Saturday, 21 June 2014

Keeping an EAR on the whales

In the last winter season sometimes it really felt like the whales were playing tricks on us! One day we went early in the morning for our daily morning check to see what the weather looked like and whether there were any whales in the fjord. As soon as we arrive at the viewpoint, perched high above the inner part of Kolgrafafjordur, we spot the whales! The weather however is not good so we can't go out, but at least we can try to photograph them if they come close to shore, for example to go under the Kolgrafafjordur bridge. We come back home to tell the rest of the team what the plan is, fetch the photo-id camera and head back to the fjord. The whole round trip must have taken 15 minutes, we go back and the whales are gone! This happened not just once but on a few occasions.

The view from Kolgrafafjordur viewpoint. In the centre you can see the bridge separating the inner fjord from the outer part of the fjord. A great place to spot the whales!
A common sight last winter: people waiting at the bridge for the whales to go under. It did make for a spectacular show particularly when the whales had to cross against the strong current.

Luckily this year some of the hard work was done for us. Better yet, we could keep track of the whales for 24 hours a day and even in stormy weather! We had an autonomous acoustic recorder called the EAR (Ecological Acoustic Recorder). Thanks to Dr. Marc Lammers, from the Oceanwide Science Institute, we deployed an EAR in late February on the inner part of the fjord where the whales spent most of their time. It stayed in the fjord for more than one month, recording the sounds in the environment for 5 minutes every 10 minutes. This meant that by the end of the season we had more than 400 hours of recordings to go through! But because the EAR was there for such a long time it provided us valuable information about when whales were present in the inner part of the fjord, as long as they were producing sounds.

Deploying the EAR buoy
400 hours may sound like a lot, but going through all these recordings has been fascinating. We have learned that the whales came to the fjord to feed often during the night! This type of information would have been impossible for us to gather with our usual methods, as we cannot work during hours of darkness.

But it is not like the whales were only feeding at night. Or for that matter it's not even like they would be there every night. So what is it that determines their choice of when to go feeding in a particular area or when to leave? Our photographic records seem to suggest that the whales may come to the fjords for a few days but then leave and only come back a few days (or weeks) later. Where they go in the meantime is unknown. But it certainly looks like they are constantly on the move!

It is not uncommon for killer whales to move around. Our recent post about the movements between Iceland and Scotland is a testament to just that and long movements are known also in other populations. But we are still far from understanding the finer details of what drives killer whales to move between areas or to temporarily leave what seem to be good feeding grounds, as they do in Iceland.  

Tuesday, 10 June 2014

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