Extended Data Fig. 10: Limited wing-beat frequency variability across flights.

a, Scatter plot and histogram for the wing-beat frequency calculated from the FFT of the absolute acceleration during a flight (vertical axis) or as the average during flight of the time-varying frequency obtained from the Hilbert transform (Methods). Each dot is one flight (n = 1,442 flights from 6 bats). Note the high correlation between the two measures and their narrow distributions. b, Heat maps representing the accelerometer signal (filtered between 7 Hz and 9 Hz) during repeated executions of the same flight in a path (three example paths from different bats). Number below the heat map indicates duration of the shown flight interval. c, Distribution of the coefficient of variation (CV) for the wing-beat frequency across flights belonging to the same path (n = 80 flight paths from 6 bats). The vertical line represents the coefficient of variation of the wing-beat frequency across all flights (n = 1,442 flights from 6 bats). Note that most of the coefficients of variation of wing-beat frequency within a path were significantly smaller than the coefficient of variation across all flights (97.5%, P = 0.025). d, Scatter plot for the average speed versus average wing-beat frequency during flight (each dot is a flight, n = 1,442 flights from 6 bats). To improve visibility, only data within 5th–99th percentiles are shown. c and p: value and two-sided P value of Spearman’s correlation. e, Example trajectories (left insets), average speed profile (solid line) and average wing-beat frequency (dotted line) for straight flights (n = 1,057, top) versus loops (n = 385, bottom; Methods). Shaded areas represent s.e.m. Average profiles are calculated by rescaling the speed (or wing-beat frequency) between 0 (take-off) and 100 (landing) and then averaging the obtained traces across flights. Flight tails are excluded to avoid edge effects. f, Unfiltered power spectral densities of the raw accelerometer signal during flight for all sessions (n = 22, 6 bats; coloured lines, scaled between 0 and 1). Black line shows the average.