Porpoise

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For other uses, see Porpoise (disambiguation).

Porpoises Fossil range: ?Latest Oligocene - recent
Phocoena phocoena, Harbour Porpoise
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Cetacea Family: Phocoenidae Gray, 1825
Genera
Neophocaena Phocoena - Harbor porpoise Phocoenoides - Dall's porpoise

The porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen. The most obvious visible difference between the two groups is that porpoises have spatulate (flattened) teeth distinct from the conical teeth of dolphins. In addition, porpoises are relatively r-selected compared with dolphins: that is, they rear more young more quickly than dolphins.

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.

[edit] 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 falcate (curved) like that of many dolphins and large whales.

These animals are the smallest cetaceans, reaching body lengths up to 2.5 m (8 feet); the smallest species is the Vaquita, reaching up to 1.5 m (5 feet). In terms of weight the lightest is the Finless Porpoise at 30-45 kg (65-100 lb) and the heaviest is Dall's Porpoise at 130-200kg (280-440 lb).

[edit] Behaviour

Porpoises are predators of fish, squid, and crustaceans. Although they are capable of dives up to 200  m, they generally hunt in shallow coastal waters. They are found most commonly in small groups of fewer than ten individuals. Rarely, some species form brief aggregations of several hundred animals. Like all toothed whales they are capable of echolocation for finding prey and group coordination. Porpoises are fast swimmers—Dall's porpoise is said to be one of the fastest cetaceans, with a speed of 55 km/h (15 m/s). Porpoises tend to be less acrobatic and more wary than dolphins. When a porpoise swims upside down, it is searching for a mate.

[edit] Taxonomy

Porpoises are the six species of toothed whale found in the Phocoenidae family of cetaceans.

• Sub-order Odontoceti: toothed whales

[edit] Evolution of porpoises

Porpoises, along with whales and dolphins, are descendants of land-living mammals, most likely of the Cletis order. They entered the water roughly 50 million years ago. See evolution of cetaceans for the details.

[edit] Human impact

In many countries, porpoises are hunted for food or bait meat. Additionally, bycatch (accidental entanglement) in fishing nets is responsible for a decline in porpoise numbers. One of the most endangered cetacean species is the Vaquita, having a limited distribution in the Gulf of California, a highly industrialized area.^[1]

Porpoises are rarely held in captivity in zoos or oceanaria, as they are generally not as capable of adapting to tank life nor as easily trained as dolphins.

[edit] See also

Cetaceans Portal

• Dolphin
• Whale

[edit] References

Cetaceans (Dolphins, Whales, and Porpoises)
Suborder Mysticeti (baleen whales): Eschrichtiidae (gray whales) - Balaenopteridae (rorquals) - Balaenidae (right whales) - Neobalaenidae (pygmy right whale)
Suborder Odontoceti (toothed whales): Platanistoidea (river dolphins) - Delphinidae (oceanic dolphins) - Phocoenidae (porpoises) - Monodontidae (beluga and narwhal) - Physeteridae (sperm whales) - Kogiidae (pygmy and dwarf sperm whales) - Ziphiidae (beaked whales)