Hearing loss in stranded odontocete dolphins and whales.
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 significant role in some cetacean stranding events, and the hearing of all cetaceans in rehabilitation should be tested.
College of Marine Science, University of South Florida, St. Petersburg, Florida, United States of America. dmann@marine.usf.edu
David
D
Mann
Mandy
M
Hill-Cook
Charles
C
Manire
Danielle
D
Greenhow
Eric
E
Montie
Jessica
J
Powell
Randall
R
Wells
Gordon
G
Bauer
Petra
P
Cunningham-Smith
Robert
R
Lingenfelser
Robert
R
DiGiovanni
Abigale
A
Stone
Micah
M
Brodsky
Robert
R
Stevens
George
G
Kieffer
Paul
P
Hoetjes
D000367:Age Factors; D000818:Animals; D001299:Audiometry / Q000379:methods; D004289:Dolphins / Q000145:classification / Q000502:physiology*; D004455:Echolocation / Q000502:physiology*; D005260:Female; D034381:Hearing Loss / Q000503:physiopathology*; D006801:Humans; D008297:Male; D013045:Species Specificity; D014907:Whales / Q000145:classification / Q000502:physiology*