Porpoise

Dall's Porpoise

The porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are, however distinct from dolphins, although the word "porpoise" is often used to refer to any small dolphin, especially in North America. A key difference is the shape of the teeth and of the head.

Porpoises, divided into six species, live in all oceans, mostly near the shore. Probably best known is the harbour porpoise, which can be found across the northern hemisphere.

Table of contents

1 Anatomy
2 Behaviour
3 Taxonomy
4 Human impact

Anatomy

Porpoises tend to be smaller but stouter than dolphins. They have small, rounded heads and blunt jaws instead of beaks. Their teeth are spade-shaped, whereas dolphins have conical teeth. In addition, a porpoise's dorsal fin is generally triangular, rather than curved like that of many dolphins.

These animals are among the small cetaceans, reaching body lengths up to 2.5 m; the smallest species ist the vaquita with maximal 1.5 m.

Behaviour

Porpoises are predators hunting mainly fish, often also squid and crustaceans. Most common are small groups of up to ten individuals, which in some species may join forming aggregations of several hundred animals. Different click and whistle sounds are used for communication. Like all toothed whales they are capable of echolocation by means of ultrasound. Porpoises are fast swimmers - Dall's porpoise is said to be one of the fastest cetaceans with a speed of 55 km/h. Porpoises tend to be less acrobatic and more wary than dolphins.

Taxonomy

ORDER CETACEA
- Suborder Mysticeti
  - Family Eschrichtiidae: Gray Whale
  - Family Balaenopteridae: rorquals
  - Family Balaenidae right whales
  - Family Neobalaenidae: Pygmy Right Whale
- Suborder Odontoceti
  - Family Platanistoidea: river dolphins
  - Family Delphinidae: oceanic dolphins
  - Family Phocoenidae
    - Vaquita, Phocaena sinus
    - Finless Porpoise, Neophocaena phocaenoides
    - Harbour Porpoise, Phocaena phocaena
    - Burmeister's Porpoise, Phocaena spinipinnis
    - Spectacled Porpoise, Phocaena dioptrica
    - Dall's Porpoise, Phocoenoides dalli
  - Family Monodontidae: Beluga and Narwhal
  - Family Physeteridae: Sperm Whale
  - Family Kogiidae: Pygmy Sperm Whale and Dwarf Sperm Whale
  - Family Ziphiidae: beaked whales

Human impact

In many countries, porpoises are hunted for food or bait meat. Additionally, bycatch in fishing gear is responsible for a decline of the stocks. One of the most endangered cetacean species is the vaquita, having a limited distribution in a highly industrialized area.
Porpoises are rarely held in captivity in zoos or oceanaria - in contrast to the dolphins, which are overall far more popular.