Aarhus University Seal / Aarhus Universitets segl

The effect of ship noise

Seals and underwater noise

The development of a new type of DTAG and the combination of movement and visual recordings have resulted in new knowledge about seal behavior and noise. They are actually more affected than we thought, and this new study by Lonnie Mikkelsen and colleagues shows that seals might change their behavior when encountered by a boat, whether they are sleeping, travelling or resting on land.

  • Mikkelsen et al. 2019 Long term sound and movement recording tags to study natural behaviour and reactions to ship noise in seals.
We all need our rest! Two harbour seals were tagged with a DTAG, recording; acceleration, depth and movement together with a video recording device. Watch a harbour seal catch and eat a fish before it dives down to rest at the seabed. Production by Maria Kristina Holst Palner and Lonnie Mikkelsen.

Porpoises react on heavy ship noise

- New research!!

The inner Danish waters and sounds are some of the most heavily trafficked waters in the world. These waters are mostly dominated by noise from ships and are also home for Denmark’s only breeding whale species, the harbour porpoise.

In collaboration with Danish fishermen, seven randomly captured porpoises were equipped with advanced instruments on their backs using suction cups. These advanced D-tags record both underwater sounds and three-dimensional movement. With this technology, we are able to investigate how underwater noise affects the porpoises in inner Danish waters and how it affects their behavior when foraging.

The new recordings revealed that noise from engines, propellers and sonar was clearly transmitted 17-89% of the time. Whenever the noise reached a certain level, the porpoise forage activity showed a significant drop. The animal would dive downwards and swim fast along the seabed while ending all sonar activity. It is still too soon to draw conclusions about the overall effect of noise on porpoise well-being, reproduction and survival, but it is clear that the noise produced from human ship activity has consequences for porpoise foraging.

This project is part of an international collaboration between the Department of Bioscience at Aarhus University, the Veterinary University in Hannover (TiHo, project manager) and the University of St. Andrews, Scotland. The project is funded by BfN under the German Ministry of Environment.

Part of the German documentary "Wale vor Unserer Küste"


AU - News

Read the artikel at Bioscience news.

Acoustic D-Tag

Porpoise released after mounting of acoustic D-Tag by Florian Graner, PhD, Sealife Productions

Animation - ferry vs porpoise

Animation showing how the porpoise seeks the bottom when the ferry passes by, from Wisniewska et al. 2018