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.