Tuesday, 17 June 2008

Data collection is now progressing well and we've had 6 dedicated research trips on Pedro already. We've encountered Heavside's dolphins (or Benguela dolphins as many people call them here) on all of those and bottlenose on 4 of them (with some re-sightings already). However, all encounters are not equal and some days the Heaviside's dolphins can be very difficult to approach for photography.

We're trying to stay on top of the data processing by grading our images for quality and picking out the distinctive animals as we go. Only good quality photographs of well marked animals will be used in the mark-recapture calculations. This means fins need to be well focused, close up, and perpendicular to the camera to minimise the chances of mis-identifying any animals. I've put a few example photographs below of the types of natural-marks we use to identify animals. The bits of missing fin are mainly the result of interactions with other animals, they never heal and can be used to identify individuals for many years (if they don't get disguised by the addition of too many more marks!). These images are not all of a good enough quality for abundance estimates - but I've included a few of the very well marked ones we've seen in the last week, just to show that they're out there. As you can see, the Heaviside's (left column) are not nearly as well marked as some of the bottlenose fins (right column). (For scale - the Heaviside's fins are actually much smaller than those of the bottlenose).

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