Collective exploration and area marking in the ant Lasius niger

The aphid tending ant species, Lasius niger collectively explore new areas. Scouts are mobilised within the first five minutes of exploration with activity thereafter decreasing and stabilising after 40 minutes. Collective path choices of colonies underline the existence of chemical recruitment and area marking during exploration. To identify the territorial or home-range role of exploratory marking, we examined its influence on agonistic behaviour during intraspecific encounters. Ten nestmates and ten alien conspecifics were confronted: (i) on a paper marked by their own colony, (ii) on a paper marked by the alien colony or (iii) on a paper not chemically marked by ants. Residents and intruders showed a weak level of aggression and behaved similarly whatever the type of area marking. As no colony-specificity was observed in the odds of eliciting aggression, exploratory area marking in Lasius niger seems to be rather a home-range than a true territorial marking. We discuss the role of collective exploration, homerange marking and intraspecific interactions in the structuring and use of foraging space by neighbour Lasius niger colonies.