Audiogram of a Cook Inlet beluga whale (Delphinapterus leucas)

Abstract

Author Posting. © Acoustical Society of America, 2020. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 148(5), (2020): 3141, doi:10.1121/10.0002351.Noise is a stressor to wildlife, yet the precise sound sensitivity of individuals and populations is often unknown or unmeasured. Cook Inlet, Alaska belugas (CIBs) are a critically endangered and declining marine mammal population. Anthropogenic noise is a primary threat to these animals. Auditory evoked potentials were used to measure the hearing of a wild, stranded CIB as part of its rehabilitation assessment. The beluga showed broadband (4–128 kHz) and sensitive hearing (<80 dB) for a wide-range of frequencies (16–80 kHz), reflective of a healthy odontocete auditory system. Data were similar to healthy, adult belugas from the comparative Bristol Bay population (the only other published data set of healthy, wild marine mammal hearing). Repeated October and December 2017 measurements were similar, showing continued auditory health of the animal throughout the rehabilitation period. Hearing data were compared to pile-driving and container-ship noise measurements made in Cook Inlet, two sources of concern, suggesting masking is likely at ecologically relevant distances. These data provide the first empirical hearing data for a CIB allowing for estimations of sound-sensitivity in this population. The beluga's sensitive hearing and likelihood of masking show noise is a clear concern for this population struggling to recover.The work was conducted under Permit No. MMHSRP MMPA/ESA #18786-02 to T.R. and approved via the Institute for Animal Care and Use Protocol from the Woods Hole Oceanographic Institution. This publication was partially funded by the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement No. NA15OAR4320063.2021-05-2