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For other uses, see Porpoise (disambiguation).
Porpoises
Temporal range: 15.970–0Ma
Miocene to Recent
Harbor.Porpoise.4.jpg
Phocoena phocoena, harbour porpoise near Denmark
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Suborder: Odontoceti
Superfamily: Delphinoidea
Family: Phocoenidae
Gray, 1825
Genera

See text

Porpoises (/ˈpɔrpəs/; also called mereswine) 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 shorter beaks and flattened, spade-shaped teeth distinct from the conical teeth of dolphins.

The name derives from French pourpois, possibly from Medieval Latin porcopiscis (porcus pig + piscis fish; cf. classical porcus marīnus ("sea hog").[1]

Porpoises, divided into six species, live in all oceans, and mostly near the shore. Freshwater populations of the finless porpoise also exist. Probably the best known species is the harbour porpoise, which can be found across the Northern Hemisphere. Like all toothed whales, porpoises are predators, using sounds (echolocation in sonar form) to locate prey and to coordinate with others. They hunt fish, squid, and crustaceans.

Taxonomy and evolution[edit]

Porpoises, along with whales and dolphins, are descendants of land-living ungulates (hoofed animals) that first entered the oceans around 50 million years ago (Mya). During the Miocene (23 to 5 Mya), mammals were fairly modern. The cetaceans diversified, and fossil evidence suggests porpoises and dolphins diverged from their last common ancestor around 15 Mya. The oldest fossils are known from the shallow seas around the North Pacific, with animals spreading to the European coasts and Southern Hemisphere only much later, during the Pliocene.[2]

Suborder Odontoceti toothed whales

Recently discovered hybrids between male harbour porpoises and female Dall's porpoises indicate the two species may actually be members of the same genus.[6]

Physical characteristics[edit]

A harbour porpoise at an aquarium.

Porpoises tend to be smaller but stouter than dolphins. They have small, rounded heads and blunt jaws instead of beaks. While dolphins have a round, bulbous "melon", porpoises do not. 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 and large whales. Some species have small bumps, known as tubercles, on the leading edge of the dorsal fin. The function of these bumps is unknown.[6]

These animals are the smallest cetaceans, reaching body lengths up to 2.5 metres (8.2 ft); the smallest species is the vaquita, reaching up to 1.5 metres (4.9 ft). In terms of weight, the lightest is the finless porpoise at 30 to 45 kilograms (66 to 99 lb), and the heaviest is Dall's porpoise at 130 to 200 kilograms (290 to 440 lb). Because of their small size, porpoises lose body heat to the water more rapidly than other cetaceans. Their stout shape, which minimizes surface area, may be an adaptation to reduce heat loss. Thick blubber also insulates them from the cold. The small size of porpoises requires them to eat frequently, rather than depending on fat reserves.[6]

Life history[edit]

Porpoises bear young more quickly than dolphins. Female Dall's and harbour porpoises often become pregnant with a single calf each year, and pregnancy lasts for about 11 months. Porpoises have been known to live 8–10 years, although some have lived to be 20.[6]

Behavior[edit]

"Rooster tail" spray around swimming Dall's porpoises

Porpoises prey on 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, referred to as pods. 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 (34 mph). Porpoises tend to be less acrobatic and more sexually aggressive than dolphins.[7]

Humans and porpoises[edit]

Accidental entanglement (bycatch) in fishing nets is the main threat to porpoises today.[8] One of the most endangered cetacean species is the vaquita, having a limited distribution in the Gulf of California, a highly industrialized area. In some countries, porpoises are hunted for food or bait meat.[citation needed]

Porpoises are rarely held in captivity in zoos or oceanaria, as they are generally not as capable of adapting to tank life or as easily trained as dolphins.[citation needed]

See also[edit]

References[edit]

  1. ^ "Porpoise - Define Porpoise at Dictionary.com". Dictionary.com. 
  2. ^ Gaskin, David E. (1984). Macdonald, D., ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 196–199. ISBN 0-87196-871-1. 
  3. ^ Ichishima, H. & Kimura, M.. 2005. "Harborophocoena toyoshimai, a new early Pliocene porpoise (Cetacea, Phocoenidae) from Hokkaido, Japan". Journal of Vertebrate Paleontology 25(3):655–664
  4. ^ Ichishima, H. & Kimura, M.. 2000. "A new fossil porpoise (Cetacea; Delphinoidea; Phocoenidae) from the early Pliocene Horokaoshirarika Formation, Hokkaido, Japan". Journal of Vertebrate Paleontology 20(3):561–576
  5. ^ Lambert, O.. 2008. "A new porpoise (Cetacea, Odontoceti, Phocoenidae) from the Pliocene of the North Sea". Journal of Vertebrate Paleontology 28(3):863–872
  6. ^ a b c d Read, Andrew (1999). Porpoises. Stillwater, MN, USA: Voyageur Press. ISBN 0-89658-420-8. 
  7. ^ http://appreviews4u.com/2013/03/11/porpoises-the-ignored-species/
  8. ^ "Phocoena sinus". 

External links[edit]

Media related to Phocoenidae at Wikimedia Commons


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Porpoise — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
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7604 news items

 
Washington Post
Sun, 07 Dec 2014 17:17:13 -0800

Little is known about the shy vaquita porpoises that spend long periods feeding under muddy coastal waters off Mexico, but this much is certain: They are the world's smallest porpoise — cute as a button — and they could soon disappear forever if they ...

The Guardian

The Guardian
Wed, 26 Nov 2014 03:33:55 -0800

That makes the seals the major cause of harbour porpoise deaths in the Netherlands, alongside being killed as fishing bycatch. “This is a new behaviour. They're normally fish eaters, they can eat a large fish, around half a metre. It's a switch from ...

Christian Science Monitor

Discovery News
Wed, 10 Dec 2014 07:11:15 -0800

[See Images of the Elusive Vaquita Porpoise]. "They look like they're wearing dark lipstick and mascara," said Rebecca Lent, executive director of the Marine Mammal Commission, an independent federal agency that aims to protect and conserve marine ...

WBUR

WBUR
Tue, 02 Dec 2014 06:30:32 -0800

It pits Mexican drug cartels and Chinese wildlife traffickers against a species of porpoise so beautiful, it is sometimes described as the cutest mammal in the sea. And time is short. Many conservationists say we may only have three years to save the ...

KOMO News

KOMO News
Mon, 15 Dec 2014 16:38:30 -0800

FRIDAY HARBOR, Wash. -- In a rare and valuable analysis late Monday of a dead Dall's Porpoise found the day before on San Juan Island, marine mammal scientists finishing a necropsy say they found a fungal infection in the porpoise's lungs and she was ...

TakePart

TakePart
Thu, 27 Nov 2014 07:31:57 -0800

The vaquita, a small porpoise found only in the Gulf of California, is the world's most endangered marine mammal. Fewer than 100 exist in the wild. Without drastic and immediate action, this species will almost certainly go the way of the Chinese river ...

New York Times

New York Times
Mon, 01 Dec 2014 14:19:52 -0800

Gray seals are a major predator of harbor porpoises, according to DNA analysis of porpoise bite wounds. The seals probably wound the porpoises and then tear off large sections of blubber, researchers say. More than 1,000 autopsies of porpoises ...
 
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Mon, 15 Dec 2014 09:37:30 -0800

A close relative of the harbor porpoise, the vaquita, Phocoena sinus, is generally considered the most endangered cetacean in the world. The vaquita inherited that dubious honor when the Yangtze River dolphin or baiji was declared extinct in 2006. Like ...
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