Ketten Darlene R.

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Darlene R.

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Beaked whale necropsy findings for strandings in the Bahamas, Puerto Rico, and Madeira, 1999-2002

(Woods Hole Oceanographic Institution, 2005-11) Ketten, Darlene R.

Necropsy and histologic findings for examinations performed on beaked whales stranding between October, 1999 and June, 2002 are summarized and the finding interpreted. They are presented in chronological order of exams and comprise strandings from the following areas: I. Puerto Rican collections from Virgin Islands and Puerto Rican waters, 1999-2000 II. Northern Bahamas III. Madeira IV. Puerto Rico coastal, 2002.
A manual for the removal, fixation and preservation of cetacean ears

(Woods Hole Oceanographic Institution, 2007-01) Ketten, Darlene R. ; Cramer, Scott R. ; Arruda, Julie

This chapter is intended as an instructional guide for the removal, fixation and preservation of auditory system tissues of marine mammals. Each section describes procedures for a major ear type for marine mammals. The main intention is to provide both inexperienced and seasoned stranding responders with sufficient instructions to locate, document and remove all structures related to the ears and hearing in order to optimize the fixation and preservation of these tissues for later, more extensive examination. It is strongly recommended that examination be performed collaboratively with auditory system experts, but careful documentation and preservation are the critical first steps that will allow accurate diagnoses.
Potential for sound sensitivity in cephalopods

( 2010-07) Mooney, T. Aran ; Hanlon, Roger T. ; Madsen, Peter T. ; Christensen-Dalsgaard, Jakob ; Ketten, Darlene R. ; Nachtigall, Paul E.

Hearing is a primary sense in many marine animals and we now have a reasonable understanding of what stimuli generate clear responses, the frequency range of sensitivity, expected threshold values and mecha-nisms of sound detection for several species of marine mammals and fishes (Fay 1988; Au et al. 2000). For marine invertebrates, our knowledge of hearing capabilities is relatively poor and a definition or even certainty of sound detection is not agreed upon (Webster et al. 1992) despite their magnitude of biomass and often central role in ocean ecosystems. Cephalopods (squid, cuttlefish, octopods and nautilus) are particularly interesting subjects for inver-tebrate sound detection investigations for several reasons. Ecologically, they occupy many of the same niches as sound-sensitive fish (Budelmann 1994) and may benefit from sound perception and use for the same reasons, such as to detect predators, navigate, or locate conspecifics. Squid, for example, are often the prey of loud, echolocating marine mammals (Clarke 1996), and may therefore be expected to have evolved hearing to avoid predators. Anatomically, squid have complex statocysts that are considered to serve primarily as vestibular and acceleration detectors (Nixon and Young 2003). However, statocysts may also be analogs for fish otolithic organs, detecting acoustic stimuli (Budelmann 1992). Previous studies have debated the subject of squid hearing and recently there has been a revival of research on the subject. Here, we briefly review what is known about squid sound detection, revisit hearing definitions, discuss potential squid susceptibility to anthropogenic noise and suggest potential future research direc-tions to examine squid acoustic sensitivity.
Possible limitations of dolphin echolocation: a simulation study based on a cross-modal matching experiment

(Nature Research, 2021-03-23) Wei, Chong ; Hoffmann-Kuhnt, Matthias ; Au, Whitlow W. L. ; Ho, Abel Zhong Hao ; Matrai, Patricia A. ; Feng, Wen ; Ketten, Darlene R. ; Zhang, Yu

Dolphins use their biosonar to discriminate objects with different features through the returning echoes. Cross-modal matching experiments were conducted with a resident bottlenose dolphin (Tursiops aduncus). Four types of objects composed of different materials (water-filled PVC pipes, air-filled PVC pipes, foam ball arrays, and PVC pipes wrapped in closed-cell foam) were used in the experiments, respectively. The size and position of the objects remained the same in each case. The data collected in the experiment showed that the dolphin’s matching accuracy was significantly different across the cases. To gain insight into the underlying mechanism in the experiments, we used finite element methods to construct two-dimensional target detection models of an echolocating dolphin in the vertical plane, based on computed tomography scan data. The acoustic processes of the click’s interaction with the objects and the surrounding media in the four cases were simulated and compared. The simulation results provide some possible explanations for why the dolphin performed differently when discriminating the objects that only differed in material composition in the previous matching experiments.
Aminoglycoside-induced damage in the statocyst of the longfin inshore squid, Doryteuthis pealeii

(Marine Biological Laboratory, 2014-08-01) Scharr, Alexandra L. ; Mooney, T. Aran ; Schweizer, Felix E. ; Ketten, Darlene R.

Squid are a significant component of the marine biomass and are a long-established model organism in experimental neurophysiology. The squid statocyst senses linear and angular acceleration and is the best candidate for mediating squid auditory responses, but its physiology and morphology are rarely studied. The statocyst contains mechano-sensitive hair cells that resemble hair cells in the vestibular and auditory systems of other animals. We examined whether squid statocyst hair cells are sensitive to aminoglycosides, a group of antibiotics that are ototoxic in fish, birds, and mammals. To assess aminoglycoside-induced damage, we used immunofluorescent methods to image the major cell types in the statocyst of longfin squid (Doryteuthis pealeii). Statocysts of live, anesthetized squid were injected with either a buffered saline solution or neomycin at concentrations ranging from 0.05 to 3.0 mmol l−1. The statocyst hair cells of the macula statica princeps were examined 5 h post-treatment. Anti-acetylated tubulin staining showed no morphological differences between the hair cells of saline-injected and non-injected statocysts. The hair cell bundles of the macula statica princeps in aminoglycoside-injected statocysts were either missing or damaged, with the amount of damage being dose-dependent. The proportion of missing hair cells did not increase at the same rate as damaged cells, suggesting that neomycin treatment affects hair cells in a nonlethal manner. These experiments provide a reliable method for imaging squid hair cells. Further, aminoglycosides can be used to induce hair cell damage in a primary sensory area of the statocyst of squid. Such results support further studies on loss of hearing and balance in squid.
Auditory temporal resolution and evoked responses to pulsed sounds for the Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis)

( 2011-08-09) Mooney, T. Aran ; Li, Songhai ; Ketten, Darlene R. ; Wang, Kexiong ; Wang, Ding

Temporal cues are important for some forms of auditory processing, such as echolocation. Among odontocetes (toothed whales, dolphins, and porpoises), it has been suggested that porpoises may have temporal processing abilities which differ from other odontocetes because of their relatively narrow auditory filters and longer duration echolocation signals. This study examined auditory temporal resolution in two Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis) using auditory evoked potentials (AEPs) to measure: (i) rate following responses and modulation rate transfer function for 100 kHz centered pulse sounds and (ii) hearing thresholds and response amplitudes generated by individual pulses of different durations. The animals followed pulses well at modulation rates up to 1250 Hz, after which response amplitudes declined until extinguished beyond 2500 Hz. The subjects had significantly better hearing thresholds for longer, narrower-band pulses similar to porpoise echolocation signals compared to brief, broadband sounds resembling dolphin clicks. Results indicate that the Yangtze finless porpoise follows individual acoustic signals at rates similar to other odontocetes tested. Relatively good sensitivity for longer duration, narrow-band signals suggests that finless porpoise hearing is well-suited to detect their unique echolocation signals.
Hearing abilities and sound reception of broadband sounds in an adult Risso’s dolphin (Grampus griseus )

( 2015-04) Mooney, T. Aran ; Yang, Wei-Cheng ; Yu, Hsin-Yi ; Ketten, Darlene R. ; Jen, I-Fan

While odontocetes do not have an external pinna that guides sound to the middle ear, they are considered to receive sound through specialized regions of the head and lower jaw. Yet odontocetes differ in the shape of the lower jaw suggesting that hearing pathways may vary between species, potentially influencing hearing directionality and noise impacts. This work measured the audiogram and received sensitivity of a Risso’s dolphin (Grampus griseus) in an effort to comparatively examine how this species receives sound. Jaw hearing thresholds were lowest (most sensitive) at two locations along the anterior, midline region of the lower jaw (the lower jaw tip and anterior part of the throat). Responses were similarly low along a more posterior region of the lower mandible, considered the area of best hearing in bottlenose dolphins. Left and right side differences were also noted suggesting possible left-right asymmetries in sound reception or differences in ear sensitivities. The results indicate best hearing pathways may vary between the Risso’s dolphin and other odontocetes measured. This animal received sound well, supporting a proposed throat pathway. For Risso’s dolphins in particular, good ventral hearing would support their acoustic ecology by facilitating echo-detection from their proposed downward oriented echolocation beam.
Functional analyses of peripheral auditory system adaptations for echolocation in air vs. water

(Frontiers Media, 2021-09-06) Ketten, Darlene R. ; Simmons, James A. ; Riquimaroux, Hiroshi ; Simmons, Andrea Megela

The similarity of acoustic tasks performed by odontocete (toothed whale) and microchiropteran (insectivorous bat) biosonar suggests they may have common ultrasonic signal reception and processing mechanisms. However, there are also significant media and prey dependent differences, notably speed of sound and wavelengths in air vs. water, that may be reflected in adaptations in their auditory systems and peak spectra of out-going signals for similarly sized prey. We examined the anatomy of the peripheral auditory system of two species of FM bat (big brown bat Eptesicus fuscus; Japanese house bat Pipistrellus abramus) and two toothed whales (harbor porpoise Phocoena phocoena; bottlenose dolphin Tursiops truncatus) using ultra high resolution (11–100 micron) isotropic voxel computed tomography (helical and microCT). Significant differences were found for oval and round window location, cochlear length, basilar membrane gradients, neural distributions, cochlear spiral morphometry and curvature, and basilar membrane suspension distributions. Length correlates with body mass, not hearing ranges. High and low frequency hearing range cut-offs correlate with basilar membrane thickness/width ratios and the cochlear radius of curvature. These features are predictive of high and low frequency hearing limits in all ears examined. The ears of the harbor porpoise, the highest frequency echolocator in the study, had significantly greater stiffness, higher basal basilar membrane ratios, and bilateral bony support for 60% of the basilar membrane length. The porpoise’s basilar membrane includes a “foveal” region with “stretched” frequency representation and relatively constant membrane thickness/width ratio values similar to those reported for some bat species. Both species of bats and the harbor porpoise displayed unusual stapedial input locations and low ratios of cochlear radii, specializations that may enhance higher ultrasonic frequency signal resolution and deter low frequency cochlear propagation.
The auditory anatomy of the minke whale (Balaenoptera acutorostrata) : a potential fatty sound reception pathway in a baleen whale

(John Wiley & Sons, 2012-05-12) Yamato, Maya ; Ketten, Darlene R. ; Arruda, Julie ; Cramer, Scott R. ; Moore, Kathleen M. T.

Cetaceans possess highly derived auditory systems adapted for underwater hearing. Odontoceti (toothed whales) are thought to receive sound through specialized fat bodies that contact the tympanoperiotic complex, the bones housing the middle and inner ears. However, sound reception pathways remain unknown in Mysticeti (baleen whales), which have very different cranial anatomies compared to odontocetes. Here, we report a potential fatty sound reception pathway in the minke whale (Balaenoptera acutorostrata), a mysticete of the balaenopterid family. The cephalic anatomy of seven minke whales was investigated using computerized tomography and magnetic resonance imaging, verified through dissections. Findings include a large, well-formed fat body lateral, dorsal, and posterior to the mandibular ramus and lateral to the tympanoperiotic complex. This fat body inserts into the tympanoperiotic complex at the lateral aperture between the tympanic and periotic bones and is in contact with the ossicles. There is also a second, smaller body of fat found within the tympanic bone, which contacts the ossicles as well. This is the first analysis of these fatty tissues' association with the auditory structures in a mysticete, providing anatomical evidence that fatty sound reception pathways may not be a unique feature of odontocete cetaceans.
Hearing pathways in the Yangtze finless porpoise, Neophocaena asiaeorientalis asiaeorientalis

(Company of Biologists, 2013-10-18) Mooney, T. Aran ; Li, Songhai ; Ketten, Darlene R. ; Wang, Kexiong ; Wang, Ding

How an animal receives sound may influence its use of sound. While ‘jaw hearing’ is well supported for odontocetes, work examining how sound is received across the head has been limited to a few representative species. The substantial variation in jaw and head morphology among odontocetes suggests variation in sound reception. Here, we address how a divergent subspecies, the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) hears low-, mid- and high-frequency tones, as well as broadband clicks, comparing sounds presented at different locations across the head. Hearing was measured using auditory evoked potentials (AEPs). Click and tone stimuli (8, 54 and 120 kHz) were presented at nine locations on the head and body using a suction-cup transducer. Threshold differences were compared between frequencies and locations, and referenced to the underlying anatomy using computed tomography (CT) imaging of deceased animals of the same subspecies. The best hearing locations with minimum thresholds were found adjacent to a mandibular fat pad and overlaying the auditory bulla. Mean thresholds were not substantially different at locations from the rostrum tip to the ear (11.6 dB). This contrasts with tests with bottlenose dolphins and beluga whales, in which 30–40 dB threshold differences were found across the animals' heads. Response latencies increased with decreasing response amplitudes, which suggests that latency and sensitivity are interrelated when considering sound reception across the odontocete head. The results suggest that there are differences among odontocetes in the anatomy related to receiving sound, and porpoises may have relatively less acoustic ‘shadowing’.
Imaging procedures for stranded marine mammals

(Woods Hole Oceanographic Institution, 2008-01) Ketten, Darlene R. ; Montie, Eric W.

This section provides an introduction to biomedical imaging techniques and guidelines for diagnostic imaging of marine mammals to assist with both live examination and necropsy procedures. The procedures described are based on imaging equipment and techniques that are relatively common in human and veterinary facilities and to provide the majority of stranding response groups with the most likely options that will assist their efforts. The imaging techniques described include basic radiography, computed tomography (CT), and magnetic resonance imaging (MRI) and are applicable to both live and post-mortem cases. Special emphasis has been placed on whole body, airway, head and ear imaging procedures. Sub-sections cover basic information on the basic principles and appropriate applications for radiography vs. CT vs. MRI, handling and preparation of live and dead animals in clinical settings, and image and data formats that may be encountered. The protocols are also listed in outline form in order to provide a rapid overview. The introductory discussion of principles behind techniques is not required to employ the protocols but does provide additional information that can aid in deciding which techniques are most efficacious and what the limitations are for interpretation of imaging data. Examples of some pathology imaged with these procedures are also provided.
A model and experimental approach to the middle ear transfer function related to hearing in the humpback whale (Megaptera novaeangliae)

(Acoustical Society of America, 2018-08-01) Tubelli, Andrew A. ; Zosuls, Aleksandrs ; Ketten, Darlene R. ; Mountain, David C.

At present, there are no direct measures of hearing for any baleen whale (Mysticeti). The most viable alternative to in vivo approaches to simulate the audiogram is through modeling outer, middle, and inner ear functions based on the anatomy and material properties of each component. This paper describes a finite element model of the middle ear for the humpback whale (Megaptera novaeangliae) to calculate the middle ear transfer function (METF) to determine acoustic energy transmission to the cochlea. The model was developed based on high resolution computed tomography imaging and direct anatomical measurements of the middle ear components for this mysticete species. Mechanical properties for the middle ear tissues were determined from experimental measurements and published values. The METF for the humpback whale predicted a better frequency range between approximately 15 Hz and 3 kHz or between 200 Hz and 9 kHz based on two potential stimulation locations. Experimental measures of the ossicular chain, tympanic membrane, and tympanic bone velocities showed frequency response characteristics consistent with the model. The predicted best sensitivity hearing ranges match well with known vocalizations of this species.
Digital three-dimensional imaging techniques provide new analytical pathways for malacological research

(BioOne Complete, 2018-12-01) Ziegler, Alexander ; Bock, Christian ; Ketten, Darlene R. ; Mair, Ross W. ; Mueller, Susanne ; Nagelmann, Nina ; Pracht, Eberhard D. ; Schröder, Leif

Research on molluscan specimens is increasingly being carried out using high-throughput molecular techniques. Due to their efficiency, these technologies have effectively resulted in a strong bias towards genotypic analyses. Therefore, the future large-scale correlation of such data with the phenotype will require a significant increase in the output of morphological studies. Three-dimensional (3D) scanning techniques such as magnetic resonance imaging (MRI) or computed tomography (CT) can achieve this goal as they permit rapidly obtaining digital data non-destructively or even entirely non-invasively from living, fixed, and fossil samples. With a large number of species and a relatively complex morphology, the Mollusca would profit from a more widespread application of digital 3D imaging techniques. In order to provide an overview of the capacity of various MRI and CT techniques to visualize internal and external structures of molluscs, more than twenty specimens ranging in size from a few millimeters to well over one meter were scanned in vivo as well as ex vivo. The results show that all major molluscan organ systems can be successfully visualized using both MRI and CT. The choice of a suitable imaging technique depends primarily on the specimen's life condition, its size, the required resolution, and possible invasiveness of the approach. Apart from visual examples derived from more than two dozen scans, the present article provides guidelines and best practices for digital 3D imaging of a broad range of molluscan taxa. Furthermore, a comprehensive overview of studies that previously have employed MRI or CT techniques in malacological research is given.
Sonar-induced pressure fields in a post-mortem common dolphin

(Acoustical Society of America, 2012-02) Foote, Kenneth G. ; Hastings, Mardi C. ; Ketten, Darlene R. ; Lin, Ying-Tsong ; Reidenberg, Joy S. ; Rye, Kent

Potential physical effects of sonar transmissions on marine mammals were investigated by measuring pressure fields induced in a 119-kg, 211-cm-long, young adult male common dolphin (Delphinus delphis) cadaver. The specimen was instrumented with tourmaline acoustic pressure gauges used as receiving sensors. Gauge implantation near critical tissues was guided by intraoperative, high-resolution, computerized tomography (CT) scanning. Instrumented structures included the melon, nares, ear, thoracic wall, lungs, epaxial muscle, and lower abdomen. The specimen was suspended from a frame equipped with a standard 50.8-mm-diameter spherical transducer used as the acoustic source and additional receiving sensors to monitor the transmitted and external, scattered field. Following immersion, the transducer transmitted pulsed sinusoidal signals at 5, 7, and 10 kHz. Quantitative internal pressure fields are reported for all cases except those in which the gauge failed or no received signal was detected. A full necropsy was performed immediately after the experiment to examine instrumented areas and all major organs. No lesions attributable to acoustic transmissions were found, consistent with the low source level and source-receiver distances.
Deadly diving? Physiological and behavioural management of decompression stress in diving mammals

(Royal Society, 2011-12-21) Hooker, Sascha K. ; Fahlman, Andreas ; Moore, Michael J. ; Aguilar De Soto, Natacha ; Bernaldo de Quiros, Yara ; Brubakk, A. O. ; Costa, Daniel P. ; Costidis, Alexander M. ; Dennison, Sophie ; Falke, K. J. ; Fernandez, Antonio ; Ferrigno, Massimo ; Fitz-Clarke, J. R. ; Garner, Michael M. ; Houser, Dorian S. ; Jepson, Paul D. ; Ketten, Darlene R. ; Kvadsheim, P. H. ; Madsen, Peter T. ; Pollock, N. W. ; Rotstein, David S. ; Rowles, Teresa K. ; Simmons, S. E. ; Van Bonn, William ; Weathersby, P. K. ; Weise, Michael ; Williams, Terrie M. ; Tyack, Peter L.

Decompression sickness (DCS; ‘the bends’) is a disease associated with gas uptake at pressure. The basic pathology and cause are relatively well known to human divers. Breath-hold diving marine mammals were thought to be relatively immune to DCS owing to multiple anatomical, physiological and behavioural adaptations that reduce nitrogen gas (N2) loading during dives. However, recent observations have shown that gas bubbles may form and tissue injury may occur in marine mammals under certain circumstances. Gas kinetic models based on measured time-depth profiles further suggest the potential occurrence of high blood and tissue N2 tensions. We review evidence for gas-bubble incidence in marine mammal tissues and discuss the theory behind gas loading and bubble formation. We suggest that diving mammals vary their physiological responses according to multiple stressors, and that the perspective on marine mammal diving physiology should change from simply minimizing N2 loading to management of the N2 load. This suggests several avenues for further study, ranging from the effects of gas bubbles at molecular, cellular and organ function levels, to comparative studies relating the presence/absence of gas bubbles to diving behaviour. Technological advances in imaging and remote instrumentation are likely to advance this field in coming years.
Does rotation during echolocation increase the acoustic field of view? Comparative numerical models based on CT data of a live versus deceased dolphin

(IOP Publishing, 2023-04-04) Wei, Chong ; Houser, Dorian ; Erbe, Christine ; Zhang, Chuang ; Matrai, Eszter ; Finneran, James J. ; Au, Whitlow W.

Spinning is a natural and common dolphin behavior; however, its role in echolocation is unknown. We used computed tomography (CT) data of a live and a recently deceased bottlenose dolphin together with measurements of the acoustic properties of head tissues to perform acoustic property reconstrcution. The anatomical configuration and acoustic properties of the main forehead structures between the live and deceased dolphins were compared. Finite element analysis (FEA) was applied to simulate the generation and propagation of echolocation clicks, to compute their waveforms and spectra in both near- and far-fields, and to derive echolocation beam patterns. Model results from both the live and deceased dolphins were in good agreement with click recordings from live, echolocating individuals. FEA was also used to estimate the acoustic scene experienced by a dolphin rotating 180ã about its longitudinal axis to detect fish in the far-field at elevation angles of 0ã –20ã . The results suggest that the spinning behavior provides a wider insonification area and compensates for the dolphin’s relatively narrow biosonar beam and constraints on the pointing direction that are limited by head movement. The results also have implications for examining the accuracy of FEA in acoustic simulations using freshly deceased specimens.
Understanding the impacts of anthropogenic sound on beaked whales

(International Whaling Commission, 2023-03-14) Cox, T. M. ; Ragen, T. J. ; Read, A. J. ; Vos, E. ; Baird, R. W. ; Balcomb, K. ; Barlow, J. ; Caldwell, J. ; Cranford, T. ; Crum, L. ; D'Amico, A. ; D'Spain, G. ; Fernandez, A. ; Finneran, J. ; Gentry, R. ; Gerth, W. ; Gulland, F. ; Hildebrand, J. ; Houser, D. ; Hullar, T. ; Jepson, P. D. ; Ketten, D. ; MacLeod, C. D. ; Miller, P. ; Moore, S. ; Mountain, D. C. ; Palka, D. ; Ponganis, P. ; Rommel, S. ; Rowles, T. ; Taylor, B. ; Tyack, P. ; Wartzok, D. ; Gisiner, R. ; Mead, J. ; Benner, L.

This review considers the effect of anthropogenic sound on beaked whales2. Two major conclusions are presented: (1) gas-bubble disease, induced in supersaturated tissue by a behavioural response to acoustic exposure, is a plausible pathologic mechanism for the morbidity and mortality seen in cetaceans associated with sonar exposure and merits further investigation; and (2) current monitoring and mitigation methods for beaked whales are ineffective for detecting these animals and protecting them from adverse sound exposure. In addition, four major research priorities, needed to address information gaps on the impacts of sound on beaked whales, are identified: (1) controlled exposure experiments to assess beaked whale responses to known sound stimuli; (2) investigation of physiology, anatomy, pathobiology and behaviour of beaked whales; (3) assessment of baseline diving behaviour and physiology of beaked whales; and (4) a retrospective review of beaked whale strandings.
Biosonar signal propagation in the harbor porpoise's (Phocoena phocoena) head : the role of various structures in the formation of the vertical beam

(Acoustical Society of America, 2017-06-07) Wei, Chong ; Au, Whitlow W. L. ; Ketten, Darlene R. ; Song, Zhongchang ; Zhang, Yu

Harbor porpoises (Phocoena phocoena) use narrow band echolocation signals for detecting and locating prey and for spatial orientation. In this study, acoustic impedance values of tissues in the porpoise's head were calculated from computer tomography (CT) scan and the corresponding Hounsfield Units. A two-dimensional finite element model of the acoustic impedance was constructed based on CT scan data to simulate the acoustic propagation through the animal's head. The far field transmission beam pattern in the vertical plane and the waveforms of the receiving points around the forehead were compared with prior measurement results, the simulation results were qualitatively consistent with the measurement results. The role of the main structures in the head such as the air sacs, melon and skull in the acoustic propagation was investigated. The results showed that air sacs and skull are the major components to form the vertical beam. Additionally, both beam patterns and sound pressure of the sound waves through four positions deep inside the melon were demonstrated to show the role of the melon in the biosonar sound propagation processes in the vertical plane.
Three-dimensional geometry of the narwhal (Monodon monoceros) flukes in relation to hydrodynamics

( 2010-09-03) Fontanella, Janet E. ; Fish, Frank E. ; Rybczynski, Natalia ; Nweeia, Martin T. ; Ketten, Darlene R.

Cetaceans (whales, porpoises, and dolphins) use only their flukes for propulsion. Flukes are distally located extensions of the tail, and from a biomechanical standpoint, function as a pair of wings (Vogel 1994). Flukes function to produce thrust generated as an anteriorly directed lift force as flukes oscillate vertically (Fish 1998 a,b). Their cross-sections resemble hydrofoils. For a hydrofoil to be effective, a large lift must be produced while drag is minimized; this, in turn, increases the thrust generated (Weihs 1989; Vogel 1994).
Finite element simulation of broadband biosonar signal propagation in the near- and far-field of an echolocating Atlantic bottlenose dolphin (Tursiops truncatus)

(Acoustical Society of America, 2018-05-02) Wei, Chong ; Au, Whitlow W. L. ; Ketten, Darlene R. ; Zhang, Yu

Bottlenose dolphins project broadband echolocation signals for detecting and locating prey and predators, and for spatial orientation. There are many unknowns concerning the specifics of biosonar signal production and propagation in the head of dolphins and this manuscript represents an effort to address this topic. A two-dimensional finite element model was constructed using high resolution CT scan data. The model simulated the acoustic processes in the vertical plane of the biosonar signal emitted from the phonic lips and propagated into the water through the animal's head. The acoustic field on the animal's forehead and the farfield transmission beam pattern of the echolocating dolphin were determined. The simulation results and prior acoustic measurements were qualitatively extremely consistent. The role of the main structures on the sound propagation pathway such as the air sacs, melon, and connective tissue was investigated. Furthermore, an investigation of the driving force at the phonic lips for dolphins that emit broadband echolocation signals and porpoises that emit narrowband echolocation signals suggested that the driving force is different for the two types of biosonar. Finally, the results provide a visual understanding of the sound transmission in dolphin's biosonar.

Ketten Darlene R.

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