What’s the difference between dolphins and whales?



I read that killer whales aren’t whales, they’re dolphins. But I also read that dolphins are whales. I’m so confused. So what are these things?

In: Biology

Well, the difference is at what level of the scientific classification you break them up.


They are all cetaceans, which is the infraorder of the scientific classification system for all of these animals. But you go one level down and and now whales and killer whales are in different families.

Killer whales are a member of Delphinidae which is the dolphin family, whereas Grey Whales are a member of the Eschrichtiidae family which includes grey whales and other similar animals.

If you go high enough up in the scientific classes, they are related to Humans as well.

Yes, killer whales are one dolphin species and all dolphins are ‘whales’/cetaceans, too, but there are two subgroups of whales: toothed whales and baleen whales.

Killer whales and dolphins are toothed whales, they have teeth and hunt other marine animals. Baleen whales like blue whales and humpback whales – which is what you classically think of when you hear whale -feed by filtering water through their baleen bristles for very small marine animals like krill.

So there’s this group of animals called whales.

We divide that group into two categories: toothed whales and baleen whales.

The toothed whales are dolphins and porpoises. This includes the killer whale. So – all dolphins are whales. The killer whale is a dolphin *and* a whale.

The baleen whales are what you think of when you think “whale”. Humpback whales, blue whales, etc.

There are exceptions to this general overview, but it is a rule of thumb and an easy way to think about it. All dolphins are whales, but not all whales are dolphins. All whales are whales.