Decreased resting and nursing in short-finned pilot whales when exposed to louder petrol engine noise of a hybrid whale-watch vessel

• Published in: Scientific Reports
• Main Authors: Arranz, P., Glarou, M., Sprogis, K. R.
• Other Authors: Consejería de Educación, Universidades y Sostenibilidad, Gobierno de Canarias, Fundación Española para la Ciencia y la Tecnología, Fondo de Desarrollo de Canarias, Oficina de Transferencia de Resultados de Investigación de la Universidad de La Laguna, H2020 Marie Skłodowska-Curie Actions
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2021
• Subjects: Multidisciplinary; toothed whales
• Online Access: http://dx.doi.org/10.1038/s41598-021-00487-0; https://www.nature.com/articles/s41598-021-00487-0.pdf; https://www.nature.com/articles/s41598-021-00487-0

Abstract Vessel noise is a primary driver of behavioural disturbance in cetaceans, which are targeted during whale-watch activities. Despite the growing, global effort for implementing best-practice principles, to date, there are no regulations on whale-watch vessel noise levels. Here, we test the hypothesis that a whale-watch vessel with a low noise emission will not elicit short-term behavioural responses in toothed whales compared to a vessel with a louder engine. We measured behavioural responses (n = 36) of short-finned pilot whales ( Globicephala macrorhynchus ) to whale-watch vessel approaches (range 60 m, speed 1.5 kn). Treatment approaches with a quieter electric engine (136–140 dB) compared to the same vessel with a louder petrol engine (151–139 dB) (low-frequency–mid-frequency weighted source levels, re 1 µPa RMS @ 1 m) were examined. Focal whales were resting mother and calves in small group sizes. During petrol engine treatments, the mother’s mean resting time decreased by 29% compared to the control (GLM, p = 0.009). The mean proportion of time nursing for the calf was significantly influenced by petrol engine vessel passes, with a 81% decrease compared to the control (GLM, p = 0.01). There were no significant effects on behaviour from the quieter electric engine. Thus, to minimise disturbance on the activity budget of pilot whales, whale-watch vessels would ideally have source levels as low as possible, below 150 dB re 1 µPa RMS @ 1 m and perceived above ambient noise.