Whale, Dolphin or Porpoise - Characteristics of Different Cetaceans

Are Dolphins and Porpoises Whales?

ORCA WHALE WITH DOLPHIN
Michael Melford/ The Image Bank/ Getty Images

Are dolphins and porpoises whales? These marine mammals have many things in common. Whales, dolphins, and porpoises all fall under the order Cetacea. Within this order, there are two suborders, the Mysticeti, or baleen whales, and the Odontoceti, or toothed whales, which includes dolphins and porpoises as well as sperm whales. If you consider that, dolphins and porpoises are really whales. 

Size Matters for Being Called a Whale or Not

While dolphins and porpoises are in the same order and suborder as whales, they generally aren't given a name that includes the word whale.

The term whale is used as a way to distinguish size among species, with cetaceans longer than about nine feet considered whales, and those less than nine feet long considered to be dolphins and porpoises.

Within the dolphins and porpoises, there is a wide range in size, from the orca (killer whale), which can reach lengths up to about 32 feet, to the Hector’s dolphin, which can be less than four feet long. That's how the orca comes to have the common name of killer whale.

This distinction keeps alive our image of a whale being something very large. When we hear the word whale, we think of Moby Dick or the whale that swallowed Jonah in the Bible story. We don't think of Flipper, the bottlenose dolphin of the 1960s television series. But Flipper could rightly claim he was, in fact, classified with the whales.

Difference Between Dolphins and Porpoises:

While dolphins and porpoises are very similar and people often use the term interchangeably, scientists generally agree that there are four major differences between dolphins and porpoises:

  • Dolphins have cone-shaped teeth while porpoises have flat or spade-shaped teeth.
  • Dolphins usually have a pronounced “beak,” while porpoises do not have a beak.
  • Dolphins generally have a very curved or hooked dorsal fin, while porpoises have a triangular dorsal fin.
  • Porpoises are generally smaller than dolphins.

    Meet the Porpoises

    To get even more specific, the term porpoise should also refer only to the seven species that are in the family Phocoenidae (harbor porpoise, vaquita, spectacled porpoise, Burmeister’s porpoise, Indo-Pacific finless porpoise, narrow-ridged finless porpoise and Dall’s porpoise.)

    Similarities Between All Whales - the Cetaceans

    All of the cetaceans have a streamlined body and adaptations for living in the water and never coming onto land.  But whales are mammals, not fish. They are related to land mammals, such as the hippopotamus. They are descended from land animals that looked like a short-legged wolf.

    All cetaceans breathe air into their lungs rather than getting oxygen from water via gills.That means they can drown if they can't surface to bring in air. They give birth to live young and nurse them. They also are able to regulate their body temperature and are warm-blooded.

    Sources:

    • American Cetacean Society. 2004. ACS Cetacean Curriculum (Online), American Cetacean Society.
    • Waller, Geoffrey, ed. SeaLife: A Complete Guide to the Marine Environment. Smithsonian Institution Press. Washington, D.C. 1996.