The Difference Between A Dolphin And A Porpoise

“The dolphins will be mad. Love the dolphins.” —Thomas Pynchon, The Crying of Lot 49

In A Nutshell

Dolphins and porpoises both belong to the Cetacea order of mammals, but they do belong to different families. In spite of a general similarity in shape and appearance, dolphins and porpoises have distinctly different features, such as the shapes of their fins and heads. They also vocalize in a very different manner, and demonstrate very different behavior patterns.

The Whole Bushel

Dolphins belong to the Delphinidae family, while porpoises belong to the Phocoenidae family. Dolphin species are much more numerous, with at least 32 marine dolphin species to date and more being discovered. (As recently as October 2013, a new species of humpback dolphin was discovered off the coast of Australia, similar in appearance to other species but with drastically different DNA.) There are also five species of river dolphins, but there are only six different species of porpoise.

One of the most major differences between the two is also the least noticeable—their teeth. The teeth of a dolphin are conical, while the teeth of a porpoise are flatter and spade-shaped. Their faces also have a different shape, with dolphins tending to have a longer, narrower beak than porpoises, most of whom have a shorter, more squat face.

Most dolphins and porpoises can also be differentiated by their dorsal fin, although the difference in shapes can be less pronounced in some species. On the whole, the dorsal fin of a porpoise is triangular, while the dorsal fin of a dolphin has a curve. The body of a dolphin tends to be longer and leaner than that of a porpoise, though there are some species of both that bend this rule a bit.

Both groups are highly intelligent and have a complex communication system. The difference is that we can hear dolphins. Dolphins communicate in a wide variety of clicks and whistles that we are able to hear, record, and easily study. Porpoises, on the other hand, have a more limited range of vocalizations that the human ear can’t detect. Their clicks and whistles are on a much higher frequency than we are capable of hearing, and on a much more narrow band of frequencies than dolphin communication.

Behaviorally, dolphins tend to be a lot more playful than porpoises. Notorious for their ability to jump completely out of the water, dolphins can be seen doing this frequently. Porpoises do not show this behavior.

And perhaps the most disturbing difference is that dolphins will kill porpoises with shocking brutality. The two coexist in coastal regions around the world, and studies have shown that the sharing of waters is rarely peaceful, with fights often strongly favoring the bigger, bolder dolphins. For several decades, biologists have been studying groups of dolphins and porpoises that share waters off the coast of Virginia, the east coast of Scotland and the coast of Wales. Mutilated bodies of porpoises have long been washing up on all shores, showing signs of extreme blunt force trauma and the teeth marks of dolphins. Dolphins have since been caught on video viciously attacking their shy cousins, leaving scientists wondering exactly why porpoises are such easy and frequent targets for dolphins. Even those who share the same bays tend to alternate occupying it during the daytime or nighttime, and food doesn’t seem to be a point of contention.

While the idea of dolphins as killers might seem a little bizarre, the largest species of dolphin has it right in its name—the killer “whale” is actually a dolphin.

Show Me The Proof

NOAA: Dolphins and porpoises differ in their faces, fins, and body shapes
BBC: New species of dolphin identified
Telegraph: Killer dolphins baffle marine experts
The Guardian: Dolphins bully porpoises, researcher discovers

  • Hadeskabir

    I’ve always suspected that Dolphins were up to no good.

    • Lisa

      Except for flipper!

      • Hadeskabir

        I forgot about flipper. I miss him!

  • Karmala

    Didn’t know dolphins attacked porpoises, that’s pretty sad.

    • Ray

      Porpoises taste good. They’re a bit better tasting than dolphin.

      • Hadeskabir

        You must be Japanese.

      • Karmala

        Neither taste as good as sea turtle or humpbacked whale. Now that’s some sweet, sweet meat.

        • lbatfish

          Sea turtle is great, if you like greasy, strong-flavored very dark meat.

          I never had whale meat, but did have some beluga mungduk once (the half-inch or so of skin over the blubber). VERY chewy and a mild greasy/nutty taste.

          • Karmala

            Lol. I stand corrected 🙂

          • lbatfish

            LOL! I wasn’t correcting you — I like greasy, strong-flavored very dark meat. Not enough to kill a sea turtle, but because the islanders had already killed it and cooked it . . . why not enjoy it? Same for the mungduk, though in a very different part of the world.

          • Karmala

            Its actually interesting to hear these things, i’d have no idea what they would taste like otherwise. Are you like some kind of roving anthropologist? I’d try something like that if it’d already been killed and cooked, you’re hardly encouraging them to do it.

          • lbatfish

            I was mainly a computer teacher and school-computer-lab-starter-upper, but I’ve started them up in a number of rather offbeat places (sometimes using solar power when there wasn’t any line power available).

            Sea turtles and whales would usually both be on my do-not-kill list, but the Pacific islanders and Alaska natives don’t really consume enough to make a dent in the local populations. If they were selling them, that would be different, but they’re not. They’re just shared by the people who live there, and are healthier than foods like canned corn beef or Spam. Plus the “tradition” thing.

          • Karmala

            I don’t know how people can eat that corned beef. That’s a very cool thing to do, interesting for you and beneficial for those communities.

  • Check

    For what porpoise do dolphins kill their own cousins?

    • P5ychoRaz

      Just what exactly are you porpoising?