| Summary: | This chapter looks at the active orientation mechanisms developed by some animals. The chapter focuses on echolocation, a mechanism to negotiate an animal's surroundings based on the emission of sound, its reflection by objects located within the emission beam, and the analysis of the returning echo. Echolocation has been found in bats, toothed whales, and oilbirds. The chapter revisits the beginning of echolocation research at the end of the eighteenth century when several scientists conducted a series of experiments on how bats orient in the dark. It describes the two major categories of sounds produced by bats: frequency-modulated (FM) signals which are used to estimate the distance of the bat from an object, and constant-frequency (CF) signals which are well suited for the so-called Doppler shift analysis. Lastly, the chapter discusses the adaptations developed by some insects to counteract bat echolocation.
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