Are orcas whales or dolphins?

We are currently on a cruise up the Norway fjords (yeah, I know, ME on a cruise), and there was a little flurry of excitement as we passed a small pod of whales. There was some discussion as to what kind of whales they were, and there was some talk about orcas (it turns out they were almost certainly fin whales).

But I was struck by a youngish American woman turning to her partner and sneering - and yes, it was definitely a disdainful sneer - "Orcas aren't even whales!" I realized that I wasn't as sure about that as she clearly was. Now, I know orcas are also popularly known as "killer whales", or at least they used to be: that seems to be no longer politically correct in the business. But I also know that orcas are really just oversized dolphins. So, is an orca a whale?

Orcas are indeed the largest (by far) of the dolphin family. But dolphins are also whales (kind of). A quick look at the cetacean family tree shows that cetaceans are split into baleen whales and toothed whales, and the toothed whales are in turn split into five families: narwhals and belugas, sperm whales, beaked whales, dolphins, and porpoises. Orcas are part of the dolphin family, but that does mean that orcas (as well as all other dolphins and porpoises) are in fact toothed whales.

So, Ms. Disdain was unfortunately incorrect. Orcas are not baleen whales, but they are still whales.