ECHOLOCATION INVESTIGATIONS ON BATS AND HUMANS: TARGET LOCALIZATION AND EVALUATION

A device was developed to trigger cameras and echomasking sounds in relation to variations in the pulse rates of bat signals. Pursuit inhibiting effects by white noise tend to increase with the distance of noise initiation from the expected point of target capture and with increased bandwidth around the central frequencies of the signals. Observations on the resolution capabilities of bats indicate a capacity to select a chosen target from other targets within a centimeter or two. Pairs of target-sized objects, radiated with frequency-swept ultrasonic pulses, give rise to systematic variations in interference patterns as a function of separation and relative angle. Though human listeners can identify only gross features when such echoes are slowed by as much as 128 times, bats may be able to make real time use of specific interference features. When sharp pulses are used for object localization by human listeners the pulse rates and burst lengths providing the best localizing information vary with the size, range, texture, and configural complexity of the objects localized. Variations seen both in the pulse sequences of individual bats and in the pulse structures of different kinds of bats may reflect adaptations to different requirements and different environmental configurations. (Author)