Auditory Brain Stem Responses Associated with Echolocation in an Atlantic Bottlenose Dolphin (Tursiops truncatus)

Abstract

Dolphins and toothed whales (odontocetes) possess highly developed sound production systems and hearing capabilities (Au 1993; Au et al. 2000). Because sound is transmitted much more efficiently than light and other possible stimuli through water, hearing plays a fundamental role as a primary sensory modality in dolphins and toothed whales and functions to aid in navigation, orientation, foraging, and communication (Au 1993; Nachtigall and Moore 1988; Richardson et al. 1995). Any sound in the water is detectable when the received level of the sound exceeds a certain hearing detection threshold of the animal. The efficiency of underwater sound propagation allows underwater noise created by ships and other human activities to be detected by aquatic animals far away from the source. Dolphins and toothed whales may be listening to many sounds from natural and human-made sources in addition to the sounds from themselves. Both natural and human-made sounds could have deleterious effects on the animals through interference with the animals’ ability to detect signals from conspecifics and echoes of echolocation clicks.