Indo-Pacific finless porpoise

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Indo-Pacific finless porpoise
Stamps of Indonesia, 040-05.jpg
Illustration for an Indonesian stamp
CITES Appendix I (CITES) [2]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Phocoenidae
Genus: Neophocaena
Species:
N. phocaenoides
Binomial name
Neophocaena phocaenoides
(G. Cuvier, 1829)
Range Neophocaena phocaenoides.png

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. Overlapping with this species in the Taiwan Strait and replacing it northwards is the East Asian finless porpoise (N. sunameri).

Contents

Distribution

The Indo-Pacific finless porpoise lives in the coastal waters of Asia, especially around Indonesia, Malaysia, India, and Bangladesh. At the western end, their range includes the length of the western coast of India and continues up into the Persian Gulf. On the eastern edge of their range, they are found throughout the Indonesian archipelago and range north to the Taiwan Strait. Finless porpoises are also one of the species protected at Sundarbans National Park.

Description

Size compared to an average human Finless porpoise size.svg
Size compared to an average human

Finless porpoises can grow to as much as 2.27 m (7 ft 5 in) in length, and can weigh up to 72 kg (159 lb), although most are rather smaller. [3] The flippers are moderately large, reaching up to 20% of the total body length. Adults are typically a uniform, light grey colour, although some may have lighter patches of skin around the mouth or darker patches in front of the flippers. Newborn calves of the central and eastern subspecies are mostly black with grey around the dorsal ridge area, becoming fully grey after four to six months. However, newborn calves of the western subspecies are a light creamy grey, and become darker as they age. [3]

Adults grow more than 1.55 m (5 ft) in length and up to 30–45 kg (65–100 lb) in weight.[ citation needed ]

Internal anatomy

Skeleton in the collection of Museo di storia naturale e del territorio dell'Universita di Pisa NeophocaenaPhocaenoides.JPG
Skeleton in the collection of Museo di storia naturale e del territorio dell'Università di Pisa

The anatomy of finless porpoises has been relatively well studied, compared with that of some other cetacean species. For example, the tubercles along the dorsal ridge are known to contain numerous nerve endings that may possess a sensory function. The auditory system also appears well-developed, with numerous large nerve fibres specialised for rapid communication between the ears and the brain. On the other hand, sight is relatively poor, with a reduced lens and a limited number of fibres in the optic nerve and to the muscles moving the eyes. [3]

The skeleton is unusually light, accounting for only 5% of total weight. There are between 58 and 65 vertebrae, about half of them in the tail, and with the first three cervical vertebrae fused into a single structure. There are ten to fourteen pairs of ribs in the chest, and an additional set of vestigial ribs has sometimes been reported in the neck, in association with the seventh cervical vertebra. [3] There are 44 sets of spinal nerves. [4]

The nasal passage contains nine or ten air sacs, which have a complicated structure, and are capable of sealing off all air within the passage. Behind these are an additional set of vomeronasal sacs. [5] The trachea, however, is short, with only four cartilaginous rings. [3] The stomach has three chambers, there is no caecum, and no distinct difference between the small and large intestines. [6] [7]

Diet

Finless porpoises are opportunistic feeders using various kinds of available food items available in their habitat, including fish, crustaceans, and cephalopods. [8] They are reported[ by whom? ] to eat fish, shrimp and squid off Pakistan. Seasonal changes in their diets have not been studied. They also apparently ingest some plant material when living in estuaries, mangroves, and rivers, including leaves, rice, and eggs deposited on vegetation.[ citation needed ]

Behaviour

Recent data[ clarification needed ] suggest the basic unit of a finless porpoise pod is a mother/calf pair or two adults, and schools of three or more individuals are aggregations of these units or of solitary individuals. Social structure seems to be underdeveloped in the species, and the mother/calf pair is probably the only stable social unit.[ citation needed ]

Like other porpoises, their behaviour tends to be not as energetic and showy as that of dolphins. They do not ride bow waves, and in some areas appear to be shy of boats. [3]

Finless porpoises make both high frequency clicking sounds, and longer, low frequency tones, the latter perhaps being for communication, rather than echolocation. [9] The clicks are narrow-band, with peaks of over 100 kHz. [10]

A new study from Woods Hole Oceanographic Institution (WHOI) study that was published in The Journal of Experimental Biology , "highlights the differences in dolphins' ability to hear across species, reshaping the previous 'one-size-fits-all' approach taken on the hearing ability of the cetaceans". [11]

Swimming style

Although they show no acrobatics in the water,[ citation needed ] finless porpoises are believed to be very active swimmers. They typically swim just beneath the surface of the water and roll to one side when surfacing to breathe. This rolling movement disturbs very little water on the surface, so they are often overlooked when rising to breathe. Surfacing generally lasts for one minute, as they take three to four quick successive breaths, then quickly submerge into the water. They often surface a great distance from the point where they dive beneath the water's surface.[ citation needed ] Dives lasting over four minutes have been recorded, and a common pattern of behaviour is to take one long dive, followed by two shorter ones. [3]

Reproduction

Breeding occurs in late spring and early summer.[ citation needed ]. The young are born in spring, summer, or winter, depending on the geographic locality, after a gestation period of ten to eleven months. Newborn finless porpoises are reported to 72 to 84 cm (28 to 33 in) in length. [3] [12] Males reach sexual maturity at four to six years of age, and females at six to nine years. [12] Finless porpoises have lived up to 33 years. [3]

It has been claimed that young calves cling to the denticulated area of skin on their mother's back and are carried by her as she swims, but there is no clear evidence of this happening. [3] Calves are weaned at 6–15 months.[ citation needed ]

Conservation

The finless porpoise is listed on Appendix II [13] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II [13] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.

Since this species remains in coastal waters, it has a high degree of interaction with humans, which often puts the finless porpoise at risk. Like other porpoises, large numbers of this species are killed by entanglement in gill nets. The primary danger to the species is environmental degradation. Unlike other members of this family, finless porpoises have lived in captivity for over 15 years.[ citation needed ]

There are no well-established estimates of the animals' abundance. However, a comparison of two surveys, one from the late 1970s and the other from 1999–2000, shows a decline in population and distribution. Scientists believe this decline has been ongoing for decades, and the current population is just a fraction of its historical levels. Along the southern coast of Pakistan in the Arabian Sea it is declared as an endangered species.[ citation needed ]

The WWF Website states that the finless porpoise is Critically endangered. [14] However, it is not the official 'IUCN Endangered Status'.

See also

Related Research Articles

<span class="mw-page-title-main">Porpoise</span> Small cetacean of the family Phocoenidae

Porpoises are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas than to the true dolphins. There are eight extant species of porpoise, all among the smallest of the toothed whales. 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 also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates.

<span class="mw-page-title-main">River dolphin</span> Superfamily of dolphins

River dolphins are a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant river dolphins are placed in two superfamilies, Platanistoidea and Inioidea. They comprise the families Platanistidae, the recently extinct Lipotidae, Iniidae and Pontoporiidae. There are five extant species of river dolphins. River dolphins, alongside other cetaceans, belong to the clade Artiodactyla, with even-toed ungulates, and their closest living relatives the hippopotamuses, from which they diverged about 40 million years ago. Specific types of dolphins can be pink.

<span class="mw-page-title-main">Indo-Pacific humpback dolphin</span> Species of mammal

The Indo-Pacific humpback dolphin is a species of humpback dolphin inhabiting coastal waters of the eastern Indian and western Pacific Oceans. This species is often referred to as the Chinese white dolphin in mainland China, Macau, Hong Kong, Singapore and Taiwan as a common name. Some biologists regard the Indo-Pacific dolphin as a subspecies of the Indian Ocean humpback dolphin which ranges from East Africa to India. However, DNA testing studies have shown that the two are distinct species. A new species, the Australian humpback dolphin, was split off from S. chinensis and recognized as a distinct species in 2014. Nevertheless, there are still several unresolved issues in differentiation of the Indian Ocean-type and Indo-Pacific-type humpback dolphins.

<span class="mw-page-title-main">White-beaked dolphin</span> Species of mammal

The white-beaked dolphin is a marine mammal belonging to the family Delphinidae in the suborder Odontoceti.

<span class="mw-page-title-main">Dusky dolphin</span> Species of mammal

The dusky dolphin is a dolphin found in coastal waters in the Southern Hemisphere. Its specific epithet is Latin for "dark" or "dim". It is very closely genetically related to the Pacific white-sided dolphin, but current scientific consensus holds they are distinct species. The dolphin's range is patchy, with major populations around South America, southwestern Africa, New Zealand, and various oceanic islands, with some sightings around southern Australia and Tasmania. The dusky dolphin prefers cool currents and inshore waters, but can also be found offshore. It feeds on a variety of fish and squid species and has flexible hunting tactics. The dusky dolphin is known for its remarkable acrobatics, having a number of aerial behaviours. The status of the dolphin is unknown, but it has been commonly caught in gill nets.

<span class="mw-page-title-main">Finless porpoise</span> Genus of porpoises

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 the most basal living member of the porpoise family.

<span class="mw-page-title-main">Harbour porpoise</span> Species of mammal

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<span class="mw-page-title-main">Dall's porpoise</span> Species of porpoise endemic to the North Pacific

Dall's porpoise 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.

<span class="mw-page-title-main">Indo-Pacific bottlenose dolphin</span> Species of mammal

The Indo-Pacific bottlenose dolphin is a species of bottlenose dolphin. This dolphin grows to 2.6 m (8.5 ft) long, and weighs up to 230 kg (510 lb). It lives in the waters around India, northern Australia, South China, the Red Sea, and the eastern coast of Africa. Its back is dark grey and its belly is lighter grey or nearly white with grey spots.

<span class="mw-page-title-main">Indian Ocean humpback dolphin</span> Species of mammal

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<span class="mw-page-title-main">Peale's dolphin</span> Species of mammal

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<span class="mw-page-title-main">Pantropical spotted dolphin</span> Species of mammal

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<span class="mw-page-title-main">Spinner dolphin</span> Species of mammal

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<span class="mw-page-title-main">Atlantic white-sided dolphin</span> Species of mammal

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<span class="mw-page-title-main">Ocean Park Conservation Foundation Hong Kong</span>

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<span class="mw-page-title-main">Baiji</span> Species of river dolphin

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<span class="mw-page-title-main">East Asian finless porpoise</span> Species of porpoise

The East Asian finless porpoise is a species of porpoise native to the East China Sea, Yellow Sea, and the seas around Japan. The Yangtze finless porpoise was formerly considered a subspecies but is now thought to be a distinct species.

<span class="mw-page-title-main">Yangtze finless porpoise</span> Species of porpoise endemic to China

The Yangtze finless porpoise is a species of toothed whale in the family Phocoenidae, the porpoise family. It is endemic to the Yangtze River in China, making it the country's only known freshwater cetacean following the possible extinction of the baiji, a freshwater dolphin also native to the Yangtze. The Yangtze finless porpoise is considered critically endangered and it is estimated that only about 1,000 remain. This small toothed whale faces many of the same threats as the baiji: High human activity on the Yangtze, such as illegal fishing, pollution, boat traffic, and dam construction. Due to the rapidly declining population of the species, the Chinese government and conservation charities are working to help save it from extinction.

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References

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