Dolphin Hearing Capabilities and Dolphin Hearing Capabilities and Loss: Physiological ApproachLoss: Physiological Approach

OverviewOverview AnatomyAnatomy Lipid CompositionLipid Composition Capabilities and Capabilities and

Sound ProductionSound Production Measuring HearingMeasuring Hearing Human Hearing Human Hearing Beaching in Beaching in

DolphinsDolphins ApplicationsApplications ResearchResearch WalrusesWalruses

Infant Risso dolphin undergoing hearing tests

What is BioacousticsWhat is Bioacoustics

Field closely related animal Field closely related animal behavior and animal physiology.behavior and animal physiology.

Understand relationships between Understand relationships between the features of the sounds an the features of the sounds an animal produces and the nature of animal produces and the nature of the environment in which they are the environment in which they are used and the functions they are used and the functions they are designed to serve. designed to serve.

Dolphin Hearing: AnatomyDolphin Hearing: Anatomy No pinna, utilizes the No pinna, utilizes the

panbone for bone panbone for bone conductance. conductance.

Middle ear has air Middle ear has air just like ours only just like ours only the ear is suspended the ear is suspended from the bone via from the bone via the auditory bulla. the auditory bulla.

Cochlea is longer Cochlea is longer and more rigid.and more rigid.

Accommodates a Accommodates a wider hearing range.wider hearing range.

Air Sacks

Brain

Auditory Bulla

Blowhole Eye

Dolphin Hearing: Lipid Dolphin Hearing: Lipid CompositionComposition

The lipid bi-layer (intramandibular fat The lipid bi-layer (intramandibular fat body) surrounding the jaw and leading body) surrounding the jaw and leading to the tympano-periotic complex aids to the tympano-periotic complex aids in the conductance of sound.in the conductance of sound.

The lipid chains are shorter than in The lipid chains are shorter than in other areas and are made of isovaleric other areas and are made of isovaleric acid. acid.

Dolphin Hearing: Dolphin Hearing: Capabilities and sound Capabilities and sound productionproduction

Hearing Range: 1 Hearing Range: 1 kHz to 150 kHz. kHz to 150 kHz.

Peak is 40kHz to Peak is 40kHz to 100kHz.100kHz.

Human Range: Human Range: 0.02 to 17 kHz.0.02 to 17 kHz.

Sounds: clicks Sounds: clicks and whistlesand whistles

Dolphin Sound Spectogram

   

                                                                                                                        

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Technology: Measuring Technology: Measuring hearing in Dolphinshearing in Dolphins

Jawphones: suction Jawphones: suction cups with cups with hydrophones hydrophones placed over various placed over various places on a places on a dolphin’s head to dolphin’s head to determine where determine where the best place of the best place of conductance is.conductance is.

Found to be on the Found to be on the pan bone or pan bone or acoustic window, acoustic window, beneath the eye. beneath the eye.

Testing Hearing In WaterTesting Hearing In Water

Speed of sound Speed of sound 1500m/s in Water1500m/s in Water 340m/s in Air340m/s in Air

Hydrophone in WaterHydrophone in Water No Jaw PhoneNo Jaw Phone

Go/ No-Go ParadigmGo/ No-Go Paradigm Animal Stations and touches a paddle Animal Stations and touches a paddle

for a yes and remains stationed if no. for a yes and remains stationed if no.

Human Hearing LossHuman Hearing Loss Presbycusis: Hearing Presbycusis: Hearing

loss due to old age. loss due to old age. Hearing loss is due Hearing loss is due

to genetics, to genetics, exposure to certain exposure to certain frequencies, frequencies, presbycusis.presbycusis.

Bottlenose dolphin Bottlenose dolphin males experience males experience hearing loss similar hearing loss similar to PRESBYCUSIS in to PRESBYCUSIS in humans. humans.

Beaching BehaviorBeaching Behavior

Dolphins intentionally beach Dolphins intentionally beach themselves for unknown reasons.themselves for unknown reasons.

Found that a large group of Found that a large group of dolphins and whales beach shortly dolphins and whales beach shortly after military noise testing. after military noise testing.

Speculation about rupturing of Speculation about rupturing of tympanic membranes and loss of tympanic membranes and loss of equilibrium or the bends. equilibrium or the bends.

Applications in Behavior & Applications in Behavior & PhysiologyPhysiology

Changes in Changes in behavior occur as behavior occur as a result in dolphins a result in dolphins and humans due and humans due to hearing loss.to hearing loss.

No behavioral No behavioral documentation on documentation on how they change how they change with hearing loss.with hearing loss.

Must do research!Must do research!

Dolphins are subject Dolphins are subject to underwater noise to underwater noise that could impair that could impair their hearing their hearing capabilities if we capabilities if we understand how to understand how to prevent or reverse prevent or reverse it we could it we could understand how to understand how to better human better human hearing and the hearing and the ocean ecology. ocean ecology.

Research IdeasResearch Ideas No research done No research done

on behavioral on behavioral aspects of hearing aspects of hearing loss in dolphins and loss in dolphins and the implications the implications this has. this has.

Do Dolphin males Do Dolphin males with a hearing loss with a hearing loss exhibit behavioral exhibit behavioral changes? changes?

Could this explain Could this explain beaching?beaching?

Dolphin SummaryDolphin Summary

Research on Research on dolphin hearing dolphin hearing and development and development of a model of of a model of dolphin auditory dolphin auditory pathways could pathways could help many people help many people and the health of and the health of our oceans. our oceans.

Walrus Hearing and Walrus Hearing and VocalizationsVocalizations

My thesis research on My thesis research on their vocalizations.their vocalizations.

Very few studies done Very few studies done on vocalizations and on vocalizations and hearing abilities. hearing abilities.

Record underwater in Record underwater in captive setting.captive setting.

Walruses have an air Walruses have an air sack. sack. Used to make unique Used to make unique

vocalizations.vocalizations.

How are Sounds How are Sounds Produced?Produced?

LarynxLarynx MelonMelon BlowholeBlowhole Pharyngeal pouchPharyngeal pouch Anatomy and Anatomy and

Physiology Physiology determine determine vocalizationsvocalizations

How are Cetaceans and How are Cetaceans and Pinnipeds Different?Pinnipeds Different?

Bone Bone conductanceconductance

PinnaPinna

Pinnipeds hear Pinnipeds hear low frequency low frequency soundssounds

Cetaceans hear Cetaceans hear high frequency high frequency sounds.sounds.

Walrus VocalizationsWalrus Vocalizations

MalesMales WhistlesWhistles BellsBells KnocksKnocks Tapping sequenceTapping sequence ClicksClicks GruntsGrunts RoarsRoars

FemalesFemales GruntsGrunts KnocksKnocks TapsTaps ClicksClicks GruntsGrunts GLUGS!GLUGS!

Glugs by JoanGlugs by Joan

Pinniped Hearing RangesPinniped Hearing Ranges

Estimated to be upwards of 50kHzEstimated to be upwards of 50kHz Each species is differentEach species is different Limited studies on Walrus. Limited studies on Walrus. Typical u-shaped curves Typical u-shaped curves

Pinniped Sensory AbilitiesPinniped Sensory Abilities

Highly tactileHighly tactile VibrassaeVibrassae Sounds for MatingSounds for Mating

Future ResearchFuture Research EcholocatioEcholocatio

n studiesn studies Further Further

studies of studies of Female Female WalrusWalrus

Further Further studies on studies on Harbor Harbor SealsSeals

ReferencesReferences Ames et. al. 2002. Comparison of lipids in selected tissues of the Ames et. al. 2002. Comparison of lipids in selected tissues of the

Florida manatee (Order Sirenia) and bottlenose dolphin (Order Florida manatee (Order Sirenia) and bottlenose dolphin (Order Cetacea;Suborder Odontoceti). Comp. Biochem. and Phys. 132: Cetacea;Suborder Odontoceti). Comp. Biochem. and Phys. 132: 625-634.625-634.

Aroyan, J. L. 2001. Three-dimensional modeling of hearing in Aroyan, J. L. 2001. Three-dimensional modeling of hearing in Delphinus delphis. Delphinus delphis. J. Acoust. Soc. Am. 110 (6) 3305-3317.J. Acoust. Soc. Am. 110 (6) 3305-3317.

Brill et. al. 2001. Assessment of dolphin (Brill et. al. 2001. Assessment of dolphin (Tursiops truncatusTursiops truncatus) ) auditory sensitivity and hearing loss using jawphones. J. Acoust. auditory sensitivity and hearing loss using jawphones. J. Acoust. Soc. Am. 109 (4) 1717-1722.Soc. Am. 109 (4) 1717-1722.

Hemila et. al. 1999. A model of the odontocete middle ear. Hearing Hemila et. al. 1999. A model of the odontocete middle ear. Hearing Research 133: 82-97. Research 133: 82-97.

Houser et. al. 2004. Structural and functional imaging of bottlenose Houser et. al. 2004. Structural and functional imaging of bottlenose dolphin (dolphin (Tursiops truncatusTursiops truncatus) cranial anatomy. J. Exp. Bio. 207: 3657-) cranial anatomy. J. Exp. Bio. 207: 3657-3665. 3665.

Ketten et. al. 2001. Aging, injury, disease, and noise in marine Ketten et. al. 2001. Aging, injury, disease, and noise in marine mammal ears. J. Acoust. Soc. Am. 110 (5) 2721. mammal ears. J. Acoust. Soc. Am. 110 (5) 2721.

Mohl et. al. 1999. Dolphin hearing: Relative sensitivity as a function Mohl et. al. 1999. Dolphin hearing: Relative sensitivity as a function of point of application of a contact sound source in the jaw and of point of application of a contact sound source in the jaw and head region. J. Acoust. Soc. Am. 105 (6) 3421-3424.head region. J. Acoust. Soc. Am. 105 (6) 3421-3424.