Temporary threshold shifts in naïve and experienced belugas: Can dampening of the effects of fatiguing sounds be learned?

Abstract

In belugas (Delphinapterus leucas), substantial (10–15 dB) differences in temporary threshold shifts (TTSs) were observed between the first and subsequent experimental sessions in the same subjects. In the first session (naïve subject state), the TTSs produced by exposure to fatiguing noises were larger than the TTSs produced in subsequent sessions (experienced subject state). After one to two sessions, the TTSs stabilized. The baseline hearing thresholds did not differ between the naïve and experienced states. One possible explanation for this effect is that the animals learned to dampen their hearing during exposure to fatiguing noises and thus mitigate the impact of those noises.