Influence of abiotic factors on activity in a larval stream salamander assemblage

Abstract Larval stream salamanders are the numerically dominant predators in many headwater stream systems. Nonetheless, little is known about their activity patterns or the extent to which their movements are influenced by prevailing environmental conditions. In this study, we used capture rates from passive trapping as an index of activity level and sought to identify the environmental variables most responsible for fluctuations in larval stream salamander activity. Over the course of two months, we captured stream salamanders in aquatic funnel traps during both day- and night-trapping sessions at a first-order stream in the North Carolina Piedmont. Using an information-theoretic approach, we constructed models to elucidate the effects of (1) water temperature, (2) cloud cover, (3) days since last rainfall, and (4) time of day on larval salamander activity. We found that the model incorporating time of day and cloud cover was the best predictor of larval salamander activity. In our study, larval salamander activity was highest at night and also demonstrated a weak positive correlation with increasing cloud cover. Using model-averaging, we further determined that our time of day and cloud cover variables demonstrated a significant correlation with observed activity levels. This pattern of peak activity under low light conditions could be a behavioral adaptation that limits predation risk for larval salamanders.