Indus river dolphin

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Indus river dolphin
A-Platanista-gangetica-showing-the-body-shape-and-especially-the-head-with-a-long-beak.png
Ganges and Indus river dolphin size.svg
Size compared to an average human
CITES Appendix I (CITES) [1]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Platanistidae
Genus: Platanista
Species:
P. minor
Binomial name
Platanista minor
Owen, 1853
SouthAsianRiverDolphin distribution2019.png
Ranges of the Indus river dolphin and Ganges river dolphin

The Indus river dolphin (Platanista minor) is a species of freshwater dolphin in the family Platanistidae. It is endemic to the Indus River basin in Pakistan and Beas River in northwestern India. [1] This dolphin was the first discovered side-swimming cetacean. It is patchily distributed in five small, sub-populations that are separated by irrigation barrages. [2]

Contents

From the 1970s until 1998, the Ganges River dolphin (Platanista gangetica) and the Indus dolphin were regarded as separate species; however, in 1998, their classification was changed from two separate species to subspecies of a single species. However, more recent studies support them being distinct species. It has been named as the national mammal of Pakistan and the state aquatic animal of Punjab, India.

Taxonomy

The long jaws and deep brain pan of the Indus river dolphin are visible from this skull cast. From the collection of The Children's Museum of Indianapolis. Indus River dolphin skull cast.jpg
The long jaws and deep brain pan of the Indus river dolphin are visible from this skull cast. From the collection of The Children's Museum of Indianapolis.

The Indus river dolphin was described in 1853 by Richard Owen under the name Platanista gangetica, var. minor, based on a dolphin skull, which was smaller than skulls of the Ganges river dolphin. [3]

The Indus and Ganges river dolphins were initially classified as a single species, Platanista gangetica. In the 1970s, they were considered to be distinct species, but again grouped as a single species in the 1990s. However, more recent studies of genes, divergence time, and skull structure support both being distinct species. [4]

The Ganges river dolphin split from the Indus river dolphin during the Pleistocene, around 550,000 years ago. [5]

Description

Dolphins leaping B-Platanista-gangetica-in-natural-habitat.png
Dolphins leaping

The Indus dolphin has the long, pointed nose characteristic of all river dolphins. The teeth are visible in both the upper and lower jaws even when the mouth is closed. The teeth of young animals are almost an inch long, thin and curved; however, as animals age the teeth undergo considerable changes and in mature adults become square, bony, flat disks. The snout thickens towards its end. The species does not have a crystalline eye lens, rendering it effectively blind, although it may still be able to detect the intensity and direction of light. Navigation and hunting are carried out using echolocation. The body is a brownish color and stocky at the middle. The species has a small triangular lump in place of a dorsal fin. The flippers and tail are thin and large in relation to the body size, which is about 2–2.2 m (6 ft 7 in – 7 ft 3 in) in males and 2.4–2.6 m (7 ft 10 in – 8 ft 6 in) in females. The oldest recorded animal was a 28-year-old male 199 cm (78 in) in length. [6] Mature adult females are larger than males. Sexual dimorphism is expressed after females reach about 150 cm (59 in); the female rostrum continues to grow after the male rostrum stops growing, eventually reaching approximately 20 cm (7.9 in) longer.[ citation needed ]

Distribution

The Indus river dolphin presently only occurs in the Indus River system. [1] [2] These dolphins occupied about 3,400 km of the Indus River and the tributaries attached to it in the past. [2] But today, its only found in one fifth of this previous range. Its effective range today has declined by 80% since 1870. [2] It no longer exists throughout the tributaries, and its home range is only 690 km of the river. [2] [7] This dolphin prefers a freshwater habitat with a water depth greater than 1 meter and that have more than 700 meters squared of cross-sectional area. Today this species can only be found in the Indus River's main stem, along with a remnant population in the Beas River. A population can be found in the Harike Wetland located in Punjab, India. [8]

Since the two originally inhabited river systems – between the Sukkur and Guddu barrage in Pakistan's Sindh Province, and in the Punjab and Khyber Pakhtunkhwa Provinces – are not connected in any way, how they were colonized remains unknown. The river dolphins are unlikely to have travelled from one river to another through the sea route, since the two estuaries are very far apart. A possible explanation is that several north Indian rivers such as the Sutlej and Yamuna changed their channels in ancient times while retaining their dolphin populations. [9]

Behaviour and ecology

It is thought that Indus river dolphin swims on its side to efficiently navigate shallow waters during the dry season. [10]

Threats

Illustration by Friedrich Specht Schnabeldelphin-drawing.jpg
Illustration by Friedrich Specht

The Indus river dolphin has been very adversely affected by human use of the river systems in the subcontinent. Entanglement in fishing nets can cause significant damage to local population numbers. Some individuals are still taken each year and their oil and meat used as a liniment, as an aphrodisiac and as bait for catfish. Irrigation has lowered water levels throughout their ranges. Poisoning of the water supply from industrial and agricultural chemicals may have also contributed to population decline. Perhaps the most significant issue is the building of dozens of dams along many rivers, causing the segregation of populations and a narrowed gene pool in which dolphins can breed. There are currently three sub-populations of Indus dolphins considered capable of long-term survival if protected. [2]

Conservation status

The Indus river dolphin is protected under Appendix I of the Convention on the International Trade of Endangered Species which prohibits the commercial international trade of the species (including parts and derivatives). [2] It is listed as Endangered on the IUCN Red List, [1] and by the U.S. government National Marine Fisheries Service under the U.S. Endangered Species Act. It is the second most endangered cetacean in the world. As of 2017 it is estimated that there are only about 1,800 individuals remaining (up from 1,200 estimated in 2001). [11] A demonstrable increase in the main river population of the Indus subspecies between 1974 and 2008 may have been driven by permanent immigration from upstream tributaries, where the species no longer occurs. [12]

It is threatened by extensive fishing that reduces their prey availability. [13] Accidentally entangling in fishing nets causes fatalities. [14] Deforestation along the river basins is causing sedimentation which degrades the dolphin's habitat. [13] Another factor for its decline is the construction of cross-river structures such as dams and barrages causing more isolation of the already small sub-populations. [13] A major threat is human induced water pollution through industrial and human waste, or agricultural run-off containing high amounts of chemical fertilizers and poisonous pesticides. [13]

Studies suggest that a better understanding of this species ecology is needed in order to develop good conservation plans. Regular monitoring is necessary to assess the population's status and factors causing its decline. [13] A satellite tagging effort was begun in 2022. [15]

See also

Related Research Articles

<span class="mw-page-title-main">Indus River</span> River in Asia

The Indus is a transboundary river of Asia and a trans-Himalayan river of South and Central Asia. The 3,120 km (1,940 mi) river rises in mountain springs northeast of Mount Kailash in Western Tibet, flows northwest through the disputed region of Kashmir, bends sharply to the left after the Nanga Parbat massif, and flows south-by-southwest through Pakistan, before emptying into the Arabian Sea near the port city of Karachi.

<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">South Asian river dolphin</span> Genus of freshwater dolphin

South Asian river dolphins are toothed whales in the genus Platanista, which inhabit the waterways of the Indian subcontinent. They were historically considered to be one species with the Ganges river dolphin and the Indus river dolphin being subspecies. Genetic and morphological evidence led to their being described as separate species in 2021. The Ganges and Indus river dolphins are estimated to have diverged 550,000 years ago. They are the only living members of the family Platanistidae and the superfamily Platanistoidea. Fossils of ancient relatives date to the late Oligocene.

<span class="mw-page-title-main">Beas River</span> River in north India

The Beas River is a river in north India. The river rises in the Himalayas in central Himachal Pradesh, India, and flows for some 470 kilometres (290 mi) to the Sutlej River in the Indian state of Punjab. Its total length is 470 kilometres (290 mi) and its drainage basin is 20,303 square kilometres (7,839 sq mi) large.

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

The Irrawaddy dolphin is a euryhaline species of oceanic dolphin found in scattered subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia. It closely resembles the Australian snubfin dolphin, which was not described as a separate species until 2005. It has a slate blue to a slate gray color. Although found in much of the riverine and marine zones of South and Southeast Asia, the only concentrated lagoon populations are found in Chilika Lake in Odisha, India and Songkhla Lake in southern Thailand.

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

The Atlantic humpback dolphin is a species of humpback dolphin that is found in coastal areas of West Africa.

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

The Ganges river dolphin is a species of freshwater dolphin classified in the family Platanistidae. It lives in the Ganges and related rivers of South Asia, namely in the countries of India, Nepal, and Bangladesh. It is related to the much smaller Indus river dolphin which lives in the Indus River in Pakistan and the Beas River of northwestern India.

<span class="mw-page-title-main">Gharial</span> Crocodilian native to the Indian subcontinent

The gharial, also known as gavial or fish-eating crocodile, is a crocodilian in the family Gavialidae and among the longest of all living crocodilians. Mature females are 2.6 to 4.5 m long, and males 3 to 6 m. Adult males have a distinct boss at the end of the snout, which resembles an earthenware pot known as a ghara, hence the name "gharial". The gharial is well adapted to catching fish because of its long, narrow snout and 110 sharp, interlocking teeth.

<span class="mw-page-title-main">Sutlej</span> River in Asia

The Sutlej River is the longest of the five rivers that flow through the historic crossroads region of Punjab in northern India and Pakistan. The Sutlej River is also known as Satadru. It is the easternmost tributary of the Indus River. The Bhakra Dam is built around the river Sutlej to provide irrigation and other facilities to the states of Punjab, Rajasthan and Haryana.

<span class="mw-page-title-main">Ghaghara</span> Asian river and tributary of the Ganges

The Ghaghara River, also known as the Karnali River in Nepal, Mapcha Tsangpo in Tibet, and the lower Ghaghara in Awadh is known as the Sarayu River, is a perennial trans-boundary river that originates in the northern slopes of the Himalayas in the Tibetan Plateau, cuts through the Himalayas in Nepal and joins the Sharda River at Brahmaghat in India. Together they form the Ghaghara River, a major left-bank tributary of the Ganges. With a length of 507 km (315 mi), it is the longest river in Nepal. The total length of the Ghaghara up to its confluence with the Ganges at Revelganj in Bihar is 1,080 km (670 mi). It is the largest tributary of the Ganges by volume and the second largest by length after Yamuna.

Chashma and Taunsa Barrage Dolphin Sanctuary is located in Mianwali District, Punjab, Pakistan. It was declared open to the public in 1972. Since the 1970s, the population of the Indus river dolphins has significantly increased there. It is a very important breeding and wintering area for wide variety of waterfowl regularly 20000 birds it is the largest preservation area for endangered indus dolphins.

<span class="mw-page-title-main">Wildlife of Pakistan</span>

The wildlife of Pakistan comprises a diverse flora and fauna in a wide range of habitats from sea level to high elevation areas in the mountains, including 195 mammal, 668 bird species and more than 5000 species of Invertebrates. This diverse composition of the country's fauna is associated with its location in the transitional zone between two major zoogeographical regions, the Palearctic, and the Oriental. The northern regions of Pakistan, which include Khyber Pakhtunkhwa and Gilgit Baltistan include portions of two biodiversity hotspot, Mountains of Central Asia and Himalayas.

<span class="mw-page-title-main">Fauna of Pakistan</span> Overview of fauna in Pakistan

Pakistan's native fauna reflect its varied climatic zones. The northern Pakistan, which includes Khyber Pakhtunkhwa and Gilgit Baltistan, has portions of two biodiversity hotspots, Mountains of Central Asia and Himalayas.

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

The baiji is a possibly extinct species of freshwater dolphin native to the Yangtze river system in China. It is thought to be the first dolphin species driven to extinction due to the impact of humans. This dolphin is listed as "critically endangered: possibly extinct" by the IUCN, has not been seen in 20 years, and several surveys of the Yangtze have failed to find it. In China, the species is also called the Chinese river dolphin, Yangtze river dolphin, Yangtze dolphin and whitefin dolphin. Nicknamed the "Goddess of the Yangtze", it was regarded as the goddess of protection by local fishermen and boatmen. It is not to be confused with the Chinese white dolphin or the finless porpoise. This is the only species in the genus Lipotes.

<span class="mw-page-title-main">Harike Wetland</span> Largest wetland in northern India

Harike Wetland also known as "Hari-ke-Pattan", with the Harike Lake in the deeper part of it, is the largest wetland in northern India in the border of Tarn Taran Sahib district and Ferozepur district of the Punjab state in India.

The Beas Conservation Reserve covers an 185 km stretch of the river Beas. The area of the Reserve lies primarily in north-west Punjab. It was declared a conservation reserve by the government of Punjab, India in 2017. The Beas flows down meandering from the Himalayan foothills to Harike Headworks, where it spreads into multiple channels. The braided channels form islands and sand bars creating a complex environment that supports rich biodiversity. In September 2019, the reserve was declared a Ramsar site under the aegis of the 1971 Ramsar Convention on Wetlands of International Importance.

<i>Pebanista</i> Extinct genus of freshwater dolphins

Pebanista is an extinct genus of platanistid "river dolphin" that lived during the Early to Middle Miocene in Peru. As a member of the Platanistidae, Pebanista is most closely related to the extant Ganges and Indus river dolphins (Platanista) of South Asia and shares no close relation to the modern Amazon river dolphin that inhabits the same region today. Like its close relatives, Pebanista possesses enlarged crests that would have covered the melon in life, possibly helping to focus their biosonar while hunting in murky waters. Pebanista further stands out as being the largest "river dolphin" yet discovered, reaching lengths between 2.8–3.47 m at minimum, much larger than the biggest recorded freshwater cetaceans of today. Given its relatively robust if elongated snout, it is thought that Pebanista was an active predator, profiting from the rich prey selection available to it in the enormous Pebas wetlands that covered South America during the early parts of the Miocene. Only a single species of Pebanista is known so far: P. yacuruna.

References

  1. 1 2 3 4 5 Braulik, G.T.; Khan, U.; Malik, M. & Aisha, H. (2023) [errata version of 2022 assessment]. "Platanista minor". IUCN Red List of Threatened Species . 2022: e.T41757A243168232. doi: 10.2305/IUCN.UK.2022-1.RLTS.T41757A243168232.en . Retrieved 4 March 2024.
  2. 1 2 3 4 5 6 7 Braulik, G.T. (2006). "Status assessment of the Indus river dolphin, Platanista gangetica minor, March–April 2001". Biological Conservation. 129 (4): 579–590. Bibcode:2006BCons.129..579B. doi:10.1016/j.biocon.2005.11.026.
  3. Braulik, G.T.I.; Archer, F.; Khan, U.; Imran, M.; Sinha, R.K.; Jefferson, T.A.; Donovan, C. & Graves, J.A. (2021). "Taxonomic revision of the South Asian River dolphins (Platanista): Indus and Ganges River dolphins are separate species". Marine Mammal Science. 37 (3): 1022–1059. Bibcode:2021MMamS..37.1022B. doi: 10.1111/mms.12801 . hdl: 10023/21691 .
  4. "Explore the Database". www.mammaldiversity.org. Retrieved 2021-08-27.
  5. "Fossilworks: Platanista gangetica".
  6. Kasuya, T., 1972. Some information on the growth of the Ganges dolphin with a comment on the Indus dolphin. Sci. Rep. Whales Res. Inst. 24: 87–108.
  7. "Indus River Dolphin". WWF Pakistan.
  8. Puri, Gurbax (16 April 2022). "Tarn Taran diary: Harike, an abode for birds, rare Indus dolphins". The Tribune.
  9. Sanyal, S. (2012). Land of the Seven Rivers: A Brief History of India's Geography. Penguin.
  10. Herald, E. S.; Brownell, R. L.; Frye, F. L.; Morris, E. J.; Evans, W. E.; Scott, A. B. (1969). "Blind river dolphin: first side-swimming cetacean". Science. 166 (3911): 1408–1410. Bibcode:1969Sci...166.1408H. doi:10.1126/science.166.3911.1408. PMID   5350341.
  11. "Signs of hope as population of endangered Indus River dolphin jumps in Pakistan". WWF. Retrieved 2017-12-17.
  12. Braulik, G. T.; Noureen, U.; Arshad, M.; Reeves, R. R. (2015). "Review of status, threats, and conservation management options for the endangered Indus River blind dolphin". Biological Conservation. 192: 30–41. Bibcode:2015BCons.192...30B. doi:10.1016/j.biocon.2015.09.008.
  13. 1 2 3 4 5 "Indus River dolphin: the survivor of River Beas, Punjab, India". India Biodiversity Portal. Retrieved 2021-08-27.
  14. Khan, M.S. (2013). "Indus River Dolphin: The Survivor of River Beas, Punjab, India". Current Science. 104 (11): 1464–1465.
  15. "First ever satellite tagging of river dolphins in Asia". WWF. 2022. Retrieved 2 February 2022.

Further reading