Environmental and temporal factors affecting the detection efficiency of nocturnal stag beetles (Coleoptera: Lucanidae) in light-trap surveys in Taiwan

Forest ecosystem conservation has become an important topic in modern conservation biology. Saproxylic insects, including Lucanidae stag beetles, play vital roles in nutrient cycling and energy flow within forests, yet their cryptic habits make them difficult to monitor. To evaluate the applicability of a noninvasive and efficient monitoring method, we examined the environmental factors, including moon phase, elevation, and humidity, that may affect the detection efficiency of light traps. From 34 sites across Taiwan over a three-year sampling period, our results showed that relative humidity was significantly positively correlated with capture rates of Lucanidae, whereas elevation and moonlight illuminance had significant negative effects. In addition, nocturnal activity patterns differed among genera and between sexes. These findings demonstrate that environmental conditions and species-specific behaviors strongly influence light-trap efficiency. Therefore, combining multiple complementary survey methods is essential for obtaining reliable estimates of Lucanidae diversity and population trends. The present study highlights the importance of considering environmental and temporal factors when monitoring nocturnal stag beetles. Adjusting the sampling design according to the phenological patterns of the target taxa can improve sampling efficiency.