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Hearing sensitivity during target presence and absence while a whale echolocates
Alexander Ya Supin1, Paul E Nachtigall, Marlee Breese
1Institute of Ecology and Evolution of the Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia. alex-supin@mail.ru
The Journal of the Acoustical Society of America
|January 8, 2008
Summary
False killer whale hearing sensitivity changes when searching for targets. Researchers found a significant difference in hearing thresholds during echolocation tasks, suggesting adaptive hearing.
Area of Science:
- Marine biology
- Bioacoustics
- Auditory neuroscience
Background:
- Echolocation is crucial for marine mammals like false killer whales.
- Understanding hearing sensitivity during active sensing is vital for ecological studies.
Purpose of the Study:
- To measure hearing sensitivity in a false killer whale during echolocation.
- To investigate if hearing thresholds vary based on target presence or absence during echolocation.
Main Methods:
- Auditory evoked potentials (AEPs) were recorded using 22.5-kHz sinusoidally amplitude-modulated probe stimuli.
- Hearing thresholds were measured in a go/no-go echolocation task (target-present vs. target-absent trials).
- Sonar click statistics were analyzed to assess potential masking effects.
Main Results:
- A significant difference in hearing thresholds was observed: 90.4 dB re 1 μPa in target-absent trials and 109.8 dB re 1 μPa in target-present trials (19.4 dB difference).
- Analysis of emitted sonar clicks showed no evidence of increased energy in target-present trials that could explain the threshold difference.
- Click statistics (level, number, train energy) were slightly higher in target-absent trials.
Conclusions:
- False killer whale hearing sensitivity is not fixed and appears to adapt based on the presence or absence of a target during echolocation.
- The observed difference in hearing thresholds is likely due to changes in the whale's auditory system sensitivity rather than acoustic masking by sonar clicks.
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