Bats in Motion: Stereo Object Recognition and Trajectory Analysis of Flying Bats

Edward Y. Lee, Margrit Betke, and Thomas H. Kunz, Boston University, Boston, MA

The flight activity of Brazilian free-tailed bats (Tadarida brasiliensis) was recorded at 60 Hz with two infrared thermal cameras in a stereoscopic configuration. The use of stereoscopic imaging made it possible to develop a number of tools for image analysis that could not have been applied to data collected with a single camera.  In particular, a method was developed to reconstruct flight paths in three dimensions and calculate additional spatial information, such as distances between points in the scene.  Flight characteristics such as velocity, acceleration, and turning radius were computed. The methods were tested on stereoscopic data collected from bats emerging from a cave at dusk, foraging over a cotton field, and returning to a cave at dawn from high altitude.  Flight characteristics during those activities were then calculated and analyzed.  The analytical tools that we developed have the potential to be invaluable for modeling the flight behavior of Brazilian free-tailed bats and their insect prey.