Citizen science reveals meteorological determinants of frog calling at a continental scale

Abstract

Aim: Here we investigate the strength of the relationships between meteorological factors and calling behaviour of 100 Australian frog species using continent-wide citizen science data. First, we use this dataset to quantify the meteorological factors that best predict frog calling. Second, we investigate the strength of interactions among predictor variables. Third, we assess whether frog species cluster into distinct groups based on shared drivers of calling. Location: Australia. Method: To assess the relationship between calling and meteorological traits, we used spatio-temporal subsampling (daily data fitted to 10 km2 grid cells) of call and meteorological data as inputs to a boosted regression tree. We scaled the model outputs, which created a descriptive ranking of predictor importance. For strongly day-driven species, we conducted further analyses to examine the influences of meteorological factors within the breeding season. Results: We found a strong seasonal signal, with day of year the strongest relationship to calling in 67 out of our 100 species, moderate relationships between temperature and calling, and weak relationships between rainfall and calling. Despite the common narratives, we found that frogs did not group into distinct categories based upon the influence of meteorological factors. For strongly day-driven species, we found similar patterns within the breeding season. Main conclusions: We demonstrate the importance of day of year and temperature thresholds in predicting frog calling behaviour in Australia. Understanding how meteorological conditions influence phenological events, such as breeding, will be increasingly important considering the rapid changes in environmental conditions and stability throughout most of the world, and how important breeding is to species survival.