Temporary Threshold Shift in Turtles

Temporary threshold shifts (TTS) have been studied in a variety of aquatic organisms from fish to marine mammals, but never in sea turtles. Here, turtle TTS was measured in air, and the in-air to underwater sensitivity difference was used to estimate TTS in water in an aquatic turtle. Red-eared sliders (Trachemys scripta elegans) were exposed to broadband noise in air for 24 h, and auditory sensitivity was assessed by auditory evoked potentials from the brainstem before exposure, immediately after exposure and during the following recovery period. All animals showed a depression of sensitivity immediately after exposure and full recovery 3–5 h after exposure. Based on differences in hearing thresholds in air and water, the exposure would be equivalent to 111 dB Leq (re 1 μPa) for aquatic sound, resulting in a sound exposure level of 160 dB re 1 μPa2s from the 24 h exposure. It is likely that long-term underwater sound level exposure at such levels will cause underwater TTS in turtles.