Dolphins vs. Porpoises

Dolphins and porpoises belong to the same scientific order, Cetacea. This order includes all whales, even the great whales, to which both dolphins and porpoises are related. All cetaceans are completely aquatic mammals, have a streamlined body, a tail fluke, and a blowhole (which is what these air-breathing animals use to breathe). The dolphins and porpoises are also classified in the scientific suborder, Odontoceti, which are the toothed whales. All odontocetes also have the ability to echolocate, the ability to detect objects in their underwater environment using the echoes of a sound, much like sonar.

Porpoises and dolphins are classified into two different families. The porpoises are in the family Phocoenidae and the dolphins are in the family Delphinidae. When separated at the family level, dolphins and porpoises are as physically different as cats and dogs.

In comparison to dolphins, porpoises are very small. Porpoises seldom exceed 7 feet in length, whereas many dolphins can exceed 10 feet in length. Porpoises are also more robust than dolphins. Dolphins have a lean sleek body, whereas porpoises often appear chubby. The dorsal fin (the fin on the back of the animal) in porpoises is also triangular, looking more like a shark. The dorsal fin of the dolphin is shaped in a wave. Porpoises lack a rostrum or a beak. This rostrum is very prominent in dolphins. The teeth of the porpoise are spade-shaped, whereas the teeth of the dolphin are conical or cone-shaped.

Many porpoises do not live past their mid-teens. Porpoises have an intensive reproduction schedule that may play a role in their lack of longevity. A porpoise can become pregnant each year, give birth, and then it can become pregnant again five or six weeks later, so it can be nursing and pregnant at the same time. This can also happen in dolphins, but dolphins are larger in size and it seems their body is suited for handling such occurrences, and anyhow it is less common. Dolphins can live in an upwards of fifty years.

There are many behavior differences as well as physical differences. For the most part, porpoises are shy. They do not often approach people or boats. The dolphin, on the other hand, if often seen riding the bow wave of fishing boats. We rarely see porpoises at the surface unless they are coming up for a breath.

The dolphin, rather than the porpoise, is often seen in marine animal shows. This comes back to the idea that dolphins tend to show a lesser fear of man than porpoises. This is often why dolphins, not porpoises, get stuck in tuna nets. For this reason dolphins are widely studied whereas porpoises are not.

Dolphins and porpoises have a lot in common. There are some differences, but the similarities among their behavior and looks outweigh the minute differences. You are more likely to see a dolphin, both in the wild and captivity. Consider yourself lucky if you encounter a porpoise in either situation.