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Friday, 18 December 2015 12:16

Diving deep into the sound of blue whales to help them prosper with ships

The plight of blue whales whose vital communications are affected by the noise from shipping could be eased thanks to the work of a tireless Icelandic scientist, Dr Marianne Helene Rasmussen.

BlueWhaleSounds1Growing up to 30 m long and 180 tons, the blue whale's calls can be heard thousands of kilometres away and far below the ocean's surface. But very little is known about these calls - such as how man-made noises can interfere with them and what the implications really are - so Project Blue Whale was created to dive deeper into these issues.

Because of the work of Dr Rasmussen and her team, scientists are now beginning to understand more about how, why and when these majestic animals communicate - and what can be done to help them prosper.

Blue whales communicate using the lowest frequency sound recorded among cetaceans with loud, low-pitched moans and whines that can be heard over very large distances. These 'down-sweep' calls have frequencies from 107 Hz to 21 Hz (or lower) and show an incredible variety, with eleven different types of sound.

Unfortunately, this is the same frequency range as a wide variety of man-made sounds, such as ship engines, low-frequency active sonar, seismic air gun array explorations and other oil exploration activities, to name but a few.

There is growing evidence that noise interference can disturb their vital life functions, such as feeding, breeding, navigation and communication. This is a very serious problem, especially for an endangered species.

BlueWhaleSounds2Project Blue Whale's objectives fell into two parts: firstly, the project aimed to gain a better understanding of the communications of blue whales, and secondly if and how shipping affects their communications.

Dr Rasmussen has broad experience in marine research using hydrophone arrays to record beam patterns and sound levels, as she had been part of a similar project in Andenes in Northern Norway that recorded the sounds made by sperm whales using Type 8101 hydrophones supplied by Brüel & Kjær. Because of the project's  success it was an easyl decision to use the same equipment again for Project Blue Whale.

The blue whales communicate via low frequencies (for a 15 Hz signal, the wavelength is around 100 m) so a special method was also needed to locate exactly where the whales were. This was achieved using four boats positioned in a line, 500 m or 1 km apart, with the hydrophones at a depth of 30 m. Then - once a whale was spotted - the boats just needed to stay in place to record the whale sounds and locations for approximately one hour at a time.

Such an endeavour required a large amount of planning. Dr Rasmussen chose Skjálfandy Bay in Northeast Iceland as the best area to conduct the research; it is easy to get to, close to shore and Iceland's round-the-clock daylight meant that the research team could go out very early in the morning, long before the whale-watching boats started up their engines.

BlueWhaleSounds3Aside from a few days of bad weather and some minor technical glitches, everything went as planned and the team managed to gather over 100 whale calls and a wealth of good positional data. Now, all that is left for this part of the project is to analyse the recordings, which is done on shore and will be completed within the next six months.

Of course, the project doesn't end there and the second part – examining how ship noises mask and affect the whales' communication – is still to be done. Nevertheless, the data so far has already revealed some interesting results about the nature of these fascinating sea mammals, how they communicate, what frequencies they use, why and when.

The second part of the project will try to find out if and how underwater ship noises affect these communications. This will involve projecting noises at certain frequencies to mask the sounds created by blue whales and investigate their responses. The Projcet Blue Whale team are hoping these results will be a catalyst for new dialogue with authorities about shipping lane regulations and what more we can do to safeguard the whales' natural habitat.

LINKS
Project Blue Whale
University of Iceland's Research Center in Húsavík
Brüel & Kjær hydrophones
Brüel & Kjær Notar recorder