Saturday 25 June 2011

Bottlenose dolphin acoustics - by Mel Ngo

20 June 2011
This past weekend, we were given Saturday and Sunday off to relax and explore the wonders of Namibia. A couple of interns went on a camping trip to Spitzkop, which is about 3 hours away from Walvis Bay. From the stories and pictures they shared, they had a great time seeing the kind of glory Namibia has to offer.

This week has been the most productive by far. After coming back from our two day break, we were all re-energized and eager to get back to work. On Monday, we had an encounter with the bottlenose dolphins, which we haven’t seen much of this month.  This season the NDP has brought in some new technology, a hydrophone to record the sounds made by the bottlenose dolphins (and anything else they encounter), focusing on whistles and other sounds they are able to make which are mostly for communication.

Back in the office, the ‘acoustic team’ uploaded the data on to the computer; from there we are able to look more closely at the data to see (and hear) if we have recorded any whistles.  Unfortunately, there were no whistles from Monday’s encounter, but there were a couple of other interesting sounds such as clicks, buzzes and burst pulses.

The next day, Tuesday, we did our normal routine of launching the boat around 8 am. The boat team for that day was Simon, Heidi, Hannah, Kuan and I. As always, we were on search for whales and dolphins, and heading north just off the fishery docks we spotted bottlenose dolphins again. I was very excited as it was my first time seeing them this season and for some of the others as well. I forgot how massive and big these dolphins are and I was happy I got to see them again. Some were friendly in the beginning, approaching the boat and others were jumping and socializing from a distance. With Tess not being on the boat I’d been ‘promoted’ to run the acoustic recordings. Once we found them, I immediately prepared the equipment, hooking up the hydrophone to the boat, connecting it with the recorder, finding a spot for the recorder, and plugging the headphone to the device. When everything was set up and the hydrophone was placed in the water and the recording was on, I listened to the eerie mysterious sound of the sea for the first time. It was quite an interesting experience, it was very quiet when the engines were off, kind of spooky in a way. Within the first couple of seconds that the recorder was recording and the headphones were on my head I heard these amazing animals whistles. I jumped and shouted “They’re whistling!”. Simon and Heidi just looked at me and laughed as I could not believe what I was hearing. VERY COOL! We did several recordings and most of those files had at least a few whistles and many clicks the bottlenose produced. SO VERY COOL!!!!

At the time of the recording at sea, listening in on the dolphin’s secrets, it seemed like no sound was being made much of the time, but once everything was downloaded on to the computer, I found other whistles in the files that I did not hear when at sea. It’s much easier to pick the whistles out visually on the computer than by ear on a noisy boat! It was one of the coolest experiences I have got to experience again with the NDP team this season. I cannot wait to learn and find out more!!

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