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Wake capture is used by many animals to increase the power and efficiency of their flight or swimming.

The basic idea is this: vorticies form in fluids when something moves through them quickly. For example if you have ever paddled a canoe, you will have seen this happen. Vorticies form on either side of the paddle as you move it through the water. The same is true of the tail fin of a fish, or the wings of an insect. In general, these vorticies represent lost energy, as it takes energy to make them, and that energy does not move the animal forward. However, most flying insects and many swimming animals push off of the vorticies that they create, thus recapturing some of the wasted energy and adding power to each stroke.

Insect flight was not well understood for a long time, because insect wings are simply not large enough to keep them aloft, let alone allow them to accelerate quickly and perform incredible feats of aerobatics. It turns out that they combine wake capture with wing rotation to great effect.

Fish and a other aquatic animals also use wake capture. For example, due to its use of wake capture, the tuna can accelerate at around 6 g's (over 58 m/s2).

References:
Dickinson, M.H., Lehmann, F.-O. and Sane, S.P. (1999). Wing rotation and the aerodynamic basis of insect flight Science 284:1954-1960.

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