The raw data on nightly activity timing of bats and R codes

The timing of daily activity in animals is influenced by light conditions, weather, and their reproductive phase, yet the relative importance of these factors remains uncertain. Insectivorous bats exploit the nocturnal niche and are sensitive to environmental risks during nighttime. Here, we used least horseshoe bats (Rhinolophus pusillus) to explore the relative contributions of light conditions, weather variables, and reproductive phase to nightly activity timing at the colony level. During summer and autumn of 2024, we monitored the timing of nightly activity in a colony of R. pusillus in southwest China by recording their echolocation calls at roost entrance. We measured nightly light intensity and ambient temperature at roost entrance using high-precision sensors. Additional variables relevant to bat activity were recorded, including rainfall, wind speed, and reproductive phase. To account for natural temporal variations, the timing of bat emergence, return, and the duration of nocturnal activity were standardized relative to sunset, sunrise, and night length, respectively. Our analyses revealed that bats delayed evening emergence under conditions of elevated light intensity. During the lactation period, bats returned later and spent a larger proportion of the night outside the roost compared to the weaning and pre-hibernation periods. Ambient temperature and reproductive phase had interactive effects on both return time and the proportion of the night utilized. Light intensity was the sole significant predictor of emergence time, whereas reproductive phase explained the majority of variation in return time and the proportion of the night utilized. These results provide evidence indicating that both light conditions and reproductive phase are key determinants of nightly activity timing in bats. This study provides new insights suggesting that light-induced environmental risks and reproductive demands exert differential effects on the emergence and return behaviors in bats.