Apologies in
advance, to those of you on both listserves who will receive cross-postings.
The following are the contents and abstracts for the most recent issue of Aquatic Mammals. This journal was
established by the European Association for Aquatic Mammals (EAAM) in 1974. The
EAAM and the Board of the Alliance of Marine Mammal Parks and Aquariums sponsor
the journal.
Aquatic Mammals accepts a wide variety of papers on
the care, conservation, medicine, and science of marine mammals. Dr. Jeanette
Thomas of
The latest issue of
Aquatic Mammals is a special
issue entitled: Electrophysiological Measurements of Hearing in Marine Mammals.
The issue is divided into six parts: review, bottlenose dolphin, harbor
porpoise, Pacific white-sided dolphin, new techniques, and pinnipeds, with a
foreword by Michel André and Paul Nachtigall, the organizers of this special
issue.
The special issue
is available on CD, as well as a limited number of hard copies. See the
journal’s Web site for more details at: http://www.aquaticmammalsjournal.org.
Please find below, the
addresses (including email) of the authors to whom reprint requests and other
inquiries should be directed. Thank you for your continued interest in these
postings, as well as other publication postings to the listserves.
With regards,
Dagmar Fertl
Geo-Marine, Inc.
dfertl@geo-marine.com
**********************
André, M.*, and P.E. Nachtigall. 2007. Electrophysiological
measurements of hearing in marine mammals. Aquatic Mammals 33(1):1-5.
*LAB, Laboratori
d’Applicacions Bioacústiciques, Universitat Politècnica de Catalunya,
Rambla Exposició s/n, 08800 Vilanova I la Geltrú,
No abstract was provided, what follows is a summary.
In March 2006, an international workshop was organized by
Michel André and Paul Nachtigall and hosted by the European Cetacean Society
during its 20th Conference in
*************
Nachtigall, P.E., T.A. Mooney, K.A. Taylor, and M.M.L. Yuen.
2007. Hearing and auditory evoked potential methods applied to odontocete
cetaceans. Aquatic Mammals 33(1):6-13.
*Marine Mammal Research Program, Hawaii Institute of Marine
Biology, University of Hawaii, P.O. Box 1106, Kailua, HI 96734, USA. Email: nachtiga@hawaii.edu
Auditory evoked potential (AEP)
procedures have been increasingly used to measure hearing processes in aquatic
mammals. They have been demonstrated to be useful in measuring the audiograms
of stranded animals like infant sperm whales (Physeter
macrocephalus) and Risso’s dolphins (Grampus griseus). Modulation rate transfer
functions (MRTF) demonstrating appropriate stimulus presentation rates are
usually measured prior to recording audiograms with odontocetes. Measures
comparing behavioral and AEP audiograms with the same animals have generally
shown good correspondence between data gathered using the two procedures. AEPs
and acoustic brainstem responses (ABRs) also have been used to measure hearing
while an animal is actively echolocating. This technique of measuring the
animal’s ability to hear its own outgoing signals, as well as the
returning echoes, allows experimenters to develop a new understanding of the
processes underlying echolocation.
*******************
Supin, A.Ya.* and V.V. Popov. 2007. Improved techniques of
evoked-potential audiometry in odontocetes. Aquatic Mammals 33(1):14-23.
*
Efficiency of the auditory
evoked-potential (AEP) method of audiometry in odontocetes can be markedly
increased by the use of (1) stimulus parameters providing maximal AEP amplitude
and (2) methods of better extraction of AEP from background noise. A train of
short tone pips is a very effective stimulus that allows using the same
analysis technique as the sinusoidally amplitude-modulated (SAM) stimulus, but
provides much higher AEP amplitude. For AEP extraction from background noise,
apart from a commonly used averaging method (mean-based extraction), mean-based
extraction is very effective when the noise is not stationary and includes
short, but big spikes or bursts.
*************
Popov, V.V.*, A.Ya. Supin, M.G.
Pletenko, M.B. Tarakanov, V.O. Klishin, T.N. Bulgakova, and E.I. Rosanova.
2007. Audiogram variability in normal bottlenose dolphins (Tursiops truncatus). Aquatic Mammals
33(1):24-33.
Institute of Ecology and Evolution,
In odontocetes, underwater audiograms
have been obtained mostly in one or two individuals in a species. A
representative number of animals should be investigated to document
variability. In the present study, an attempt has been made to estimate the
audiogram mean and scatter among normal bottlenose dolphins (Tursiops truncatus). Measurements were
made in dolphins captured in the wild and kept in captivity for three to five
months, using auditory evoked potential
(AEP) technique (envelope-following response [EFR]) to measure underwater
hearing thresholds. Fourteen subjects, 11 males and 3 females, provisionally
from 3 to 15 years old, were investigated. Hearing thresholds were measured at
frequencies from 8 to 152 kHz with ¼-octave steps. All the subjects had
qualitatively similar audiograms, except one. The averaged audiogram featured
the best sensitivity (the threshold below 50 dB re 1 μPa) at
45 kHz. Thresholds rose slowly to lower frequencies (up to 65 dB at 8 kHz) and
steeply at higher frequencies (up to 97 dB at 152 kHz). Inter-individual standard
deviations varied, depending on frequency, from 4.4 to 11.7 dB, mostly not more
than 10 dB. One animal featured a significant hearing loss with increased
thresholds at frequencies above 54 kHz. An analytical formula for a standard
audiogram is suggested based on these data.
*************
Hernandez, E.N.*, S. Kuczaj, D.S.
Houser, and J.J. Finneran. 2007. Middle- and long-latency auditory evoked
potentials in bottlenose dolphins (Tursiops
truncatus) resulting from frequent and oddball stimuli. Aquatic
Mammals 33(1):34-42.
*Department of Psychology, Box 5025,
The University of Southern Mississippi, 118 College Drive, Hattiesburg, MS
39406, USA. Email: erica.hernandez@yahoo.com
Middle- and
long-latency auditory evoked potentials
9AEP) have not been extensively studied in marine mammals. Differences in
longer latency potentials resulting from infrequent “oddball”
stimuli inserted within a train of repeated, or “standard,”
auditory stimuli can potentially be used to detect the discrimination ability
of an individual. To investigate the characteristics of evoked responses
resulting from the oddball paradigm, AEPs were recorded using
100-ms pure tones as stimuli and recording AEP epochs of 500 ms from two bottlenose
dolphins (Tursiops truncatus).
The P50 response to a 40-kHz pure tone was attenuated when that stimulus was
repeated (the standard stimulus), with an 80% probability of occurrence. When a
30-kHz oddball tone was presented (20% probability of occurrence), however, the
P50 response amplitude increased, indicating dishabituation to the novel
stimulus. The attenuation of the P50 response to the standard tone was observed
when the standard and oddball tones were reversed (30-kHz standard; 40-kHz
oddball). The results demonstrated sensory gating, either habituating to a
repeated stimulus (“gating out”) and/or dishabituating to a novel
stimulus (“gating in”). The presence of one or both of these
responses suggests that the P50 response to oddball stimuli has the potential
to indicate discrimination of a particular set of auditory stimuli.
*******************
Finneran, J.J.*, D.S. Houser, and
C.E. Schlundt. 2007. Objective detection of bottlenose dolphin (Tursiops truncatus) steady-state auditory
evoked potentials in response to AM/FM tones. Aquatic Mammals 33(1):43-54.
*
Auditory steady-state responses were
measured in a bottlenose dolphin (Tursiops
truncatus) and used to illustrative objective techniques to
determine the presence and absence of a response. Experimental measurements
were conducted under water in a quiet pool. Sound stimuli were pure tones that
were both amplitude and frequency modulated. Evoked responses were recorded
using noninvasive surface electrodes. Two frequency-domain techniques were used
to assess the presence or absence of a response. The F test compares the evoked
potential power at a single frequency (the amplitude modulation frequency) to
the noise power averaged over adjacent frequencies. Magnitude-squared coherence
(MSC) is a ratio of the signal power at a single frequency to the
signal-plus-noise power and reflects the degree to which the system output is
determined by the input. For the measurements here, both techniques provided
identical results. Evoked potential thresholds based on the lowest detected
response compared favorably to behavioral thresholds obtained in the same
environment.
*************
Lucke, K.*, P.A. Lepper, B. Hoeve, E. Everaarts, N. van Elk, and U.
Siebert. 2007. Perception of low-frequency acoustic signals by a harbour porpoise
(Phocoena phocoena) in the
presence of simulated offshore wind turbine noise. Aquatic Mammals
33(1):55-68.
*FTZ Westkueste,
Christian-Albrechts-Universitaet zu
Using auditory
evoked potential (AEP) methods, a study was conducted on a harbour porpoise (Phocoena phocoena) at the Dolfinarium
Harderwijk in The Netherlands. The study measured the audible range of wind
turbine sounds and their potential masking of wind turbine sounds and their
potential masking effects on the acoustic perception of the animal. AEPs were
evoked with two types of acoustic stimuli: (1) click-type signals and (2)
amplitude-modulated signals. The masking noise resembling the underwater sound
emissions of an operational wind turbine was simulated. At first, the
animal’s hearing threshold was measured at frequencies between 0.7 and 16
kHz. Subsequently, these measurements were repeated at frequencies between 0.7
and 2.8 kHz in the presence of two different levels of masking noise. The
resulting data show a masking effect of the simulated wind turbine sound at 128
dB re 1 μPa at 0.7, 1.0, and 2.0 kHz. This masking effect varied between
4.8 and 7.3 dB at those frequencies. No significant masking was measured at a
masking level of 115 dB re 1 μPa. The available data indicate that the
potential masking effect would be limited to short ranges in the open sea, but
limitations exist to this conclusion and all estimates are based on existing
turbine types, not taking into account future developments of larger and
potentially noisier turbine types.
******************
Beedholm, K.*, and
*
A previous study indicated no
automatic gain control (AGC) in the auditory system of a harbor porpoise (Phocoena phocoena) as revealed by
recording auditory evoked
potentials to simulated echoes (Beedholm et al., 2006). The same harbor
porpoise did change the rate and amplitude of its echolocation clicks during
stationary echolocation when presented with an artificial target at a fixed
delay. The animal spontaneously changed its click rate in such a way that
emitted level (in dB, arbitrary reference) of a click decreased as the
inter-click interval (ICI) decreased (click emission rate increases), according
to a 14.5 log (ICI) function. The same relationship was found when the animal
swam toward a target (a fish). It reduced the amplitude of its clicks as it
approached the target with a -14 to -17 log r (best-fit), which is close to the
expected -20 log r found in other studies. The combined results indicate an
incomplete AGC working on the transmitter side and might be explained by
constraints in the sound production apparatus that couple the sound amplitude
to the click rate.
******************
Au, W.W.L.*, J.A. Thomas, and K.T.
Ramirez. 2007. Characteristics of the auditory brainstem evoked potential
of a Pacific white-sided dolphin (Lagenorhynchus obliquidens).
Aquatic Mammals 33(1):76-84.
*Marine Mammal Research Program,
Hawaii Institute of Marine Biology, University of Hawaii, P.O. Box 1106,
Kailua, HI 96734, USA. Email: wau@hawaii.edu
Auditory brainstem responses (ABRs)
of a Pacific white-sided dolphin (Lagenorhynchus obliquidens) in the presence
of masking noise were measured at John G. Shedd Aquarium in
******************
Delory, E., J. del Rio, J. Castell,
M. van der Schaar, and M. André. 2007. OdiSEA: An autonomous portable auditory
screening unit for rapid assessment of hearing in cetaceans. Aquatic Mammals
33(1):85-92.
*LAB, Laboratori
d’Applicacions Bioacústiciques, Universitat Politècnica de Catalunya, Rambla
Exposició s/n, 08800 Vilanova I la Geltrú,
The screening of marine
mammals’ auditory capabilities is a vital and delicate diagnosis
elaboration process. A self-configurable, compact, and portable
battery-operated screening tool is now available, named OdiSEA, which enables
the collection of species-related auditory characteristics and a rapid
diagnosis of hearing impairment, both in controlled and field situations such
as rehabilitation facilities and at stranding sites, respectively. Acoustic
stimulation is achieved with a calibrated piezoelectric ceramic that transduces
sound either through a gel-filled suction cup or, more conventionally, from a
few meters distance to the subject in a pool. System portability and the
integration of a wideband (>150 kHz) auditory brainstem response (ABR) and
multiple auditory steady-state response (multiple ASSR) evoked potentials
system shortens diagnosis times significantly for both simple auditory tests
and more detailed screening of auditory function. This unit should simplify and
significantly accelerate the collection of audiograms in cetaceans.
******************
*Marine Mammal Research Program,
Hawaii Institute of Marine Biology, University of Hawaii, P.O. Box 1106,
Kailua, HI 96734, USA. Email: kristent@hawaii.edu
We have created a portable system
that is capable of measuring the hearing thresholds of marine mammals. It was
designed for the purpose of testing the auditory capabilities for a wide range
of marine mammal individuals and species. This system consists of multiple
individual components, independently purchased or assembled. The major
component of the system is a standard laptop computer with custom software that
is able to both generate outgoing signals and acquire the corresponding brain
measurements in response to those outgoing signals. The system has been, and
still is, in an ongoing state of improvement and optimization with the goal of
having a final system that could be used in nearly all field conditions.
******************
André, M.*, E. Delory, E. Degollada,
J-M Alonos, J. del Rio, M. van Der Schaar, J.V. Castell, and M. Morell. 2007.
Identifying cetacean hearing impairment at stranding sites. Aquatic Mammals
33(1):100-109.
*LAB, Laboratori
d’Applicacions Bioacústiciques, Universitat Politècnica de Catalunya,
Rambla Exposició s/n, 08800 Vilanova I la Geltrú,
While noise is now considered a
marine hazard that can directly affect cetaceans and induce a stranding, no
clinical approach has yet introduced that detection of a possible hearing loss
at a stranding site as a necessary practice. This can be explained by the lack
of time when facing vital decisions for the animal’s welfare as well as
the unavailability of reliable, lightweight, autonomous, and portable
audiometry equipment. Herein, we correlate measured electrophysiological
evidence of a permanent threshold shift (PTS) in a rehabilitated striped
dolphin (Stenella coeruleoalba)
that prevented its release, with the postmortem analysis of an abnormal
dilation of the central nervous system ventricles that prevented the correct
acoustic reception of the animal. We further propose to follow a five-minute auditory evoked potential (AEP) standard
protocol of hearing measurements in-air on cetaceans at a stranding site that
includes the stimulation of auditory brainstem responses (ABRs)
with a single 4-μs broadband (>150 kHz) pulse at three decreasing
levels (129, 117, and 105 dBpp re 1 μPa at 15 cm), which covers
most of the cetaceans’ known maximum acoustic sensitivity and allow the
immediate sensing of an individual’s hearing capability before any final
clinical decision is taken.
Houser, D.S.*, D.E. Crocker, C. Kastak,
J. Mulsow, and J.J. Finneran. 2007. Auditory evoked potentials in northern
elephant seals (Mirounga angustirostris).
Aquatic Mammals 33(1):110-121.
*BIOMEMETICA,
Auditory evoked potentials (AEPs) were
investigated in northern elephant seals (Mirounga angustirostris) to characterize
the responses elicitied by different acoustic stimulus types, examine temporal
resolving capabilities, and evaluate the potential for using evoked responses
to estimate hearing sensitivity. Clicks and tone pips were presented to
individual seals to characterized evoked responses to broad- and narrowband
stimuli. Tone pip trains and sinusoidally amplitude-modulated (SAM) tones were
used to determine modulation rate transfer functions (MRTF) of the auditory
system and to determine if the magnitude of the envelope-following response (EFR)
relative to stimulus level can be used to estimate hearing thresholds. Click
evoked responses were characterized by three early positive peaks (app. 2.6,
4.4, and 6.1 ms) and a dominant negative peak at 7.2 ms and had average
amplitudes of 264 nV (peak-to-peak [pk-pk]) for a corresponding stimulus level
of 126 dB re 20 μPa (pk-pk). The use of dissociative drugs for the
immobilization of the seals showed no demonstrable effect on the latencies or
amplitudes of the click evoked response. Both the rate following response (RFR)
and EFR amplitudes were maximal when the stimulus repetition rate or the
amplitude modulation rate, respectively, were <100 Hz. EFR amplitudes at the
rate of amplitude modulation tracked near linearly with stimulus level.
Thresholds for a 4-kHz, SAM tone were estimated to be 45 dB re 20 μPa.
Thus, the recording of AEPs is a viable means of studying auditory processes in
the northern elephant seal.
******************************
Mulsow, J.* and C. Reichmuth. 2007. Electrophysiological
assessment of temporal resolution in pinnipeds. Aquatic Mammals 33(1):122-131.
*Department of Ocean Sciences, Earth and Marine Sciences
Building, University of California-Santa Cruz, Santa Cruz, CA 95060, USA.
Email: jmulsow@ucsc.edu
Studies of auditory temporal processing in marine mammals
have traditionally focused on the highly refined temporal capabilities of
dolphins and other odontocete cetaceans. However, a recent electrophysiological
investigation of manatee (Trichechus manatus) hearing has shown their temporal
resolution to be better than expected, leading to speculation that enhanced
temporal processing capabilities are adaptive for underwater sound
localization. This study measured evoked responses from several
******************************
Reichmuth, C.*, J. Mulsow, J.J. Finneran, D.S. Houser, and
A.Ya. Supin. 2007. Measurement and response characteristics of auditory
brainstem responses in pinnipeds. Aquatic Mammals 33(1):132-150.
*Institute of Marine Sciences, Long Marine Laboratory, 100
Shaffer Road, University of California-Santa Cruz, Santa Cruz, CA 95060, USA.
Email: coll@ucsc.edu
The measurement of auditory evoked potentials (AEPs) has
proven to be a useful tool for examining the auditory physiology of odontocete
cetaceans and there is growing interest in applying this electrophysiological
approach to study the hearing of other marine mammals. The aim of the current
investigation was to examine some of the basic measurement and response
characteristics of the auditory brainstem response (ABR) in pinnipeds. The
subjects were