Ultrasound Production, Emission, and Reception

Abstract

All bats use acoustic signals for passive listening to ambient sounds and for intra- and inter-species communication. In addition, most bats have evolved an active sonar system that uses calls for exploring the environment acoustically. In the majority of bats, the larynx produces these echolocation pulses. Echolocation is absent in the family of Old World fruit bats except for one genus, Rousettus, which “reinvented” echolocation by producing sonar pulses using tongue clicks. This chapter first discusses how sounds are produced by the bat larynx by outlining its characteristic morphological features and detailing general sound production mechanisms, including non-linear features that play a key role in enabling echolocating bats to switch between echolocation and communication sounds. Subsequently, details are presented on the neuronal basis for sound production in echolocating bats by briefly discussing the neural innervation pattern of the larynx and how this affects spectral and temporal features of sounds, followed by a summary of the neuronal connection patterns and mechanisms within the brain stem as well as in higher-order brain structures. The chapter then explores the role of various forms of sensory feedback in sound production, such as auditory and somatosensory stimulation, and highlights how sound production is intertwined with other motor patterns, such as flying. The chapter also briefly explores the diversity in the shape of nose leafs and pinnae in different species of echolocating bats and the role that dynamic changes of such facial characteristics may play in echolocation. Finally, the tongue-click echolocation in Rousettus is discussed.