There are very few predators that feed only with their mouths (no claws) that target prey larger than themselves. I have to wonder if the Orcas really attacked full grown healthy humpbacks? The babys are not calved in the Alaskan waters. I suppose that they could have subsisted entirely on old and dying whales or some of the smaller species like beluga, etc. The whole theory is speculative since I would bet the researchers have absolutely no data to show that whales were a primary food source. Look at an Orca mouth and imagine it trying to kill a whale 3 or 10 times its size. How would it get a bite onto anything other than a fluke or tail area. The whole thing seems like a really big stretch to support the anti-whaling sentiment (I don't like whaling either).

Just my ill informed opinion.

-David