Auditory Evoked Potential Measurement of Hearing Sensitivity in Pinnipeds

Abstract

The majority of research on marine mammal hearing sensitivity has focused on the odontocete cetaceans (dolphins and porpoises) who possess morphological and neural adaptations that support sensitive passive hearing and a refined echolocation system. Fewer studies have examined the hearing sensitivity of the amphibious pinnipeds (sea lions, seals, and the walrus) who do not possess a sophisticated echolocation system. Passive hearing in pinnipeds is, nonetheless, important in behaviors related to reproduction, foraging, and predator avoidance. Many of these studies have used behavioral psychophysical methods to directly measure an animal’s perceptual experience. Although the high-quality data provided by psychophysical methods are the most accurate description of hearing sensitivity, the methods are limited because they require trained subjects tested in captive environments. As a result, psychophysically measured profiles describing hearing sensitivity as a function of frequency (audiograms) are available for a small proportion of pinniped and odontocete species, and each examined species is usually represented by only a few individuals.