Sonar Signals of Bats and Toothed Whales

Abstract

This chapter reviews echolocation signals of bats and toothed whales. It addresses mechanisms of sound production and reception, signal structure, patterns of call production, and the role of echolocation in the diversification of these animals. Echolocating toothed whales and bats operate in a range of situations ranging from open to cluttered habitats. Toothed whales use four general echolocation signal types while bats demonstrate much higher diversity of signals. All toothed whales and most bats prevent outgoing pulses from interfering with echo detection by separating pulse and echo in time (low duty cycle) whereas some bat species avoid this problem by separating pulse and echo in frequency (high duty cycle). While phylogeny plays an important role in shaping elements of signal design, signal type variability within some families suggests that phylogeny does not necessarily constrain signal structure. Convergence of sonar signals across phylogenetic borders for taxa in similar habitats suggests that signal form may have been selected by ecological function. However, convergence across taxa in very different habitats and the high variability in call structure within species suggest much more unexplored complexity in the evolution of biosonar signals. Toothed whales and bats show a continuum of function between echolocation and social signals. Echolocation signals may simultaneously convey information to other animals, or may be specifically adapted to certain communication functions, especially during short-range interactions such as aggressive encounters. Comparative data from laboratory and field studies have demonstrated the flexibility of both bat and toothed whale biosonar.