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Conditioned hearing sensitivity reduction in a bottlenose dolphin (Tursiops truncatus)
Paul E Nachtigall1, Alexander Ya Supin2
1Hawaii Institute of Marine Biology, University of Hawaii, PO Box 1106, Kailua, HI 96734, USA nachtiga@hawaii.edu.
The Journal of Experimental Biology
|May 24, 2014
Summary
Bottlenose dolphins exhibit conditioned hearing changes, showing increased hearing thresholds before anticipated loud sounds. This suggests a learned dampening of hearing sensitivity in anticipation of noise.
Area of Science:
- Marine biology
- Bioacoustics
- Animal behavior
Background:
- Auditory evoked potential (AEP) recording is a key method for assessing hearing in marine mammals.
- Previous studies have shown conditioned hearing changes in other cetacean species, like the false killer whale.
Purpose of the Study:
- To investigate conditioned changes in hearing sensitivity in bottlenose dolphins.
- To determine if hearing threshold increases are due to conditioning or unconditioned effects of loud sounds.
Main Methods:
- Hearing sensitivity was measured using pip-train test stimuli and auditory evoked potential (AEP) recording.
- The study examined the effect of warning sound duration and inter-trial interval on hearing thresholds.
Main Results:
- Hearing thresholds increased up to 15 dB before a loud sound when preceded by a warning stimulus.
- Shorter warning durations resulted in greater threshold increases compared to longer warnings.
- The effect was largely independent of the inter-trial interval duration.
Conclusions:
- The observed hearing threshold increases in bottlenose dolphins are a manifestation of conditioned hearing dampening.
- This indicates a learned anticipatory response to anticipated loud sounds, similar to findings in false killer whales.
