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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] Because porpoises have a spongy material within their loose, layered skin which beats rhythmically with the motion of the water to strongly reduce water drag, porpoises can swim faster than any other creature in the sea.[citation needed]

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. ^ http://dictionary.reference.com/browse/porpoise?o=102213
  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. ^ http://www.iucnredlist.org/details/17028/0

External links[edit]

Media related to Phocoenidae at Wikimedia Commons


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Porpoise — Please support Wikipedia.
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1218 news items

National Geographic

National Geographic
Wed, 13 Aug 2014 03:55:28 -0700

The vaquita, a small porpoise found only in the Gulf of California, is rapidly going extinct, an international team of scientists reported earlier this month. The researchers say that the marine mammals—whose name means "little cow" in Spanish—are ...
 
Fox News Latino
Tue, 26 Aug 2014 09:18:45 -0700

Environmentalist groups have asked the Mexican government to declare a total and immediate ban on fishing nets in order to avoid the extinction of the vaquita, a rare species of porpoise found only in the northern Gulf of California. The International ...

The Guardian

The Guardian
Tue, 12 Aug 2014 05:58:51 -0700

The world's smallest porpoise faces imminent extinction unless the Mexican government eliminates gill-net fishing in its only habitat, the upper Sea of Cortez, scientists have warned. Recent studies conducted using underwater acoustic technology show ...
 
Post-Bulletin
Tue, 26 Aug 2014 07:51:54 -0700

A Porpoise must swim a 200 IM, tread water holding a 10-pound brick, lead a synchronize swim routine, be able to perform a stride jump, carry a 10-pound object 15 yards and finally help teach 24 hours in the YMCA swim lesson program. This is an ...
 
Austin Herald
Tue, 19 Aug 2014 06:36:18 -0700

Katie began lessons in the YMCA Learn to Swim Program in 2007 as a preschooler and went through all the levels of our school aged program. She swam with the Austin Y Aqua Pack Swim Team. Like many of our Porpoise graduates over the past six years ...
 
Science AAAS
Mon, 04 Aug 2014 14:33:45 -0700

An international team of scientists says that the critically endangered vaquita, a species of porpoise (Phocoena sinus) found only in Mexico's Gulf of California, is fast approaching extinction and that all gillnet fishing in the animal's range must be ...

89.3 KPCC

89.3 KPCC
Thu, 07 Aug 2014 10:15:00 -0700

A porpoise known as the Vaquita - or "little cow" translated from Spanish - is the most endangered marine mammal species in the world. It swims in the Gulf of California - also known as the Sea of Cortez - off Baja California and its population is ...

Nature World News

Nature World News
Thu, 14 Aug 2014 14:11:15 -0700

Vaquita porpoises are on the verge of extinction unless the Mexican government eliminates gill-net fishing in its only habitat, according to an environmental report released earlier this month. (Photo : NOAA). Vaquita porpoises are on the verge of ...
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