▁her ds ▁of ▁gra zing ▁z eb ra ▁and ▁ant el op es ▁might ▁combine , ▁both ▁the ▁better ▁to ▁observe ▁the ▁approach ▁of ▁pred ators , ▁and ▁to ▁improve ▁the ▁odd s ▁of ▁escape ▁in ▁the ▁event ▁of ▁attack ▁by ▁pred ators . ▁Sometimes ▁there ▁might ▁be ▁some ▁interaction , ▁such ▁as ▁mixed ▁f lock s ▁of ▁birds ▁that ▁observe ▁each ▁other ' s ▁for aging ▁behaviour ▁in ▁searching ▁for ▁food . ▁Sometimes ▁there ▁might ▁be ▁quite ▁order ly ▁common ▁action , ▁such ▁as ▁the ▁que uing ▁up ▁for ▁a ▁resource ; ▁for ▁example ▁different ▁species ▁of ▁fish es ▁may ▁aggregate ▁around ▁a ▁clean ing ▁station ▁where ▁cleaner ▁wr asse ▁and ▁cleaner ▁sh rim p ▁are ▁active , ▁more ▁or ▁less ▁taking ▁turns ▁for ▁attention . ▁Such ▁aggreg ations , ▁where ▁there ▁is ▁no ▁particular ▁association ▁of ▁species ▁or ▁sizes , ▁may ▁be ▁referred ▁to ▁lo os ely ▁as ▁un struct ured ▁aggreg ations . ▁Comm only ▁they ▁are ▁very ▁temporary ▁and ▁may ▁be ▁loose , ▁with ▁f lock s ▁or ▁her ds ▁associ ating ▁cas ually ▁and ▁separ ating ▁equally ▁cas ually ▁within ▁hours . ▁ ▁Struct ured ▁aggreg ations ▁tend ▁to ▁be ▁longer - term ▁and ▁of ▁a ▁specific ▁life - cycle ▁function ▁and ▁context . ▁Typ ically , ▁though ▁not ▁necessarily , ▁they ▁will ▁be ▁of ▁a ▁single ▁species . ▁O ften ▁they ▁will ▁be ▁of ▁a ▁single ▁age ▁and ▁possibly ▁of ▁a ▁single ▁sex , ▁such ▁as ▁sho als ▁of ▁fish ▁f ry ▁that ▁have ▁specific ▁e colog