Gentoo penguins (Pygoscelis papua) react to underwater sounds

Marine mammals and diving birds face several physiological challenges
under water, affecting their thermoregulation and locomotion as well as
their sensory systems. Therefore, marine mammals have modified ears for
improved underwater hearing. Underwater hearing in marine birds have been
studied in a few species, but for the record-holding divers, such as
penguins, there are no detailed data. We played underwater noise bursts to
gentoo penguins (Pygoscelis papua) in a large tank at sound pressure
levels between 100 and 120 dB re 1 µPa rms. The penguins showed a graded
reaction to the noise bursts, ranging from no reactions at 100 dB to
strong reactions in more than 62% of the playbacks at 120 dB re 1 µPa. The
responses were always directed away from the sound source. The fact that
penguins can detect and react to underwater stimuli may indicate that they
make use of sound stimuli for orientation and prey detection during dives.
Further, it suggests that penguins may be sensitive to anthropogenic
noise, like many species of marine mammals.