Terrestrial hearing in bearded seals (<i>Erignathus barbatus</i>)

As the Arctic becomes more accessible to human activities—and thus to anthropogenic noise sources—it becomes increasingly important to understand the auditory sensitivity of sound-reliant marine mammals, such as bearded seals (Erignathus barbatus). To address knowledge gaps, the in-air hearing of one adult bearded seal was measured outdoors in ambient noise conditions using psychophysical methods. 50% detection thresholds were measured for 10 frequencies (0.04–51.2 kHz) that extended across the subject’s hearing range. For low to mid frequencies (0.04–12.8 kHz), thresholds were limited, or masked, by ambient noise. Thresholds obtained at higher frequencies (25.6–51.2 kHz) were sufficiently elevated above background noise to provide absolute measures of hearing sensitivity. These data reveal that the in-air, high-frequency roll off for bearded seals is in alignment with available data for related species despite more than 12 million years of evolutionary isolation. Furthermore, the masked data collected at low and mid frequencies enable an unconventional approach for estimating critical ratios, a key parameter in masking models. These findings highlight auditory similarities within the northern clade of phocid seals and improve our ability to predict potential noise effects for these species in a rapidly changing soundscape.