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Understanding the causes and consequences of animal flight speed has long been a challenge in biology. Aerodynamic theory is used to predict the most economical flight speeds, minimizing energy expenditure either per distance (maximal range speed, V_mr) or per time (minimal power speed, V_mp). When foraging in flight, flight speed also affects prey encounter and energy intake rates. According to optimal flight speed theory, such effects may shift the energetically optimal foraging speed to above V_mp.

Therefore, we predicted that if energetic considerations indeed have a substantial effect on flight speed of aerial‐hawking bats, they will use high speed (close to V_mr) to commute from their daily roost to the foraging sites, while a slower speed (but still above V_mp) will be preferred during foraging. To test these predictions, echolocation calls of commuting and foraging Pipistrellus kuhlii were recorded and …