Fig. 3.

The experimental setup and methods. (A) The microphone array, three synchronized flashes, two cameras, and a trigger line. The array blocked the entire width of the pond. (B) A typical spectrogram showing two flashes (dashed ellipses around 10–20 kHz) and the closest two pulses (solid ellipses). (C) Head feature markers used by the neural network. (D) Performance of the neural network in measuring the gapes from data from the same bats that were used for training (red dots) and the gapes of new validation data points from the fourth bat (black ×s). Notice that 15 images were taken for each gape, but the data points are overlaid on each other. (E) Tail to head vector (white arrow) and flight angle (θ). The red dashed line represents the pond’s horizontal surface. The cameras were mounted horizontally. (F) Flight angle (estimated vs. real values for different yaws).