Vigilance for predators: detection and dilution effects

摘要: Grouped individuals are less vigilant for predators than solitary conspecifics because (1) grouping increases the likelihood of predator detection (detection effect) and (2) makes it likely that any given individual will be preyed upon (dilution effect). However, many models vigilance behaviour consider only effect, interaction two effects has been insufficiently considered. I present test them using data on elk, Cervus elaphus. The first model, based effect alone, is implicit in published formulations relationship between group size. Although predicts direction size, provides a poor explanation form relationship. second model incorporates both dilution effects. Regression analysis this “security model” indicates good prediction explaining 69% variance frequency. security demonstrates important determining frequency but relative importance these changes across with providing relatively benefit as size increases. even when groups large, should exhibit at least some although alone much protection from predation, low level greatly an survive repeated predation attempts.