Sound localization in chinchillas. II. Front/back and vertical localization

The ability of chinchillas to make front/back and vertical locus discriminations was examined behaviorally using a conditioned avoidance procedure. Their minimum audible angle for localizing single broadband noise bursts was 36 degrees for front/back localization and 23 degrees for vertical localization. Sound localization tests using filtered noise demonstrated that the signal must contain high frequencies in order for chinchillas to make front/back and vertical locus judgements and that frequencies in their highest audible octave (i.e., above 16 kHz) contribute to localization. These results support the view that a major selective advantage of high-frequency hearing in mammalian evolution was its utility for monaural as well as binaural sound localization.