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

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 in3 underwater airgun producing high-intensity noise pulses (2−3 second intervals) for one minute. 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 ≤24 hours. When we exposed porpoises to airgun pulses at ranges of 420−690 m with noise level estimates of 135−147 dB re 1µPa2s (SEL), 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 fo...