Air is an important habitat for aerial insectivorous vertebrates, yet interactions among volant organisms in their aerial habitats have been poorly studied because of technological limitations to track and monitor movement behaviors in the aerosphere. We examined spatio-temporal variation in timing of emergence behavior and migratory patterns of Brazilian free-tailed bats (Tadarida brasiliensis) in south-central Texas, demonstrating the potential of radar technology for advancing understanding of ecological interactions in the aerosphere. Brazilian free-tailed bats disperse nightly in dense columns from cave and bridge roosts and forage at high altitudes (300 – 2500 m AGL) over large spatial extents that are easily detectable with Doppler weather radar (WSR-88D) installations. Understanding variation in emergence behavior of Brazilian free-tailed bats provides a model system for testing hypotheses about the influence of abiotic factors on the dynamics of group behavior.
Using high resolution Level II NEXRAD radar products, we tested hypotheses about the influence of weather conditions such as surface temperature, precipitation and wind conditions on timing and relative magnitude of bat emergences to determine how atmospheric cues determine group behavior of an aerial nocturnal predator. We found that both seasonal and daily conditions influence the timing of emergence behavior and that seasonal context influences the relationship of daily conditions on emergence behavior. We used a novel system of mosaic composite radar data developed by the National Severe Storms Laboratory to look at regional patterns of migratory arrival and departure times of Brazilian free-tailed bats in Texas to investigate questions about migratory movements and phenology. Radar visualizations have great utility for generating new hypotheses about migratory and foraging behavior of aerial species by making it possible to ‘observe’ behavior at temporal and spatial scales not previously possible.