Whale-watching boat noise should be capped to minimise disturbance

Embargoed until: Publicly released: 2021-11-16 08:27

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Underwater photograph of a Short-finned pilot whale (Globicephala macrorhynchus) mother nursing its calf off Tenerife, Canary Islands. Credit: Francis Perez.

Despite growing efforts to establish best practices, there are no regulations on how quiet whale-watching boats must be to reduce their impact on whale and dolphin behaviour. To test what might be a safe level of noise, researchers recreated how a whale-watching boat would pass by short-finned pilot whales in the Canary Islands, either with a quieter, electric engine or a loud, petrol engine. When the petrol boat passed by the whales, the time that calves nursed plummeted by 81 per cent compared to not being approached by a vessel at all, and the mum whales’ resting time also decreased by 29 per cent. The electric boat, however, had no significant short-term impacts on the whales, and the team suggests capping boat noise levels at 150 dB.

Media release

From: Springer Nature

Whale-watch vessels with louder petrol engines significantly disrupt short-finned pilot whale resting and nursing, according to a study published in Scientific Reports.

Previous research has found that noise produced by whale-watch vessels can affect whale behaviour. However, the impact of engine noise levels on toothed whale behaviour has been unclear and whale-watch vessel noise levels are not currently regulated.

Patricia Arranz and colleagues used drones to observe the behaviour of short-finned pilot whale mother and calf pairs off the coast of Tenerife, Spain. 13 pairs were observed without a vessel present while 23 were observed as a whale-watch vessel with either a louder petrol engine or a quieter electric engine slowly passed them from 60 metres away, in compliance with Canary Islands whale-watching guidelines. The researchers found that compared to those not approached by a vessel, mothers who were approached by the vessel with the petrol engine spent on average 29% less time resting and 81% less time nursing their calves. No significant reductions in resting or nursing were observed among whales approached the vessel with the quieter electric engine, compared to those not approached by a vessel. The researchers suggest that decreases in resting and nursing could increase the energy consumption of mothers and reduce calf energy intake, with potential negative implications for calf survival.

The findings demonstrate that, even if whale-watch vessels comply with current guidelines, louder engines can have a greater impact on whale behaviour. The authors suggest that the noise produced by whale-watch vessels be minimised and that whale-watch guidelines specify maximum engine noise levels, in order to limit disturbance to whales.

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Research Springer Nature, Web page

Journal/
conference: Scientific Reports

Research:Paper

Organisation/s: University of La Laguna, Spain; Aarhus University, Denmark; University of Iceland, Iceland

Funder: PA was supported via the Agustín de Betancourt Program funded by the Cabildo Insular de Tenerife under the Tenerife 2030 Strategy and the Strategic Framework for Island Development (MEDI) and co-funded by the Canary Islands Development Fund (FDCAN) of the Government of the Canary Islands). Field equipment and experiments were funded by the Technology Transfer Ofce of the University of La Laguna, the Spanish Foundation for Science and Technology project FILMAR (FCT-19-1441) and the Canary Islands Government project INMAR (EIS-2020-07).

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