Ear Adaptations in Deep Divers

Abstract

Abstract : Because of concerns for anthropogenic acoustic impacts in the oceans, much of the focus of the ONR marine program has been on expanding our knowledge of hearing in marine mammals and particularly understanding hearing in species likely to be low frequency sensitive. For practical reasons, most marine mammal hearing research is on audiometry for captive odontocetes and pinnipeds and on playback responses and modeling of hearing in mysticetes, which are mid to shallow range divers. However, another jgroup of marine mammals, the deep divers, also needs to be assessed, particularly because these are ears that may have significant pressure adaptations. Prior to%this study, pressure and auditory adaptations of deep divers had not been systematically investigated. Beaked whales are a particular focus in this study because they are ubiquitous but poorly understood. Beaked whales are large, pelagic, and elusive. They rarely strand. Consequently our knowledge of them is limited primarily to off-shore sitings, surface observations, and gross surface measurements of poorly preserved animals. For some species, well-preserved material is available but has not been dissected because of its rarity. In the last several years, by-catch specimens have dwindled because fisheries that impacted beaked whales are progressively being closed. Consequently, this study was opportunistic and brief; i.e., it was a small focused, exploratory study that utilized a narrow window of opportunity to obtain material for the rarest of the deep-diving species,the beaked whale. 114. Subject Terms 115. NumberofPages