Wednesday, 26 May 2010

Bottlenose dolphins double their known range!

Dr Jean Paul Roux from the Ministry of Fisheries, who we collaborate with down in Luderitz sent me some photos they captured from shore in April of a group of bottlenose dolphins in Guano Bay (the main Heaviside's dolphin concentration area in Luderitz).

Although they occasionally see bottlenose dolphins down there, they tended to be very poorly marked (undistinctive) animals, and have always been assumed to belong to the offshore stock of bottlenose dolphins (which live in the open ocean off the continental shelf, and don't mix with the local population). The Walvis Bay population has a known range from Sandwich Harbour to Cape Cross (only about ~250km along shore), but with observer effort very low north and south of these points, we assumed they probably did range a bit further than that, there was just no one there to see them.

So this sighting was really exciting as we now have photographic proof of 'our' population of bottlenose dolphins in Luderitz, about 400km south of the known limit of their range! There were about 12 animals, several well marked ones including some of those tagged in the lagoon in 2009 and some of the mother-calf pairs.

We'll be back in Walvis Bay at the beginning of June to work all of June and July and plan to spend some more time in Luderitz in August. This will give us a chance to see if these animals were simply on a summer holiday trip and have come back to Walvis Bay, or if they have 'permanently' emigrated.