Sound-localization acuity and its relation to vision in large and small fruit-eating bats: I. Echolocating species, Phyllostomus hastatus and Carollia perspicillata.

Passive sound-localization acuity for 100-ms noise bursts was determined behaviorally for two species of bats: Phyllostomus hastatus, a large bat that eats fruit and vertebrates, and Carollia perspicillata, a small species that eats fruit and nectar. The mean minimum audible angle for two P. hastatus was 9 degrees , and that for two C. perspicillata was 14.8 degrees . This places their passive sound-localization acuity near the middle of the range for mammals. Sound localization varies widely among mammals and the best predictor of a species' acuity remains the width of the field of best vision (r=.89, p<.0001). The five echolocating bats that have been tested do not deviate from this relationship suggesting that despite their specialization for echolocation, the use of hearing to direct the eyes to the source of a sound still serves as an important selective factor for sound localization.