Atlantic Green Turtles and Hawksbill Turtles: Behavioral Responses to Sound

Effects of sounds on the behavior of sea turtles were investigated, to (1) determine whether sounds can be used to deter turtles from areas of human activity and (2) inform Environmental Impact Assessments by evaluating how anthropogenic sounds affect sea turtles. Two Atlantic green turtles Chelonia mydas and two hawksbill turtles Eretmochelys imbricata in a pool were exposed to synthetic sounds, an impulsive sound, Helicopter Long-Range Active Sonar (HELRAS) down-sweeps, and recordings of killer whale Orcinus orca vocalizations. Typical responses were increased swimming speed and/or changes in swimming pattern or direction, but the pure tones, impulsive sound, HELRAS, and killer whale sounds elicited no response. Strong responses occurred to series of 0.2–1 kHz up-sweeps with 100% duty cycle, duration 0.5 s, and sound pressure level >151 dB re 1 μPa. Above this threshold, the spectrum, frequency modulation, and temporal pattern of the sounds, and the behavioral state of the turtles, determined their response. Most responses occurred during exposure to sounds with frequencies between 0.2 and 1 kHz, within the hearing range of turtles. This pilot study suggests that turtles respond to high-amplitude, low-frequency anthropogenic sounds and that deterring sounds should be low in frequency and temporally and spectrally complex.