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.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2021
• Subjects: toothed whales
• Online Access: https://pure.au.dk/portal/da/publications/decreased-resting-and-nursing-in-shortfinned-pilot-whales-when-exposed-to-louder-petrol-engine-noise-of-a-hybrid-whalewatch-vessel(7519716f-25ac-4dc2-a6c5-564acde2312f).html; https://doi.org/10.1038/s41598-021-00487-0; http://www.scopus.com/inward/record.url?scp=85118957918&partnerID=8YFLogxK

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.