Porpoise
Encyclopedia
Porpoises are small cetacea
ns of the family
Phocoenidae; they are related to whale
s and dolphin
s. 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, originally from Medieval Latin
porcopiscus (porcus pig + piscus fish).
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 History
Porpoises, along with whales and dolphins, are descendants of land-living ungulate
s (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
.
Suborder Odontoceti toothed whales
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns of the family
Family
In human context, a family is a group of people affiliated by consanguinity, affinity, or co-residence. In most societies it is the principal institution for the socialization of children...
Phocoenidae; they are related to whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s and dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors
Sailors
Sailors is the plural form of Sailor, or mariner.Sailors may also refer to:*Sailors , a 1964 Swedish film*Ken Sailors , American basketball playerSports teams*Erie Sailors, baseball teams in Pennsylvania, USA...
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
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
pourpois, originally from Medieval Latin
Medieval Latin
Medieval Latin was the form of Latin used in the Middle Ages, primarily as a medium of scholarly exchange and as the liturgical language of the medieval Roman Catholic Church, but also as a language of science, literature, law, and administration. Despite the clerical origin of many of its authors,...
porcopiscus (porcus pig + piscus fish).
Porpoises, divided into six species, live in all oceans, and mostly near the shore. Freshwater populations of the finless porpoise
Finless Porpoise
The finless porpoise is one of six porpoise species. In the waters around Japan, at the northern end of its range, it is known as the sunameri . A freshwater population found in the Yangtze River in China is known locally as the jiangzhu or "river pig". There is a degree of taxonomic uncertainty...
also exist. Probably the best known species is the harbour porpoise
Harbour Porpoise
The harbour porpoise is one of six species of porpoise. It is one of the smallest marine mammals. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar porpoise to whale watchers. This porpoise often ventures up rivers, and has been seen...
, which can be found across the Northern Hemisphere. Like all toothed whales, porpoises are predators, using sounds (echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
in sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
form) to locate prey and to coordinate with others. They hunt fish, squid, and crustaceans.
Taxonomy and History
Porpoises, along with whales and dolphins, are descendants of land-living ungulate
Ungulate
Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive...
s (hoofed animals) that first entered the oceans around 50 million years ago (Mya). During the Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
(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
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
.
Suborder Odontoceti toothed whales
- Infraorder Delphinida
- Superfamily DelphinoideaDelphinoideaDelphinoidea is the largest group of toothed whales with 66 genera in 6 families. The largest living member of the superfamily is the killer whale, which can reach 6 tonnes, while the smallest, Commerson's Dolphin, is also the smallest living cetacean....
- Family Phocoenidae - porpoises
- Genus †Haborophocoena
- H. toyoshimai
- Genus Neophocaena
- N. phocaeniodes - Finless porpoiseFinless PorpoiseThe finless porpoise is one of six porpoise species. In the waters around Japan, at the northern end of its range, it is known as the sunameri . A freshwater population found in the Yangtze River in China is known locally as the jiangzhu or "river pig". There is a degree of taxonomic uncertainty...
- N. phocaeniodes - Finless porpoise
- Genus †Numataphocoena
- N. yamashitai
- Genus Phocoena
- P. phocoena - harbour porpoiseHarbour PorpoiseThe harbour porpoise is one of six species of porpoise. It is one of the smallest marine mammals. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar porpoise to whale watchers. This porpoise often ventures up rivers, and has been seen...
- P. sinus - vaquitaVaquitaThe vaquita is a rare species of porpoise. It is endemic to the northern part of the Gulf of California. Estimates of the number of individuals alive range from 100 to 300. The word "vaquita" is Spanish for little cow...
- P. dioptrica - spectacled porpoiseSpectacled PorpoiseThe Spectacled Porpoise is a rarely seen member of the porpoise family. The species is readily distinguished from other porpoises by a characteristic dark ring around the eyes, which gives the animals their name. This ring is commonly surrounded by a farther lighter ring...
- P. spinipinnis - Burmeister's PorpoiseBurmeister's PorpoiseBurmeister's Porpoise is a species of porpoise endemic to the coast of South America. It was first described by Hermann Burmeister, for whom the species is named, in 1865...
- P. phocoena - harbour porpoise
- Genus Phocoenoides
- P. dalli - Dall's porpoiseDall's PorpoiseDall's porpoise is a species of porpoise found on the North Pacific. It came to worldwide attention in the 1970s when it was disclosed for the first time to the public that salmon fishing trawls were killing a lot, thousands of Dall's porpoises and other cetaceans each year by accidentally...
- P. dalli - Dall's porpoise
- Genus †Septemriocetus
- S. bosselaersii
- Genus †Haborophocoena
- Family Phocoenidae - porpoises
- Superfamily Delphinoidea
- P. aenigmaticus
- P. longirostris
- P. boreios
- P. tedfordi
Recently discovered hybrids between male harbour porpoises and female Dall's porpoise
Dall's Porpoise
Dall's porpoise is a species of porpoise found on the North Pacific. It came to worldwide attention in the 1970s when it was disclosed for the first time to the public that salmon fishing trawls were killing a lot, thousands of Dall's porpoises and other cetaceans each year by accidentally...
s indicate the two species may actually be members of the same genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
.
Physical characteristics
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Melon (whale)
The melon is an ovoid-shaped, fatty organ found in the forehead of all toothed whales , including dolphins and porpoises and believed to be used in echolocation....
", 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.
These animals are the smallest cetaceans, reaching body lengths up to 2.5 metres (8.2 ft); the smallest species is the vaquita
Vaquita
The vaquita is a rare species of porpoise. It is endemic to the northern part of the Gulf of California. Estimates of the number of individuals alive range from 100 to 300. The word "vaquita" is Spanish for little cow...
, reaching up to 1.5 metres (4.9 ft). In terms of weight, the lightest is the finless porpoise
Finless Porpoise
The finless porpoise is one of six porpoise species. In the waters around Japan, at the northern end of its range, it is known as the sunameri . A freshwater population found in the Yangtze River in China is known locally as the jiangzhu or "river pig". There is a degree of taxonomic uncertainty...
at 30 to 45 kg (66.1 to 99.2 lb), and the heaviest is Dall's porpoise
Dall's Porpoise
Dall's porpoise is a species of porpoise found on the North Pacific. It came to worldwide attention in the 1970s when it was disclosed for the first time to the public that salmon fishing trawls were killing a lot, thousands of Dall's porpoises and other cetaceans each year by accidentally...
at 130 to 200 kg (286.6 to 440.9 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
Blubber
Blubber is a thick layer of vascularized adipose tissue found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber–laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature...
also insulates them from the cold. The small size of porpoises requires them to eat frequently, rather than depending on fat reserves.
Life history
Porpoises are relatively r-selected
R/K selection theory
In ecology, r/K selection theory relates to the selection of combinations of traits in an organism that trade off between quantity or quality of offspring...
compared with dolphins: that is, they 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.
Behavior
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
for finding prey and group coordination. Porpoises are fast swimmers—Dall's porpoise
Dall's Porpoise
Dall's porpoise is a species of porpoise found on the North Pacific. It came to worldwide attention in the 1970s when it was disclosed for the first time to the public that salmon fishing trawls were killing a lot, thousands of Dall's porpoises and other cetaceans each year by accidentally...
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 wary than dolphins.
Human impact
Accidental entanglement (bycatch
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
) in fishing nets is the main threat to porpoises today. One of the most endangered cetacean species is the vaquita, having a limited distribution in the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
, a highly industrialized area.
In some countries, porpoises are hunted for food or bait meat.
Porpoises are rarely held in captivity in zoo
Zoo
A zoological garden, zoological park, menagerie, or zoo is a facility in which animals are confined within enclosures, displayed to the public, and in which they may also be bred....
s or oceanaria, as they are generally not as capable of adapting to tank life or as easily trained as dolphins.
External links