Porpoises are a group of fully
aquatic marine mammal
Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their reli ...
s, all of which are classified under the family Phocoenidae, parvorder
Odontoceti
The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of ...
(toothed whales). Although similar in appearance to
dolphin
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...
s, they are more closely related to
narwhal
The narwhal, also known as a narwhale (''Monodon monoceros''), is a medium-sized toothed whale that possesses a large "tusk" from a protruding canine tooth. It lives year-round in the Arctic waters around Greenland, Canada and Russia. It is o ...
s and
beluga The beluga whale (/bɪˈluːɡə/) (Delphinapterus leucas) is an Arctic and sub-Arctic cetacean. It is one of two members of the family Monodontidae, along with the narwhal, and the only member of the genus Delphinapterus. It is also known as the wh ...
s than to the
true dolphins.
There are eight extant species of porpoise, all among the smallest of the
toothed whales
The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of t ...
. Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins (e.g.
Hector's dolphin
Hector's dolphin (''Cephalorhynchus hectori'') is one of four dolphin species belonging to the genus ''Cephalorhynchus''. Hector's dolphin is the only cetacean endemic to New Zealand, and comprises two subspecies: ''C. h. hectori'', the more nu ...
) also lack a pronounced beak. Porpoises, and other
cetacea
Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
ns, belong to the clade
Cetartiodactyla
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
with
even-toed ungulate
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
s.
Porpoises range in size from the
vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
, at in length and in weight, to the
Dall's porpoise
Dall's porpoise (''Phocoenoides dalli'') is a species of porpoise endemic to the North Pacific. It is the largest of porpoises and the only member of the genus ''Phocoenoides''. The species is named after American naturalist W. H. Dall.
Taxono ...
, at and . Several species exhibit
sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
in that the females are larger than males. They have streamlined bodies and two limbs that are modified into flippers. Porpoises use
echolocation as their primary
sensory system
The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neural pathways, and parts of the brain involved i ...
. Some species are well adapted for diving to great depths. As all cetaceans, they have a layer of fat, or blubber, under the skin to keep them warm in cold water.
Porpoises are abundant and found in a multitude of environments, including rivers (
finless porpoise
''Neophocaena'' is a genus of porpoise native to the Indian and Pacific oceans, as well as the freshwater habitats of the Yangtze River basin in China
China, officially the People's Republic of China (PRC), is a country in East Asia. ...
), coastal and shelf waters (
harbour porpoise
The harbour porpoise (''Phocoena phocoena'') is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar ...
,
vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
) and open ocean (
Dall's porpoise
Dall's porpoise (''Phocoenoides dalli'') is a species of porpoise endemic to the North Pacific. It is the largest of porpoises and the only member of the genus ''Phocoenoides''. The species is named after American naturalist W. H. Dall.
Taxono ...
and
spectacled porpoise
The spectacled porpoise (''Phocoena dioptrica'') is a small to midsize porpoise indigenous to the Southern Ocean. It is one of the most poorly studied cetaceans, partly due to its remote range in the southern ocean. What little is known about th ...
), covering all water temperatures from tropical (
Sea of Cortez
The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja C ...
,
vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
) to polar (
Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...
,
harbour porpoise
The harbour porpoise (''Phocoena phocoena'') is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar ...
). Porpoises feed largely on fish and squid, much like the rest of the odontocetes. Little is known about reproductive behaviour. Females may get one calf every year under favourable conditions.
Calves are typically born in the spring and summer months and remain dependent on the female until the following spring. Porpoises produce ultrasonic clicks, which are used for both navigation (
echolocation) and social communication. In contrast to many dolphin species, porpoises do not form large social groups.
Porpoises were, and still are, hunted by some countries by means of
drive hunting. Larger threats to porpoises include extensive
bycatch
Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...
in
gill net
Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...
s, competition for food from fisheries, and
marine pollution
Marine pollution occurs when substances used or spread by humans, such as industrial waste, industrial, agricultural pollution, agricultural and municipal solid waste, residential waste, particle (ecology), particles, noise, excess carbon dioxid ...
, in particular heavy metals and
organochlorides
An organochloride, organochlorine compound, chlorocarbon, or chlorinated hydrocarbon is an organic compound containing at least one covalently bonded atom of chlorine. The chloroalkane class (alkanes with one or more hydrogens substituted by chlor ...
. The
vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
is nearly extinct due to bycatch in gill nets, with a predicted population of fewer than a dozen individuals. Since the extinction of the
baiji
The baiji (; IPA: ; ''Lipotes vexillifer'', ''Lipotes'' meaning "left behind" and ''vexillifer'' "flag bearer") is a possibly extinct species of freshwater dolphin native to the Yangtze river system in China. It is thought to be the first dolph ...
, the
vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
is considered the most endangered cetacean. Some species of porpoises have been and are kept in captivity and trained for research, education and public display.
Taxonomy and evolution
Porpoises, along with
whale
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
s and
dolphin
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...
s, are descendants of land-living
ungulate
Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, cam ...
s (hoofed animals) that first entered the oceans around 50 million years ago (Mya). During the
Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
(23 to 5
Mya), mammals were fairly modern, meaning they seldom changed
physiologically
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
from the time. 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
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58[Artiodactyla
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...](_blank)
**Infraorder
Cetacea
Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
***Parvorder
Odontoceti
The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of ...
toothed whales
****Superfamily
Delphinoidea
Delphinoidea 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 tons, while the smallest is the vaquita.
Taxonomy
Based on McGowen ''et al''., ...
*****Family Phocoenidae – porpoises
******Genus †''
Haborophocoena''
*******''
H. toyoshimai''
******Genus ''
Neophocaena
''Neophocaena'' is a genus of porpoise native to the Indian and Pacific oceans, as well as the freshwater habitats of the Yangtze River basin in China. They are commonly known as finless porpoises. Genetic studies indicate that ''Neophocaena'' is ...
''
*******''N. phocaeniodes'' –
Indo-Pacific finless porpoise
The Indo-Pacific finless porpoise (''Neophocaena phocaenoides'') is one of eight porpoise species. The species ranges throughout most of the Indian Ocean, as well as the tropical and subtropical Pacific from Indonesia north to the Taiwan Strait ...
*******''N. sunameri'' –
East Asian finless porpoise
The East Asian finless porpoise (''Neophocaena sunameri'') is a species of porpoise native to the East China Sea, Yellow Sea, and the seas around Japan. The Yangtze finless porpoise (''N. asiaeorientalis'') was formerly considered a subspecies ...
*******''N. asiaeorientalis'' –
Yangtze finless porpoise
The Yangtze finless porpoise (''Neophocaena asiaeorientalis'') is a species of toothed whale in the family Phocoenidae. It is endemic to the Yangtze River in China, making it the country's only known freshwater cetacean following the possible ...
******Genus †''
Numataphocoena''
*******''
N. yamashitai''
******Genus ''
Phocoena
''Phocoena'' is a genus of porpoises with four extant species:
References
External links
*
*''Phocoena''in ''Mammal Species of the World
''Mammal Species of the World: A Taxonomic and Geographic Reference'' is a standard reference work in ...
''
*******''P. phocoena'' –
harbour porpoise
The harbour porpoise (''Phocoena phocoena'') is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar ...
*******''P. sinus'' –
vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
*******''P. dioptrica'' –
spectacled porpoise
The spectacled porpoise (''Phocoena dioptrica'') is a small to midsize porpoise indigenous to the Southern Ocean. It is one of the most poorly studied cetaceans, partly due to its remote range in the southern ocean. What little is known about th ...
*******''P. spinipinnis'' –
Burmeister's porpoise
Burmeister's porpoise (''Phocoena spinipinnis'') 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. Locally it is known as ''marsopa espinosa'' (t ...
******Genus ''
Phocoenoides''
*******''P. dalli'' –
Dall's porpoise
Dall's porpoise (''Phocoenoides dalli'') is a species of porpoise endemic to the North Pacific. It is the largest of porpoises and the only member of the genus ''Phocoenoides''. The species is named after American naturalist W. H. Dall.
Taxono ...
******Genus †''
Semirostrum''
*******''
S.ceruttii''
******Genus †''
Septemtriocetus''
*******''
S. bosselaersii''
******Genus †''
Piscolithax''
*******''
P. aenigmaticus''
*******''
P. longirostris''
*******''
P. boreios''
*******''
P. tedfordi''
Recently discovered
hybrid
Hybrid may refer to:
Science
* Hybrid (biology), an offspring resulting from cross-breeding
** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species
** Hybridity, the property of a hybrid plant which is a union of two dif ...
s between male harbour porpoises and female
Dall's porpoise
Dall's porpoise (''Phocoenoides dalli'') is a species of porpoise endemic to the North Pacific. It is the largest of porpoises and the only member of the genus ''Phocoenoides''. The species is named after American naturalist W. H. Dall.
Taxono ...
s indicate the two species may actually be members of the same
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
.
Biology
Anatomy
![Cambridge Natural History Mammalia Fig 183](https://upload.wikimedia.org/wikipedia/commons/5/5e/Cambridge_Natural_History_Mammalia_Fig_183.jpg)
Porpoises have a bulbous head, no external ear flaps, a non-flexible neck, a torpedo shaped body, limbs modified into flippers, and a tail fin. Their skull has small eye orbits, small, blunt snouts, and eyes placed on the sides of the head. Porpoises range in size from the and
Vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
to the and
Dall's porpoise
Dall's porpoise (''Phocoenoides dalli'') is a species of porpoise endemic to the North Pacific. It is the largest of porpoises and the only member of the genus ''Phocoenoides''. The species is named after American naturalist W. H. Dall.
Taxono ...
. Overall, they tend to be dwarfed by other cetaceans. Almost all species have female-biased sexual dimorphism, with the females being larger than the males,
although those physical differences are generally small; one exception is Dall's porpoise.
[
Odontocetes possess teeth with ]cementum
Cementum is a specialized calcified substance covering the root of a tooth. The cementum is the part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament.Illustrated Dental Embryology, Histology, a ...
cells overlying dentine
Dentin () (American English) or dentine ( or ) (British English) ( la, substantia eburnea) is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth. It is usually covered by ena ...
cells. Unlike human teeth, which are composed mostly of enamel on the portion of the tooth outside of the gum, whale teeth have cementum outside the gum. Porpoises have a three-chambered stomach, including a fore-stomach and fundic and pyloric chambers. Porpoises, like other odontocetes, possess only one blowhole. Breathing involves expelling stale air from the blowhole, forming an upward, steamy spout, followed by inhaling fresh air into the lungs. All porpoises have a thick layer of blubber
Blubber is a thick layer of vascularized adipose tissue under the skin of all cetaceans, pinnipeds, penguins, and sirenians.
Description
Lipid-rich, collagen fiber-laced blubber comprises the hypodermis and covers the whole body, except for pa ...
. This blubber can help with insulation from the harsh underwater climate, protection to some extent as predators would have a hard time getting through a thick layer of fat, and energy for leaner times. Calves are born with only a thin layer of blubber, but rapidly gain a thick layer from the milk, which has a very high fat content.
Locomotion
Porpoises have two flippers on the front and a tail fin. Their flippers contain four digits. Although porpoises do not possess fully developed hind limbs, they possess discrete rudimentary appendages, which may contain feet and digits. Porpoises are fast swimmers in comparison to seals, which typically cruise at . The fusing of the neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility, making it impossible for them to turn their head. When swimming, they move their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering. Flipper movement is continuous. Some species log
Log most often refers to:
* Trunk (botany), the stem and main wooden axis of a tree, called logs when cut
** Logging, cutting down trees for logs
** Firewood, logs used for fuel
** Lumber or timber, converted from wood logs
* Logarithm, in mathe ...
out of the water, which may allow them to travel faster, and sometimes they porpoise
Porpoises are a group of fully aquatic marine mammals, all of which are classified under the family Phocoenidae, parvorder Odontoceti (toothed whales). Although similar in appearance to dolphins, they are more closely related to narwhals an ...
out of the water, meaning jump out of the water. Their skeletal anatomy allows them to be fast swimmers. They have a very well defined and triangular dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
, allowing them to steer better in the water. Unlike their dolphin counterparts, they are adapted for coastal shores, bays, and estuaries.
Senses
The porpoise ear has specific adaptations to the marine
Marine is an adjective meaning of or pertaining to the sea or ocean.
Marine or marines may refer to:
Ocean
* Maritime (disambiguation)
* Marine art
* Marine biology
* Marine debris
* Marine habitats
* Marine life
* Marine pollution
Military
* ...
environment. In humans, the middle ear
The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear).
The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the ...
works as an impedance equaliser between the outside air's low impedance and the cochlea
The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. A core component of the cochlea is the Organ of Corti, the sensory org ...
r fluid's high impedance. In whales, and other marine mammals, there is no great difference between the outer and inner environments. Instead of sound passing through the outer ear to the middle ear, porpoises receive sound through the throat, from which it passes through a low-impedance fat-filled cavity to the inner ear. The porpoise ear is acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater. Odontocetes send out high frequency clicks from an organ known as a melon
A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a "pepo". The ...
. This melon consists of fat, and the skull of any such creature containing a melon will have a large depression. The large bulge on top of the porpoises head is caused by the melon.
The porpoise eye is relatively small for its size, yet they do retain a good degree of eyesight. As well as this, the eyes of a porpoise are placed on the sides of its head, so their vision consists of two fields, rather than a binocular view like humans have. When porpoises surface, their lens and cornea correct the nearsightedness that results from the refraction of light; their eyes contain both rod and cone
A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex.
A cone is formed by a set of line segments, half-lines, or lines con ...
cells, meaning they can see in both dim and bright light. Porpoises do, however, lack short wavelength sensitive visual pigments in their cone cells indicating a more limited capacity for colour vision than most mammals. Most porpoises have slightly flattened eyeballs, enlarged pupils (which shrink as they surface to prevent damage), slightly flattened corneas and a tapetum lucidum
The ''tapetum lucidum'' ( ; ; ) is a layer of tissue in the eye of many vertebrates and some other animals. Lying immediately behind the retina, it is a retroreflector. It reflects visible light back through the retina, increasing the light a ...
; these adaptations allow for large amounts of light to pass through the eye and, therefore, they are able to form a very clear image of the surrounding area.
The olfactory lobes
The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...
are absent in porpoises, suggesting that they have no sense of smell.
Porpoises are not thought to have a good sense of taste, as their taste buds are atrophied or missing altogether. However, some have preferences between different kinds of fish, indicating some sort of attachment to taste.
Sleep
Unlike most animals, porpoises are conscious breathers. All mammals sleep, but porpoises cannot afford to become unconscious for long because they may drown. While knowledge of sleep in wild cetaceans is limited, porpoises in captivity have been recorded to sleep with one side of their brain at a time, so that they may swim, breathe consciously, and avoid both predators and social contact during their period of rest.
This means that the brain hemispheres take turns alternating between slow wave sleep and being awake. While one hemisphere displays slow waves, the other displays wake patterns on an electroencephalogram. It has been suggested that the brainstem controls this activity. All the while, porpoises also employ a minimal amount of suppressed REM sleep while swimming.
The same neural systems that regulate sleep in bihemispheric mammals are used in harbor porpoises. Cetaceans use many of the same neurotransmitters that other mammals use, although they have a significantly higher number. Although the way porpoises sleep is different from other mammals, they use the same neural mechanisms and pathways. One key difference is that porpoises seem to inhibit REM sleep more than most mammals, likely to prevent losing muscle tone and thus decreasing the risk of drowning or suffering from hypothermia. Porpoises differ from other mammals in terms of the neurons that regulate their sleep-wake cycle, however, the sleep-wake cycle overall is surprisingly similar to other mammals. This shows that despite differences in sleeping patterns, the sleep wake mechanism is conserved across species. The anatomy of the cetacean brain varies slightly from that of other mammals, with the area governing sleep-wake cycles (caudal to the posterior commissures) being significantly larger.
It is difficult to use traditional methods to determine whether a porpoise is sleeping, since half of the brain is awake at any given time. Parabolic dives have been shown to potentially be correlated to sleeping periods in porpoises, with decreased bioacoustics being transmitted during these periods. This means that during parabolic dives, porpoises generally do not employ echolocation clicks (about fifty percent of the time). This may be related to the side of the brain that is asleep. For instance, the left hemisphere signals to the right side of the brain, which controls the production of echolocation clicks. Thus, when the left side of the brain is asleep, echolocation cannot be produced.
Along with using less bioacoustics, porpoises roll less, use a lower vertical descent rate, and are overall less active while performing parabolic dives. Parabolic dives have shown to be of shallow depth and use a low amount of energy. These are different behaviors than the those displayed during foraging dives. Moreover, these behaviors are consistent with stereotypical sleeping behavior.
Interestingly, parabolic dives are more common during the daytime than during the nighttime and only take up a small amount of a wild porpoise's total time, as opposed to the time spent sleeping in other mammals. Meanwhile, captive cetaceans have been shown to spend up to fifty percent of their time sleeping and up to sixty-six percent of their time resting. A thought that deserves further consideration is that wild porpoises spend a significant fraction of their time near the surface of the water, and it is difficult to determine if this time is being spent resting or sleeping.
Behaviour
Life cycle
Porpoises are fully aquatic creatures. Females deliver a single calf after a gestation period
In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once it ...
lasting about a year. Calving takes place entirely under water, with the foetus positioned for tail-first delivery to help prevent drowning. Females have mammary glands, but the shape of a newborn calf's mouth does not allow it to obtain a seal around the nipple— instead of the calf sucking milk, the mother squirts milk into the calf's mouth. This milk contains high amounts of fat, which aids in the development of blubber; it contains so much fat that it has the consistency of toothpaste. The calves are weaned at about 11 months of age. Males play no part in rearing calves. The calf is dependent for one to two years, and maturity occurs after seven to ten years, all varying between species. This mode of reproduction produces few offspring, but increases the probability of each one surviving.
Diet
Porpoises eat a wide variety of creatures. The stomach contents of harbour porpoises suggests that they mainly feed on benthic fish
Demersal fish, also known as groundfish, live and feed on or near the bottom of seas or lakes (the demersal zone).Walrond Carl . "Coastal fish - Fish of the open sea floor"Te Ara - the Encyclopedia of New Zealand. Updated 2 March 2009 They o ...
, and sometimes pelagic fish
Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that do live on or near the bottom, and reef fish that are associated with coral reef ...
. They may also eat benthic invertebrates. In rare cases, algae, such as ''Ulva lactuca
''Ulva lactuca'', also known by the common name sea lettuce, is an edible green alga in the family Ulvaceae. It is the type species of the genus ''Ulva''. A synonym is ''U. fenestrata'', referring to its "windowed" or "holed" appearance.
Descrip ...
'', is consumed. Atlantic porpoises are thought to follow the seasonal migration of bait fish
300px, Feeder Goldfish are common baitfish.
Bait fish (or baitfish) are small-sized fish caught and used by anglers as bait to attract larger predatory fish, particularly game fish. Baitfish species are typically those that are common and bree ...
, like herring
Herring are forage fish, mostly belonging to the family of Clupeidae.
Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans, i ...
, and their diet varies between seasons. The stomach contents of Dall's porpoises reveal that they mainly feed on cephalopod
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...
s and bait fish, like capelin
The capelin or caplin (''Mallotus villosus'') is a small forage fish of the smelt family found in the North Atlantic, North Pacific and Arctic oceans. In summer, it grazes on dense swarms of plankton at the edge of the ice shelf. Larger capelin ...
and sardine
"Sardine" and "pilchard" are common names for various species of small, oily forage fish in the herring family Clupeidae. The term "sardine" was first used in English during the early 15th century, a folk etymology says it comes from the Ital ...
s. Their stomachs also contained some deep-sea benthic organisms.
The finless porpoise is known to also follow seasonal migrations. It is known that populations in the mouth of the Indus River
The Indus ( ) is a transboundary river of Asia and a trans-Himalayan river of South and Central Asia. The river rises in mountain springs northeast of Mount Kailash in Western Tibet, flows northwest through the disputed region of Kashmir, ...
migrate to the sea from April through October to feed on the annual spawning of prawn
Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs (which is a member of the order decapoda), some of which can be eaten.
The term "prawn"Mortenson, Philip B (2010''This is not a weasel: a close look at nature ...
s. In Japan, sightings of small pods of them herding sand lance
A sand lance or sandlance is a fish belonging to the family Ammodytidae. Several species of sand lances are commonly known as "sand eels", though they are not related to true eels. Another variant name is launce, and all names of the fish are ...
onto shore are common year-round.
Little is known about the diets of other species of porpoises. A dissection of three Burmeister's porpoises shows that they consume shrimp and euphausiid
Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word ', meaning "small fry of fish", which is also often attributed to species of fish.
Krill are consi ...
s (krill). A dissection of a beached Vaquita showed remains of squid and grunts. Nothing is known about the diet of the spectacled porpoise.
Interactions with humans
Research history
In Aristotle
Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatetic school of phil ...
's time, the 4th century BCE, porpoises were regarded as fish due to their superficial similarity. Aristotle, however, could already see many physiological and anatomical similarities with the terrestrial vertebrates, such as blood (circulation), lungs, uterus and fin anatomy. His detailed descriptions were assimilated by the Romans, but mixed with a more accurate knowledge of the dolphins, as mentioned by Pliny the Elder
Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...
in his "Natural history". In the art of this and subsequent periods, porpoises are portrayed with a long snout (typical of dolphins) and a high-arched head. The harbour porpoise
The harbour porpoise (''Phocoena phocoena'') is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar ...
was one of the most accessible species for early cetologists
Cetology (from Greek , ''kētos'', "whale"; and , ''-logia'') or whalelore (also known as whaleology) is the branch of marine mammal science that studies the approximately eighty species of whales, dolphins, and porpoises in the scientific order ...
, because it could be seen very close to land, inhabiting shallow coastal areas of Europe. Much of the findings that apply to all cetaceans were first discovered in porpoises. One of the first anatomical descriptions of the airways of the whales on the basis of a harbor porpoise dates from 1671 by John Ray. It nevertheless referred to the porpoise as a fish, most likely not in the modern-day sense, where it refers to a zoological group, but the older reference as simply a creature of the sea (cf. for example ''star-fish'', ''cuttle-fish'', ''jelly-fish'' and ''whale-fish'').
In captivity
Harbour porpoises have historically been kept in captivity, under the assumption that they would fare better than their dolphin counterparts due to their smaller size and shallow-water habitats. Up until the 1980s, they were consistently short-lived. Harbour porpoises have a very long captive history, with poorly documented attempts as early as the 15th century, and better documented starting in the 1860s and 1870s in London Zoo
London Zoo, also known as ZSL London Zoo or London Zoological Gardens is the world's oldest scientific zoo. It was opened in London on 27 April 1828, and was originally intended to be used as a collection for science, scientific study. In 1831 o ...
, the now-closed Brighton
Brighton () is a seaside resort and one of the two main areas of the City of Brighton and Hove in the county of East Sussex, England. It is located south of London.
Archaeological evidence of settlement in the area dates back to the Bronze A ...
Aquarium & Dolphinarium, and a zoo in Germany.[ At least 150 harbour porpoises have been kept worldwide, but only about 20 were actively caught for captivity.] The captive history is best documented from Denmark where about 100 harbour porpoises have been kept, most in the 1960s and 1970s. All but two were incidental catches in fishing nets or strandings. Nearly half of these died within a month of diseases caught before they were captured or from damage sustained during capture. Up until 1984, none lived for more than 14 months.[ Attempts of rehabilitation seven rescued individuals in 1986 only resulted in three that could be released 6 months later.] Very few have been brought into captivity later, but they have lived considerably longer. In recent decades the only place keeping the species in Denmark is the Fjord & Bælt Centre, where three rescues have been kept, along with their offspring. Among the three rescues, one (father of world's first harbour porpoise born in captivity) lived for 20 years in captivity and another 15 years, while the third (mother of first born in captivity) is still alive in 2021 after 23 years. This is older than the typical age reached in the wild, which is 14 years or less. Very few harbour porpoises have been born in captivity. Historically, harbour porpoises were often kept singly and those who were together often were not mature or of the same sex. Disregarding one born more than 100 years ago that was the result of a pregnant female being brought into captivity, the world's first full captive breeding was in 2007 in the Fjord & Bælt Centre, followed by another in 2009 in the Dolfinarium Harderwijk
Dolfinarium Harderwijk, better known as the Dolfinarium, is a marine mammal park in Harderwijk, the Netherlands. It is the largest marine mammal park in Europe. Visitor numbers were steady from 2005 to 2011, numbering between 700,000 and 800,000, ...
, the Netherlands. In addition to the few kept in Europe, harbour porpoise were displayed at the Vancouver Aquarium
The Vancouver Aquarium is a public aquarium located in Stanley Park in Vancouver, British Columbia, Canada. In addition to being a major tourist attraction for Vancouver, the aquarium is a centre for marine research, ocean literacy education, cl ...
(Canada) until recently. This was a female that had beached herself onto Horseshoe Bay in 2008 and a male that had done the same in 2011. They died in 2017 and 2016 respectively.
Finless porpoises have commonly been kept in Japan, as well as China and Indonesia. As of 1984, ninety-four in total had been in captivity in Japan, eleven in China, and at least two in Indonesia. As of 1986, three establishments in Japan had bred them, and there had been five recorded births. Three calves died moments after their birth, but two survived for several years. This breeding success, combined with the results with harbour porpoise in Denmark and the Netherlands, proved that porpoises can be successfully bred in captivity, and this could open up new conservation options. The reopened Miyajima Public Aquarium (Japan) houses three finless porpoises. As part of an attempt of saving the narrow-ridged (or Yangtze) finless porpoise, several are kept in the Baiji Dolphinarium in China. After having been kept in captivity for 9 years, the first breeding happened in 2005.
Small numbers of Dall's porpoises have been kept in captivity in both the United States and Japan, with the most recent being in the 1980s. The first recorded instance of a Dall's taken for an aquarium was in 1956 captured off Catalina Island in southern California. Dall's porpoises consistently failed to thrive in captivity. These animals often repeatedly ran into the walls of their enclosures, refused food, and exhibited skin sloughing
Skin sloughing is the process of shedding dead surface cells from the skin. It is most associated with cosmetic skin maintenance via exfoliation, but can also occur biologically or for medical reasons.
Cellular Process
Skin Composition
Kerat ...
. Almost all Dall's porpoises introduced to aquaria died shortly after, typically within days. Only two have lived for more than 60 days: a male reached 15 months at Marineland of the Pacific
Marineland of the Pacific was a public oceanarium and tourist attraction located on the Palos Verdes Peninsula coast in Los Angeles County, California, Los Angeles County, California. Architect William Pereira designed the main structure. It wa ...
and another 21 months at a United States Navy facility.[
As part of last-ditch effort of saving the extremely rare ]vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
(the tiny remaining population is rapidly declining because of bycatch in gillnets), there have been attempts of transferring some to captivity.[ The first and only caught for captivity were two females in 2017. Both became distressed and were rapidly released, but one of them died in the process.] Soon after the project was abandoned.[
Only a single ]Burmeister's porpoise
Burmeister's porpoise (''Phocoena spinipinnis'') 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. Locally it is known as ''marsopa espinosa'' (t ...
and a single spectacled porpoise
The spectacled porpoise (''Phocoena dioptrica'') is a small to midsize porpoise indigenous to the Southern Ocean. It is one of the most poorly studied cetaceans, partly due to its remote range in the southern ocean. What little is known about th ...
have been kept in captivity. Both were stranded individuals that only survived a few days after their rescue.
Threats
Hunting
Porpoises and other smaller cetaceans have traditionally been hunted in many areas for their meat and blubber. A dominant hunting technique is drive hunting, where a pod of animals is driven together with boats and usually into a bay or onto a beach. Their escape is prevented by closing off the route to the ocean with other boats or nets. This type of fishery for harbour porpoise
The harbour porpoise (''Phocoena phocoena'') is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar ...
s is well documented from the Danish Straits
The Danish straits are the straits connecting the Baltic Sea to the North Sea through the Kattegat and Skagerrak. Historically, the Danish straits were internal waterways of Denmark; however, following territorial losses, Øresund and Fehmarn Be ...
, where it occurred regularly until the end of the 19th century, and picked up again during World war I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
and World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
. The Inuit
Inuit (; iu, ᐃᓄᐃᑦ 'the people', singular: Inuk, , dual: Inuuk, ) are a group of culturally similar indigenous peoples inhabiting the Arctic and subarctic regions of Greenland, Labrador, Quebec, Nunavut, the Northwest Territories ...
in the Arctic
The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...
hunt harbour porpoises by shooting and drive hunt for Dall's porpoise
Dall's porpoise (''Phocoenoides dalli'') is a species of porpoise endemic to the North Pacific. It is the largest of porpoises and the only member of the genus ''Phocoenoides''. The species is named after American naturalist W. H. Dall.
Taxono ...
still takes place in Japan. The number of individuals taken each year is in the thousands, although a quota of around 17,000 per year is in effect today making it the largest direct hunt of any cetacean
Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
species in the world and the sustainability of the hunt has been questioned.
Fishing
Porpoises are highly affected by bycatch
Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...
. Many porpoises, mainly the vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
, are subject to great mortality due to gillnetting
Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...
. Although it is the world's most endangered marine cetacean, the vaquita continues to be caught in small-mesh gillnet fisheries throughout much of its range. Incidental mortality caused by the fleet of El Golfo de Santa Clara was estimated to be at around 39 vaquitas per year, which is over 17% of the population size. Harbour porpoises also suffer drowning by gillnetting, but on a less threatening scale due to their high population; their mortality rate per year increases a mere 5% due to this.
The fishing market, historically has always had a porpoise bycatch. Today, the Marine Mammal Protection Act of 1972
The Marine Mammal Protection Act (MMPA) was the first act of the United States Congress to call specifically for an ecosystem approach to wildlife management.
Authority
MMPA was signed into law on October 21, 1972, by President Richard Nixon ...
has enforced the use of safer fishing equipment to reduce bycatch.
Environmental hazards
Porpoises are very sensitive to anthropogenic
Anthropogenic ("human" + "generating") is an adjective that may refer to:
* Anthropogeny, the study of the origins of humanity
Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows:
* Human im ...
disturbances, and are keystone species
A keystone species is a species which has a disproportionately large effect on its natural environment relative to its abundance, a concept introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaini ...
, which can indicate the overall health of the marine environment. Populations of harbor porpoises in the North and Baltic Seas are under increasing pressure from anthropogenic causes such as offshore construction, ship traffic, fishing, and military exercises. Increasing pollution is a serious problem for marine mammals. Heavy metals and plastic waste
Plastic pollution is the accumulation of plastic objects and particles (e.g. plastic bottles, bags and microbeads) in the Earth's environment that adversely affects humans, wildlife and their habitat. Plastics that act as pollutants are catego ...
are not biodegradable, and sometimes cetaceans consume these hazardous materials, mistaking them for food items. As a result, the animals are more susceptible to diseases and have fewer offspring. Harbour porpoises from the English Channel
The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais) or ( Jèrriais), (Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Kana ...
were found to have accumulated heavy metals.
The military and geologists employ strong sonar
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...
and produce an increases in noise in the oceans. Marine mammal
Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their reli ...
s that make use of biosonar
Echolocation, also called bio sonar, is a biological sonar used by several animal species.
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 ...
for orientation and communication are not only hindered by the extra noise, but may race to the surface in panic. This may lead to a bubbling out of blood gases, and the animal then dies because the blood vessels become blocked, so-called decompression sickness
Decompression sickness (abbreviated DCS; also called divers' disease, the bends, aerobullosis, and caisson disease) is a medical condition caused by dissolved gases emerging from solution as bubbles inside the body tissues during decompressio ...
. This effect, of course, only occurs in porpoises that dive to great depths, such as Dall's porpoise.
Additionally, civilian vessels produce sonar waves to measure the depth of the body of water in which they are. Similar to the navy, some boats produce waves that attract porpoises, while others may repel them. The problem with the waves that attract is that the animal may be injured or even killed by being hit by the vessel or its propeller.
Conservation
The harbour porpoise, spectacled porpoise, Burmeister's porpoise, and Dall's porpoise are all listed on Appendix II of the (CMS).["] In addition, the Harbour porpoise is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS), the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS) and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. Their conservation statuses are either at least concern
A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...
or data deficient
A data deficient (DD) species is one which has been categorized by the International Union for Conservation of Nature (IUCN) as offering insufficient information for a proper assessment of conservation status to be made. This does not necessaril ...
.
As of 2014, only 505 Yangtze finless porpoise
The Yangtze finless porpoise (''Neophocaena asiaeorientalis'') is a species of toothed whale in the family Phocoenidae. It is endemic to the Yangtze River in China, making it the country's only known freshwater cetacean following the possible ...
s remained in the main section of the Yangtze, with an alarming population density in Ezhou and Zhenjiang. While many threatened species decline rate slows after their classification, population decline rates of the porpoise are actually accelerating. While population decline tracked from 1994 to 2008 has been pegged at a rate of 6.06% annually, from 2006 to 2012, the porpoise population decreased by more than half. Finless porpoise population decrease of 69.8% in just a 22-year span from 1976 to 2000. 5.3%. A majority of factors of this population decline are being driven by the massive growth in Chinese industry since 1990 which caused increased shipping and pollution and ultimately environmental degradation. Some of these can be seen in damming of the river as well as illegal fishing
Illegal, unreported and unregulated fishing (IUU) is an issue around the world. Fishing industry observers believe IUU occurs in most fisheries, and accounts for up to 30% of total catches in some important fisheries.
Illegal fishing takes pl ...
activity. To protect the species, China's Ministry of Agriculture classified the species as being National First Grade Key Protected Wild Animal, the strictest classification by law, meaning it is illegal to bring harm to a porpoise. Protective measures in the Tian-e-Zhou Oxbow Nature Reserve The Tian-e-Zhou Oxbow Nature Reserve is an area of wetland in the Yangtze basin near Shishou, Hubei province, People's Republic of China. Inside the reserve is the Tian'e-Zhou lake which was an intended sanctuary for the baiji (Yangtze river dolph ...
has increased its population of porpoises from five to forty in 25 years. The Chinese Academy of Science
The Chinese Academy of Sciences (CAS); ), known by Academia Sinica in English until the 1980s, is the national academy of the People's Republic of China for natural sciences. It has historical origins in the Academia Sinica during the Republic ...
's Wuhan Institute of Hydrobiology has been working with the World Wildlife Fund
The World Wide Fund for Nature Inc. (WWF) is an international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the Wo ...
to ensure the future for this subspecies, and have placed five porpoises in another well-protected area, the He-wang-miao oxbow. Five protected natural reserves have been established in areas of the highest population density and mortality rates with measures being taken to ban patrolling and harmful fishing gear in those areas. There have also been efforts to study porpoise biology to help specialize conservation through captivation breeding. The Baiji Dolphinarium, was established in 1992 at the Institute of Hydrobiology of the Chinese Academy of Sciences in Wuhan which allowing the study of behavioral and biological factors affecting the finless porpoise, specifically breeding biology like seasonal changes in reproductive hormones and breeding behavior.
Because vaquita
The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...
s are indigenous to the Gulf of California, Mexico is leading conservation efforts with the creation of the International Committee for the Recovery of the Vaquita
International is an adjective (also used as a noun) meaning "between nations".
International may also refer to:
Music Albums
* ''International'' (Kevin Michael album), 2011
* ''International'' (New Order album), 2002
* ''International'' (The T ...
(CIRVA), which has tried to prevent the accidental deaths of vaquitas by outlawing the use of fishing nets within the vaquita's habitat. CIRVA has worked together with the CITES
CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
, the Endangered Species Act
The Endangered Species Act of 1973 (ESA or "The Act"; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of ec ...
, and the Marine Mammal Protection Act
The Marine Mammal Protection Act (MMPA) was the first act of the United States Congress to call specifically for an ecosystem approach to wildlife management.
Authority
MMPA was signed into law on October 21, 1972, by President Richard Nixon ...
(MMPA) to nurse the vaquita population back to a point at which they can sustain themselves. CIRVA concluded in 2000 that between 39 and 84 individuals are killed each year by such gillnets. To try to prevent extinction, the Mexican government has created a nature reserve covering the upper part of the Gulf of California and the Colorado River delta
The Colorado River Delta is the region where the Colorado River flows into the Gulf of California (also known as the Sea of Cortez) in eastern Mexicali Municipality in the north of the state of Baja California in northwesternmost Mexico. The d ...
. They have also placed a temporary ban on fishing, with compensation to those affected, that may pose a threat to the vaquita.
See also
* List of individual cetaceans
Cetaceans are the animals commonly known as whales, dolphins, and porpoises. This list includes individuals from real life or fiction, where fictional individuals are indicated by their source. It is arranged roughly taxonomically.
Baleen wh ...
References
* Dell, Leigh‐Anne, et al. "Organization of the sleep‐related neural systems in the brain of the harbour porpoise (Phocoena phocoena)." Journal of Comparative Neurology 524.10 (2016): 1999–2017.
* Wright, Andrew J., et al. "Silent porpoise: potential sleeping behaviour identified in wild harbour porpoises." Animal Behaviour 133 (2017): 211–222.
External links
*
Whale Trackers – An online documentary series about whales, dolphins and porpoises.
{{Authority control
*
Langhian first appearances
Extant Miocene first appearances
Animals that use echolocation
Taxa named by John Edward Gray