High risk of predation suppresses behavioural differences among bold and shy social prey individuals

Prey animals must attempt to optimize foraging success while reducing the probability of being captured. Within social prey groups, intrinsic differences in bold-shy personality among individuals influence their respective risk-taking tendencies. We examined the foraging and refuge use behaviour of mixed groups of goldfish (Carassius auratus) containing half bold individuals and half shy individuals under variable levels of predation risk from a live avian predator (Egretta garzetta). At the group level, the fish groups significantly decreased their foraging time by spending more time under the refuge when the predator spent more time at the focal pool. As expected, the bold fish tended to be the first to leave the refuge, and foraged outside the refuge more often than shy fish under control conditions and at lower risk levels. However, the behavioural differences between bold and shy fish disappeared under higher risk conditions. In terms of mortality, the predator captured significantly more bold fish than shy fish. Our study illustrates how bold individuals in social groups often take greater risks to achieve foraging success, but demonstrates that innate differences in boldness can be diminished in times of elevated predation risk.