How Are Dolphins and Porpoises Different?

Dolphin

Dolphins and porpoises are commonly seen in various parts of the UK. In fact, the country has several resident pods of dolphins. Just last year, England’s first and only group of resident bottlenose dolphins was discovered off the coast of Cornwall. Aside from this pod, there are also two other groups of dolphins living in Moray Firth and Cardigan Bay.

Meanwhile, porpoises, specifically the harbour type, are the most common Cetacean species in Britain. In the early 90s, their population was estimated to be over 200,000. Some resident porpoises are found in eastern Scotland, west Wales and Northern Isles.

Aside from those that permanently reside in the UK waters, there are also some vagrant dolphins and porpoises that regularly visit.

Nowadays, dolphins and porpoises are popular wildlife attractions in Britain. Every year, thousands of wildlife watchers go on water safaris or visit known lookouts to see these marine mammals. Some of the famous sites for watching dolphins and porpoises are Land’s End, Mount Bay and Lundy Island. While these creatures are present all year round, spring and summer are still the best time to look for them.

If you are planning to go watch dolphins and porpoises, it would be helpful if you know how to differentiate them. Most of the time, people often confuse dolphins for porpoises and vice versa. In fact, many think that porpoises are dolphins.

So, what are the similarities and differences between dolphins and porpoises? Below are some key features and characteristics that make them alike and set them apart.

Similarities Between Dolphins and Porpoises

Both dolphins and porpoises, just like whales, belong to order Cetacea – marine mammals. The Cetacean order is composed of more than 80 different aquatic mammals. It is further divided into two groups – Mysticeti or baleen whales and Odontoceti or toothed whales.

Porpoise with its triangular dorsal fin

Baleen whales are mainly composed of large whales which possess two blowholes. Moreover, as their name suggests, they have baleen plates with bristles which are mainly used to filter food. On the other hand, toothed whales have only one blowhole and bear teeth instead of baleen plates. Dolphins and porpoises are members of the Odontoceti or toothed whale suborder.

Apart from eating the same food and giving birth to their young, these two Cetacean species are highly intelligent. Both possess big and complex brains. They are also capable of echolocation. They rely on this ability to search for food, navigate their habitat and talk with other members of the species.

Differences Between Dolphins and Porpoises

While these creatures belong to the same order, Cetacea, they are from different families. Dolphins belong to the family Delphinidae which is composed of 36 species. Given the number of species under this family, it is considered as the family in the Cetacean order with the most diverse members. Meanwhile, porpoises belong to the Phocoenidae family which consists of seven species.

Anatomically, the most obvious difference is that dolphins have elongated or pointed “beaks” or rostrums, while porpoises have shorter mouths. However, some dolphin species, like the Risso’s dolphin, have no rostrum. Hence, it is best not to use this characteristic alone when distinguishing a dolphin from a porpoise.

Dolphins have elongated rostrum and cone-shaped teeth

Moreover, dolphins have flexible necks which enable them to move their head; porpoises have round heads with immobile necks. In addition, while both belong to the toothed whale suborder, their teeth are shaped differently. Those belonging to the Delphinidae family have cone-shaped teeth; members of the Phocoenidae family have spade-shaped teeth.

Another key difference is the appearance of their dorsal fin. Dolphins’ dorsal fins are curved or hooked, while those of porpoises are triangular in shape much like those seen in sharks. Furthermore, the body of dolphins are generally longer and more slender or streamlined. Their size can range from 1.2 to 9.1 metres. On the other hand, porpoises are shorter in length, rarely growing beyond 2.5 metres. Their bodies are also more plump.

In terms of behaviour, dolphins are very sociable; they love interacting with one another. They even live and travel in pods composed of at most 12 individuals. Sometimes, one pod, known as superpods, can have over a thousand members. Porpoises are solitary animals. Although they may live in groups at times, the bond in these groups is not as strong as that in dolphin pods because the members easily move from one group to another.

Porpoises have shorter mouths and spade-shaped teeth

Dolphins tend to interact more with humans. They often approach boats and even bow-ride at times. Their smaller cousins do the opposite, usually actively avoiding boats. These shy sea mammals keep a low profile most of the time.

Both creatures communicate by whistling through there blowholes. However, scientists believe that porpoises do not use this ability as often as their long-snouted cousins do. Some say that this is primarily because of the structure of their blowhole.

Despite their similarities, these marine mammals have noticeable differences that can help you distinguish one from the other. So, when you encounter what might be a dolphin or a porpoise, check out the fin, rostrum, face and fin or even its behaviour to know exactly what it is.

—

Dolphin photo by ajmexico

Porpoise with its triangular dorsal fin photo by www.metaphoricalplatypus.com

Dolphins have elongated rostrum and cone-shaped teeth photo by ross_hawkes

Porpoises have shorter mouths and spade-shaped teeth photo by colink.