Hey Ron manatees do not echolocate either; the underwater hearing and acoustical behavior of West Indian manatees

A comprehensive series of underwater psychoacoustic tests were conducted with captive manatees to measure their hearing abilities under varying acoustic conditions. Forced‐choice paradigms with either a staircase, or method of constants, psychometric were used to define their audiogram, critical ratios, temporal integration, and directional hearing abilities. Pure tones, complex, broad and narrow‐band noise were presented with a masker, at different intensities, to measure simultaneous masking effects at ambient levels recorded in manatee habitats. Masked thresholds across frequencies increased linearly with masker intensity. Critical ratios for pulsed signals were lower than nonpulsed, suggesting an inhibitory process affecting perception of nonpulsed tones. Comparisons with other mammals indicate manatees have acute filtering abilities for detecting pulsed sounds. While manatees do not exhibit a vocal repertoire to account for acute filtering, they are passive listeners, well adapted to selectively filt...