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The recent sighting of 50-100 whales off Kalpitiya on the north west coast of Sri Lanka has generated a lot of interest. Rightly so. It was also a great example of how Sri Lankans have become more aware of their cetacean neighbours. To me that's very exciting.
I found out about the event through a text message from Arjan Rajasuriya forwarded to me by Dharshana Jayawardena (www.divesrilanka.com). In short, on the 14th of April 2012, approximately 100 sperm whales were sighted off Bar Reef.
Following this text message, Arjan started an email discussion on the topic asking lots of really valid questions about the sighting. It was testament to how easy communication has become with modern technology. Here I was sitting at my desk in Perth, analysing data but still able to contribute. Of course I would have LOVED to be out there observing, recording and photographing but one can't always have everything in life.
I extended the discussion we were having to Prof. Hal Whitehead of Dalhousie University, a world renown sperm whale expert and one of the key members of the of the Tulip project (along with Dr. Jonathan Gordon) that spent three years (from 1982) off Sri Lanka studying the social behaviour of living sperm whales in the Indian Ocean.
Here's some of what was discussed over the past few days.
We still don't have a full grasp on the numbers sighted, but it can be quite confusing when you have many of these giants logging at the surface, fluking and moving. However, to answer the first question - is this unusual? No. Tropical waters are the preferred habitat of maternal groups and it is possible that this is a sighting of a number of maternal groups using the same area. Its actually hard to define a group in this situation however, according to Dr. Whitehead, sightings of thousands of sperm whales is not unheard of. The whales off Sri Lanka were about 10-12 m in length (on the last estimate) which confirms that they are maternal groups as opposed to full grown males (or bulls) which are between 15-20 m.
So nothing to be too alarmed about. HOWEVER, what is most unusual about this sighting is the depth where the whales were seen. Based on the reports they were in waters approximately 30 m deep (in one case as shallow as 15 m). This is reasonably close to a steep drop in the shelf BUT these deep water dwellers are rarely seen in such shallow waters. While Dr. Whitehead thinks this might be something to think about, local researchers Arjan and Nishan Perera reckon that there might be lots of food around at the moment. There have been reports of fish and seabird activity. However, this may or may not be an indicator of squid availability.
So we are still left with one big question - Why are these whales gathering in shallow waters?
Maybe they were here to say Subha Aluth Avuruddhak Wewa! (Happy new year!) and hoping that an incredible sighting like this would make us marvel more and want our future generations to have the same opportunities we have had.
Click on this link for a report by the Navy (and to see photographs): http://www.navy.lk/index.php?id=3427.
This link will lead you to a Times Online article: http://www.sundaytimes.lk/index.php?option=com_content&view=article&id=18199%3Aover-100-sperm-whales-gather-in-kalpitiya-onlookers-puzzled-&catid=1%3Alatest-news&Itemid=547
But remember, just because we haven't witnessed this ourselves before, doesn't mean it's not happening.
NB: Just got an update about the location of the sperm whales. Yesterday and day before the whales were seen in an area where the water was 4-500 m deep. Good to hear they are shifting to more familiar territory (thanks Riaz Cader!)