Hearing Loss in Stranded Odontocete Dolphins and Whales

• Main Authors: David Mann, Y Hill-cook, Charles Manire ¤a, Danielle Greenhow, Eric Montie, All Wells, Gordon Bauer, Petra Cunningham-smith, Robert Lingenfelser, Abigale Stone, Micah Brodsky, Robert Stevens, George Kieffer, Paul Hoetjes
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: toothed whales
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.349.3461

The causes of dolphin and whale stranding can often be difficult to determine. Because toothed whales rely on echolocation for orientation and feeding, hearing deficits could lead to stranding. We report on the results of auditory evoked potential measurements from eight species of odontocete cetaceans that were found stranded or severely entangled in fishing gear during the period 2004 through 2009. Approximately 57 % of the bottlenose dolphins and 36 % of the rough-toothed dolphins had significant hearing deficits with a reduction in sensitivity equivalent to severe (70–90 dB) or profound (.90 dB) hearing loss in humans. The only stranded short-finned pilot whale examined had profound hearing loss. No impairments were detected in seven Risso’s dolphins from three different stranding events, two pygmy killer whales, one Atlantic spotted dolphin, one spinner dolphin, or a juvenile Gervais ’ beaked whale. Hearing impairment could play a