3.20 - Evolution of Sound Localization in Mammals

Abstract

The ability to localize sound sources in a complex environment is of paramount importance for orientation in a biological habitat, and intraspecies as well as interspecies communication. The accurate localization of an approaching predator or competitor can be a matter of life or death. This topical essay discusses the major features of the evolution of sound localization in mammals in terms of the physical cues for sound localization, the major brain structures involved, and behavioral measures of localization acuity across taxa. Sound localization in mammals builds upon similar systems shared by lower vertebrates that utilize bilateral hearing, and adds unique abilities arising from the development of the external ear and from the development of the isocortex (neocortex). The evolution of sound localization in mammals is not characterized by a straightforward sequence of changes in the underlying brain structures concomitant with an improvement in ability but rather is more related to the ecological niche of each species. Different habitats and different behavioral strategies for survival require different solutions for sound localization. Many species from a variety of taxa have developed a remarkable acuity for localizing sounds, which comes close to or matches human localization acuity. However, while acuity may be similar, for example, across echolocating bats (microchiroptera), homologous brain structures involved in sound localization can be anatomically or functionally different.