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High-frequency vessel noise can mask porpoise echolocation
Line Hermannsen1,2,3, Michael Ladegaard1, Pernille Tønnesen1
1Zoophysiology, Department of Biology, Aarhus University, C. F. Møllers Allé 3, 8000 Aarhus C, Denmark.
The Journal of Experimental Biology
|March 19, 2025
Summary
High-frequency noise from vessels masks porpoise echolocation, impairing their ability to detect targets. Even with increased click output and spatial release, performance degraded, highlighting risks to foraging and navigation.
Area of Science:
- Marine biology
- Bioacoustics
- Animal behavior
Background:
- Ultrasonic cavitation noise from vessels spectrally overlaps with toothed whale echolocation.
- This overlap poses a risk of auditory masking, potentially degrading echolocation performance.
Purpose of the Study:
- To test the hypothesis that vessel noise masks porpoise echolocation.
- To quantify the impact of masking noise on a trained porpoise's target discrimination abilities.
Main Methods:
- Two trained porpoises equipped with DTAGs were exposed to controlled levels of noise (2 kHz and 125 kHz).
- An active target discrimination task was used to assess performance under different noise conditions.
- Noise source location was manipulated to test for spatial release from masking.
Main Results:
- High-level masking noise (125 kHz) caused porpoises to increase click source levels (Lombard response).
- Despite adjustments, porpoise discrimination success rates significantly decreased in high-level masking noise.
- Spatial release from masking partially restored echolocation performance.
Conclusions:
- Moderate levels of high-frequency noise can significantly mask porpoise echolocation.
- Masking effects cannot always be fully compensated for, impacting foraging and navigation.
- Impact assessments of vessel noise on toothed whales must consider masking effects on biosonar.
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