Escorted by pod of approx 10 dolphins
No interactions present.
I think you're probably right with the ID. The other big dolphin that is commonly seen off Dorset is the white-beaked, but they do usually have quite obvious white markings on their sides and behind the dorsal fin. However populations do vary in the 'distinctness' of their markings.
By the way, the WDCS now has its species guide up and running again at http://www2.wdcs.org/species/index.php , although I have to say I don't find it as easy to use as the old one as you don't seem to be able to browse and expandable 'tree' of species - you have to know the name already and put it in the search box.
OU Certificate in Contemporary Science
From comparing size with objects on deck, they seem to be about the right length and bulk. Fin shape is correct (with the variations) and one animal shows the countershading - no hourglass so definitely not Common Dolphin, and no "lock of hair" so not Striped (too big for these species anyway). Whitebeaked have been excluded above, so all that would be left is Risso's - but there are no light grey scratches and general colouration and the fins are not quite tall enough. Did you see any beaks, which would also exclude Risso's if you did. Interaction with boats is more BND gizz as well.
IWDG also has a general guide to species at http://www.iwdg.ie/species_profiles.asp?id=24 though the BND section could now include that we found a large (100+) offshore group of BND living near the western shelf edge last August.
I agree with the comments above. David, it's good to hear about the new large group discovered.
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