Extrinsic and intrinsic factors influencing the emergence and return of
Asian particolored bats Vespertilio sinensis
Abstract
The circadian rhythm is an adaptive biological process, allows organisms
to anticipate daily environmental changes and implement appropriate
strategies. Circadian rhythms play a crucial role in the health and
survival of organisms. However, little is known concerning how intrinsic
and extrinsic factors affect animal daily rhythms in the field,
especially in nocturnal animals. Here, we investigated the emergence and
return times of Vesperilio sinensis, and also integrated environmental
conditions (temperature, humidity and light intensity) and biotic
factors (reproductive status and predation risk) to determine causes of
variation in the activity rhythms of the bats. We found that variation
in the first emergence time, the mid-emergence time, and the final
return time were distinct. The results demonstrated that the emergence
and return times of bats were affected by light intensity, reproductive
status, and predation risk in a relatively complex pattern. Light
intensity had the greatest contribution to activity rhythms. Moreover,
we first investigated the effects of actual predators on the activity
rhythms of bats; the results showed that the mid-emergence time of bats
was earlier as predators were hunting, but the final return time was
later when predators were present. This challenges the traditional view
that high predation risk leads to later emergence and earlier return.
Finally, our results also highlighted the importance of higher energy
demands during the lactation period in bats to variation in activity
rhythms. These results improve our understanding of the patterns and
causes of variation in activity rhythms in bats and other nocturnal
animals.