Monitoring of activity rhythms
Roost emergence time and final return time were recorded from the middle of July to early September, from 2019 to 2021. The monitoring was stopped when it was raining heavily. In this study, we arrived at the roost of bats one hour before sunset. The first emergence time was defined as the first bat to emerge and leave the roost. We also arrived at the roost of the bats an hour and a half before sunrise. The final return time was observed and recorded when the last bat returned to the day roost. Additionally, previous studies showed that median emergence time was a better parameter to describe the emergence time of the whole roost than first emergence (Bullock., Combes., Eales., & Pritchard., 1987). Therefore, we also included the median emergence time as a descriptive parameter for emergence time ofV. sinensis . We defined the median of the first emergence time and the end time of emergence as the mid-emergence time. In order to calculate the median time between the starting and ending of the emergence events, we recorded the data until the end of emergence. When there were no bats flying out for five minutes, we considered the emergence activities of the bats to have finished.
Collection ofenvironmental data
We recorded the sunrise and sunset times through the network https://richurimo.51240.com/ based on the longitude and latitude of the roost of V. sinensis . Here, the time was accurate to the nearest second. One researcher recorded the first emergence time and the final return time. Another researcher simultaneously measured the light intensity, air temperature, and humidity using a Five in One Multifunctional Environment Meter (HT-8500, Guangzhou, China). The environmental data were measured at the same location on the highway bridge without objects blocking natural light or external artificial light sources. In this study, the final return times were recorded in 2019 and 2021. Additionally, we recorded the light intensity of natural light every 30 seconds in 2019 and 2021. Then, we determined the light intensity of the median of emergence events by selecting the point in time closest to the median of emergence.