Investigating the Dolphin's Peripheral Hearing System: Acoustic Sensitivity About the Head and Lower Jaw

摘要

For this report, jawphones were used to behaviorally measure the relative hearing thresholds at four frequencies (10, 30, 60, and 90 kHz) on more than 40 sites of a dolphin's head, from the tip of the rostrum to the base of the pectoral fins. Measurements were converted into iso-sensitivity curves projected onto a two-dimensional, heuristic representation of the head area investigated. The results suggest high-frequency sensitivity along the lower jaw with greater sensitivity forward of the panbone area, sensitivity to low frequency in the area of the external auditory meatus, and an asymmetry in sensitivity favoring the left side of the head. These results may have correlates in the underlying anatomy and suggest that the dolphin's peripheral hearing system is more complex than has previously been assumed.