Which dolphins don’t have dorsal fins, please?

One-minute read

Thank goodness you asked, and so nicely to boot! There are only two, and the first is the southern right whale dolphin. The second, and you might be seeing the pattern here, is the northern right whale dolphin.

They’re both named after big filter-feeding whales without dorsal fins that occupy the same waters. But why don’t they have dorsal fins?

In order to answer that first I need to explain why most whales do have them. Simply put, it keeps them stable in the water. It’s like the daggerboard sticking out the bottom of a boat, preventing the animal from rolling around in the waves.

They’re so effective that 99% of dolphins have them, but the two that don’t have different priorities. What they lose in stability they gain in streamlining. Having a giant dorsal fin sticking out of your back is only going to slow you down if speed is your MO.

Both right whale dolphin species are extremely fast, agile and graceful. And while they’re the only dolphins without dorsal fins there are more examples in the wider whale family.

Speed isn’t the goal of a big whale, it needs stability. But what they lack in the back is made up for in the pectoral fins. Humpback whales only have the tiniest hint of a dorsal fin, but their pectoral fins are a third of their total body length. They create a lot of resistance and keep the whale upright, or indeed whatever orientation it chooses.

The bowhead whale, right whale, grey whale, sperm whale and beluga whale are all lacking in the dorsal department, but the most apt and adorable example is the finless porpoise.

Instead of a triangular fin they have a long, narrow ridge along the spine. It’s covered in little round nubs called tubercles but scientists aren’t sure what function they serve. It could have something to do with streamlining or help individuals identify one another. Either way, whales without dorsal fins are in the minority.

Learn more about both our finned (and finless) friends by listening to my 10-episode documentary podcast A Dolphin Pod.