The impact factors for the final return time of V.
sinensis
We recorded 78 final return events
of V. sinensis , and all final return events occurred and ended
approximately 7–79 minutes before sunrise. There were no significant
differences in the final return time between 2019 and 2020 (Paired
sample t test, t = 1.730, P = 0.093).
Our analyses indicated that the best model of variation in the final
return time of V. sinensis used LIFR and PAPDA as the predictor
variables (Table 5). However, model averaging revealed that three
predictive variables (LIFR, LISR, and PAPDA) were also significantly
associated with the final return time of V. sinensis (Table 6).
First, differences between the final return time and sunrise time were
significantly and positively associated with light intensity
at sunrise (t = 4.054,P < 0.001; Fig. 3a). That is, the higher the light
intensity at sunrise, the earlier the final return time of V.
sinensis. Second, differences between sunrise and final return time
were significantly and negatively associated with light intensity
at final return (linear regression:t = −8.194, P < 0.001, Fig. 3b; curvilinear
regression: t = −10.226, P < 0.001, Fig. 5c).
Finally, bats also returned to the roost later when predators were
present (t = −5.746, P < 0.001; Fig. 3c). We
found that predators were often (60% records at dawn) present before
the ending of the final return events at dawn. However, the number of
successful predation events occurring at dawn was significantly less
than at dusk (Mann-Whitney U test, Z = -1.993, P = 0.046).
Consistent with the results of the
hierarchical partitioning analysis, the independent contributions of
LIFR, LISR, and PAPDA were 56.34%, 6.18%, and 37.49%, respectively
(Fig. 4c).