English: Video sequence portraying a representative of the evolved milling behaviour (evolution no. 6). Polarization is low and momentum high throughout the entire simulation run and the evolved behaviour can be classified as milling behaviour. Note that the local density is higher than in the case when prey behaviour evolved with no predator present (see S1 Video). Prey agents learned to stay inside the borders of the living area, to avoid each other (prevent collisions) and group (by circling around an empty core in an ordered fashion), as well as react to predator attacks (see frames 1900–2100, 2700–2900 and 4700–5000). At frame 4900–4950 one can also observe the formation of a vacuole. Note that soon after the disturbances induced by the predator attacks the milling behaviour re-stabilizes.