[Selection of strays from the group by predators during prey]

Equally sated three-spined sticklebacks (Gasterosteus aculeatus) that had a free view of stray individuals and of a swarm of Daphnia magna preferentially preyed upon the strays; the resulting risk to the strays increased with swarm density (a leads to c leads to e in Fig. 1). This applied also to situations with constant swarm numbers but varied density (a leads to b, d leads to e). The results from two experiments with equal swarm density (b/e, c/d) suggest selection to be affected also by swarm number and/or volume.