Audiogram Variability in Normal Bottlenose Dolphins (&lt;I&gt;Tursiops truncatus&lt;/I&gt;)

Supin

2014

Self Cite

The conditioned change in hearing sensitivity during a warning sound preceding a loud sound was investigated in the bottlenose dolphin. Hearing sensitivity was measured using pip-train test stimuli and auditory evoked potential recording. When the test/warning stimulus with a frequency of 22.5 or 32 kHz preceded the loud sound with a frequency of 22.5 kHz and a sound pressure level of 165 dB re. 1 μPa rms, hearing thresholds before the loud sound increased relative to the baseline. The threshold increased up to 15 dB. In order to further investigate whether the observed threshold increase was due to conditioning, the dependence of the effect on warning duration and inter-trial interval was investigated. The duration of the warning substantially influenced the effect. Shorter warnings resulted in deeper suppression of responses and higher threshold increases than longer warnings. In contrast, the effect was nearly independent of the duration of the inter-trial interval, i.e. it was independent of the delay from the loud sound to the test/warning sound in the subsequent trial. These data are considered as evidence that the observed hearing threshold increases were not a result of the unconditioned effect of the loud sound and were instead a manifestation of a conditioned dampening of hearing when the bottlenose dolphin anticipated the quick appearance of a loud sound in the same way as previously demonstrated in the false killer whale.

Section: Evoked Potential Features and Threshold Determinationcontrasting

confidence: 66%

Conditioned hearing sensitivity reduction in a bottlenose dolphin (Tursiops truncatus)

Supin

2014

Self Cite

“…Extensive work with Tursiops truncatus has shown that intraspecific variations in hearing measurements exist and are often related to the age of the subjects. Popov and colleagues measured the hearing capabilities of 14 T. truncatus and showed that thresholds between individuals varied with frequency (Popov et al, 2007). In addition, the authors showed that one animal exhibited significant high frequency hearing loss above 50kHz.…”

Section: Discussionmentioning

confidence: 99%

Audiogram of a formerly stranded long-finned pilot whale (Globicephala melas) measured using auditory evoked potentials

Pacini

Kloepper

et al. 2010

SUMMARYLong-finned pilot whales are highly social odontocetes found in temperate and subpolar regions. This species is particularly known for its interaction with fisheries as well as its mass strandings. Recent tagging work has provided some information about pilot whales in the wild but, even though they have been successfully kept in captivity, little is known about their sensory capabilities. This study investigates the hearing abilities of a rehabilitated 2year old male long-finned pilot whale. A complete audiogram was collected using auditory evoked potential techniques that included measurements of nine frequencies from 4 to 100kHz presented as sinusoidally amplitude-modulated tones. The results indicated that the region of best hearing was between 11.2 and 50kHz and the subject had relatively poor high frequency hearing compared with other odontocete species. This study emphasizes the importance of collecting basic hearing measurements from new species, understanding diagnostic life histories as well as continuously increasing the sample size of audiometry measurements within and between odontocete species as animals become available.

“…The US National Research Council (National Research Council, 1994;National Research Council, 2000) has recommended that population level audiograms be obtained in order to discover population audiometrics and to determine normal hearing loss levels for marine mammals. AEP measurements can be effectively used to quickly measure groups of odontocetes (Popov et al, 2007), and the catch-and-release procedure, combined with hearing tests using the AEP technique, provides a method for fulfilling those recommendations. These data therefore provide two new important pieces of information about the general hearing of marine mammal species.…”

Section: Discussionmentioning

confidence: 99%

Shipboard measurements of the hearing of the white-beaked dolphin Lagenorhynchus albirostris

Mooney

Taylor

et al. 2008

SUMMARYThis is the first report of an underwater audiogram from a dolphin in a capture-and-release scenario. Two bow-riding white-beaked dolphins Lagenorhynchus albirostris (a female and a male) were captured using the hoop-net technique in Faxaflói Bay, Iceland. The dolphins were transferred to a stretcher and hoisted into a plastic research tank on board a small fishing vessel. Two underwater transducers were used to cover the frequency range from 16 to 215·kHz. Two human EEG electrodes mounted in suction cups, one placed near the blow hole and the other on the dorsal fin, picked up bioelectrical responses to acoustic stimuli. Responses to about 1000 sinusoidal amplitude modulated stimuli for each amplitude/frequency combination were averaged and analyzed using a fast Fourier transform to obtain an evoked auditory response. Threshold was defined as the zero crossing of the response using linear regression. Two threshold frequencies at 50·kHz and 64·kHz were obtained from the female. An audiogram ranging from 16 to 181·kHz was obtained from an adult male and showed the typical ʻUʼ shaped curve for odontocetes. The thresholds for both white-beaks were comparable and demonstrated the most sensitive high frequency hearing of any known dolphin and were as sensitive as the harbor porpoise.