“…Although the formation of groups frequently reduces predation risk in prey, there are numerous mechanisms by which predators have adapted to minimise the effects of, or even to take advantage of, social behaviour in prey. Aggregation can, in some circumstances, increase risk for prey species hunted by predators with the ability to consume multiple prey in a single encounter (Turner & Pitcher, 1986), such as filter feeders (Rieucau, Fernö, Ioannou, & Handegard, 2015;Rode et al, 2013), or those that set traps for collectively foraging prey (Bauer, Federle, Seidel, Grafe, & Ioannou, 2015). To alleviate the confusion effect, predators can reduce vigilance for their own predators, allowing increased attention for prey capture, but increasing their own risk of predation (Milinski, 1984), target the edges of prey groups where prey may be less dense (Duffield & Ioannou, 2017), or selectively target phenotypically odd individuals within the prey group, which stand out from the "background" of other, homogenous group members.…”