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Biological relevance and methodological implications of unexpected hearing thresholds in a diving bird
Helen Rößler1,2, Anne May1, Michael Dähne3,4
1Deutsches Meeresmuseum, Katharinenberg 14 - 20, 18439, Stralsund, Germany.
Scientific Reports
|December 23, 2024
Summary
Humboldt penguins possess unique hearing abilities in air, with most sensitive hearing at 2 kHz. Unexpectedly, they detect low frequencies at low sound levels, warranting further investigation into their auditory adaptations.
Area of Science:
- Auditory Neuroscience
- Animal Adaptations
- Bioacoustics
Background:
- Penguins exhibit extreme adaptations for an amphibious lifestyle, switching between air and water.
- Their auditory perception in air, especially concerning underwater adaptations, remains largely unexamined.
Purpose of the Study:
- To investigate the in-air hearing capacity of Humboldt penguins (Spheniscus humboldti).
- To determine if their specialized underwater adaptations impact their aerial hearing sensitivity.
Main Methods:
- Psychophysical hearing tests were conducted on four captive Humboldt penguins.
- Auditory thresholds were measured across a range of frequencies in air.
Main Results:
- Penguins showed hearing sensitivity below 76 dB rms re 20 µPa between 0.250 kHz and 10 kHz.
- Peak sensitivity was observed at 2 kHz (mean threshold of 15.3 dB rms re 20 µPa).
- An unusual detection of 0.250 kHz at low sound levels was noted, contrasting with a sensitivity decline at 0.500 kHz.
Conclusions:
- Humboldt penguins have a distinct audiogram shape with significant inter-individual variation.
- The low-frequency hearing finding is unexpected and may be biologically relevant, requiring further research.
- Understanding these auditory adaptations can shed light on sensory mechanisms in amphibious animals.
