Dolphin Hearing Capabilities And Loss


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Guest Lecture for Animal Physiology WIU Spring 2007

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  • Ask about what the rigidity of the cochlea would lead to hearing wise. Which frequencies would have a larger range? High ones
  • Ask them to take a minute to look at differences. Notice Eustachian tube is lacking and the implications that could have towards diving physiology.
  • Bends= nitrogen bubbles in the tissue as a result of surfacing too quickly.
  • Dolphin Hearing Capabilities And Loss

    1. 1. Dolphin Hearing Capabilities and Loss: Physiological Approach
    2. 2. Overview <ul><li>Anatomy </li></ul><ul><li>Lipid Composition </li></ul><ul><li>Capabilities and Sound Production </li></ul><ul><li>Measuring Hearing </li></ul><ul><li>Human Hearing </li></ul><ul><li>Beaching in Dolphins </li></ul><ul><li>Applications </li></ul><ul><li>Research </li></ul><ul><li>Walruses </li></ul>Infant Risso dolphin undergoing hearing tests
    3. 3. What is Bioacoustics <ul><li>Field closely related animal behavior and animal physiology. </li></ul><ul><li>Understand relationships between the features of the sounds an animal produces and the nature of the environment in which they are used and the functions they are designed to serve. </li></ul>
    4. 4. Dolphin Hearing: Anatomy <ul><li>No pinna, utilizes the panbone for bone conductance. </li></ul><ul><li>Middle ear has air just like ours only the ear is suspended from the bone via the auditory bulla. </li></ul><ul><li>Cochlea is longer and more rigid. </li></ul><ul><li>Accommodates a wider hearing range. </li></ul>
    5. 7. Air Sacks Brain Auditory Bulla Blowhole Eye
    6. 8. Dolphin Hearing: Lipid Composition <ul><li>The lipid bi-layer (intramandibular fat body) surrounding the jaw and leading to the tympano-periotic complex aids in the conductance of sound. </li></ul><ul><li>The lipid chains are shorter than in other areas and are made of isovaleric acid. </li></ul>
    7. 9. Dolphin Hearing: Capabilities and sound production <ul><li>Hearing Range: 1 kHz to 150 kHz. </li></ul><ul><li>Peak is 40kHz to 100kHz. </li></ul><ul><li>Human Range: 0.02 to 17 kHz. </li></ul><ul><li>Sounds: clicks and whistles </li></ul>Dolphin Sound Spectogram
    8. 10.                                                                                                                               
    9. 11. Technology: Measuring hearing in Dolphins <ul><li>Jawphones: suction cups with hydrophones placed over various places on a dolphin’s head to determine where the best place of conductance is. </li></ul><ul><li>Found to be on the pan bone or acoustic window, beneath the eye. </li></ul>
    10. 12. Testing Hearing In Water <ul><li>Speed of sound </li></ul><ul><ul><li>1500m/s in Water </li></ul></ul><ul><ul><li>340m/s in Air </li></ul></ul><ul><li>Hydrophone in Water </li></ul><ul><ul><li>No Jaw Phone </li></ul></ul><ul><li>Go/ No-Go Paradigm </li></ul><ul><ul><li>Animal Stations and touches a paddle for a yes and remains stationed if no. </li></ul></ul>
    11. 13. Human Hearing Loss <ul><li>Presbycusis: Hearing loss due to old age. </li></ul><ul><li>Hearing loss is due to genetics, exposure to certain frequencies, presbycusis. </li></ul><ul><li>Bottlenose dolphin males experience hearing loss similar to PRESBYCUSIS in humans. </li></ul>
    12. 14. Beaching Behavior <ul><li>Dolphins intentionally beach themselves for unknown reasons. </li></ul><ul><li>Found that a large group of dolphins and whales beach shortly after military noise testing. </li></ul><ul><li>Speculation about rupturing of tympanic membranes and loss of equilibrium or the bends. </li></ul>
    13. 15. Applications in Behavior & Physiology <ul><li>Changes in behavior occur as a result in dolphins and humans due to hearing loss. </li></ul><ul><li>No behavioral documentation on how they change with hearing loss. </li></ul><ul><li>Must do research! </li></ul><ul><li>Dolphins are subject to underwater noise that could impair their hearing capabilities if we understand how to prevent or reverse it we could understand how to better human hearing and the ocean ecology. </li></ul>
    14. 16. Research Ideas <ul><li>No research done on behavioral aspects of hearing loss in dolphins and the implications this has. </li></ul><ul><li>Do Dolphin males with a hearing loss exhibit behavioral changes? </li></ul><ul><li>Could this explain beaching? </li></ul>
    15. 17. Dolphin Summary <ul><li>Research on dolphin hearing and development of a model of dolphin auditory pathways could help many people and the health of our oceans. </li></ul>
    16. 18. Walrus Hearing and Vocalizations <ul><li>My thesis research on their vocalizations. </li></ul><ul><li>Very few studies done on vocalizations and hearing abilities. </li></ul><ul><li>Record underwater in captive setting. </li></ul><ul><li>Walruses have an air sack. </li></ul><ul><ul><li>Used to make unique vocalizations. </li></ul></ul>
    17. 19. How are Sounds Produced? <ul><li>Larynx </li></ul><ul><li>Melon </li></ul><ul><li>Blowhole </li></ul><ul><li>Pharyngeal pouch </li></ul><ul><li>Anatomy and Physiology determine vocalizations </li></ul>
    18. 20. How are Cetaceans and Pinnipeds Different? <ul><li>Bone conductance </li></ul><ul><li>Pinna </li></ul><ul><li>Pinnipeds hear low frequency sounds </li></ul><ul><li>Cetaceans hear high frequency sounds. </li></ul>
    19. 21. Walrus Vocalizations <ul><li>Males </li></ul><ul><ul><li>Whistles </li></ul></ul><ul><ul><li>Bells </li></ul></ul><ul><ul><li>Knocks </li></ul></ul><ul><ul><li>Tapping sequence </li></ul></ul><ul><ul><li>Clicks </li></ul></ul><ul><ul><li>Grunts </li></ul></ul><ul><ul><li>Roars </li></ul></ul><ul><li>Females </li></ul><ul><ul><li>Grunts </li></ul></ul><ul><ul><li>Knocks </li></ul></ul><ul><ul><li>Taps </li></ul></ul><ul><ul><li>Clicks </li></ul></ul><ul><ul><li>Grunts </li></ul></ul><ul><ul><li>GLUGS! </li></ul></ul>
    20. 22. Glugs by Joan
    21. 23. Pinniped Hearing Ranges <ul><li>Estimated to be upwards of 50kHz </li></ul><ul><li>Each species is different </li></ul><ul><li>Limited studies on Walrus. </li></ul><ul><li>Typical u-shaped curves </li></ul>
    22. 24. Pinniped Sensory Abilities <ul><li>Highly tactile </li></ul><ul><li>Vibrassae </li></ul><ul><li>Sounds for Mating </li></ul>
    23. 25. Future Research <ul><li>Echolocation studies </li></ul><ul><li>Further studies of Female Walrus </li></ul><ul><li>Further studies on Harbor Seals </li></ul>
    24. 26. References <ul><li>Ames et. al. 2002. Comparison of lipids in selected tissues of the Florida manatee (Order Sirenia) and bottlenose dolphin (Order Cetacea;Suborder Odontoceti). Comp. Biochem. and Phys. 132: 625-634. </li></ul><ul><li>Aroyan, J. L. 2001. Three-dimensional modeling of hearing in Delphinus delphis. J. Acoust. Soc. Am. 110 (6) 3305-3317. </li></ul><ul><li>Brill et. al. 2001. Assessment of dolphin ( Tursiops truncatus ) auditory sensitivity and hearing loss using jawphones. J. Acoust. Soc. Am. 109 (4) 1717-1722. </li></ul><ul><li>Hemila et. al. 1999. A model of the odontocete middle ear. Hearing Research 133: 82-97. </li></ul><ul><li>Houser et. al. 2004. Structural and functional imaging of bottlenose dolphin ( Tursiops truncatus ) cranial anatomy. J. Exp. Bio. 207: 3657-3665. </li></ul><ul><li>Ketten et. al. 2001. Aging, injury, disease, and noise in marine mammal ears. J. Acoust. Soc. Am. 110 (5) 2721. </li></ul><ul><li>Mohl et. al. 1999. Dolphin hearing: Relative sensitivity as a function of point of application of a contact sound source in the jaw and head region. J. Acoust. Soc. Am. 105 (6) 3421-3424. </li></ul>