Predation risk assessment
In order to explore the effects of diurnal predators on the activity rhythms of V. sinensis , we defined predation risk as presence or absence of predators. If the predator F. amurensis appeared near the roost and hunted bats, this was considered as the presence of predators (high predation risk) when we were monitoring the first emergence and the final return. If there were no F. amurensis, or F. amurensis only flew across the roost without predation attempts, this was considered as absence of predators (low predation risk). Since F. amurensisarrived at the roost to hunt bats every day in summer, F. amurensis was present during mid-emergence. In this case, we considered predation risk as “predators were hunting” or “predators were not hunting” when determining mid-emergence time. During the monitoring period, we did not observe any other potential diurnal avian predator near the roost. Therefore, we believed that only F. amurensisexerted diurnal predation pressure on V. sinensis as they were flying out and returning.