“…An “aggregation” can be defined as any localized assemblage of individuals where the density of individuals is higher than in the contiguous area (Camazine, ; Jeanson et al., ). Aggregation occurs in organisms ranging from vertebrates to bacteria (Ward & Webster, ), and can entail both costs (e.g., competition for resources and mates, predator attraction, parasite, and disease transmission) and benefits (dilution of predation risk, enhanced foraging, increased vigilance, and predator confusion) (Beiswenger, ; Dall, Giraldeau, Olsson, McNamara, & Stephens, ; Foster & Treherne, ; Hamilton, ; Leu, Whiting, & Mahony, ; Pulliam, ; Sansom, Cresswell, Minderman, & Lind, ; Sontag, Wilson, & Wilcox, ). However, proximate cues for aggregation are poorly understood for many organisms (Sempo, Depickère, & Detrain, ).…”