Echolocation in bats, odontocetes, birds, and insectivores

Abstract

In this chapter, the authors review basic concepts about echolocation, the variety of animals known to echolocate, the production of echolocation signals, the different types of echolocation signals, the hearing anatomy, and how echolocating animals use echolocation. The differences between echolocation signals in air versus water are discussed. Echolocation abilities have been studied intensively in bats and toothed whales, the two groups with the most sophisticated echolocation systems in terms of physiological specializations and performance. Echolocation has also been documented in oilbirds and swiftlets; and a crude form of echo-based orientation may be present in tenrecs and shrews. The authors emphasize that the ability to produce ultrasonic sounds does not necessarily imply an echolocation function. Most echolocators (i.e., a select group of bats, toothed whales, oilbirds, and swiftlets) use broadband clicks, but the majority of bats produce tonal echolocation signals of constant frequency, frequency modulation, or a combination of both. Most echolocators cannot broadcast and receive echolocation signals at the same time but separate each outgoing pulse from its returning echoes in time to detect the echoes and avoid masking caused by overlap with the outgoing signal. However, three families of bats can tolerate pulse-echo overlap and use the Doppler shift to identify prey items. A primary advantage of echolocation is allowing animals to operate and orient independently of ambient light conditions. At the same time, information leakage is a primary disadvantage of echolocation. The signals used in echolocation are audible to many other animals, such as competing conspecifics, predators, and prey.