Porpoises and dolphins are similar, although not the same, animals. They both belong to the order Cetacea, from the Greek meaning “large sea creature,” and their names are often used interchangeably. 

Porpoise swimming
Porpoise swimming

What is a Porpoise? 

There are a total of six porpoise species, far fewer than dolphins. They are, according to an article published in 1995 in Molecular Phylogenetics and Evolution

  • Harbor porpoise (Phocoena phocoena)
  • Burmeister’s porpoise (Phocoena spinipinnis)
  • Vaquita porpoise (Phocoena sinus)
  • Spectacled porpoise (Australophocaena dioptrica)
  • Dalls porpoise (Phocoenoides dalli)
  • Finless porpoise (Neophocaena phocaenoides)

Porpoise Appearance 

When one knows what to look for, it’s quite easy to tell a dolphin and a porpoise apart. A porpoise is more portly, or rounder than a dolphin is. They also have a triangular dorsal fin. Their moths are small, with teeth that look like spades. Often, researchers point to the dorsal fin are one of the main ways that the two can be distinguished. But, another is by the shape of their faces. Porpoises have rounder faces and a less prominent grin. Porpoises grow to around 5 to 6.6 feet (1.5 to 2 meters) and weigh 110 to 265 lbs. (50 to 120 kilograms), much smaller and lighter than the dolphin.

Harbor Porpoise at Vancouver Acquarium

Porpoise Habitat, Food, and Mating Practices

Although dolphins are often cited as highly intelligent animals, porpoises are thought to be quite intellectual as well. They are less talkative than dolphins, spending less of their time communicating through whistling sounds that dolphins are fond of. 

Porpoises are still highly social animals. They live in shoals that can range from a few members to thousands. Porpoises live in a variety of waters around the world, from the Gulf of California to the eastern and western parts of South America and even north of Antarctica, where researchers have found the spectacled porpoise. The common purposes live around the east coast of North America. Dall’s live in the northern rim of the Pacific Ocean, and some live in the Yellow Sea between China and Kora, such as the finless porpoise. 

Not much is known about porpoises mating habits, but it’s known that they have live births (since they’re mammals). It appears that the gestation period is around 10-11 months, and they have one baby at a time. Their children are called pups, or sometimes calves. They are sexually mature around 2 to 8 years old, depending on the species, and can live 23 years of age. 

The only porpoise on the IUCN’s list of threatened species is the Vaquita proposes due to a drastic decrease in their population numbers. The finless porpoise and the Indo-pacific are listed as vulnerable. 

What is a Dolphin? 

Dolphins are grouped into five families, the largest of which is the ocean dolphin, to which thirty-eight species belong. The remaining four are all river dolphin families with only one species per family. Often categorized as a whale, the orca is, in fact, a dolphin. It is one of the largest, along with the pilot whale and the false killer whale. The smallest are the New Zealand dolphin and tucuxi, according to Whale and Dolphin Conservation.

Atlantic Spotted Dolphin

Dolphin Appearance

Dolphins are slimmer and sleeker than porpoises are. They can move at higher speeds through the ocean while hunting with longer beaks or mouths. They also have a more pronounced smile or grin in comparison to porpoises. Their teeth are shaped differently and dolphins also have a curved or hooked fin on their backs, according to Live Science. 

Dolphins also have a variable number of teeth, ranging from 14 up to 240 in the mouth of the spinner dolphin. The size of their teeth, as well as the position and shape depends on their species. The majority of ocean dolphins have cone-shaped teeth used for catching fish. 

Dolphin Habitat, Food, and Mating Practices

Dolphins are highly social creatures. They spend time in large groups, hundreds to thousands, and communicate through a series of whistles and squeals. They also make use of something known as echolocation. This allows them to hunt via reflected sound, or echos. Dolphins are also incredibly mobile. They are considered powerful predators who are skilled at hunting fish, squid, and other marine life. 

Dolphins, like porpoises, give birth to one baby at a time. Their pregnancies last between nine and sixteen months. The babies then stay with their mothers for several years, a time period in which the mother teaches the child everything he or she needs to know to survive. Dolphins can live between twenty and eighty years. 

River Dolphins 

Unlike porpoises, there are four distinct species of river dolphins. They are smaller than their ocean cousins and have evolved to survive in shallow water. They range from five feet, or 1.5 meters, to eight feet and 2.4 meters. They are the South Asian river dolphin, the Amazon river dolphin, the La Plata dolphin, and the Baiji dolphin. The latter may or may not be extinct. Unlike their ocean counterparts, river dolphins are rarely kept in captivity. They are hard to breed, and tragically die, usually within a few months of capture. They are usually recognizable due to their elongated mouths/ beaks.

Amazon River Dolphin
Amazon River Dolphin

What’s the Difference Between Porpoises and Dolphins? 

In general, porpoises are rounder and less vocal than dolphins. They have differently shaped teeth, fins, and faces. Dolphins are faster, sleeker, and more powerful hunters. There are also far more species of dolphins than there are porpoises. When it comes to dolphins, it is harder to know that the animals that appear vastly different belong to the same family. For those who are keen on quickly recognizing which is which, it is easier to look to the dorsal fin. It is more rounded in the case of a porpoise and more hook in the case of a dolphin. 

Alternatively, one might look to the “grin” that’s often cited as featuring on dolphins and porpoises faces. Their curved mouths, which appear to be smiling can also be a signifier of whether or not the creature one is observing is a porpoise or a dolphin. The latter’s grin is far more pronounced than the former’s.

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