Fine-scale movement responses of free-ranging harbour porpoises to capture, tagging and short-term noise pulses from a single airgun

• Published in: Royal Society Open Science
• Main Authors: Floris M. van Beest, Jonas Teilmann, Line Hermannsen, Anders Galatius, Lonnie Mikkelsen, Signe Sveegaard, Jeppe Dalgaard Balle, Rune Dietz, Jacob Nabe-Nielsen
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2018
• Subjects: anthropogenic disturbance; cetaceans; movement; offshore energy; phocoena phocoena; underwater noise; Science; Q; Phocoena phocoena
• Online Access: https://doi.org/10.1098/rsos.170110; https://doaj.org/article/12ea8652b1774a1b9065699edbaaeecc

Knowledge about the impact of anthropogenic disturbances on the behavioural responses of cetaceans is constrained by lack of data on fine-scale movements of individuals. We equipped five free-ranging harbour porpoises (Phocoena phocoena) with high-resolution location and dive loggers and exposed them to a single 10 inch3 underwater airgun producing high-intensity noise pulses (2–3 s intervals) for 1 min. All five porpoises responded to capture and tagging with longer, faster and more directed movements as well as with shorter, shallower, less wiggly dives immediately after release, with natural behaviour resumed in less than or equal to 24 h. When we exposed porpoises to airgun pulses at ranges of 420–690 m with noise level estimates of 135–147 dB re 1 µPa2s (sound exposure level), one individual displayed rapid and directed movements away from the exposure site and two individuals used shorter and shallower dives compared to natural behaviour immediately after exposure. Noise-induced movement typically lasted for less than or equal to 8 h with an additional 24 h recovery period until natural behaviour was resumed. The remaining individuals did not show any quantifiable responses to the noise exposure. Changes in natural behaviour following anthropogenic disturbances may reduce feeding opportunities, and evaluating potential population-level consequences should be a priority research area.