FIGURE 1.

Field assessment of tending and defensive behaviours of the mutualistic ant Lasius niger along an urbanisation gradient in Berlin, Germany. Ant behaviour was first observed undisturbed, at the (1) group level and (2) individual level. In a second phase, we (3) recorded behavioural responses of individual ants targeted by a simulated attack using a needle. Each sampling session on a given plant host determined the unit of observation for the study. Observations were replicated along an urbanisation gradient in Berlin and repeated 4–7 times over a month.