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.