Title: Understanding Obstacle Avoidance in Myotis velifer through Analysis of Reconstructed 3D Flight Trajectories Authors: Alison Greco, Nathan Fuller, Diane Theriault, Zheng Wu, Thomas Kunz, John Baillieul, and Margrit Betke Date: October 24-27, 2012 Abstract: Flight behaviors of bats provide an extraordinary study system for scientists to understand collective behavior, obstacle avoidance, and sensory systems of flying organisms. Until recently, the technologies needed to study bat flight in detail have not existed, thus only simple observations of their flight behaviors were recorded. Using an advanced thermal imaging system, custom software, and 3D imaging techniques, we have reconstructed the flight trajectories of 334 Myotis velifer as they traveled along the edge of a forest. Most bats (82.5%) flew along a path following the margin of the forest. When faced with a natural obstacle (a hanging vine), an equal number of bats chose to pass this obstacle along paths that were cluttered and open. Bats that chose to cross the obstacle plane through the less cluttered corridor traveled at a faster average speed, whereas bats that chose the more cluttered corridor past the obstacle moved at a slower average speed while approaching the obstacle (t = 2.57, p = 0.0107) and while passing the obstacle (t = 5.16, p < 0.0001). Approach angle also varied with the chosen route around the obstacle 2 m before reaching it (F = 170.38, p < 0.0001). These results suggest that bats have already chosen their flight path 2 m before reaching an obstacle and that they prefer to fly near, but not through, clutter. These data will be useful to computational biologists and control systems engineers who seek to develop models to describe bat flight and group behavior.