Sound reception and hearing capabilities in the Little Penguin (): first predicted in-air and underwater audiograms.

Despite increasing concern about the effects of anthropogenic noise on marine fauna, relevant research is limited, particularly in those inaccessible species, such as the Little Penguin (). In this study, we collected freshly deceased Little Penguins for dissection and micro-computed tomography (microCT) scans. The head structures, including the ear apparatus, were reconstructed based on high-resolution imaging data for the species. Moreover, three-dimensional finite-element models were built based on microCT data to simulate the sound reception processes and ear responses to the incident planar waves at the selected frequencies. The received sound pressure fields and motion (i.e. displacement and velocity) of the internal ear-related structures were modelled. The synergistic response of ear components to incident aerial and underwater sounds was computed to predict the hearing capabilities of the Little Penguins across a broad frequency range (100 Hz-10 kHz), both in air and under water. Our predicted data showed good agreement with other diving birds in both the form and range of auditory sensitivity. This study demonstrates a promising method to study hearing in other inaccessible animals. The outputs from this study can inform noise impact mitigation and conservation management.