Weddell Seal Audiometry

• Main Authors: Kindermann, Lars, Bornemann, Horst, Plötz, Joachim, Boebel, Olaf
• Format: Conference Object
• Language: unknown
• Published: 2007
• Subjects: Antarctic; Atka; Weddell; Antarc*; Antarctica; Sea ice; Weddell Seal; Weddell Seals
• Online Access: https://epic.awi.de/id/eprint/18258/; https://hdl.handle.net/10013/epic.28798

Audiograms describe the fundamental ability of the sense of hearing for any species as a function of hearing threshold in respect to frequency. For most marine mammals, including all Antarctic seals, audiograms have not been described yet. In this study, we determined audiograms of Weddell seals (Leptonychotes weddellii) by auditory evoked potential (AEP) measurements. Our experiments were conducted in the wild at Atka Bay, Antarctica, (70°31S 8°13W) on sea ice in December 2005. One adult male and eleven non-lactating females, with estimated body masses between 300 and 450 kg, were sedated prior to the audiometric measurements. We determined optimal electrode positions for the auditory brainstem responses (ABRs) on the scalp of the seals, and obtained a total of 120 measurements using stimulus frequencies from 1 kHz to 80 kHz and different sound levels. Sampling of the sensitive bio-potentials was affected by signal to noise ratios, environmental conditions, and course of narcosis. Hence, the results were pooled to obtain an integrative Weddell seal audiogram. ABR measurements in the wild are unprecedented. Technical experience developed continuously during the experiments progressively improved the signal to noise ratio and resulted in an increasing success rate. The know-how developed during these initial trials will significantly benefit future studies in Weddell seals and other species.