Richard, apparently orca feeding habits are a learned behaviour with the young learning from the older members of the pod. There are regional variations in feeding - those in New Zealand are known for feeding on rays. They have been seen chasing stingrays in the shallows of our harbours (although Steve was the first to film it in water - he has other footage of how they do this but I cannot find it right now). There have been clips played on the 6pm news showing orca chasing rays in Auckland harbour (our largest city) with the rays leaping from the water in desperation. Apparently rays are orca candy ...
I have discussed the footage of orca playing with the anchor rope (2nd clip I posted) and he had heard about this happening from time to time but never seen it himself.
---------- Post added May 23rd, 2015 at 09:20 AM ----------
Richard - found some of the footage of orca eating rays in this episode of Young Ocean Explorers here (Steves side project with his daughter ) [video=youtube_share;I4kBlpfySbQ]http://youtu.be/I4kBlpfySbQ[/video]
For other stuff have a look at the Young Ocean Explorers website
Young Ocean Explorers
And the TEDx talk Riley and Steve did a couple of weeks ago [video=youtube_share;UzA_CTkn7vk]http://youtu.be/UzA_CTkn7vk[/video]