Porpoise - Wikipedia, the free encyclopedia

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Porpoise
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For other uses, seePorpoise (disambiguation).
Porpoises
Fossil range: ?LatestOligocene - recent

Phocoena phocoena,Harbour Porpoise
Source:Fjord & Bæltcentret in Denmark
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Order:Cetacea
Family: Phocoenidae
Gray, 1825
Genera
Neophocaena - Finless porpoise
Phocoena -Harbour porpoise et al.
Phocoenoides - Dall‘s porpoise
The porpoises are smallcetaceans of the family Phocoenidae; they are related towhales anddolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially bysailors andfishermen.The most obvious visible difference between the two groups is thatporpoises have flattened, spade-shaped teeth distinct from the conicalteeth of dolphins.
The name derives fromFrench pourpois, originally fromMedieval Latin porcopiscus (porcus pig + piscus fish).
Porpoises, divided into six species, live in all oceans, mostly near the shore. Probably best known is theHarbour Porpoise, which can be found across the Northern Hemisphere.
Contents
[hide]
1 Taxonomy and evolution
2 Physical characteristics
3 Life history
4 Behaviour
5 Human impact
6 See also
7 References
8 External links
[edit] Taxonomy and evolution
See also:Evolution of cetaceans
Porpoises, along with whales and dolphins, are descendants of land-living mammals and are related tohoofed animals. They entered the water roughly 50 million years ago.
Sub-orderOdontoceti: toothed whales FamilyPhocoenidae: Porpoises GenusNeophocaenaFinless Porpoise, Neophocaena phocaeniodes
GenusPhocoenaHarbour Porpoise, Phocoena phocoena
Vaquita, Phocoena sinus
Spectacled Porpoise, Phocoena dioptrica
Burmeister‘s Porpoise, Phocoena spinipinnis
GenusPhocoenoidesDall‘s Porpoise, Phocoenoides dalli
Recently-discoveredhybrids between male Harbour porpoises and femaleDall‘s Porpoises indicate that the two species may actually be members of the samegenus.[1]
[edit] Physical characteristics

AHarbour Porpoise at an aquarium. In the wild, porpoises rarely jump out of the water.
Porpoises tend to be smaller but stouter than dolphins. They havesmall, rounded heads and blunt jaws instead of beaks. While dolphinshave a round, bulbous "melon", porpoises do not. Their teeth arespade-shaped, whereas dolphins have conical teeth. In addition, aporpoise‘s dorsal fin is generally triangular, rather than curved likethat of many dolphins and large whales. Some species have small bumps,known as tubercles, on the leading edge of the dorsal fin. The functionof these bumps is unknown.[1]
These animals are the smallestcetaceans, reaching body lengths up to 2.5 metres (8 ft); the smallest species is theVaquita, reaching up to 1.5 m (5 ft). In terms of weight the lightest is theFinless Porpoise at 30-45 kilograms (65-100 lb) and the heaviest isDall‘s Porpoiseat 130-200 kg (280-440 lb). Because of their small size, porpoises losebody heat to the water more rapidly than other cetaceans. Their stoutshape, which minimizes surface area, may be an adaptation to reduceheat loss. Thickblubberalso insulates them from the cold. The small size of porpoises requiresthem to eat frequently, rather than depending on fat reserves.[1]
[edit] Life history
Porpoises are relativelyr-selectedcompared with dolphins: that is, they rear young more quickly thandolphins. Female Dall‘s and Harbour Porpoises often become pregnantwith a single calf each year, and pregnancy lasts for about 11 months.Although the lifespan of most species is not known, specimens olderthan in their mid-teens have rarely been found.[1]
[edit] Behaviour

"Rooster tail" spray around swimmingDall‘s Porpoises
Porpoises are predators of fish, squid, and crustaceans. Althoughthey are capable of dives up to 200 m, they generally hunt in shallowcoastal waters. They are found most commonly in small groups of fewerthan ten individuals. Rarely, some species form brief aggregations ofseveral hundred animals. Like alltoothed whales they are capable ofecholocation for finding prey and group coordination. Porpoises are fast swimmers—Dall‘s porpoiseis said to be one of the fastest cetaceans, with a speed of 55 km/h(34 mph). Porpoises tend to be less acrobatic and more wary thandolphins.
[edit] Human impact
Accidental entanglement (bycatch) in fishing nets is the main threat to porpoises today. One of the most endangered cetacean species is theVaquita, having a limited distribution in the Gulf of California, a highly industrialized area.[2]
In some countries, porpoises are hunted for food or bait meat.
Porpoises are rarely held in captivity inzoos oroceanaria, as they are generally not as capable of adapting to tank life nor as easily trained as dolphins.
In the 1966Batman film, Batman and Robin are rescued by a "Noble Porpoise" who intercepted a torpedo that was headed in their direction.
[edit] See also

Cetaceans Portal
Dolphin
Whale
[edit] References
^abcd Read, Andrew (1999). Porpoises. Stillwater, MN, USA: Voyageur Press.
^The Porpoise Page - Information on Porpoises. Retrieved on2006-11-03.
[hide]v • d • e
Cetaceans (whales,dolphins, and porpoises)
Suborder Mysticeti
(baleen whales)
Eschrichtiidae (gray whales) ·Balaenopteridae (rorquals) ·Balaenidae (right whales) ·Neobalaenidae (pygmy right whales)

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)
[edit] External links
Whale and Dolphin Conservation Society (WDCS)