altering their own aggressiveness. However, the fitness benefits and community-level consequences, as well as the factors that determine these behavioural responses, are almost completely unknown. Here, I propose to investigate causes and consequences of responses to allocolonial and allospecific footprints in Central European ant species. Firstly, I will assess fitness consequences of footprint responses in the ants Lasius niger and Myrmica rubra. While M. rubra indiscriminately approaches foreign footprints, L. niger is highly discriminatory, approaching concolonial footprints but avoiding those of foreign conspecifics. Responses to foreign footprints can be beneficial if they help to avoid costs from interference competition or to exploit food sources discovered by competing colonies.Secondly, I will investigate the role of chemical footprint variation and the role of behavioural variation across colonies. I will explore the ants' discriminatory ability and determine whether response differences depend on chemical differences of the cues. This is ecologically relevant especially concerning to responses to cues of novel species e.g. the invasive Lasius neglectus. In this context, I will investigate whether responses to foreign footprints are associated to colony-specific life-history traits, behavioural traits, or previous experience with competitors. Finally, I will extend these questions to the community level, and investigate behavioural variation between co-occuring ant species. The studies will be complemented by agent-based models to simulate emergent effects of individual responses. Here, I will examine the effects of different response strategies on colony fitness and community composition. The proposed project links behavioural interactions, chemical ecology and community ecology in empirical and simulation studies. It will provide novel insights into a multiple research fields, including swarm behaviour, optimal foraging strategies, chemical perception, and species co-existence mechanisms.