Sound localization acuity, use of cues, and vision in rabbits and five rodents: implications for evolution

Left/right and front/back sound-localization thresholds, as well as the ability to use binaural time and intensity cues, are presented for one lagomorph (domestic rabbits) and five species of rodents (fox squirrel, black-tailed prairie dog, groundhog, eastern chipmunk, and spiny mouse). These localization abilities are compared to those of other mammals and all three are shown to vary widely. Many species do not localize as accurately as the available physical locus cues would seem to permit. Instead, localization acuity is negatively correlated with the width of the field of best vision. This coordination of hearing and vision allows auditory information on the location of sound sources to direct the reflexive orientation of vision and attention for further evaluation. It is possible that the coordination of hearing with vision drives the evolution of sound localization among mammals. Species differences in front/back discrimination are less well studied but also vary widely, and may be influenced by complex interactions between pinna size and complexity. Finally the use of interaural phase differences varies in unexpected ways raising questions about the anatomical and neural mechanisms that underlie binaural analysis in the nervous system.