Hearing pathways and directional sensitivity of the beluga whale, Delphinapterus leucas

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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 suctioncup 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'.

Section: Relative Hearingsupporting

confidence: 68%

Section: Relative Hearingmentioning

confidence: 71%

Section: Relative Hearingmentioning

confidence: 82%

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Hearing pathways in the Yangtze finless porpoise,Neophocaena asiaeorientalis asiaeorientalis

Mooney

Ketten

et al. 2013

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“…The EFR obtained from the animal followed the typical response obtained with other species Popov et al, 2005;Mooney et al, 2008) with a delay of 4-6ms which corresponded to the latency of the neurophysiological response. When the sound stimulus SPL was well above the threshold level, a completely formed response was recorded and as the SPL decreased, the response disappeared in the ambient biological noise.…”

Section: A F Pacini and Otherssupporting

confidence: 62%

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

Pacini

Nachtigall

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 use of AEP techniques to measure hearing sensitivity of odontocetes has become increasingly popular (e.g. Popov and Supin, 1990a;Popov and Supin, 1990b;Szymanksi et al, 1999;Andre et al, 2003;Nachtigall et al, 2004;Yuen et al, 2005;Cook et al, 2006;Houser and Finneran, 2006a;Mooney et al, 2008;Nachtigall et al, 2008;Mooney et al, 2009). Thus, a powerful tool to learn more about the hearing of live-stranded cetaceans, particularly those that are rare or endangered, would be to combine CT imaging and AEP techniques.…”

Section: Introductionmentioning

confidence: 99%

Live CT imaging of sound reception anatomy and hearing measurements in the pygmy killer whale, Feresa attenuata

Montie

Manire

Mann

2011

SUMMARYIn June 2008, two pygmy killer whales (Feresa attenuata) were stranded alive near Boca Grande, FL, USA, and were taken into rehabilitation. We used this opportunity to learn about the peripheral anatomy of the auditory system and hearing sensitivity of these rare toothed whales. Three-dimensional (3-D) reconstructions of head structures from X-ray computed tomography (CT) images revealed mandibles that were hollow, lacked a bony lamina medial to the pan bone and contained mandibular fat bodies that extended caudally and abutted the tympanoperiotic complex. Using auditory evoked potential (AEP) procedures, the modulation rate transfer function was determined. Maximum evoked potential responses occurred at modulation frequencies of 500 and 1000Hz. The AEP-derived audiograms were U-shaped. The lowest hearing thresholds occurred between 20 and 60kHz, with the best hearing sensitivity at 40kHz. The auditory brainstem response (ABR) was composed of seven waves and resembled the ABR of the bottlenose and common dolphins. By changing electrode locations, creating 3-D reconstructions of the brain from CT images and measuring the amplitude of the ABR waves, we provided evidence that the neuroanatomical sources of ABR waves I, IV and VI were the auditory nerve, inferior colliculus and the medial geniculate body, respectively. The combination of AEP testing and CT imaging provided a new synthesis of methods for studying the auditory system of cetaceans. Supplementary material available online at